Installation Engineering Handbook | IEH 550
BBU Swap Validation & Troubleshoo
Troubleshooting
ting for Verizon
Owner
Nokia
Organization
Global Delivery Readiness (GDR)
Document ID
IEH 550
Product
FDD LTE 17SP
Version
Date
Author
17SP
11-10-2017
Global Delivery Readiness First Edition
(GDR)
11-10-2017 – IEH 550
1/2
Description of changes
Internal
© Nokia 2017
Release Date
Section
Title
Sections
October 11, 2017
000
Title Page
October 11, 2017
001
Introduction
October 11, 2017
002
Accessibility
October 11, 2017
003
Retainability
October 11, 2017
004
Mobility
October 11, 2017
005
Throughput
October 11, 2017
006
VoLTE
October 11, 2017
007
Appendix
11-10-2017 – IEH 550
2/2
Internal
© Nokia 2017
IEH 550, Section 001
October 11, 2017
Introduction
BBU Swap Validation & Troubleshooting for Verizon
Contents
Introduction..................................................................................................................... 2
Overview ..........................................................................................................
....................................................................................................................
.......... 2
AirScale System Module
Module ............................................................................................. 2
Basic FDD Configuration for FSM4 ............................................................................. 3
SOW Overview
f or Verizon ......................................................................................... 4
for
3
Performance
Monitoring..............................................................................................
Tools........................................................................................................................... 5
KPI Analysis ................................................................................................................... 6
Overview .................................................................................................................... 6
KPI Investigation......................................................................................................... 6
Site Acceptance Criteria ............................................................................................. 6
1st Step KPI Health Check .......................................................................................... 7
2nd Step Statistical Check Status ................................................................................ 7
PNM BTS Report ........................................................................................................ 8
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© Nokia 2017
Introduction
Overview
The primary objectives of the BBU swap is to achieve the following:
•
•
Create high capacity indoor system mo
modules
dules
•
Develop system modules supporting both TD-LTE and FD
FDD
D in one product
•
•
•
Ai rSc ale
Improve competitiveness in capacity, optical connectivity, arc
architecture
hitecture flexibility, future
feature support and implementation of single RAN. FSM-r4 shall support both TD-LTE and
FDD in one product providing better LTE-A feature support for the future
Develop products with identical architecture for both indoor and outdoor products
products to run the
same SW release
AirScale/FSM-r4 is th
the
e new Multi-RAT capable
capable system module
FSM-r4 platform consists of two basic products: Site cost optimized
optimized AirScale/FSM-r4
AirScale/FSM-r4
Outdoor and capacity optimized
op timized AirScale/FSM-r4 indoor product
Nokia AirScale System Module is designed with scalable capacity for maximum efficiency.
System Module
Flexibility
•
Capacity
Multi-RAT: GSM,
WCDMA, TDD-LTE, FDDLTE, LTE-A Pro & 5G
ready, Cloud enhanced
•
Single
RAN: 2G,in3G,
simultaneously
one4G
module
•
•
Efficiency
10Gbps BB platform
•
Supports SM chaining to
add more cell capacity
(w/o additional switches or
•
Minimized energy
consumption during zero
traffic conditions
Power Prioritizer
•
•
•
TDD – FDD convergence:
both LTE variants in one
module
Any architecture:
Centralised (stack of
modules), Cloud RAN,
Distributed RAN
•
routers)
Supports any cell size
from small RRH to macro
units
IQ compression on
interface between System
Module and RF Module
interface
•
•
•
Envelope Tracking
Optional Eden-NET
energy management
module
60% more efficient base
station permitting use of
renewable energy sources
like solar power
Continued on next page
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Introduction, Continued
Basic FDD
Configuration
for FSM4
•
A complete eNB configur
configuration
ation is composed of several independent
independent sub-configurations called
called
cell sets:
−
•
•
Sub-configurations can be flexibly combined, the maximum number of supported cells
depends on the number of installed ABIA modules
−
Basic cell set sub-configurations are defined on level of ½ ABIA module
−
Extended cell set sub-configurations require one entire ABIA module
Basic cell set:
−
up to 4 cells 5/10MHz in 2Tx/2Rx
−
up to 3 cells 15/20MHz in 2Tx/2Rx
−
up to 2 cells 15/20MHz plus 2 cells 5/10MHz in 2Tx/2Rx
−
up to 2 cells 5/10/15/20MHz with 4Tx/4Rx
Extended cell set:
−
up to 6 cells 5/10/15/20MHz in 2Tx/2Rx
−
up to 3 cells 15/20MHz with 4Tx/4Rx
NOTE: The difference in call capacity of two basic cell sets in comparison to one extended cell
set is related to advanced LTE features.
SOW Overview
for Verizon
Number of Sites:
Sites : In Verizon, there will be approximately 41,000 sites which will be migrated
to FSM4 starting from Sep-2017 with time line of 15 months of completion.
Software Rele
Release
ase:: The sites will be migrated on software FL17SP (GA1 – 9/22) and in future
the swap will be based on the availability of the software FL17A (GA2 – 11/17).
Continued on next page
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Introduction, Continued
SOW Overview
for Verizon ,
continued
Report Requirements:
Requirements :
Report Type
Granularity
Reporting
Frequency
Purpose
Hourly Report
eNB level for each
market
Once Daily at Noon
Market Time
Contains Pre-and
Post-hourly data.
Provides
performance of
migrated sites on
Day 0, up to 9 AM
market time
Daily Report
eNB level for each
market
Once Daily at Noon
Market Time
Contains Pre (14Days) and Post (up
to 5 Days) Daily
data. Provides
performance of
migrated sites from
Day 1 up to Day 5.
Also, sites that
pass/fail on any day
will be the last time
on this report.
Performance
Monitoring
The scope of service for FSM4 Network Performance Validation is to monitor site performance,
measure post-migration KPIs and compare it against baseline KPI performance, to achieve
Site Acceptance when the contractual/defined KPI criteria are met.
To achieve Site Acceptance, sites may require troubleshooting, this will be performed
remotely, mostly based on KPI/PM counters and very limited drive testing.
The network’s performance can be assessed by monitoring the following KPIs:
•
Accessibility
•
Retainability
•
Mobility
•
Throughput
•
VoLTE
Continued on next page
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Introduction, Continued
Tools
For the BBU swap project the tools mentioned below are used
u sed depending on the action to be
performed:
Description
Performance
Management/KPI Analysis
PNM/NetAct
Fault Management
PNM
KPI Analysis
NetAct
Parameter Audit
One Click
Parameter Change work
order, Site / Hardware /
Functional Reset
NetAct
Post
processing
of drive test
data and
DT Reporting
eDAT, MTAP, Falcon Smart, MapInfo
October 11, 2017 – IEH 550, Section 001
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Tools
Internal
© Nokia 2017
KPI Analysis
Overview
This section describes how to monitor the KPI trends and identify degradations for each KPI
along with analysis for possible reasons of
o f degradation.
KPI
Investigation
Key Performance Indicators provide measurements against the following metrics:
•
Accessibility
•
Retainability
•
Mobility
•
Throughput
•
VoLTE
Below are the key performance indicators for Verizon to measure the above metrics:
Site
Ac cep tan ce
Criteria
Site acceptance is based on below two criteria:
c riteria:
•
1st step KPI health
•
2nd step statistical check status
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KPI Analysis, Continued
1st Step KPI
Health Check
Post migration KPIs need to be validated with respect to the thresholds defined in the below
table. The ones highlighted in red are the threshold values and the values highlighted in green
are the post migration KPI values of the site.
If
2nd Step
Statistical
Check Status
Then
Criteria is met
Pass the site acceptance
Criteria not met
Go to the 2nd step statistical check status
The 2nd step statistical check status compares the pre and post migration metrics from the site
acceptance dump. The KPIs highlighted below in green are the post migration KPIs and the
ones highlighted in red are the pre migration KPIs.
Continued on next page
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KPI Analysis, Continued
2nd Step
Statistical
Check Status ,
continued
PNM BTS
Report
If
Criteria is met
Pass the site acceptance
Criteria not met
Go for further site troubleshooting/optimizati
troubleshooting/optimization
on using PNM BTS
daily report
This report is extracted from the PNM tool and gives a detailed breakdown of the seven major
KPIs. This is helpful in isolating issues related to degraded KPIs.
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© Nokia 2017
IEH 550, Section 002
October 11, 2017
Accessibility
BBU Swap Validation & Troubleshooting for Verizon
Contents
Introduction..................................................................................................................... 2
Overview ..........................................................................................................
....................................................................................................................
.......... 2
Accessibility KPI
KPI Information....................................................................................... 2
Call Flow..................................................................................................................... 3
Accessibility
KPI ......................................................................................................... 6
KPI
4
Flow
Chart ..................................................................................................................
RACH & RRC Issues ...................................................................................................... 7
Overview .................................................................................................................... 7
Random Access Preamble Failure(Msg1)................................................................... 9
Random Access Response Failure(Msg2) ................................................................ 12
RRC Connection Setup request failure(Msg3) .......................................................... 15
RRC Connection Setup Response Failure(Msg4) ..................................................... 17
RRC Connection Setup Complete Failure(Msg5)...................................................... 19
E-RAB Issues ............................................................................................................... 22
E-RAB setup failure .................................................................................................. 22
Other Reasons ............................................................................................................. 24
Other Reasons for degradation ................................................................................. 24
RF Quality ................................................................................................................
....................................................................... ......................................... 25
PUCCH Improvement ............................................................................................... 27
PUSCH Improvement ............................................................................................... 28
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© Nokia 2017
Introduction
Overview
Ac ces si bi li t y
KPI Information
Accessibility KPIs are used
used to measure the probability of whether services requested by a
user can be accessed. There are four broad phases under which they can be classified:
•
Random access
•
RRC connection establishment
•
S1 signaling connection establishment
•
ERAB establishment success rate (Initial and additional)
additional)
Root Cause Analysis for accessibility KPIs can been done by following the steps below:
Step
Action
1
Open current PNM BTS daily Report
2
Check RRCConnFailRate and FSMKPIsSecondary tabs for Accessibility
issues
Continued on next page
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© Nokia 2017
Introduction, Continued
Call
Call Flow
Refer to the call flow below to investigate the impacted areas. This is associated with 1 UE
entity and 2 NE entities(eNB & MME) .
Continued on next page
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Introduction, Continued
Ac ces si bi li t y
KPI
Data accessibility can be monitored with the help of the following indicators:
Indicators
Formula
RRC Connection Blocking
Rate (RRC_Conn_Blk[%]
(SIGN_CONN_ESTAB_REJ_MO_S +
(SIGN_CONN_ESTAB_REJ_MO_S
SIGN_CONN_ESTAB_REJ_MO_D
SIGN_CONN_ESTA
B_REJ_MO_D +
SIGN_CONN_ESTAB_REJ_MT)
SIGN_CONN_ESTA
B_REJ_MT) /
(SIGN_CONN_ESTAB_ATT_MO_S
(SIGN_CONN_ESTA
B_ATT_MO_S +
SIGN_CONN_ESTAB_ATT_MT
SIGN_CONN_ESTA
B_ATT_MT +
SIGN_CONN_ESTAB_ATT_MO_D
SIGN_CONN_ESTA
B_ATT_MO_D +
SIGN_CONN_ESTAB_ATT_DEL_TOL
SIGN_CONN_ESTA
B_ATT_DEL_TOL +
SIGN_CONN_ESTAB_ATT_HIPRIO
SIGN_CONN_ESTA
B_ATT_HIPRIO +
SIGN_CONN_ESTAB_ATT_EMG)
RRC Connection Failure
1-((SIGN_CONN_ESTAB_COMP)
1-((SIGN_CONN_EST
AB_COMP) /
Rate(RRC_Conn_FailR[%]
(w/o rep))
(SIGN_CONN_ESTAB_ATT_MO_S +
(SIGN_CONN_ESTAB_ATT_MO_S
SIGN_CONN_ESTAB_ATT_MT
SIGN_CONN_ESTA
B_ATT_MT +
SIGN_CONN_ESTAB_ATT_MO_D
SIGN_CONN_ESTA
B_ATT_MO_D +
SIGN_CONN_ESTAB_ATT_DEL_TOL+
SIGN_CONN_ESTAB_ATT_HIPRIO
SIGN_CONN_ESTA
B_ATT_HIPRIO +
SIGN_CONN_ESTAB_ATT_EMG
SIGN_CONN_ESTA
B_ATT_EMG ))
UE Context Failure
Rate(UE_Ctxt_Stp_FR[%])
1 - (UE_CTX_SETU
(UE_CTX_SETUP_SUCC
P_SUCC / UE_CTX_SETUP
UE_CTX_SETUP_ATT)
_ATT)
Continued on next page
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© Nokia 2017
Introduction, Continued
Ac ces si bi li t y
KPI , continued
Indicators
ERAB Setup Failure Rate
(ERAB_Stp_FR[%])
Formula
(ERAB_INI_SETUP_ATT_QCI5 +
(ERAB_INI_SETUP_ATT_QCI5
ERAB_INI_SETUP_ATT_QCI6
ERAB_INI_SET
UP_ATT_QCI6 +
ERAB_INI_SETUP_ATT_QCI7
ERAB_INI_SET
UP_ATT_QCI7 +
ERAB_INI_SETUP_ATT_QCI8
ERAB_INI_SET
UP_ATT_QCI8 +
ERAB_INI_SETUP_ATT_QCI9
ERAB_INI_SET
UP_ATT_QCI9 +
ERAB_ADD_SETUP_ATT_QCI5
ERAB_ADD_SET
UP_ATT_QCI5 +
ERAB_ADD_SETUP_ATT_QCI6
ERAB_ADD_SET
UP_ATT_QCI6 +
ERAB_ADD_SETUP_ATT_QCI7
ERAB_ADD_SET
UP_ATT_QCI7 +
ERAB_ADD_SETUP_ATT_QCI8
ERAB_ADD_SET
UP_ATT_QCI8 +
ERAB_ADD_SETUP_ATT_QCI9
ERAB_ADD_SET
UP_ATT_QCI9 (ERAB_INI_SETUP_SUCC_QCI5
+ERAB_INI_SETUP_SUCC_QCI6
+ERAB_INI_SET
UP_SUCC_QCI6 +
ERAB_INI_SETUP_SUCC_QCI7
ERAB_INI_SET
UP_SUCC_QCI7 +
ERAB_INI_SETUP_SUCC_QCI8
+ERAB_INI_SETUP_SUCC_QCI9
+ERAB_INI_SET
UP_SUCC_QCI9 +
ERAB_ADD_SETUP_SUCC_QCI5
ERAB_ADD_SET
UP_SUCC_QCI5 +
ERAB_ADD_SETUP_SUCC_QCI6
ERAB_ADD_SET
UP_SUCC_QCI6 +
ERAB_ADD_SETUP_SUCC_QCI7
+ERAB_ADD_SETUP_SUCC_QCI8
+ERAB_ADD_SET
UP_SUCC_QCI8 +
ERAB_ADD_SETUP_SUCC_QCI9)
/(ERAB_INI_SETUP_ATT_QCI5
/(ERAB_INI_SET
UP_ATT_QCI5 +
ERAB_INI_SETUP_ATT_QCI6
ERAB_INI_SET
UP_ATT_QCI6 +
ERAB_INI_SETUP_ATT_QCI7
ERAB_INI_SET
UP_ATT_QCI7 +
ERAB_INI_SETUP_ATT_QCI8
+ERAB_INI_SETUP_ATT_QCI9
+ERAB_INI_SET
UP_ATT_QCI9 +
ERAB_ADD_SETUP_ATT_QCI5
ERAB_ADD_SET
UP_ATT_QCI5 +
ERAB_ADD_SETUP_ATT_QCI6
+ERAB_ADD_SETUP_ATT_QCI7
+ERAB_ADD_SETUP_ATT_QCI8
+ERAB_ADD_SET
UP_ATT_QCI8 +
ERAB_ADD_SETUP_ATT_QCI9)
NOTE: FSMsecondary KPI’s need to be monitored in case of degradation and inform the front
office.
Continued on next page
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Introduction, Continued
Flow Chart
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© Nokia 2017
RACH & RRC Issues
Overview
During the random access phase and RRC connection phase, there are 5 major stages in
which issues may be encountered. They are listed below:
Stage
Description
Random Access
Preamble(Msg1)
Random access preamble not received by the eNB
Random Access
Response(Msg2)
Random access procedure fails due to no random access
response
RRC connection
request(Msg3)
RRC connection request is not received by eNB
RRC connection
setup(Msg4) information
needed to setup SRB1 on
DCCH
UE does not receive the RRC Connection Setup or the
Contention Resolution message
RRC connection setup
complete(Msg5)
eNB does not receive the RRC connection
c onnection setup complete
message
The graphic below shows potential issues in the RACH & RRC phase:
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RACH & RRC Issues, Continued
Overview,
continued
The table below shows the reasons & optimal solutions for RACH & RRC.
Causes
Checks
PRACH root sequence clashes
PRACH Planning
Unreliable reception of Message
Power Optimization (Tune Nominal PUCCH
power PUSCH power, Power headroom,
Optimize PDCCH)
Cell Overshooting/ Pilot Pollution
Tuning EDT, Cell Radius adjustment
Sleeping Cell
Check symptoms for sleeping cell
Poor Coverage
Perform Physical Optimization
•
UL RSSI
•
Check Power control paramet
parameters
ers
Reduce UL Interference
Poor DL SINR
Physical Optimization
CAC Failure
•
Optimize Power & load balancing,
balancing,
•
Perform P
Physical
hysical Optimization
Optimization
Hardware Issues & Alarms
Check HW issues & Alarms
Continued on next page
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RACH & RRC Issues, Continued
Random
Ac ces s
Preamble
Failure(Msg1)
This section covers the parameters to be tuned in case the eNB is not receiving the Random
Access Preamble message.
Possible causes for this failure:
•
•
•
eNB receives DL data but ffinds
inds UL synchronization with UE is lost (PDCCH order)
UE doesn't have a grant tto
o transmit UL Data a
and
nd finds PUCCH resources are not
configured/released for transmission of SR
Initial power for Random A
Access
ccess preamble transmission is low
Parameter Name
Description
raPreGrASize (Random
access preambles group A
size)
This parameter
defines the size of
the RandomAccess
Preambles Group
A.
32(7) (MINT)
4 (0), 8 (1), 12 (2),
16 (3), 20 (4), 24
(5), 28 (6), 32 (7),
36 (8), 40 (9), 44
(10), 48 (11), 52
(12), 56 (13), 60
(14)
raSmallMcsUl (Small size
random access MCS in
uplink):
5(MINT)
0…15, step 1
There is no option to
modify this parameter in
NetAct (CM Editor) as
Parameter is not
This parameter
defines the
Modulation and
Coding Scheme
(MCS) to be used
for the small size
random access
message 3 in
case of UL or DL
modifiable
and value is
set to MCS-5
data arrival.
40(9)/ 56(13)
4 (0), 8 (1), 12 (2),
16 (3), 20 (4), 24
(5), 28 (6), 32 (7),
36 (8), 40 (9), 44
(10), 48 (11), 52
(12), 56 (13), 60
(14), 64 (15)
NOTE:
•
•
Default
Value/
Verizon GPL
Ranges and
steps
Impact
Parameter modification is
possible via BTS Site
raNondedPreamb
(Number of random access
preambles):
This parameter
determines the
total number of
non-dedicated RA
preambles that a
UE can select.
The minimum
cannot be zero
The higher the value
of this parameter the
lesser no. of
dedicated preambles
left for non-contention
based RA procedure
(RA procedure
initiated by eNB will
be finisher faster)
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RACH & RRC Issues, Continued
Random
Ac ces s
Preamble
Failure(Msg1) ,
continued
Parameter
Name
ulpcIniPrePwr
(Preamble initial
received target
power)
preambTxMax
(Preamble
Transmission
Maximum)
Description
This parameter
defines the initial
power for Random
Access preamble
transmission.
This parameter
defines the
maximum number
of Random Access
transmissions.
Default Value/
Verizon GPL
-96dBm (12) /
-104dBm (8)
Ranges and
steps
Impact
-120 dBm (0), -118
dBm (1), -116 dBm
(2), -114 dBm (3), 112 dBm (4), -110
dBm (5), -108 dBm
•
Low values: eNB
eNB
reduce the
probability of
reception of
preamble
(6), -106 dBm (7), 104 dBm (8), -102
dBm (9), -100 dBm
(10), -98 dBm (11), 96 dBm (12), -94
dBm (13), -92 dBm
(14), -90 dBm (15)
•
10(6) / 5(2)
3 (0), 4 (1), 5 (2), 6
(3), 7 (4), 8 (5), 10
(6), 20 (7), 50 (8),
100 (9), 200 (10)
High Values:
Increases
potentially
interference in the
network.
2dB(1) / 2dB(1)
0dB (0), 2dB (1),
4dB (2), 6dB (3)
High Values:
Increases
potentially
interference in the
network.
IMPORTANT: The
values n50, n100
and n200 should not
be used.
prachPwrRamp
(Power ramping
step)
The power ramping
step size parameter
defines the power
increment step size
for Random Access
preamble
transmission,
including PRACH
and NPRACH.
•
•
High values:
Higher step size
leads to higher
chances of
interference.
Low values:
Delay the
success of
preamble
reception.
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RACH & RRC Issues, Continued
Random
Ac ces s
Preamble
Failure(Msg1) ,
continued
Parameter
Name
prachConfIndex
(PRACH
configuration index)
Description
Defines allowed
system frame and
subframe numbers
for random access
attempts, and the
Default Value/
Verizon GPL
3 / Planned value
for each cell
Ranges and
steps
Impact
3...56, step 1
preamble format.
Continued on next page
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RACH & RRC Issues, Continued
Random
Ac ces s
Response
Failure(Msg2)
This section covers the parameters to be tuned in case the UE does n
not
ot receive RA response
within the specified window and the possible causes for this.
Below are the possible causes for these types of failures:
•
PDCCH aggregation level not set at the correct level
•
Coding rate not defined correctly
•
Waiting time not defined at the correct level
•
PDCCH capacity not set to the appropriate value
The table below shows the parameters which are to be tuned to minimize the causes of
failures listed above.
Parameter
Name
pdcchAggRaresp
(PDCCH
aggregation for
random access
response message)
maxCrRaDl
(Maximum code
rate for random
access message 2)
Description
Default
Value/
Verizon
GPL
PDCCH aggregation for Random
Access response message defines
how many CCEs are used for one
PDCCH.
4/4
The parameter defines the
maximum code rate for random
access procedure messages 2 (RA
response). This maximum code rate
is considered during PDSCH
scheduling.
0.12(MINT)
NOTE: For small bandwidth
systems, the number of RAR
records per RAR message is limited
such that the configured code rate is
not exceeded; a single RAR record
is transmitted in any case.
Ranges
and
steps
4...8, step
4
0.05...0.5,
step 0.01
Impact
The default value of 4
provides reliability
without placing
excessive load upon
the PDCCH.
Configuring a value of
8 will increase
reliability but will also
increase the PDCCH
load and increase the
probability of PDCCH
blocking.
The default value of
(0.12) is already a low
coding rate.
Decreasing the value
of this parameter will
increase redundancy
further, and will also
increase the number
of Resource Blocks
required by each RAR
transmission.
Continued on next page
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RACH & RRC Issues, Continued
Random
Ac ces s
Response
Failure(Msg2) ,
continued
Parameter
Name
Description
Default
Value/
Verizon
GPL
Ranges
and
steps
raRespWinSize
(Random access
Random Access Response Window
Size parameter defines the window
10(7) / 10(7)
2 (0), 3 (1),
4 (2), 5 (3),
In case
raRespWinSize is
response window
size)
size for the random access
response in TTIs.
6 (4), 7 (5),
8 (6), 10
(7)
too small, then it
creates problems
with the second cell
handling on time
and could also lead
to decreased call
setup performance.
dsrTransMax
(Dedicated SR
transmission
maximum)
This is the maximum number of
allowed dedicated Scheduling
Requests. Once this limit is
exceeded, UE releases all PUCCH
resources. The value 4n
corresponds to 4 transmissions, 8n
corresponds to 8 transmissions and
so on.
64n(4) /
64n(4)
Impact
0: 4n
1: 8n
2: 16n
3: 32n
4: 64n
Indirectly provides the UE-specific
maximum time within which the UE
must receive a valid uplink grant for
a new transmission on UL-SCH. If
this time expires, the UE releases
PUCCH resources and no longer
performs a dedicated Scheduling
Request, but instead performs a
random access Scheduling
Request. This time is calculated by
cell Scheduling Request periodicity *
dedicated SR transmission
maximum.
Continued on next page
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RACH & RRC Issues, Continued
Random
Ac ces s
Response
Failure(Msg2) ,
continued
Parameter
Name
taTimer(Time
taTimer(Time
alignment timer)
Description
Default
Value/
Verizon
GPL
This parameter determines the
number of subframes after which a
10240 (6) /
10240
UE assumes it is out-of-sync in UL if
no Time Alignment command was
received.
Ranges
and
steps
Impact
1: 750
Lower Values: Ue
declares out- of-
2: 1280
sync early
0: 500
3: 1920
4: 2560
5: 5120
6: 10240
Continued on next page
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RACH & RRC Issues, Continued
RRC
Connection
Se
Setup
tup request
failure(Msg3)
RRC connection setup typically corresponds to the first RRC message, e.g. RRC Connection
Request, RRC Re-establishment Request or RRC Reconfiguration Complete.
Below are the possible reasons for failures related to this:
•
Short and long MS
MSG3
G3 block size not set appropriate
appropriately
ly
•
Power control values not set optimally
optimally
•
Re-transmission count not set ideally
The table below shows the parameters which are to be tuned to minimize the causes of
failures listed above.
Parameter
Name
Description
Default Value/
Verizon GPL
Ranges
and steps
Impact
raSmallVolUl
(Small size random
access data volume
in uplink)
Defines the data
volume to be used
for small size
Random Access
message 3 in case
of UL or DL data
arrival.
144 bits (1)(MINT)
56 bits (0),
144 bits (1),
208 bits (2),
256 bits (3)
When the coding rate is
reduced from 144 bits to 56
bits, then the transmit power
of Ue per resource block
gets doubled and vice versa.
harqMaxMsg3
(Small size random
access data volume
in uplink)
Indicates the
maximum number
of HARQ
transmissions used
for message 3 of
the contentionbased random
access procedure.
5(5) / 5
1...8, step 1
Higher value:
•
•
•
raContResoT
(Maximum
contention
resolution timer)
The maximum
contention
resolution timer
parameter defines
the maximum
amount of time
allowed for
contention
resolution.
64ms (7) / 64ms
8ms (0),
16ms (1),
24ms (2),
32ms (3),
40ms (4),
48ms (5),
56ms (6),
64ms (7)
Improves accessibi
accessibility
lity due
to the additional reliability
provided by the extra retransmissions. However
average call setup time
increases
Impacts PUSCH capacity
and UL throughputs
It generates UL
interference spike
Low value: Less time allowed
for contention resolution
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RACH & RRC Issues, Continued
RRC
Connection
Se
Setup
tup request
failure(Msg3),
continued
Parameter
Name
Description
Default
Value/
Verizon GPL
Ranges
and steps
deltaPreMsg3
(Delta preamble
random access
message 3)
Used for the
calculation of
P0_NOMINAL_PUS
CH(j=2) for PUSCH
(re)transmission
corresponding to
the random access
response grant.
1/3
-1...6, step 1
ulpcRarespTpc
(TPC command in
random access
response)
TPC command
indicated in the
Random Access
response related to
Random Access
message 3 or 1st
scheduled uplink
transmission.
4dB / 3
-6...8 dB,
step 2 dB
raSmallMcsUl
(Small size random
access MCS in
Defines the
Modulation and
Coding Scheme
5 (MINT)
0...15, step 1
uplink)
(MCS)
to be used
for the small
size
random access
message 3 in case
of UL or DL data
arrival.
raLargeMcsUl
(Large size random
access MCS in
uplink)
Defines the
Modulation and
Coding Scheme
(MCS) to be used
for large size
random access
message 3 in case
of initial access or
handover.
5(MINT)
0...15, step 1
Impact
Higher Value: Higher probability
for successfully receiving MSG-3
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RACH & RRC Issues, Continued
RRC
Connection
Setup
Response
Failure(Msg4)
This section corresponds to the RRC Connection Setup message during connection
establishment.
Below are the possible causes for failures:
•
PDCCH aggregation level not set correctly
•
Coding rate not ideally defined
•
Re-transmission count not specified appropriately
•
Waiting times n
not
ot set opti
optimally.
mally.
The table below shows the parameters which are to be tuned to minimize the causes of
failures listed above.
Parameter
Description
Name
Default Value/
Ranges and
Verizon GPL
steps
Impact
pdcchAggMs
g4 (PDCCH
aggregation for
RA msg4)
The parameter defines the reserved
number of Control Channel
Elements (CCEs) for dedicated
Random Access Message 4
assignment on PDCCH.
8/8
4...8, step 4
Default value of 8
provides reliability at
the cost of
additional PDCCH
load. Configuring a
value of 4 will
reduce the PDCCH
load but will also
reduce reliability
harqMaxTrDl
(Maximum
number of
HARQ
transmission in
Indicates the maximum number of
HARQ transmissions in DL that is
configured for each UE at initial
access to a specific cell.
5/8
1...16, step 1
Modifying this
parameter will
impact the downlink
throughput for the
lifetime of the
DL)
maxCrRa4Dl
(Maximum
code rate for
random access
message 4)
The parameter defines the
maximum code rate for random
access procedure message 4
(SRB0 message). This maximum
code rate is taken into account
during PDSCH scheduling.
0.12 (MINT)
NOTE:
For small bandwidth systems, a
sufficient number of HARQ
retransmission or according
segmentation is applied in order to
reach the configured code rate
0.05...0.5, step
0.01
connection
Decreasing the
value of this
parameter will
increase
redundancy but will
also increase the
number of Resource
Blocks required by
each MSG4
transmission
Continued on next page
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RACH & RRC Issues, Continued
RRC
Connection
Setup
Response
Failure(Msg4) ,
continued
Parameter
Name
t300 (Timer
T300)
Description
Timer T300 supervises the RRC
connection establishment
Default
Value/
Verizon GPL
Ranges and
steps
400ms (3) /
400ms
0: 100ms
2: 300ms
3: 400ms
procedure.
Start: Transmission of
RRCConnectionRequest
4: 600ms
Stop: Reception of
RRCConnectionSetup or
RRCConnectionReject message,
cell re-selection and upon abortion
of connection establishment by
upper layers.
t301 (Timer
T301)
Timer T301 supervises the RRC
connection re-establishment
procedure.
1: 200ms
5: 1000ms
Impact
Increasing the value
will increase the
window
increasehence
the chance
of successful RRC
Connection request
& cell reselection.
reselection.
6: 1500ms
7: 2000ms
400ms (3) /
1500ms
0: 100ms
1: 200ms
2: 300ms
Start: Transmission of
RRCConnectionReestabilshmentRe
quest
3: 400ms
4: 600ms
5: 1000ms
Stop: Reception of
RRCConnectionReestablishment or
RRCConnectionReestablishmentRe
ject message as well as when the
selected cell becomes unsuitable
6: 1500ms
Increasing the value
will increase the
window hence
reduce the chance
of failures.
However, this will
also increase the
usage of network
resources.
7: 2000ms
At expiry: Go to RRC_IDLE"
RRC_IDLE"
Continued on next page
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RACH & RRC Issues, Continued
RRC
Connection
Setup
Complete
Failure(Msg5)
This failure type is related to the RRC Connection Setup Complete message during
connection establishment.
Possible causes of failures:
•
No proper Resource allo
allocation
cation (MCS and Resource Blocks)
•
Re-transmission count set at a higher value
The table below shows the parameters which are to be tuned to minimize the causes of
failures listed above.
Parameter
Name
iniMcsUl
Description
Default
Value/
Verizon GPL
Ranges
and steps
Impact
Higher Values:
Higher MCS (given
by iniMcsUl) can
lead to lower HO
success rate as for
example power
head room report
will be transferred
with higher initial
MCS so if detection
probability is
reduced then this
can impact on HO
success rate
5/1
0...20, step 1
(Initial MCS in
uplink)
The parameter defines an initial
Modulation and Coding Scheme
(MCS) to be used on PUSCH for
other use than random access
message 3.
IniPrbsUl (Initial
amount of PRBs in
uplink)
Defines the initial amount of
maximum PRBs in uplink.
10 / 4
1...100, step
1
ulsMinTbs
(Minimum UL
transport block size)
Defines the minimum UL TBS
(segment size).
104 / 72
32...1544,
step 8
The lower limit of the range is
defined equal to the minimum
transport block size (TBS) in the
Table 7.1.7.2.1-1 in 3GPP TS
36.213.
Lower Values:
Using more robust
MCS increases
RLC/MAC overhead
due to consumption
of more radio
resources
The upper limit of the range is
defined equal to the TBS
belonging to modulation order 2
and 10 PRBs.
Continued on next page
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RACH & RRC Issues, Continued
RRC
Connection
Setup
Complete
Failure(Msg5) ,
continued
Parameter
Name
Description
ulsMinRbPe
rUe
(Minimum
PRB
allocation for
UEs which
are power
limited)
Defines the minimum PRB
allocation for UEs which are
power limited.
tHalfRrcCon
(Timer min
lifetime of
half-open
RRC
connection)
The minimal period during
which the internal state and
the resources associated with
a half-open RRC connection
(i.e. one for which no RRC
connection setup complete
message has yet been
received) must not be deleted
in the eNB. This parameter is
p0NomPucc
h (Nominal
power for UE
PUCCH TX
power
calculation)
Default
Value/
Verizon
GPL
Ranges
and steps
Impact
3/3
1...100, step
1
High Values: More robust
transmission increases
resource consumption
2000 ms
(MINT)
500...10000
ms, step 500
ms
Low values: Increases the
chances of RRC connection
failure
-116dBm /
-114dBm
-127...-96
dBm, step 1
dBm
This is used for the UEs for
which the maximum number of
PRBs due to power limitation
is limited to low values.
vendor-specific.
This parameter defines the cell
specific nominal power to be
used for PUCCH power
calculation in UE uplink power
control equation (P2), for
controlling mean received
SNR for control data.
•
•
Low setting of this
this
parameter (-116) has no
negative impact on the
PUCCH robustness.
Nevertheless, this parameter
shall be checked when the
UL performance is worse
than expected.
Aggressive parameter
setting can impact the QCI
drop ratio
Continued on next page
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RACH & RRC Issues, Continued
RRC
Connection
Setup
Complete
Failure(Msg5) ,
continued
Parameter
Name
pdcchAggDefUe
(PDCCH LA UE
default
aggregation)
Description
The parameter defines
default aggregation for
UE to be used in PDCCH
Link Adaptation when
enableAmcPdcch has
been disabled or when
enableAmcPdcch has
been enabled and there
is no valid Channel
Quality Indicator (CQI)
available due to an expiry
of the timer determining
CQI
October 11, 2017 – IEH 550, Section 002
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Default
Value/
Verizon
GPL
4(2) / 4
Ranges
and steps
1 (0), 2 (1), 4
(2), 8 (3)
Impact
•
•
•
Internal
Low values (1,2)- Not
recommended due to
increased probability of
PDCCH reception failure for
users in bad radio conditions
Medium (4)- Recom
Recommended
mended
since it represents average
AGG level used by the UEs
UEs
The highe
highest
st possible
aggregation level shouldn't
be set as a default unless as
the gain from increased
PDCCH robustness is
negatively consumed by the
overhead it introduces.
© Nokia 2017
E-RAB Issues
E-RAB s etup
E-RAB
failure
A graphical representation of an e-RAB setup.
The table below shows the reasons & optimal solutions for ERAB setup failure.
Causes
Checks
Poor Coverage
Perform Physical Optimization
Poor DL SINR
•
Perform P
Physical
hysical Optimization
Optimization
•
Tune potential pilot pollution
pollution
•
Check Power control paramet
parameters
ers
•
Reduce UL Interference
•
Optimize Power & load balancing,
balancing,
•
Perform P
Physical
hysical Optimization
Optimization
UL RSSI
CAC Failure
Hardware Issues & Alarms
Check HW issues & Alarms
UE Sync
Increase timer value for UE sync.
Continued on next page
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© Nokia 2017
E-RAB Issues, Continued
E-RAB s etup
E-RAB
failure,
continued
Parameter
Name
rrcGuardTimer
(RRC guard
timer radio
bearer
management)
E-RAB setup failures can be remedied by tuning the following parameters:
Description
This timer is started when an
RRC message for setup,
modification or release of a
radio bearer is sent to the UE.
When the timer expires, the
corresponding procedure is
aborted.
Default Value/
Verizon GPL
Ranges and
Steps
2000ms(MINT)
100...6000 ms,
step 100 ms
Impact
Low values:
Increases the
failure of below
procedure
−
−
−
dlSrbCqiOffset
(Downlink SRB1
CQI offset)
dFpucchF1b
(DeltaF PUCCH
format 1b)
UE Capability
Enquiry
RRC
Connection
Reconfiguration
This parameter provides the
CQI link adaptation offset
applied to downlink
transmissions containing
SRB1 messages.
-2 (MINT)
-15...0, step
0.1
The more negative
the value, the more
conservative the
MCS and PDCCH
aggregation level
will be for the
downlink SRB1
message
transmissions
The parameter defines the
transport format dependent
offset in power control for
PUCCH format 1b.
1(0) / 3
1 (0), 3 (1), 5
(2)
Increasing this
parameter value
results in improved
robustness of
PUCCH format 1b.
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RRC Security
Mode
Command
Internal
© Nokia 2017
Other Reasons
Other Reasons
for degradation
The table below lists additional reasons for Accessibility KPI degradation along with practical
solutions.
Issue
Poor coverage in
Downlink
Analysis
Check the following
•
•
Solution
•
Average CQI
Downlink BLE
BLER:
R: IInitial
nitial
and Residual
•
Tune qRx
qRxLevMin
LevMin value
to discard bad coverage
and Cell edge Ues.
Impact
•
Physical optimization
•
Poor coverage in Uplink
Check the following
•
•
•
•
CAC failures
UL RSSI
UL Noise
Uplink BLER: Initial and
Residual
•
To reduce UL
interference, tune
•
Lower value results in
larger coverage areas
Optimum values can
reduce interference
power
control values
optimally
•
Physical optimization
UL pow
power
er headr
headroom
oom
Check the following
•
•
Lower values mig
might
ht
negatively impact the
attach and detach
process
Tune CAC Strategy
Number of RRC
connections
Improvement in
Accessibility
Number of Active u
users
sers
Continued on next page
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Other Reasons, Continued
RF Quality
Parameter
Name
allowPbIndexZero
(Allow cell specific
PB ratio zero)
The table below shows the parameters which are to be tuned to improve the RF quality.
Description
The cell specific PDSCH
EPRE ratio to the cell RS
EPRE (PB) can be set to
zero.
If allowPbIndexZero is set
to ‘false’ and dlRsBoost is
equal to 0dB, then index 1
is chosen for pbIndexPdsch
(instead of index 0).
dlCellPwrRed (Cell
power reduce)
This parameter sets the
power reduction from the
antenna maximum TX
power.
Default
Value/
Verizon GPL
0 / TRUE in
some SIMO
configurations;
Ranges and
Steps
Impact
0 (false), 1 (true)
FALSE in all
MIMO
configurations
0dB / 0
0...20 dB, step
0.1 dB
0dB / 0
0...6 dB, step
0.1 dB
Cell locking is not required
if dlCellPwrRed is changed
by 0.2 dB or less. If the
feature ‘Automatic Locking
(LTE830)’ is activated, eNB
will not perform cell locking
in this case.
dlPcfichBoost
(Downlink PCFICH
Transmission power of the
Physical Control Format
transmission power
boost)
Indicator Channel is
boosted by set value
PCFICH boosting
could be applied to
improve detection of
PCFICH - especially
in coverage limited
scenarios.
Continued on next page
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Other Reasons, Continued
RF Quality ,
continued
Parameter
Name
Description
Default
Value/
Verizon
GPL
Ranges and
Steps
Impact
dlPhichBoost
(Downlink PHICH
transmission power
boost)
Transmission power of the
Physical Hybrid ARQ
Indicator Channel is
boosted by set value
0dB / 0
0...6 dB, step 0.1 dB
pMAX (Maximum
Output Power)
This parameter defines the
maximum output power of
the cell. The maximum
output power is the
maximum value for the
linear sum of the power of
all downlink physical
channels that is allowed to
be used in a cell. The
reference point is the
antenna connector.
478 for
15/20 MHz
460 for 10
MHz
430 for 5
MHz
(VERIZON
GPL)
0...60 dBm, step 0.1
dBm
Qrxlevmin
(Minimum required
RX level in cell)
It specifies the minimum
required RX RSRP level in
the cell.
-130 dBm/120 dBm
-140...-44 dBm, step
2 dBm
dlPhichBoost helps
to assure higher
reliability of PHICH
channel.
Higher Values:
Improves
accessibility with
restricted users
Continued on next page
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© Nokia 2017
Other Reasons, Continued
PUCCH
Improvement
The table below shows the parameters which need to be tuned to improve the PUCCH.
Parameter
Name
Description
dFpucchF1 (DeltaF
PUCCH format 1)
The parameter
defines the transport
format dependent
offset in power control
for PUCCH format
0(1) / 0
dFpucchF2 (DeltaF
The parameter
0(1) / 0
PUCCH format 2)
defines
the transport
format dependent
offset in power control
for PUCCH format 2.
dFpucchF2a
(DeltaF PUCCH
format 2a)
dFpucchF2b
(DeltaF PUCCH
format 2b)
Default Value/
Verizon GPL
Ranges and
Steps
Impact
-2 (0), 0 (1), 2 (2)
Higher value:
Improve robustness
of PUCCH format 1.
Lower value:
Improve PUCCH
interference
-2 (0), 0 (1), 1 (2), 2
Higher value:
(3)
Improve
robustness
of PUCCH
format 2.
Lower value:
Improve PUCCH
interference
The parameter
defines the transport
format dependent
offset in power control
for PUCCH format 2a.
0(1) / 0
The parameter
defines the transport
format dependent
0(1) / 0
-2 (0), 0 (1), 2 (2)
Higher value:
Improve robustness
of PUCCH format
2a.
Lower value:
Improve PUCCH
interference
-2 (0), 0 (1), 2 (2)
offset
in power
control
for
PUCCH
format
2b.
Higher value:
Improve robustness
of PUCCH format
2b.
Lower value:
Improve PUCCH
interference
Continued on next page
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Other Reasons, Continued
PUSCH
Improvement
Parameter
Name
ulpcAlpha(Alpha)
ulpcAlpha
(Alpha)
The table below shows the parameters which need to be tuned to improve the PUSCH.
Description
Used as a fractional path
loss compensation factor:
alpha. It controls received
SNR variance (fairness)
for user data and
sounding reference
symbol.
Default
Value/
Verizon GPL
alpha 1 (7) /
Alpha 1
Enabling/disabling of the
transport format
dependent offset on a per
UE basis.
0: alpha 0
1: alpha 0.4
2: alpha 0.5
3: alpha 0.6
Impact
Lower the alpha –
More UEs are
power limited (need
to transmit with max
power)
4: alpha 0.7
5: alpha 0.8
6: alpha 0.9
Alpha can't control the
fractional pathloss
compensation for the
sounding in the case
PUSCH masking is
activated (actPuschMask
equal to 'true') as SRS is
disabled in this case
deltaTfEnabled
(Enabled TB size
impact to UE
PUSCH power
calculation)
Ranges and
Steps
7: alpha 1
0 / False
0 (false), 1 (true)
If parameter value is
set to 1 (TRUE),
degradation of SINR
for PUSCH is
observed.
Continued on next page
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Other Reasons, Continued
PUSCH
Improvement ,
continued
Parameter
Name
Description
Default
Value/
Verizon GPL
Ranges and
Steps
Impact
actUlpcMethod
(Method for UL
power control)
Selects a working mode
for UL power control.
Offers various
combinations between
open-loop and closedloop control for PUCCH
and PUSCH/SRS power.
PuschOLPucc
hOL (0) /
PuschCLPucc
hCL
PuschOLPucchOL
(0),
PuschOLPucchCL
(1),
PuschCLPucchOL
(2),
PuschCLPucchCL
(3),
PuschCLSrsPucch
OL (4),
PuschCLSrsPucchC
L (5),
PuschIAwPucchOL
(6),
PuschIAwPucchCL
(7)
p0NomPusch
(Nominal power for
UE PUSCH TX
power calculation)
This parameter defines
the cell specific nominal
power for the PUSCH.
Used for P0_PUSCH
calculation in UE uplink
power control equation
-80dBm/ -106
dBm
-126...24 dBm, step
1 dBm
(P1) for controlling the
mean received SNR for
user data during
(re)transmission
corresponding to a
received PDCCH with
DCI format 0 associated
with a new packet
transmission. This
parameter is used to
control mean received
SNR for user data.
Continued on next page
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© Nokia 2017
Other Reasons, Continued
PUSCH
Improvement ,
continued
Parameter
Name
p0NomPuschIAw
(Nominal PUSCH
P0 for interferenceaware UL-PC)
Description
P0 setting that is
broadcast in SIB2 if
interference-aware ULPC is activated.
Default
Value/
Verizon GPL
-100dBm
(MINT)
Ranges and
Steps
Impact
-110...-70 dBm, step
1 dBm
ulpcAlpha must be set to
"alpha
1" for interferenceaware UL-PC.
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© Nokia 2017
IEH 550, Section 003
October 11, 2017
Retainability
BBU Swap Validation & Troubleshooting for Verizon
Contents
Introduction..................................................................................................................... 2
Overview ..........................................................................................................
....................................................................................................................
.......... 2
Retainability KPI Information....................................................................................... 2
Retainability KPI .........................................................................................................
................................................................. ........................................ 3
Flow Chart .................................................................................................................. 5
Troubleshooting .............................................................................................................. 6
Overview .................................................................................................................
....................................................................................................................
... 6
Radio Causes ............................................................................................................. 6
Handover Failures and Transport Issue .................................................................... 11
October 11, 2017 – IEH 550, Section 003
1 / 24
Internal
© Nokia 2017
Introduction
Overview
This KPI can be used to evaluate the call drop rate in a cell or cluster. Call drop ratio is one of
the most important metrics to assess the performance of the mobile network.
Listed below are types of call drops:
drop s:
•
RRC Connection drop rate
•
UE Contex
Contextt drop rate
•
E-RAB drop rate
The factors listed below impacts the Retainability KPI:
Retainability
KPI Information
•
Radio Causes
•
Timer expiry
•
Mobility
•
Core Issues
Root cause analysis for retainability KPIs can be done by following steps below:
Step
Action
1
Open current PNM BTS daily Report
2
Check DataERABDropRate, IntraHOFailRate, X2TotHOFailRate and
FSMKPIsSecondary tabs for retainability issues
Continued on next page
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Introduction, Continued
Retainability
KPI
Retainability KPI can be monitored from the following indicators
Indicators
Formula
Context Drop Rate
(EPC_INIT_TO_IDLE_RNL+
EPC_INIT_TO_IDLE_OTHER
EPC_INIT_TO
_IDLE_OTHER +
ENB_INIT_TO_IDLE_RNL
ENB_INIT_TO
_IDLE_RNL +
ENB_INIT_TO_IDLE_OTHER
ENB_INIT_TO
_IDLE_OTHER +
PRE_EMPT_UE_CONTEXT_NON_GBR+((UE_CTX_RE
L_MME_PART_S1_RESET+UE_CTX
L_MME_PART_S
1_RESET+UE_CTX_REL_MME_GLOB
_REL_MME_GLOB
_S1_RESET) +
(UE_CTX_REL_ENB_PART_S1_RESET+UE_CTX_REL
_ENB_GLOB_S1_RESET))
_ENB_GLOB_S1_RESE
T)) )
/
(EPC_INIT_TO_IDLE_UE_NORM_REL
(EPC_INIT_TO_IDLE_UE_NORM_
REL +
EPC_INIT_TO_IDLE_DETACH
EPC_INIT_TO_IDLE
_DETACH +
ENB_INIT_TO_IDLE_NORM_REL
ENB_INIT_TO_ID
LE_NORM_REL+EPC_INIT_TO_IDL
+EPC_INIT_TO_IDLE
E
_RNL+ EPC_INIT_TO_IDLE_OTHE
EPC_INIT_TO_IDLE_OTHER
R+
ENB_INIT_TO_IDLE_RNL
ENB_INIT_TO_ID
LE_RNL +
ENB_INIT_TO_IDLE_OTHER
ENB_INIT_TO_ID
LE_OTHER +
PRE_EMPT_UE_CONTEXT_NON
PRE_EMPT_UE_
CONTEXT_NON_GBR
_GBR +
((UE_CTX_REL_MME_PART_S
((UE_CTX_REL_M
ME_PART_S1_RESET+UE_C
1_RESET+UE_CTX_REL
TX_REL
_MME_GLOB_S1_RESET)
_MME_GLOB_
S1_RESET) +
(UE_CTX_REL_ENB_PART_S1
(UE_CTX_REL_E
NB_PART_S1_RESET+UE_CTX_
_RESET+UE_CTX_REL_
REL_
ENB_GLOB_S1_RESET))
ENB_GLOB_S1
_RESET)) + INTER_ENB_S1_HO_SUCC
INTER_ENB_S1_HO_SUCC
+ (SUCC_INTRA_ENB_HO + SUCC_INTER_ENB_HO +
HO_RLF_SUCC) )
Context Drop Rate per Erlang
3600*(EPC_INIT_TO_ID
3600*(EPC_INIT_TO_IDLE_RNL+
LE_RNL+
EPC_INIT_TO_IDLE_OTHER
EPC_INIT_TO
_IDLE_OTHER +
ENB_INIT_TO_IDLE_RNL
ENB_INIT_TO_I
DLE_RNL +
ENB_INIT_TO_IDLE_OTHER
ENB_INIT_TO
_IDLE_OTHER +
PRE_EMPT_UE_CONTEXT_NON_GBR+((UE_CTX_RE
L_MME_PART_S1_RESET+UE_CTX
L_MME_PART_S
1_RESET+UE_CTX_REL_MME_GLOB
_REL_MME_GLOB
_S1_RESET) +
(UE_CTX_REL_ENB_PART_S1_RESET+UE_CTX_REL
_ENB_GLOB_S1_RESET))
_ENB_GLOB_S1_RESE
T)) )
/
SUM_RRC_CONNECTED_UE
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Introduction, Continued
Retainability
KPI , continued
Indicators
Data ERAB Drop Rate
Formula
((ERAB_REL_HO_PART + ERAB_REL_ENB ERAB_REL_ENB_RNL_INA ERAB_REL_ENB_RNL_RED
ERAB_REL_ENB_RNL_RE
D+
EPC_EPS_BEARER_REL_REQ_RNL
EPC_EPS_BEA
RER_REL_REQ_RNL +
EPC_EPS_BEARER_REL_REQ_OTH
EPC_EPS_BEA
RER_REL_REQ_OTH +
ERAB_REL_EPC_PATH_SWITCH) –
(ERAB_REL_HO_PART_QCI1
(ERAB_REL_HO_PART
_QCI1 + ERAB_REL_ENB_QCI
ERAB_REL_ENB_QCI1
1
- ERAB_REL_ENB_RNL_INA_QCI1 ERAB_REL_ENB_RNL_RED_QCI1
ERAB_REL_ENB_RNL_RE
D_QCI1 +
EPC_EPS_BEAR_REL_REQ_R_QCI1
EPC_EPS_BEA
R_REL_REQ_R_QCI1 +
EPC_EPS_BEAR_REL_REQ_O_QCI1
EPC_EPS_BEA
R_REL_REQ_O_QCI1 +
ERAB_REL_EPC_PATH_SWITCH_QCI
ERAB_REL_EPC_PA
TH_SWITCH_QCI1)
1) (ERAB_REL_HO_PART_QCI2 + ERAB_REL_ENB_QCI
(ERAB_REL_HO_PART_QCI2
ERAB_REL_ENB_QCI2
2
- ERAB_REL_ENB_RNL_INA_QCI2 ERAB_REL_ENB_RNL_RED_QCI2
ERAB_REL_ENB_RNL_RE
D_QCI2 +
EPC_EPS_BEAR_REL_REQ_R_QCI2
EPC_EPS_BEA
R_REL_REQ_R_QCI2 +
EPC_EPS_BEAR_REL_REQ_O_QCI2
EPC_EPS_BEA
R_REL_REQ_O_QCI2 +
ERAB_REL_EPC_PATH_SWITCH_QCI2))
/
(ERAB_INI_SETUP_SUCC_QCI3+
ERAB_INI_SETUP_SUCC_QCI4+
ERAB_INI_SETUP_SUCC_QCI5+
ERAB_INI_SETUP_SUCC_QCI6
ERAB_INI_SETUP_
SUCC_QCI6 +
ERAB_INI_SETUP_SUCC_QCI7
ERAB_INI_SETUP_
SUCC_QCI7 +
ERAB_INI_SETUP_SUCC_QCI8
ERAB_INI_SETUP_
SUCC_QCI8 +
ERAB_INI_SETUP_SUCC_QCI9
+ERAB_ADD_SETUP_SUCC_QCI3
+ERAB_ADD_SETUP_SUCC_QCI4
+ERAB_ADD_SETUP_SUCC_QCI5
+ERAB_ADD_SE
TUP_SUCC_QCI5 +
ERAB_ADD_SETUP_SUCC_QCI
ERAB_ADD_SE
TUP_SUCC_QCI6
6+
ERAB_ADD_SETUP_SUCC_QCI
ERAB_ADD_SE
TUP_SUCC_QCI77 +
ERAB_ADD_SETUP_SUCC_QCI
ERAB_ADD_SE
TUP_SUCC_QCI8
8+
ERAB_ADD_SETUP_SUCC_QCI9)
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Internal
© Nokia 2017
Introduction, Continued
Flow Chart
October 11, 2017 – IEH 550, Section 003
5 / 24
Internal
© Nokia 2017
Troubleshooting
Overview
This section depicts how to investigate the Retainability KPI and steps to improve the
degradation.
Check the following to troubleshoot Retainability KPI:
•
•
Radio Causes
eNodeB Initiated
−
Radio Causes
−
Handover Failures
−
Transport Issue
MME Initiated
This section covers the possible reasons for call drop initiated by eNodeB due to Radio
causes/conditions and timers for Radio Link Failures along with steps or checks to improve
this KPI
Table: Possible Radio Causes for Drops
Causes
Checks
Poor Coverage and SINR Values
•
Physical Optimization
•
Audit cell reselection paramet
parameters
ers
•
Tune downlink related paramet
parameters
ers
•
UL RSSI
•
Check power related parameters
parameters
•
Reduce uplink interference
•
•
Hardware Issues and Alarms
Check overshooting cells causing
interference
Check for loose connect
connectors
ors and faulty
hardware
Check VS
VSWR
WR alarms
Check Hardware issue, Alarms, Improper
cabling and connector issues
Continued on next page
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Troubleshooting, Continued
Radio Causes ,
continued
Table: Parameters related to Radio Link Failure and timers
Parameter
Name
t301 (Timer
T301)
Description
Default
Value/
Verizon
GPL
Timer T301 supervises the RRC
connection re-establishment procedure.
400ms (3)/
1500ms (6)
Ranges and
Steps
0: 100ms
1: 200ms
Start: Transmission of
RRCConnectionReestabilshmentRequest
2: 300ms
Stop:
Reception of
RRCConnectionReestablishment
or
RRCConnectionReestablishmentReject
message as well as when the selected
cell becomes unsuitable
4: 600ms
5: 1000ms
3: 400ms
6: 1500ms
Impact
Increasing the
value will increase
the window hence
reduce the chance
of call drops.
However, this will
also increase the
usage of network
resources.
7: 2000ms
At expiry: Go to RRC_IDLE
RRC_IDLE
t310 (Timer
T310)
Timer T310 supervises the recovery from
physical layer problems
2000ms (6)/
0: 0ms
1000ms (5)
for
microcells
1: 50ms
2000ms (6)
for
macrocells
2: 100ms
3: 200ms
4: 500ms
5: 1000ms
6: 2000ms
t311 (Timer
T311)
Timer T311 supervises the RRC
connection re-establishment.
3000ms (1)/
5000ms (2)
0: 1000ms
1: 3000ms
2: 5000ms
3: 10000ms
4: 15000ms
5: 20000ms
6: 30000ms
Increasing the
value will increase
the window hence
reduce the chance
of call drops.
However, this will
also increase the
usage of network
resources.
Increasing the
value will increase
the window hence
reduce the chance
of call drops.
However, this will
also increase the
usage of network
resources.
Continued on next page
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Troubleshooting, Continued
Radio Causes ,
continued
Parameter
Name
n310
(Maximum
number of
out-of-sync
indications)
Description
Default
Value/
Verizon
GPL
This is the maximum number of
consecutive ‘out of sync’ indications
received from lower layers.
n10 (6)/ n10
(6) for
microcells
n1 corresponds to 1 and so on.
n20 (7) for
macrocells
Ranges and
Steps
0: n1
Impact
Increasing the
value will improve
the call drop rate.
However, this will
also increase the
1: n2
2: n3
3: n4
usage of network
resources.
4: n6
5: n8
6: n10
7: n20
n311
(Maximum
number of insync
indications)
n1 (0)/ n1 (0)
Maximum number of consecutive ‘insync’ indications received from lower
layers.
0: n1
1: n2
2: n3
n1 corresponds to 1 and so on
3: n4
4: n5
5: n6
6: n8
7: n10
rlpDetEndN
Ul (Number
of PUSCH
detections to
end radio link
problem)
Defines the number of consecutive uplink
data receptions on PUSCH without DTX
detection before the radio link problems
are assumed to be over and an indication
about radio link recovery is sent to higher
layers. This parameter is vendor-specific.
rlpDetMaxN
Ul (Number
of PUSCH
DTX
detections for
radio link
problem)
Defines the number of uplink DTX
detections on PUSCH before an
indication about radio link problems is
sent to higher layers. This parameter is
vendor-specific.
3 (MINT)
1...20, step 1
Higher value:
lower is the
recovery time from
the RLF state
which will increase
the call drop rate.
1000 (MINT)
1...1000, step
1
Lower value:
faster RLF
indication would
be triggered
hence would
increase the call
drop rate.
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Troubleshooting, Continued
Radio Causes ,
continued
Parameter
Name
Description
Default
Value/
Verizon
GPL
Ranges
and Steps
Impact
nCqiDtx
(Radio
problem
indication
based on
Number of consecutive CQI DTX
detections required for RL failure.
The parameter defines the number of
consecutive CQI DTX detections causing
radio link
100/0
0...250, step
1
Lower value: faster
RLF indication would
be triggered hence
would increase the
call drop rate.
CQI DTX)
failure indication. Special value 0 means
that the feature is disabled.
nCqiRec
(Radio
problem
recovery
based on
CQI DTX)
Number of consecutive CQIs required for
RL recovery.
The parameter defines number of
consecutive CQI non-DTX detections
causing radio link
failure recovery indication.
2/2
1...8, step 1
Higher value: lower is
the recovery time
from the RLF state
which will increase
the call drop rate.
rlpDetEndN
oDl (Number
of successful
PDSCH
transmission
s)
This parameter determines the number
DL PDSCH transmission with correct
HARQ feedback until detected radio link
problems are assumed to be over. This
parameter is vendor-specific.
3 (MINT)
1...20, step 1
Higher value: lower is
the recovery time
from the RLF state
which will increase
the call drop rate.
rlpDetMaxN
oDl (Number
of failed
PDSCH
transmission
s)
This
parameter
maximum
number
of faileddetermines
DL PDSCHthe
transmission
attempts until radio link problems are
detected. This parameter is vendorspecific.
0 (MINT)
20...5000
ms, step 1
ms
Lower
value: faster
RLF indication
would
be triggered hence
would increase the
call drop rate.
rlpDetMaxTi
meDl
(Timeframe
for failed
PDSCH
transmission
s)
Determines the timeframe for failed DL
PDSCH transmission attempts until radio
link problems are detected. This
parameter is vendor-specific.
0 (MINT)
20...5000
ms, step 1
ms
Lower value: faster
RLF indication would
be triggered hence
would increase the
call drop rate.
Continued on next page
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Troubleshooting, Continued
Radio Causes ,
continued
Parameter
Name
Description
Default
Value/
Verizon
GPL
raRespWinS
ize (Random
access
response
window size)
Random Access Response Window Size
parameter defines the window size for
the random access response in TTIs.
10 (7)/ 10 (7)
Ranges and
Steps
0: 2
In case
raRespWinSize is
too small, then
there could be
problems with
1: 3
2: 4
3: 5
second cell
handling on time
and could lead to
decreased call
setup
performance
4: 6
5: 7
6: 8
7: 10
prachCS
(PRACH
cyclic shift)
Preamble cyclic shift defines the
configuration which is used for preamble
generation. The configuration determines
how many cyclic shifts are needed to
generate preamble. Unrestricted set is
supported.
12/ Planned
value for
each cell
0...15, step 1
prachCS is by
default set to 12
(cell range 15.91
km) - to not limit
the cell range that
is given by
preambles format
0
(prachConfigIndex
)
0 (false), 1
(true)
-
Configuration also defines the zero
correlation zone and respective
maximum cell range.
The setting is commonly valid for all
legacy category UE and Cat-M UE.
prachHsFlag
(PRACH high
speed flag)
High speed flag for PRACH preamble
generation determines whether an
unrestricted or a restricted set must be
used by the UE.
0/0
Impact
false = Unrestricted; true = Restricted
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Troubleshooting, Continued
Handover
Failures
Failures and
Transport Issue
LTE handover can be classified into two phases:
phases :
•
Preparation Phase
•
Execution Phase
The table below shows the reasons & optimal solutions for LTE Intra & Inter frequency HO in
Preparation phase.
Causes
Checks
Cell Relation Issue
Check service state, Cell Relations & other
parameter related to Intra / Inter frequency
HO feature and Multi ERAB Per User
feature
Load Balancing
Offload target cell & Reduce number of HO
by physical optimization or feature
Admission reject
Audit UE Admi
Admission
ssion Control, Bearers (SRB
& DRB) Admission Control, Transport
Network Admission Control
Configuration Issue
Check configuration issues and Cell
Relations
Other Issues and Alarms
Check Alarms, Hardware, MME Pool,
Target cell status
The table below shows the reasons & optimal solutions for LTE Intra & Inter frequency HO in
Execution phase.
Causes
Checks
PCI Conflict and Confusion Issue
•
•
Poor Coverage
Audit PCI of nearby sites
Check if there is any overshooting cell
creating conflict
•
Perform P
Physical
hysical optimization
optimization
•
Audit cell reselection paramet
parameters
ers
•
Tune DL power related parameters
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11 / 24
Troubleshooting, Continued
Handover
Failures
Failures and
Transport
Issue, continued
Causes
Checks
Poor DL SINR (CQI)
UL RSSI
Hardware Issues and Alarms
•
Perform P
Physical
hysical optimization
optimization
•
Audit cell reselection paramet
parameters
ers
•
Tune DL power related parameters
•
Check Power control paramet
parameters
ers
•
Reduce UL Interference
Check HW issues, alarms, improper cabling,
connector issues
The table below shows the reasons & optimal solutions for LTE Inter RAT HO in Preparation
phase.
Causes
Checks
Configuration Issue
Check configuration issues and Cell
Relations
Target Cell Load Issue
Check load & admission control parameter
of legacy network
Hardware Issues
Check Alarms, Hardware, Target cell status
The table below shows the reasons & optimal solutions for LTE Inter RAT HO in Execution
phase.
Causes
Checks
Poor Coverage
Perform Physical optimization
Target Cell High UL Interference Issue
Reduce UL Interference
Wrong neighbor
Check Configuration & parameter of
Neighbor cell
Hardware Issues
Check Alarms, Hardware, Target cell status
For Transport Issues check the following:
Causes
Checks
Transport Issue
Check S1 and/or X2 interface
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Troubleshooting, Continued
Handover
Failures
Failures and
Transport
Issue, continued
Table: The table below shows the parameters related to handovers:
Parameter
Name
Description
Default Value/
Verizon GPL
x2LinkStatus (X2
link status)
This parameter
provides information
on whether the X2
link is successfully
established.
1/1
maxNumRRC (Max
Number RRC)
This parameter
provides the
threshold for the
maximum number
of UEs in the cell
which may establish
a RRC connection
addAUeRrHo (Add
number active UEs
radio reason
handover)
This parameter
provides the
additional margin for
the maximum
number of active
UEs in the cell
accessing the cell
via hand over with
HO-cause: ‘HO
Ranges and
Steps
Impact
Unavailable (0),
Available (1)
By default, set to 1
300/ 200 for
Microcells, 420 for 5
MHz, 580 for 10
MHz, 780 for 15/20
MHz
0...840, step 1
Decreasing
maxNumRrc will
alleviate Admission
control.
15/ 10 for 5/10 MHz,
30 for 15/20 MHz
0...1500, step 1
Decreasing
addAUeRrHo will
alleviate Admission
control.
20/ 10 for 5/10 MHz,
30 for 15/20 MHz
0..1500, step 1
Decreasing
addAUeTcHo will
alleviate Admission
control
desirable
reasons’. for radio
addAUeTcHo (Add
number active UEs
time critical
handover)
This parameter
provides additional
margin for the
maximum number
of active UEs in the
cell accessing the
cell via hand over
with HO-cause:
"Time Critical HO".
Continued on next page
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Troubleshooting, Continued
Handover
Failures
Failures and
Transport
Issue, continued
Parameter
Name
MaxNumRrcEmerg
ency (Maximum
number RRC
emergency)
Description
This parameter
provides threshold
for the maximum
number of UEs in
the cell which may
establish a RRC
Default Value/
Verizon GPL
440/ 230 for
Microcells
Ranges and
Steps
Impact
0...840, step 1
440 for 5 MHz
600 for 10 MHz
840 for 15/20 MHz
connection, used to
admit RRC
connections for
emergency calls.
a3Offset (A3 offset)
a3TimeToTrigger
(A3 time to trigger)
This parameter
provides handover
margin for better
cell HO.
This parameter
provides time for
which the specific
criteria for the
measurement event
A3 must be met in
in
3(6)/3(6)
-15...15 dB, step 0.5
dB
Low values: allow
the UE to handover
earlier
High values: delays
the handover
320ms (8)/40ms
order
to trigger a
measurement
report.
0: 0ms, 1: 40ms, 2:
64ms, 3: 80ms, 4:
100ms, 5: 128ms, 6:
160ms, 7: 256ms, 8:
320ms, 9: 480ms,
10: 512ms, 11:
Low values:
introduces pingpong phenomenon
during HO operation
640ms,
12: 1024ms,
13: 1280ms,
14:
2560ms, 15:
5120ms
increases possibility
of losing the active
connection on the
serving cell
High values: Delays
the HO and
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Troubleshooting, Continued
Handover
Failures
Failures and
Transport
Issue, continued
Parameter
Name
a3ReportInterval
(A3 report interval)
Description
This parameter
defines the interval
with which
measurement
reports are
repeatedly sent as
Default Value/
Verizon GPL
Ranges and
Steps
Impact
640ms (3)/ 240ms
(1)
0: 120ms, 1:
240ms, 2: 480ms, 3:
640ms, 4: 1024ms,
5: 2048ms, 6:
5120ms, 7:
10240ms, 8: 1min,
Increasing the
report interval will
increase the time to
make the handover,
decreasing will
impact the quality of
9: 6min, 10: 12min,
11: 30min, 12:
60min
HO measurements
-15...15 dB, step 0.5
dB
Low values: allow
the UE to handover
earlier
long as the specific
criteria for the
measurement event
A3 are met
a3OffsetRsrpInterF
req (A3 offset
RSRP inter
frequency)
a3OffsetRsrqInterF
req
(a3OffsetRsrqInterF
req)
This parameter
provides the margin
for RSRP for better
cell HO. It’s used in
measurement event
type A3 where the
event is triggered
when the inter
frequency
neighbour cell
becomes A3 offset
better than the
serving cell.
This parameter
provides margin for
RSRQ for better cell
HO. This parameter
used in
measurement event
type A3 where the
event is triggered
when the inter
frequency neighbor
cell becomes A3
offset better than
the serving cell.
3dB/30
High values: delays
the handover
NA
-15...15 dB, step 0.5
dB
Low values: allow
the UE to handover
earlier
High values: delays
the handover
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Troubleshooting, Continued
Handover
Failures
Failures and
Transport
Issue, continued
Parameter
Name
Description
Default Value/
Verizon GPL
Ranges and
Steps
hysA3Offset
(Related hysteresis
of offset a3Offset for
RSRP intra F)
This parameter
provides related
hysteresis of
handover margin for
better Cell handover
of Intra-Frequency
0 / (6 for markets
using RSRP based
triggers,2 for
markets using
RSRQ based
triggers.)
0...15 dB, step 0.5
dB
hysA3OffsetRsrpIn
terFreq (Related
hysteresis offset
a3Offset RSRP inter
frequency)
This parameter
provides related
hysteresis of
handover margin for
better cell Handover
of Inter-Frequency
0dB/30
0...15 dB, step 0.5
dB
hysA3OffsetRsrqIn
This parameter
terFreq (Related
hysteresis offset
a3Offset RSRQ
inter frequency)
provides related
hysteresis of
handover margin for
quality handover of
Inter-Frequency
Impact
Low values:
introduces pingpong phenomenon
during HO operation
High values: Delays
the HO and
increases possibility
of losing the active
connection on the
serving cell
Low values:
introduces pingpong phenomenon
during HO operation
High values: Delays
the HO and
increases possibility
of losing the active
connection on the
serving cell
NA
0...15 dB, step 0.5
Low values:
dB
introduces pingpong phenomenon
during HO operation
High values: Delays
the HO and
increases possibility
of losing the active
connection on the
serving cell
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Troubleshooting, Continued
Handover
Failures
Failures and
Transport
Issue, continued
Parameter
Name
Description
Default Value/
Verizon GPL
Ranges and
Steps
Impact
a3TimeToTriggerR
srpInterFreq (A3
time to trigger
RSRP inter
frequency)
This parameter
provides time for
which the specific
criteria for the inter
frequency
measurement event
A3 with quantity
RSRP must be met
to trigger a
measurement report
320ms (8)/ 5120ms
(15)
0: 0ms, 1: 40ms, 2:
64ms, 3: 80ms, 4:
100ms, 5: 128ms, 6:
160ms, 7: 256ms, 8:
320ms, 9: 480ms,
10: 512ms, 11:
640ms, 12: 1024ms,
13: 1280ms, 14:
2560ms, 15:
5120ms
Low values:
introduces pingpong phenomenon
during HO operation
a3TimeToTriggerR
srqInterFreq (A3
time to trigger
RSRQ inter
frequency)
This parameter
provides time for
which the specific
criteria for the inter
frequency
measurement event
A3 with quantity
RSRQ must be met
to trigger a
measurement report
NA
0: 0ms, 1: 40ms, 2:
64ms, 3: 80ms, 4:
100ms, 5: 128ms, 6:
160ms, 7: 256ms, 8:
320ms, 9: 480ms,
10: 512ms, 11:
640ms, 12: 1024ms,
13: 1280ms, 14:
2560ms, 15:
5120ms
Low values:
introduces pingpong phenomenon
during HO operation
a3ReportIntervalR
This parameter
240ms (1)/ 60 min
0: 120ms, 1: 240ms,
Increasing the
srpInterFreq (A3
report interval
RSRP inter
frequency)
defines the interval
with which
measurement
reports are
repeatedly sent if
the specific criteria
for the inter
frequency
measurement event
A3 with quantity
RSRP is met.
(12)
2: 480ms, 3: 640ms,
4: 1024ms, 5:
2048ms, 6: 5120ms,
7: 10240ms, 8:
1min, 9: 6min, 10:
12min, 11: 30min,
12: 60min
report interval will
increase the time to
make the handover,
decreasing will
impact the quality of
HO measurements
High values: Delays
the HO and
increases possibility
of losing the active
connection on the
serving cell
High values: Delays
the HO and
increases possibility
of losing the active
connection on the
serving cell
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Troubleshooting, Continued
Handover
Failures
Failures and
Transport
Issue, continued
Parameter
Name
Description
Default Value/
Verizon GPL
Ranges and
Steps
Impact
This parameter
provides time for
which the specific
criteria for the
measurement event
A5 must be met to
trigger a
measurement
report.
320ms (MINT)
0: 0ms, 1: 40ms, 2:
64ms, 3: 80ms, 4:
100ms, 5: 128ms, 6:
160ms, 7: 256ms, 8:
320ms, 9: 480ms,
10: 512ms, 11:
640ms, 12: 1024ms,
13: 1280ms, 14:
2560ms, 15:
5120ms
Low values:
introduces pingpong phenomenon
during HO operation
a3ReportInterval
(A3 report interval)
This parameter
defines the interval
with which
measurement
reports are
repeatedly sent if
the specific criteria
for the
measurement event
A3 are met.
640ms/240ms
0: 120ms, 1: 240ms,
2: 480ms, 3: 640ms,
4: 1024ms, 5:
2048ms, 6: 5120ms,
7: 10240ms, 8:
1min, 9: 6min, 10:
12min, 11: 30min,
12: 60min
Increasing the
report interval will
increase the time to
make the handover,
decreasing will
impact the quality of
HO measurements
threshold3aInterFr
This parameter,
-114dBm/31 for
-140...-43 dBm, step
Low values: allow
eq
(Threshold
for RSRP
inter th3a
frequency)
along
with
threshold3InterFreq,
determines the
criteria for interfrequency coverage
HO (RSRP-based
A5 event)
1 dBm
the
UE to handover
earlier
a5TimeToTrigger
(A5 time to trigger)
microcells
and 26
for macrocells
High values: Delays
the HO and
increases possibility
of losing the active
connection on the
serving cell
High values: delays
the handover
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Troubleshooting, Continued
Handover
Failures
Failures and
Transport
Issue, continued
Parameter
Name
Description
Default Value/
Verizon GPL
Ranges and
Steps
Impact
threshold3InterFre
q (Threshold th3 for
RSRP inter
frequency)
This parameter,
along with
threshold3aInterFre
q and
hysThreshold3Inter
Freq, determines
the criteria for interfrequency coverage
HO (RSRP-based
A5 event)
-114dBm/26
-140...-43 dBm, step
1 dBm
Low values: allow
the UE to handover
earlier
hysThreshold3Inte
rFreq (Related
hysteresis of
thresholds th3 and
th3a for RSRP)
This parameter
defines related
hysteresis of
handover margin for
coverage handover
of Inter-Frequency
0dB/6
a5TimeToTriggerIn
This parameter
terFreq
(A5 time to
trigger inter
frequency)
provides
for
which thetime
specific
criteria for the inter
frequency
measurement event
A5 must be met to
trigger a
measurement report
High values: delays
the handover
0...15 dB, step 0.5
dB
Low values:
introduces pingpong phenomenon
during HO operation
High values: Delays
the HO and
increases possibility
of losing the active
connection on the
serving cell
256ms/40ms
0: 0ms, 1: 40ms, 2:
Low values:
64ms,
4: 6:
100ms,3:5:80ms,
128ms,
160ms, 7: 256ms, 8:
320ms, 9: 480ms,
10: 512ms, 11:
640ms, 12: 1024ms,
13: 1280ms, 14:
2560ms, 15:
5120ms
introduces
pingpong phenomenon
during HO operation
High values: Delays
the HO and
increases possibility
of losing the active
connection on the
serving cell
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Troubleshooting, Continued
Handover
Failures
Failures and
Transport
Issue, continued
Parameter
Name
Description
Default Value/
Verizon GPL
Ranges and
Steps
Impact
a5ReportIntervalIn
terFreq (A5 report
interval inter
frequency)
This parameter
defines the interval
with which
measurement
reports are
repeatedly sent if
the specific criteria
for the inter
frequency
measurement event
A5 is met.
240ms/ 240ms
0: 120ms, 1: 240ms,
2: 480ms, 3: 640ms,
4: 1024ms, 5:
2048ms, 6: 5120ms,
7: 10240ms, 8:
1min, 9: 6min, 10:
12min, 11: 30min,
12: 60min
Increasing the
report interval will
increase the time to
make the handover,
decreasing will
impact the quality of
HO measurements
actRedirect
(Enable UE context
release with
redirect)
This parameter
enables the feature
UE context release
with redirect.
Enabled/ Enabled
for multi-band sites
and disabled for
single-band sites
0: disabled, 1:
enabled
BTS restart needed
for modification
actHOtoWcdma
(Enable handover
from LTE to
WCDMA)
This parameter
enables the feature
handover from LTE
to WCDMA.
0/0
0: false, 1: true
Object locking
required for
modification
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Troubleshooting, Continued
Handover
Failures
Failures and
Transport
Issue, continued
Parameter
Name
Description
Default
Value/
Verizon
GPL
Ranges
and Steps
psHoAllowed (PS
handover allowed)
The parameter controls whether PS
handover to a related neighbor cell
is allowed.
Allowed (0)
(MINT)
0: allowed,
1: forbidden
Vendor specific
tS1RelPrepG
(Supervision timer
for handover
preparation to GSM)
Guard against failure of the MME to
respond in preparation phase of S1
handover to GSM
1000ms/
2000ms
50...5000
ms, step 50
ms
Lower values: not
enough time
during SRVCC
preparation and
vice versa
tS1RelPrepU
(Supervision timer
for the preparation
HO WCDMA)
Guard against failure of the MME to
respond in preparation phase of S1
handover to another 3GPP RAT
2000ms/
2000ms
50...5000
ms, step 50
ms
Lower values: not
enough time
during SRVCC
preparation and
vice versa
Timer TS1RELOCprep_InterRAT is
used to guard against failure of the
MME to respond preparation phase
of S1 handover to another 3GPP
RAT. It is started in the source eNB
when the S1AP: HANDOVER
REQUIRED message is sent to the
MME and is stopped when the
S1AP: HANDOVER COMMAND or
S1AP: PREPARATION FAILURE
message is received in response. If
the timer expires the handover is
aborted or cancelled.
Timer tS1relprepIrat is used to
guard against failure of the MME to
respond preparation phase of S1
handover to another 3GPP
3 GPP RAT. It
is started in the source eNB when
the S1AP: HANDOVER REQUIRED
message is sent to the MME and is
stopped when the S1AP:
HANDOVER COMMAND or S1AP:
PREPARATION
PREPARAT
ION FAILURE message
is received in response. If the timer
expires the handover is aborted or
cancelled.
Impact
Continued on next page
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Troubleshooting, Continued
Handover
Failures
Failures and
Transport
Issue, continued
Parameter
Name
tS1RelPrepL
(Supervision timer
preparation intra
LTE HO)
Description
Default
Value/
Verizon GPL
Ranges
and Steps
Guard against failure of the
MME to respond in preparation
phase of intra LTE S1
handover
500ms/
2000ms
50...2000
ms, step 50
ms
1/1
0 (false), 1
(true)
Impact
Lower values: Early
timer expiration and
vice versa
Timer TS1RELOCprep_LTE is
used to guard against failure of
the MME to respond
preparation phase of intra LTE
S1 handover. It is started in the
source eNB when the S1AP:
HANDOVER REQUIRED
message is sent to the MME
and is stopped when the
S1AP: HANDOVER
COMMAND or S1AP:
PREPARATION FAILURE
message is received in
response. If the timer expires
the handover is aborted or
cancelled.
enableBetterCellH
o (Enable better cell
HO)
Flag if better cell HO is
enabled.
b2Threshold1Utra
(Threshold1 UTRA
for RSRP of serving
cell)
This parameter provides the
threshold for RSRP of serving
cell. If RSRP of serving
valueb2Threshold2UtraRscp,
-117 dBm
(MINT)
then handover is triggered (B2
event)
-140...-43
dBm, step 1
dBm
Low values:
introduces ping-pong
phenomenon during
HO operation
High values: Delays
the HO and increases
possibility of losing
the active connection
on the serving cell
Continued on next page
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Troubleshooting, Continued
Handover
Failures
Failures and
Transport
Issue, continued
Parameter
Name
Description
b2Threshold2Utra
Rscp (Threshold2
RSCP for UTRA
neighbour cell)
This parameter provides the
threshold for UTRA neighbour
cell on the current frequency,
such that it is considered to be
Default
Value/
Verizon GPL
Ranges
and Steps
Impact
-105 dBm
(MINT)
-120...-24
dBm, step 1
dBm
Low values:
introduces ping-pong
phenomenon during
HO operation
High values: Delays
the HO and increases
possibility of losing
the active connection
on the serving cell
good and reported in the
measurement result of B2
event.
b2TimeToTriggerU
traMeas (Time to
trigger UTRA
measurement
report)
This parameter provides the
duration for which the RSRP
based event B2 must be valid
320 ms(8)
(MINT)
0: 0ms, 1:
40ms, 2:
64ms, 3:
80ms, 4:
100ms, 5:
128ms, 6:
160ms, 7:
256ms, 8:
320ms, 9:
480ms, 10:
512ms, 11:
Low values:
introduces ping-pong
phenomenon during
HO operation
High values: Delays
the HO and increases
possibility of losing
the active connection
on the serving cell
640ms, 12:
1024ms, 13:
1280ms, 14:
2560ms, 15:
5120ms
hysB2ThresholdUt
ra (Related
hysteresis
thresholds
B2Th1,B2Th2 HO
TD-SCDMA)
This parameter defines related
Hysteresis of Handover Margin
for HO to TD-SCDMA
2 dB (MINT)
This parameter is used within
the entry and leave condition of
the B2 triggered reporting
condition
October 11, 2017 – IEH 550, Section 003
0...15 dB,
step 0.5 dB
Low values:
introduces ping-pong
phenomenon during
HO operation
High values: Delays
the HO and increases
possibility of losing
the active connection
on the serving cell
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IEH 550, Section 004
October 11, 2017
Mobility
BBU Swap Validation & Troubleshooting for Verizon
Contents
Introduction..................................................................................................................... 2
Overview ..........................................................................................................
....................................................................................................................
.......... 2
Mobility KPI Information .............................................................................................. 2
Mobility KPI............................................................................................................
KPI.................................................................................................................
..... 3
Flow Chart .................................................................................................................. 4
LTE Intra and Inter Frequency Handover ........................................................................ 5
Overview .................................................................................................................... 5
Analysis ...................................................................................................................... 5
LTE Inter RAT Handover .............................................................................................. 16
Overview .................................................................................................................. 16
Analysis .................................................................................................................... 16
fALU – fNokia eNB interworking .................................................................................... 21
Overview .................................................................................................................. 21
AirScale and bCEM eNB interworking....................................................................... 21
October 11, 2017 – IEH 550, Section 004
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Introduction
Overview
The process of handover is as stated below:
•
•
Handover will be initiated by a measurement report sent via the RRC protocol.
Upon the reception of this me
measurement
asurement report, tthe
he handover algorithm will decide
whether a handover should take place
•
In response to the handover deci
decision,
sion, the handover execution will be carried out using the
corresponding procedures
•
After the handover execution, the handover algorithm w
will
ill be informed,
informed, whether the
the
handover was successful or not
•
Mobility KPI
Information
The Handover procedure is composed of a number of single functions:
−
Measurements
−
Filtering of measurements
−
Reporting of measurement results
−
Hard handover algorithm
−
Execution of handover
Root Cause Analysis for mobility KPIs can been done by following the steps below:
Step
Action
1
Open current PNM BTS daily Report
2
Check IntraHOFailRate, X2TotHOFailRate and FSMKPIsSecondary tabs for
Mobility issues
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Introduction, Continued
Mobility KPI
Mobility KPI can be monitored with the following indicators
Indicators
Formula
Intra-eNB Total HO Failure
Rate
SUCC_INTRA_ENB_HO /(INTRA_ENB_HO_PRE
SUCC_INTRA_ENB_HO
/(INTRA_ENB_HO_PREPPFAIL_ENB_HO_PREP_AC)
X2 Total Handover Failure
SUCC_INTER_ENB
SUCC_INTER_ENB_HO
_HO /(INTER_ENB_HO_PRE
/(INTER_ENB_HO_PREPPINTER_X2_LB_PREP_FAIL_AC)
S1-interface Handover
Failure
(INTER_ENB_S1_HO_SUCC)
/(INTER_ENB_S1_HO_PREP)
Intra-eNB Total HO Failure
Rate (exclIFLB)
(INTRA_ENB_HO_PREP-FAIL_ENB_HO_PREP_AC
(INTRA_ENB_HO_PREP-FAIL_ENB_HO_PRE
P_AC SUCC_INTRA_ENB_HO –(M8021C23_HO_LB_ATT M8021C24_HO_LB_SUCC)) /
(INTRA_ENB_HO_PREP
(INTRA_ENB_HO_P
REP -FAIL_ENB_HO_PREP_A
-FAIL_ENB_HO_PREP_AC
CM8021C23_HO_LB_ATT)
Continued on next page
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Introduction, Continued
Flow Chart
October 11, 2017 – IEH 550, Section 004
Internal
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LTE Intra and Inter Frequency Handover
Overview
This section demonstrates how to investigate the LTE Intra / Inter HO KPI and steps to
improve the degradation in KPI.
Below are the events used for Intra & Inter frequency HO in Verizon.
Anal
An
alys
ys is
•
LTE Intra Hand
Handover:
over: A3 Event
•
LTE Inter Hand
Handover:
over: A5 Event
LTE handover process can be classified into two phases:
•
Preparation Phase
•
Execution Phase
The table below shows the reasons & optimal solutions for LTE Intra & Inter frequency HO in
Preparation phase.
Causes
Checks
License Issue
Audit License state, service state & other
parameter related to Intra / Inter frequency
HO feature and Multi ERAB Per User
feature
Load Balancing
Offload target cell & reduce number of HO
by physical optimization or feature
Admission reject
Audit UE Admi
Admission
ssion Control, Bearers (SRB
& DRB) Admission Control, Transport
Network Admission Control
Configuration Issue
Check configuration issues and Cell
Other Issues and Alarms
Relations
Check Alarms, Hardware, MME Pool, Target
cell status
Continued on next page
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LTE Intra and Inter Frequency Handover, Continued
An alys
al ys is ,
continued
The table below shows the reasons & optimal solutions for LTE Intra & Inter frequency HO in
Execution phase.
Causes
Checks
PCI Conflict and Confusion Issue
•
•
Poor Coverage
Poor DL SINR (CQI)
UL RSSI
Hardware Issues and Alarms
Audit PCI of nearby sites
Check if there is an overshooting cell
nearby, creating conflict
•
Perform P
Physical
hysical optimization
optimization
•
Audit cell reselection paramet
parameters
ers
•
Tune DL power related parameters
•
Perform P
Physical
hysical optimization
optimization
•
Audit cell reselection paramet
parameters
ers
•
Tune DL power related parameters
•
Check Power control paramet
parameters
ers
•
Reduce UL Interference
Check HW issues, alarms, improper cabling,
connector issues
Continued on next page
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LTE Intra and Inter Frequency Handover, Continued
An alys
al ys is ,
continued
Parameter
Name
The table below shows the parameters related to LTE Intra / Inter Handover failures.
Description
Default
Values /Nokia
GPL Values
x2LinkStatus (X2
link status)
This parameter provides
information whether the X2
link is successfully
established.
1/1
maxNumRRC (Max
Number RRC)
This parameter provides
the threshold for the
maximum number of UEs in
the cell which may
establish a RRC
connection
300/ 200 for
Ranges and
steps
Impact
Unavailable (0),
Available (1)
By default, set to 1
0...840, step 1
Decreasing
maxNumRrc
will
alleviate
Admission control.
Microcells,
420
for 5 MHz, 580
for 10 MHz, 780
for 15/20 MHz
addAUeRrHo (Add
number active UEs
radio reason
handover)
This parameter provides
the additional margin for
the maximum number of
active UEs in the cell
accessing the cell via hand
over with HO-cause: ‘HO
desirable for radio reasons’
15 / (10 for 5/10
MHz, 30 for
15/20 MHz)
0...1500, step 1
Decreasing
addAUeRrHo will
alleviate
Admission control.
addAUeTcHo (Add
number active UEs
time critical
handover)
This parameter provides
additional margin for the
maximum number of active
UEs in the cell accessing
20 / (10 for 5/10
MHz, 30 for
15/20 MHz)
0...1500, step 1
Decreasing
addAUeTcHo will
alleviate
Admission control
the cell via hand over with
HO-cause: ‘Time Critical
HO’
Continued on next page
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LTE Intra and Inter Frequency Handover, Continued
An alys
al ys is ,
continued
Parameter
Name
Description
Default
Values/Nokia
GPL Values
Ranges
and steps
MaxNumRrcEmerg
ency (Maximum
number RRC
emergency)
This parameter provides
threshold for the maximum
number of UEs in the cell which
may establish a RRC
connection, used to admit RRC
connections for emergency calls.
440 / (230 for
Microcells
0...840, step
1
NA
50...2000
ms, step 50
ms
Lower Values:
Early timer
expiration and
vice versa
tS1RelPrepL
(Supervision timer
preparation intra
LTE HO)
Guard against failure of the MME
to respond in preparation phase
of intra LTE S1 handover.
Impact
440 for 5 MHz
600 for 10 MHz
840 for 15/20
MHz)
500ms / 2000ms
Timer TS1RELOCprep_LTE is
used to guard against failure of
the MME to respond preparation
phase of intra LTE S1 handover.
It is started in the source eNB
when the S1AP: HANDOVER
REQUIRED message is sent to
the MME and is stopped when
the S1AP: HANDOVER
COMMAND or S1AP:
PREPARATION
PREPARATI
ON FAILURE
message is received in
response. is
If aborted
the timerorexpires the
handover
cancelled.
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LTE Intra and Inter Frequency Handover, Continued
An alys
al ys is ,
continued
Parameter
Name
Description
Default Values
/Nokia GPL
Values
Ranges and
steps
Impact
enableBetterCellH
o (Enable better cell
HO)
Flag if better cell
HO is enabled.
1 / True
0 (false), 1 (true)
NA
a3Offset (A3 offset)
This parameter
provides handover
margin for better
cell HO.
3(6) / 6
-15...15 dB, step 0.5
dB
Low values: allow
the UE to handover
earlier
a3TimeToTrigger
(A3 time to trigger)
High values: delays
the handover
This parameter
provides time for
which the specific
criteria for the
measurement event
A3 must be met in
in
order to trigger a
measurement
report.
320ms(8) / 40ms
a3ReportInterval
This parameter
640ms (3)/ 240ms
(A3 report interval)
defines the interval
with which
measurement
reports are
repeatedly sent as
long as the specific
criteria for the
measurement event
A3 are met
(1)
0: 0ms, 1: 40ms, 2:
64ms, 3: 80ms, 4:
100ms, 5: 128ms, 6:
160ms, 7: 256ms, 8:
320ms, 9: 480ms,
10: 512ms, 11:
640ms, 12: 1024ms,
13: 1280ms, 14:
2560ms, 15:
5120ms
Low values:
introduces pingpong phenomenon
during HO operation
0: 120ms, 1:
Increasing the
240ms, 2: 480ms, 3:
640ms, 4: 1024ms,
5: 2048ms, 6:
5120ms, 7:
10240ms, 8: 1min,
9: 6min, 10: 12min,
11: 30min, 12:
60min
report interval will
increase the time to
make the handover,
decreasing will
impact the quality of
HO measurements
High values: Delays
the HO and
increases possibility
of losing the active
connection on the
serving cell
Continued on next page
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LTE Intra and Inter Frequency Handover, Continued
An alys
al ys is ,
continued
Parameter
Name
Description
Default Values
/Nokia GPL
Values
Ranges and
steps
Impact
a3OffsetRsrpInterF
req (A3 offset
RSRP inter
frequency)
This parameter
provides margin for
RSRP for better cell
HO. This parameter
used in
measurement event
3dB / 30
-15...15 dB, step 0.5
dB
Low values: allow
the UE to handover
earlier
High values: delays
the handover
type
the
eventA3
is where
triggered
when the inter
frequency
neighbour cell
becomes A3 offset
better than the
serving cell.
a3OffsetRsrqInterF
req
(a3OffsetRsrqInterF
req)
This parameter
provides margin for
RSRQ for better cell
HO. This parameter
used in
measurement event
type A3 where the
event is triggered
when the inter
frequency neighbor
cell becomes A3
offset better than
the serving cell.
NA
hysA3Offset
(Related hysteresis
of offset a3Offset for
RSRP intra F)
This parameter
provides related
hysteresis of
handover margin for
better Cell handover
of Intra-Frequency
0 / (6 for markets
using RSRP based
triggers,2 for
markets using
RSRQ based
triggers.)
-15...15 dB, step 0.5
dB
Low values: allow
the UE to handover
earlier
High values: delays
the handover
0...15 dB, step 0.5
dB
Low values:
introduces pingpong phenomenon
during HO operation
High values: Delays
the HO and
increases possibility
of losing the active
connection on the
serving cell
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LTE Intra and Inter Frequency Handover, Continued
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Parameter
Name
Description
Default Values /
Nokia GPL
Values
hysA3OffsetRsrpIn
terFreq (Related
hysteresis offset
a3Offset RSRP inter
frequency)
This parameter
provides related
hysteresis of
handover margin for
better cell Handover
of Inter-Frequency
0dB / 30
Ranges and
steps
Impact
0...15 dB, step 0.5
dB
Low values:
introduces pingpong phenomenon
during HO operation
High values: Delays
the HO and
increases possibility
of losing the active
connection on the
serving cell
hysA3OffsetRsrqIn
terFreq (Related
hysteresis offset
a3Offset RSRQ
inter frequency)
This parameter
provides related
hysteresis of
handover margin for
quality handover of
Inter-Frequency
NA
a3TimeToTriggerR
srpInterFreq (A3
time to trigger
RSRP inter
frequency)
This parameter
provides time for
which the specific
criteria for the inter
frequency
measurement event
A3 with quantity
RSRP must be met
to trigger a
measurement report
320ms (8) / 5120ms
0...15 dB, step 0.5
dB
Low values:
introduces pingpong phenomenon
during HO operation
High values: Delays
the HO and
increases possibility
of losing the active
connection on the
serving cell
0: 0ms, 1: 40ms, 2:
64ms, 3: 80ms, 4:
100ms, 5: 128ms, 6:
160ms, 7: 256ms, 8:
320ms, 9: 480ms,
10: 512ms, 11:
640ms, 12: 1024ms,
13: 1280ms, 14:
2560ms, 15:
5120ms
Low values:
introduces pingpong phenomenon
during HO operation
High values: Delays
the HO and
increases possibility
of losing the active
connection on the
serving cell
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LTE Intra and Inter Frequency Handover, Continued
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Parameter
Name
Description
Default Values /
Nokia GPL
Values
Ranges and
steps
Impact
a3TimeToTriggerR
srqInterFreq (A3
time to trigger
RSRQ inter
frequency)
This parameter
provides time for
which the specific
criteria for the inter
frequency
measurement event
NA
0: 0ms, 1: 40ms, 2:
64ms, 3: 80ms, 4:
100ms, 5: 128ms, 6:
160ms, 7: 256ms, 8:
320ms, 9: 480ms,
10: 512ms, 11:
Low values:
introduces pingpong phenomenon
during HO operation
640ms, 12: 1024ms,
13: 1280ms, 14:
2560ms, 15:
5120ms
increases possibility
of losing the active
connection on the
serving cell
0: 120ms, 1: 240ms,
2: 480ms, 3: 640ms,
4: 1024ms, 5:
2048ms, 6: 5120ms,
7: 10240ms, 8:
1min, 9: 6min, 10:
12min, 11: 30min,
12: 60min
Increasing the
report interval will
increase the time to
make the handover,
decreasing will
impact the quality of
HO measurements
0: 120ms, 1: 240ms,
2: 480ms, 3: 640ms,
4: 1024ms, 5:
2048ms, 6: 5120ms,
7: 10240ms, 8:
1min, 9: 6min, 10:
12min, 11: 30min,
12: 60min
Increasing the
report interval will
increase the time to
make the handover,
decreasing will
impact the quality of
HO measurements
A3 with quantity
RSRQ must be met
to trigger a
measurement report
a3ReportIntervalR
srpInterFreq (A3
report interval
RSRP inter
frequency)
This parameter
defines the interval
with which
measurement
reports are
repeatedly sent if
the specific criteria
for the inter
frequency
measurement event
A3 with quantity
RSRP is met.
a3ReportIntervalR
srqInterFreq (A3
report interval
RSRQ inter
frequency)
This parameter
defines the interval
with which
measurement
reports are
repeatedly sent if
the specific criteria
for the inter
frequency
measurement event
A3 with quantity
RSRQ is met
240ms (1) / 60min
NA
High values: Delays
the HO and
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LTE Intra and Inter Frequency Handover, Continued
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Parameter
Name
Threshold3a
(Threshold th3a for
RSRP)
threshold3
(Threshold th3 for
RSRP)
hysThreshold3
(Related hysteresis
of thresholds th3
and th3a for RSRP)
a5TimeToTrigger
(A5 time to trigger)
Description
Default Values /
Nokia GPL
Values
This parameter
determines criteria
for intra-frequency
coverage HO (A5event).
-114 dBm / 1
This
parameter
determines
criteria
for intra-frequency
coverage HO (A5event).
-116dBm / 0
This parameter
provides related
hysteresis of
handover margin for
coverage handover
of Intra-Frequency
0dB / 30
This
parameter
provides
time for
which the specific
criteria for the
measurement event
A5 must be met to
trigger a
measurement
report.
320ms (8) / 5120ms
Ranges and
steps
Impact
-140...-43 dBm, step
1 dBm
Low values: allow
the UE to handover
earlier
High values: delays
the handover
-140...-43
dBm, step
1 dBm
Low
values:
allow
the UE
to handover
earlier
High values: delays
the handover
0...15 dB, step 0.5
dB
Low values:
introduces pingpong phenomenon
during HO operation
High values: Delays
the HO and
increases possibility
of losing the active
connection on the
serving cell
Enum
0ms, 1:3:
40ms, [0:
2: 64ms,
80ms, 4: 100ms, 5:
128ms, 6: 160ms, 7:
256ms, 8: 320ms, 9:
480ms, 10: 512ms,
11: 640ms, 12:
1024ms, 13:
1280ms, 14:
2560ms, 15:
5120ms]
Low
values:pingintroduces
pong phenomenon
during HO operation
High values: Delays
the HO and
increases possibility
of losing the active
connection on the
serving cell
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LTE Intra and Inter Frequency Handover, Continued
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continued
Parameter
Name
a3ReportInterval
(A3 report interval)
Description
This parameter
defines the interval
with which
measurement
reports are
repeatedly sent if
Default Values /
Nokia GPL
Values
Ranges and
steps
Impact
640ms (3) / 240ms
0: 120ms, 1: 240ms,
2: 480ms, 3: 640ms,
4: 1024ms, 5:
2048ms, 6: 5120ms,
7: 10240ms, 8:
1min, 9: 6min, 10:
Increasing the
report interval will
increase the time to
make the handover,
decreasing will
impact the quality of
12min, 11: 30min,
12: 60min
HO measurements
-140...-43 dBm, step
1 dBm
Low values: allow
the UE to handover
earlier
the specific criteria
for the
measurement event
A3 are met.
threshold3aInterFr
eq (Threshold th3a
for RSRP inter
frequency)
This parameter,
along with
threshold3InterFreq,
determines the
criteria for interfrequency coverage
HO (RSRP-based
A5 event)
-114 dBm / (31 for
microcells;
threshold3InterFre
q (Threshold th3 for
RSRP inter
frequency)
This parameter,
along with
threshold3aInterFre
q and
-116dBm / 26
26 for macrocells)
High values: delays
the handover
-140...-43 dBm, step
1 dBm
High values: delays
the handover
hysThreshold3Inter
Freq, determines
the criteria for interfrequency coverage
HO (RSRP-based
A5 event)
hysThreshold3Inte
rFreq (Related
hysteresis of
thresholds th3 and
th3a for RSRP)
This parameter
defines related
hysteresis of
handover margin for
coverage handover
of Inter-Frequency
Low values: allow
the UE to handover
earlier
0dB / 6
0...15 dB, step 0.5
dB
Low values:
introduces pingpong phenomenon
during HO operation
High values: Delays
the HO and
increases possibility
of losing the active
connection on the
serving cell
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LTE Intra and Inter Frequency Handover, Continued
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continued
Parameter
Name
Description
Default Values /
Nokia GPL
Values
Ranges and
steps
Impact
a5TimeToTriggerIn
terFreq (A5 time to
trigger inter
frequency)
This parameter
provides time for
which the specific
criteria for the inter
frequency
measurement event
256ms (7) / 40ms
Enum [0: 0ms, 1:
40ms, 2: 64ms, 3:
80ms, 4: 100ms, 5:
128ms, 6: 160ms, 7:
256ms, 8: 320ms, 9:
480ms, 10: 512ms,
Low values:
introduces pingpong phenomenon
during HO operation
11: 640ms, 12:
1024ms, 13:
1280ms, 14:
2560ms, 15:
5120ms]
increases possibility
of losing the active
connection on the
serving cell
Enum [0: 120ms, 1:
240ms, 2: 480ms, 3:
640ms, 4: 1024ms,
5: 2048ms, 6:
5120ms, 7:
10240ms, 8: 1min,
9: 6min, 10: 12min,
11: 30min, 12:
60min]
Increasing the
report interval will
increase the time to
make the handover,
decreasing will
impact the quality of
HO measurements
A5 must be met to
trigger a
measurement report
a5ReportIntervalIn
terFreq (A5 report
interval inter
frequency)
This parameter
defines the interval
with which
measurement
reports are
repeatedly sent if
the specific criteria
for the inter
frequency
measurement event
A5 is met.
240ms (1) / 240ms
High values: Delays
the HO and
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LTE Inter RAT Handover
Overview
This section depicts how to investigate the Inter RAT HO KPI and steps to improve the
degradation in KPI.
Anal
An
alys
ys is
The table below shows the reasons & optimal solutions for LTE Inter RAT HO in Preparation
phase.
Causes
Checks
Configuration Issue
Check configuration and Cell Relations
Target Cell Load Issue
Check load & admission control parameter
of legacy network
Hardware Issues
Check Alarms, Hardware, Target cell status
The table below shows the reasons & optimal solutions for LTE Inter RAT HO in Execution
phase.
Causes
Checks
Poor Coverage
Perform Physical optimization
Target Cell High UL Interference Issue
Reduce UL Interference
Wrong neighbor
Check Configuration & parameter of
Neighbor cell
Hardware Issues
Check Alarms, Hardware, Target cell status
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LTE Inter RAT Handover, Continued
An alys
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continued
The table below shows the parameter related to LTE Inter RAT Handover failure:
Parameter
Name
Description
Default Values /
Nokia GPL
Values
actRedirect
(Enable UE context
release with
redirect)
This parameter
enables the feature
UE context release
with redirect.
enabled (1) /
(Enabled for multiband sites ;
Disabled for singleband)
actHOtoWcdma
(Enable handover
from LTE to
WCDMA)
This
parameter
enables
the feature
handover from LTE
to WCDMA.
psHoAllowed (PS
handover allowed)
b2Threshold1Utra
(Threshold1 UTRA
for RSRP of serving
cell)
Ranges and
steps
Impact
Enum [0: disabled,
1: enabled]
BTS restart needed
for modification
0 / False
Boolean
[0: false, 1:
true]
Object
locking
required
for
modification
This parameter
controls whether PS
handover to the
related neighbor cell
is allowed.
allowed (0) (MINT)
Enum [0: allowed, 1:
forbidden]
Vendor specific
This parameter
provides the
threshold for RSRP
of serving cell. If
RSRP of serving
valueb2Threshold2
UtraRscp, then
-117 dBm(MINT
dBm(MINT))
-140...-43 dBm, step
1 dBm
Low values:
introduces pingpong phenomenon
during HO operation
handover is
triggered (B2 event)
High values: Delays
the HO and
increases possibility
of losing the active
connection on the
serving cell
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LTE Inter RAT Handover, Continued
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continued
Parameter
Name
b2Threshold2Utra
Rscp (Threshold2
RSCP for UTRA
neighbour cell)
Description
Default Values /
Nokia GPL
Values
Ranges and
steps
Impact
This parameter
provides the
threshold for UTRA
neighbour cell on
the current
frequency, such that
-105 dBm(MINT
dBm(MINT))
-120...-24 dBm, step
1 dBm
Low values:
introduces pingpong phenomenon
during HO operation
High values: Delays
the HO and
increases possibility
of losing the active
connection on the
serving cell
it is considered to
be good and
reported in the
measurement result
of B2 event.
b2TimeToTriggerU
traMeas (Time to
trigger UTRA
measurement
report)
This parameter
provides the
duration for which
the RSRP based
event B2 must be
valid
320 ms(8) (MINT)
hysB2ThresholdUt
ra (Related
hysteresis
thresholds B2Th1,
B2Th2 HO TDSCDMA)
This parameter
defines related
Hysteresis of
Handover Margin
for HO to TDSCDMA
2 dB(MINT)
This parameter is
used within the
entry and leave
condition of the B2
triggered reporting
condition
Enum [0: 0ms, 1:
40ms, 2: 64ms, 3:
80ms, 4: 100ms, 5:
128ms, 6: 160ms, 7:
256ms, 8: 320ms, 9:
480ms, 10: 512ms,
11: 640ms, 12:
1024ms, 13:
1280ms, 14:
2560ms, 15:
5120ms]
Low values:
introduces pingpong phenomenon
during HO operation
0...15 dB, step 0.5
dB
Low values:
introduces pingpong phenomenon
during HO operation
High values: Delays
the HO and
increases possibility
of losing the active
connection on the
serving cell
High values: Delays
the HO and
increases possibility
of losing the active
connection on the
serving cell
Continued on next page
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LTE Inter RAT Handover, Continued
An alys
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continued
Parameter
Name
tS1RelPrepG
(Supervision timer
for handover
preparation to GSM)
Description
Guard against
failure of the MME
to respond in
preparation phase
of S1 handover to
GSM
Default Values /
Nokia GPL
Values
1000ms / 2000
Ranges and
steps
50...5000 ms, step
50 ms
Impact
Lower Values: not
enough time during
SRVCC preparation
and vice versa
Timer
TS1RELOCprep_Int
erRAT is used to
guard against failure
of the MME to
respond preparation
phase of S1
handover to another
3GPP RAT. It is
started in the source
eNB when the
S1AP: HANDOVER
REQUIRED
message is sent to
the MME and is
stopped when the
S1AP: HANDOVER
COMMAND or
S1AP:
PREPARATION
FAILURE message
is received in
response. If the
timer expires the
handover is aborted
or cancelled.
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LTE Inter RAT Handover, Continued
An alys
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continued
Parameter
Name
tS1RelPrepU
(Supervision timer
for the preparation
HO WCDMA)
Description
Default Values /
Nokia GPL
Values
Guard against
failure of the MME
to respond in
preparation phase
of S1 handover to
another 3GPP RAT
2000ms / 2000
Timer tS1relprepIrat
is used to guard
against failure of the
MME to respond in
preparation phase
of S1 handover to
another 3GPP RAT.
It is started in the
source eNB when
the S1AP:
HANDOVER
REQUIRED
message is sent to
the MME and is
stopped when the
S1AP: HANDOVER
COMMAND or
S1AP:
PREPARATION
FAILURE message
is received in
response. If the
timer expires the
handover is aborted
or cancelled.
Ranges and
steps
50...5000 ms, step
50 ms
Impact
Lower Values: not
enough time during
SRVCC preparation
and vice versa
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fALU – fNokia eNB interworking
Overview
Ai rSc ale an d
bCEM eNB
interworking
Below are the classification of interworking in BBU Swap:
•
FSM4 to FSM4
•
bCEM to bCEM
•
FSM4 to bCEM
Listed below are some features which are used for interworking between AirScale & bCEM
eNBs.
Feature
Interworking
concerns
Proposed mitigation
Nokia
recommendation
X2 Setup / eNB
Configuration Update
Message size, given the
maximum number of
neighbors included by
bCEM eNB.
It is possible to reduce the
number of neighbors
included by fALU eNB by
requesting that only
real neighbors are sent.
This does not seem to be
enabled in the VzW
network currently.
Already performed
(passed)
X2 link lock/unlock
None
None
Already performed
(passed)
X2 Reset
None
None
Already performed
(passed)
X2 Error handling
None
None
No
Mobility (incl. RRE)
•
•
•
Re-establishment in
unprepared cell
between fALU and fNok
eNB will not work.
Both eNBs do not have
the same definition of
handover failures,
leading to different KPI
results.
fNok eNB does not
request direct data
forwarding during S1
HO, but supports it as
target.
•
•
•
None for reestablishment issue, a
software evolution is
needed to solve it.
•
•
Basic X2 and S1 HO:
already tested (passed)
Re-establishment: not
needed
None for mobility KPI
KPI
issue, as it would need
different counter
pegging (may be
possible to attenuate
the impact through
updating KPI
computation formulas)
None for direct data
forwarding issue.
Continued on next page
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fALU – fNokia eNB interworking, Continued
Ai rSc ale an d
bCEM eNB
interworking ,
continued
Feature
eUTRAN sharing
Interworking
concerns
•
•
fNok eNB does not
support different VLAN
on X2 interface (one
per sharing PLMN).
fNok eNB does not
Proposed mitigation
•
•
support automatic
PLMN-based
blacklisting.
Not sure it is a real
issue depending on
deployed configurations
in customer networks.
Manual blacklisting of
None
None
ANR
None
Can be disabled both in
fALU and fNok eNB
(assumption being that
topology will not change
during swap)
fNok eNB does not
include Neighboring
Information IE in X2
messages, while this is
used by fALU eNB to
detect PCI confusion.
It is needed to check
customer configurations,
and if PCI coordination is
acceptable with foreign
operators (fNok solution)
PCI used by foreign
operators on country
borders.
Dynamic X2
Auto PCI
Nokia
recommendation
•
•
VzW does not use autoPCI feature.
No
•
•
No if feature is
disabled.
It is needed to check if
customers are willing to
disable it.
Yes – lower priority (for
conflict detection)
Auto-PCI feature should
be disabled on fALU
eNB when enabled.
However,
will only
inhibit PCIthis
correction,
but not conflict
detection with alarms
Continued on next page
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fALU – fNokia eNB interworking, Continued
Ai rSc ale an d
bCEM eNB
interworking ,
continued
Feature
MRO (Mobility
Robustness Optimization)
Feature 128530
Interworking
concerns
•
•
fALU and fNokia
solutions do not peg
MRO counters in a
similar way.
Both solution
solutions
s do not
optimize exactly the
same mobility
parameters, and fALU
eNB has specific
behavior for VoLTE
calls.
•
RSI Optimization
•
•
Proposed mitigation
•
•
•
None so ffar,
ar,
recommendation being
however to keep MRO
enabled during swap.
Nokia
recommendation
Yes
VzW does not plan to
deploy EdenNet.
Vzw uses MRO selfoptimization in select
markets
fALU so
solution
lution h
has
as
distributed
implementation using
proprietary IE over X2,
while fNok has
centralized one
(EdenNet) that may not
support fALU eNBs.
fNok eNB does not
include PRACH
RSI optimization feature
should be disabled on
Configuration IE in X2
messages, while this is
used by fALU eNB for
RSI conflict detection
and correction.
fALU eNB when enabled.
•
•
No if feature is
disabled.
It is needed to check if
customers are willing to
disable it.
fNok solu
solution
tion uses
centralized
implementation
(EdenNet).
Continued on next page
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fALU – fNokia eNB interworking, Continued
Ai rSc ale an d
bCEM eNB
interworking ,
continued
Feature
Load balancing
Interworking
concerns
•
fALU and fNok eNB use
different algorithms for
selection of suitable
target cell for load
balancing, potentially
leading
mobility.to unexpected
•
eICIC
fALU eNB uses specific
X2 values to signal
start/continue offloading
and end offloading,
while theses values
would not be
considered by receiving
fNok eNB.
Proposed mitigation
•
•
Inter-frequency Load
equalization &
balancing (on fALU)
should be disabled
inter-eNB (is it enabled
Nokia
recommendation
•
•
No if feature is
disabled.
It is needed to check if
customers are willing to
disable it.
in customer networks?).
Intra-frequency load
balancing should be
disabled completely
ABS patterns computation
uses different algorithms
in fALU and fNok eNBs.
eICIC should be disabled
(is it possible when metro
cells are deployed, this
will impact KPI).
OTDOA
Possible
misalignment
PRS broadcast
in fALUof
and fNok eNB cells.
None
Yes
General sync alignment
Possible SFN and E2E
timing alignment issue
between fALU and fNok
eNB.
None
Yes
UL Comp
None as only intra-eNB
UL CoMP is supported in
fALU and fNok eNB.
None
No
•
•
No if feature is
disabled.
It is needed to check if
customers are willing to
disable it.
Continued on next page
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fALU – fNokia eNB interworking, Continued
Ai rSc ale an d
bCEM eNB
interworking ,
continued
Feature
Interference-aware UL
power control
Interworking
concerns
Not supported by fALU
eNB, so that these eNBs
will not control their UL
interference towards
neighbour eNBs, while
fNok eNB will.
Proposed mitigation
Should not be enabled in
fNok eNB during swap.
Nokia
recommendation
•
•
No if feature is
disabled.
It is needed to check if
customers are willing to
disable it.
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IEH 550, Section 005
October 11, 2017
Throughput
BBU Swap Validation & Troubleshooting for Verizon
Contents
Introduction..................................................................................................................... 2
Overview ..........................................................................................................
....................................................................................................................
.......... 2
Throughput KPI Information ........................................................................................ 2
Throughput KPI ..........................................................................................................
............................ .............................................................................. 3
Flow Chart .................................................................................................................. 4
Troubleshooting .............................................................................................................. 5
Overview .................................................................................................................... 5
Downlink Throughput .................................................................................................. 5
Uplink Throughput ....................................................................................................
......................................................................................... ........... 17
Latency ..................................................................................................................... 25
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Introduction
Overview
Throughput KPI
Information
This KPI represents how E-UTRAN impacts the service quality provided to the end user.
Below are the major factors that impacts throughput:
•
Mobility
•
Features
•
RF Quality
•
End Server
•
Core Network/ PDN Performa
Performance
nce
•
End to E
End
nd dimensioning
•
eNodeB setup
Root cause analysis for throughput KPIs can be done by following steps below:
Step
Action
1
Open current PNM BTS daily Report
2
Check DLPotTputMbps, ULBytesTTIULRLCT
ULBytesTTIULRLCTput
put and FSMKPIsSecondary tabs
for throughput issues
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Introduction, Continued
Throughput KPI
Uplink and Downlink User Throughput KPIs can be monitored with the help of the following
indicators:
Indicators
DL Potential Thput [Mbps]
Formula
(VOL_ORIG_TRANS_DL_SCH_TB)
(VOL_ORIG_TRANS_DL_SCH_TB) * 400 /
PRB_USED_PDSCH when
PRB_USED_PDSCH
PRB_USED_PDSCH
PRB_USED_PDS
CH > 50,000 per cell per
15min interval (PRB_USED_PDSCH only
includes PRBs for unicast data while
VOL_ORIG_TRANS_DL_SCH_TB
VOL_ORIG_TRA
NS_DL_SCH_TB includes
both unicast and broadcast data)
(M8012C0) * 400 / M8011C54
DL RLC Tput (Mbps)
8*(RLC_PDU_VOL_TRANSM
8*(RLC_PDU_VOL_TRANSMITTEDITTEDRRC_DL_VOL)/ACTIVE_TTI_DL
(M8012C18 -M8012C78)/M8012C90
DL Burst User Thput [Mbps]
((IP_TPUT_VO
((IP_TPUT_VOL_DL_QCI_6
L_DL_QCI_6 +
IP_TPUT_VOL_DL_QCI_7
IP_TPUT_VO
L_DL_QCI_7 +
IP_TPUT_VOL_DL_QCI_8
IP_TPUT_VO
L_DL_QCI_8 +
IP_TPUT_VOL_DL_QCI_9)
IP_TPUT_VO
L_DL_QCI_9) / 1000) /
(IP_TPUT_TIME_DL_QCI_6
(IP_TPUT_TIM
E_DL_QCI_6 +
IP_TPUT_TIME_DL_QCI_7
IP_TPUT_TIM
E_DL_QCI_7 +
IP_TPUT_TIME_DL_QCI_8
IP_TPUT_TIM
E_DL_QCI_8 +
IP_TPUT_TIME_DL_QCI_9)
UL Potential Thput [Mbps]
(VOL_ORIG_REC_UL_SCH_TB
(VOL_ORIG_REC_UL_SCH_TB +
VOL_RE_REC_UL_SCH_TB)
VOL_RE_REC_UL_SCH_T
B) * 400 /
PRB_USED_PUSCH
(M8012C3 + M8012C1) * 400 / M8011C50
UL RLC Tput (Mbps)
(RLC_PDU_VOL_RECEIV
(RLC_PDU_VOL_RECEIVEDEDRRC_UL_VOL)/ACTIVE_TTI_UL
(M8012C17 -M8012C77)/M8012C89
UL Burst User Thput [Mbps]
((IP_TPUT_VO
((IP_TPUT_VOL_UL_QCI_6
L_UL_QCI_6 +
IP_TPUT_VOL_UL_QCI_7
IP_TPUT_VO
L_UL_QCI_7 +
IP_TPUT_VOL_UL_QCI_8+
IP_TPUT_VOL_UL_QCI_9
IP_TPUT_VO
L_UL_QCI_9 )/1000)/
(IP_TPUT_TIME_UL_QCI_6 +
(IP_TPUT_TIME_UL_QCI_6
IP_TPUT_TIME_UL_QCI_7
+IP_TPUT_TIME_UL_QCI_8
+IP_TPUT_TIM
E_UL_QCI_8 +
IP_TPUT_TIME_UL_QCI_9)
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Introduction, Continued
Flow Chart
The flow chart shown below is to troubleshoot Throughput KPIs.
© Nokia 2017
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Troubleshooting
Overview
This section talks about how to investigate throughput KPI issues and steps to improve the
degradation in KPI. Parameter consistency checks and performance of other KPIs must be
checked before starting throughput troubleshooting. This will help to get us get a holistic
overview of performance to makes analysis simpler.
Troubleshooting throughput can be loosely categorized into:
Downlink
Throughput
•
Downlink Throughput
•
Uplink Throughput
•
Latency
This section covers the parameters to be tuned to improve downlink throughput and possible
causes for degradation.
The possible causes for downlink throughput degradation are:
•
Radio Causes
•
eNodeB Configuration
•
Hardware and Alarm IIssues
ssues
Table: Possible causes and mitigative actions to improve downlink throughput.
Causes
Transmission Mode
Poor coverage and SINR values
Checks
•
Check the number of Tx antenna used
•
Verify the transmission mo
mode
de used
•
Physical optimization
•
Check power related parameters
parameters
•
Check cell reselect
reselection
ion related parameters
•
Uplink RSSI
Check overshooting cells causing
interference
•
Check power related parameters
parameters
•
Reduce Uplink interference
•
•
Check for loose connect
connectors
ors and faulty
hardware
Check VS
VSWR
WR alarms
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Troubleshooting, Continued
Downlink
Throughput,
continued
Causes
Checks
Rank Indicators and Scheduling Algorithm
•
•
Other Important counters
Check algorithm for Proportional Fair for
High/Medium/Low
•
Check number of connected users
•
PRB and PDCCH utiliz
utilization
ation
•
•
•
Important features
High samples should be of rank 4
Traffic offload to less utilized
utilized neighboring
cells
Reduce control channel resources (Check
PDCCH utilization before that)
Reduce Inactivity ttimer
imer value so that
inactive users can be released early
Important features include the following:
•
256 QAM
•
MIMO modes
•
Carrier Aggregation
•
Downlink MCS
RF Bandwidth/ Power Control/ MAC and
RLC Configuration
Verify Parameter Settings
Cell Availiblity
Check relevant Alarms
Hardware Issues
Check Hardware issue, Alarms, Improper
cabling and connector issues
Table: Parameters related to downlink throughput
Parameter
Name
inactivityTimer
Description
Default Value/
Verizon GPL
Ranges and
Steps
Impact
The parameter
defines the time for
the indication of the
UE inactivity in both
DL and UL
directions.
30s/ 5
5...65535 s, step 1 s
Long values of RRC
inactivityTimer may
result in high
number of
connected users
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Troubleshooting, Continued
Downlink
Throughput,
continued
Parameter
Name
actLdPdcch
(Activate load
adaptive PDCCH)
Description
Activate or deactivate the
load adaptive number of
PDCCH symbols in a cell.
The actual OFDM symbol
amount used for PDCCH in a
TTI is selected from values
between the minimum
reasonable number of
symbols for the selected DL
bandwidth and maximum
allowed number of PDCCH
symbols (maxNrSymPdcch).
Default
Value/
Verizon GPL
Ranges and
Steps
Impact
0/1
0 (false), 1 (true)
It is highly
recommended to
activate the feature
to maximize the
PDSCH throughput
and minimize the
risk of PDCCH
blocking.
NOTE: for FDD cell
If the bandwidth is set to '3
MHz'. it is recommended to
set the parameter to 'false'.
NOTE: for TDD cell
Not every sub-frame need
adaptive PDCCH symbol
adjustment because not
every sub-frame has
PDSCH.
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Troubleshooting, Continued
Downlink
Throughput,
continued
Parameter
Name
actOlLaPdcch
(Activate outer loop
link adaptation)
Description
Activate / Deactivate Outer
Outer
Loop Link Adaptation for
PDCCH
Default
Value/
Verizon GPL
Ranges and
Steps
Impact
1/1
0 (false), 1 (true)
It is highly
recommended to
enable the feature
1/1
0 (false), 1 (true)
It is highly
recommended to
enable the feature
O&M switch for activating /
deactivating an additional
Outer Loop Link Adaptation
for PDCCH. This additional
PDCCH Outer Loop Link
Adaptation controls the
PDCCH link adaptation CQI
shift such that the PDCCH
and HARQ Response Target
BLER is achieved when the
OLQC Target BLER is
achieved.
If PDCCH OLLA is
additionally based on
PUSCH TX/DTX detection,
PDCCH Outer Loop Link
Adaptation controls the
PDCCH link adaptation CQI
shift such that the PDCCH
target BLER and PUSCH
missed detection is achieved.
enableAmcPdcch
(Enable AMC for
PDCCH link
adaptation)
The parameter defines the
switch for enable/disable
Channel Quality Indicator
(CQI) based Adaptive
Modulation and Coding
(AMC) for PDCCH link
adaptation. If the parameter
is disabled, default
aggregation is used implicitly.
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Troubleshooting, Continued
Downlink
Throughput,
continued
Parameter
Name
Description
Default
Value/
Verizon GPL
Ranges and
Steps
The parameter defines the
switch for enabling / disabling
power control on PDCCH. If
the parameter is disabled, a
flat downlink Power Spectral
Density (PSD) is used.
1/1
0 (false), 1 (true)
pdcchAggPaging
(PDCCH
aggregation for
paging)
PDCCH aggregation for
paging defines how many
CCEs shall be used for one
PDCCH.
4/4
4...8, step 4
This value should fit
for network settings
(it is tradeoff
between UE
reachability and
PDCCH resources
consumption).
pdcchAggMsg4
(PDCCH
The parameter defines the
reserved number of Control
8/8
4...8, step 4
pdcchAggMsg4
agrregation level
aggregation for RA
msg4)
Channel Elements (CCEs)
for dedicated RandomAccess Message 4
assignment on PDCCH.
pdcchAggRaresp
(PDCCH
aggregation for
random access
response message)
PDCCH aggregation for
Random Access response
message defines how many
CCEs are used for one
PDCCH.
enablePcPdcch
(Enable PDCCH
power control)
Impact
It is highly
recommended to
enable the PDCCH
PC at all times.
If the feature is
disabled, there is no
power
relocation/boosting/r
eduction, which
leads to increased
blocking.
should be in line
with the Code Rate
for PDSCH.
4/4
4...8, step 4
Higher value can
result in more
control messages in
the same PDCCH.
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Troubleshooting, Continued
Downlink
Throughput,
continued
Parameter
Name
pdcchAlpha
(PDCCH
allocation limit)
Description
The parameter defines the limit for
PDCCH allocations. PDCCH UEspecific search space capacity is
Default
Value/
Verizon
GPL
Ranges
and
Steps
8/8
0.5...2,
step 0.05
multiplied by this factor.
Impact
Low values: the
scheduling probability
increases, but overall
PDCCH capacity
decreases which lead to
smaller number of UE's
allocated in PDCCH, and
higher latency for all the
UE's in general
NOTE: for FDD cells
The parameter will be ignored if
dlChBw is set to '1.4 MHz'.
If dlChBw equals '3 MHz' it is
recommended to set the parameter to
'1.0'.
Medium values: PDCCH
will be loaded close to
100% with acceptable
level of blocking
High values: PDCCH
capacity is virtually
increased, therefore
PDCCH scheduler will
want to allocate more
UE's in PDCCH user
search space. This can
drastically increase the
PDCCH blocking and
latency.
pdcchAggSib
(PDCCH
aggregation for
secondary
system
information)
PDCCH aggregation for secondary
system information defines how many
CCEs should be used for one
PDCCH.
4/4
4...8,
step 4
Higher value improves
robustness during poor
RF conditions.
pdcchAggPre
amb (PDCCH
aggregation
level for
preamble
assignments)
The parameter defines the
aggregation level by means of control
channel elements (CCEs) for
preamble assignments on PDCCH.
The preamble assignment is message
0 sent during the non-contention
4/4
4...8,
step 4
Higher value improves
robustness during poor
RF conditions.
based
Random
AccessUL
procedure
if
DL data
arrives during
out-of-sync.
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Troubleshooting, Continued
Downlink
Throughput,
continued
Parameter
Name
Description
Default
Value/
Verizon
GPL
Ranges
and
Steps
Impact
0.01/1
0.1...3 %,
step 0.1 %
Default value of 1%
BLER
pdcchHarqTargetB
ler (PDCCH and
HARQ response
BLER target for PDCCH outer loop link
adaptation in percent.
Defines target Block Error Ratio (BLER)
Increasing this
target BLER)
of PDCCH and UL HARQ response for
initial downlink transmissions for
PDCCH Outer Loop Link Adaptation in
percent.
value result in link
adaption to be less
aggressive
If PDCCH OLLA is additionally based
on PUSCH TX/DTX detection, the
parameter defines target Block Error
Ratio (BLER) of PDCCH and PUSCH
missed detection for initial uplink
transmissions for PDCCH Outer Loop
Link Adaptation in percent.
pdcchCqiShift
(PDCCH LA CQI
shift)
The fine-tuning parameter for
adjustment of measured and averaged
CQI towards lower or higher
aggregation in PDCCH Link Adaptation.
-5/ 0, -2,
-5
-10...10,
step 0.1
The parameter gives the initial starting
point for PDCCH shift dynamic control
in case actOlLaPdcch is true.
The configured PDCCH CQI shift value
is automatically adjusted for control
channels boosting in need basis.
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Troubleshooting, Continued
Downlink
Throughput,
continued
Parameter
Name
Description
Default
Value/
Verizon
GPL
Ranges
and Steps
dlChBw
(Downlink
channel
Downlink channel bandwidth defines the DL
bandwidth for the eNodeB transmission in a
cell, and also defines the number of available
10 MHz
(100)/
5MHz (50)
14: 1.4 MHz
bandwidth)
Physical
Resource
Blocks.
The downlink
channel
bandwidth mapping to
number of physical eNB will dynamically
decide dependent on the current and newly
required DSP deployment if eNB restart or
dropping of all cells is needed.
Following configuration rules need to be
considered:
FSMD:
maximum downlink channel bandwidth is 10
MHz if more than 2 cells are configured.
FSME:
maximum downlink channel bandwidth is 10
MHz if more than 3 cells are configured.
Cell bandwidth 1.4 MHz or 3 MHz:
- is not supported with 4 TX/RX configuration
- is not supported with WCDMA RF sharing
and 10
MHz (100)
100: 10 MHz
Impact
30: 3 MHz
50: 5 MHz
150: 15 MHz
200: 20 MHz
Cell
bandwidth
1.4 with
MHz:FSMF/FBBC
- is only
supported
- is not supported with GSM RF sharing
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Troubleshooting, Continued
Downlink
Throughput,
continued
Parameter
Name
Description
Default
Value/
Verizon
GPL
maxNrSymPdcch
(Maximum number
of OFDM symbols
The parameter defines how many OFDM
symbols can be used for PDCCH channel
transmission. eNB selects based on
3/3
for PDCCH)
usage the actual value for each TTI,
which and value is signaled to the UEs in
PCFICH.
blocking & higher
PDSCH
throughput
If dlChBw equals '3 MHz' it is
recommended to set the parameter to '3'.
Higher setting:
lower probability
of PDCCH
blocking & lower
PDSCH
throughput
iniMcsDl (Initial
MCS in downlink)
The parameter defines an initial
Modulation and Coding Scheme (MCS)
to be used on PDSCH for other use than
BCCH, PCH or random-access
messages.
Ranges
and Steps
1...4, step 1
4/4
0...28, step 1
5/8
1...16, step 1
Impact
Lower setting:
higher probability
of PDCCH
iniMcsDl is applicable for PDSCH LA only
if both dlOlqcEnable and dlamcEnable
are set to 'false' where it determines the
static target code rate for PDSCH user
data transmissions. Otherwise, UE
reported CQI or default CQI
(dlamcCqiDef) with or without OLQC
correction determines the target code
rate.
harqMaxTrDl
(Maximum number
of HARQ
transmission in
DL)
Indicates the maximum number of HARQ
transmissions in DL that is configured for
each UE at initial access to a specific
cell.
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Troubleshooting, Continued
Downlink
Throughput,
continued
Parameter
Name
dlMimoMode
(Downlink MIMO
mode)
Description
Default
Value/
Verizon
GPL
Cell-specific downlink transmission/MIMO
mode
TXDiv (10)/
Closed
Loop Mimo
Listed below are DL MIMO mode for
each physical channel:
SingleTx
•
•
TXDiv
•
4-way TXDiv
‘
’
NOTE: 4-way TXDiv must not be
NOTE:
configured in dual band configurations.
•
Dynamic Open Loop M
MIMO:
IMO: If
dlMimoMode is set to Dynamic Open
Loop MIMO', mimoOlCqiThD,
mimoOlCqiThU, mimoOlRiThD,
mimoOlRiThU are relevant. Default
values will be used if no dedicated
values are configured.
‘
•
•
•
(40)
Ranges
and Steps
Impact
0: SingleTX
10: TXDiv
11: 4-way
TXDiv
30: Dynamic
Open Loop
MIMO
40: Closed
Loop Mimo
41: Closed
Loop MIMO
(4x2)
43: Closed
Loop MIMO
(4x4)
Closed Loop M
MIMO:
IMO: Dynamic Closed
Loop MIMO
Closed Loop M
MIMO
IMO (4x2): Fast
Adaptive Closed Loop MIMO4x2
MIMO4x2
Closed Loop M
MIMO
IMO (4x4): Fast
Adaptive Closed Loop MIMO4x4
MIMO4x4
SRB1(DCCH) and RBs(DTCH) on
PDSCH are transmitted using either
Single Stream Downlink Transmit
Diversity or Single or Dual Stream MIMO
with Closed Loop spatial multiplexing
depending on radio conditions and UE
category; SRB0(CCCH), BCCH and
PCCH on PDSCH and all other physical
channels are transmitted using Single
Stream Downlink Transmit Diversity
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Troubleshooting, Continued
Downlink
Throughput,
continued
Parameter
Name
Description
Default
Value/
Verizon
GPL
mimoClCqiThD
(CQI threshold for
fallback to CL
CQI Threshold for fallback to closed loop
MIMO single codeword transmission (in
CQI) in case of activated 'Dynamic MIMO
7/7
0...16, step
0.1
MIMO 1 CW
mode)
Switch' (i.e. actFastMimoSwitch is set to
'false'). Not applicable if
actFastMimoSwitch set to 'true'.
mimoClRiThD
(Rank threshold
for fallback to CL
MIMO 1 CW
mode)
Rank Threshold for fallback to closed
loop MIMO single codeword transmission
in case of activated 'Dynamic MIMO
Switch' (i.e. actFastMimoSwitch is set to
'false'). Not applicable if
actFastMimoSwitch set to 'true'.
1.4/1.4
1...2, step
0.05
mimoOlCqiThD
(CQI threshold for
fallback to MIMO
diversity)
CQI threshold for fallback to Open Loop
MIMO diversity (in CQI).
7/7
0...16, step
0.1
mimoOlRiThD
(Rank threshold
Rank threshold for fallback to Open Loop
MIMO diversity.
1.4/1.4
Ranges
and Steps
Impact
1...2, step
0.05
for fallback to
MIMO diversity)
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Troubleshooting, Continued
Downlink
Throughput,
continued
Parameter
Name
Description
mimoClCqiThU
(CQI threshold for
activation of CL
CQI Threshold for activation of closed
loop MIMO dual codeword transmission
(in CQI) in case of activated 'Dynamic
MIMO 2 CW
mode)
MIMO Switch' (i.e. actFastMimoSwitch is
set to 'false'). Not applicable if
actFastMimoSwitch set to 'true'.
mimoClRiThU
(Rank threshold
for activation of CL
MIMO 2 CW
mode)
Rank Threshold for activation of closed
loop MIMO dual codeword transmission
in case of activated 'Dynamic MIMO
Switch' (i.e. actFastMimoSwitch is set to
'false'). Not applicable if
actFastMimoSwitch set to 'true'.
mimoOlCqiThU
(CQI threshold for
activation of OL
MIMO SM)
CQI threshold for activation of Open Loop
MIMO Spatial Multiplexing (in CQI).
mimoOlRiThU
(Rank threshold
for activation of OL
MIMO SM)
Rank threshold for activation of Open
Loop MIMO Spatial Multiplexing.
Default
Value/
Verizon
GPL
8/8
Ranges
and Steps
0...16, step
0.1
Impact
Increase in value
with raise the CQI
threshold for
MIMO CL for 2
code words. This
could reduce
throughput in
good channel
conditions
1.6/1.6
1...2, step
0.05
Increase in value
with raise the RI
threshold for
MIMO CL for 2
code words. This
could reduce
throughput in
good channel
conditions
8/8
0...16, step
0.1
1.6/1.6
1...2, step
0.05
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Troubleshooting, Continued
Uplink
Throughput
This section covers the parameters to be tuned to improve uplink throughput and possible
causes for degradation.
Possible causes of eNodeB configuration, Hardware and Alarms have already discussed
d iscussed in
Downlink throughput section. Below are the possible causes other than discussed in downlink
throughput.
Table: Possible Causes
Causes
Checks
Power Headroom
•
Tune nominal P
PUSCH
USCH and PUCCH
PUCCH power
Scheduling Algorithm/ Important Features
•
Mixed FD
•
16 QAM and 64 QA
QAM
M High MCS
•
MIMO
•
UL MCS
Important Counters
Poor coverage and SINR values
•
•
Load balancing
•
Physical optimization
•
Check power related parameters
parameters
•
Check cell reselect
reselection
ion related parameters
•
Uplink RSSI
High PRB Uti
Utilization
lization would im
impact
pact the
uplink throughput
Check overshooting cells causing
interference
•
Check power related parameters
parameters
•
Reduce Uplink interference
•
•
Check for loose connect
connectors
ors and faulty
hardware
Check VS
VSWR
WR alarms
RF Bandwidth/ Power Control/ MAC and
RLC Configuration
Verify Parameter Settings
Cell Availiblity
Check relevant Alarms
Hardware Issues
Check Hardware issue, Alarms, Improper
cabling and connector issues
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Troubleshooting, Continued
Uplink
Throughput,
continued
Table: Parameters to improve Uplink Throughput
Parameter
Name
Description
Default
Value/
Verizon
GPL
p0NomPucch
(Nominal power for
UE PUCCH TX
This parameter defines the cell specific
nominal power to be used for PUCCH
power calculation in UE uplink power
-116 dBm/ 114 dBm
power calculation)
control equation (P2), for controlling
mean received SNR for control data.
dFpucchF1
(DeltaF PUCCH
format 1)
The parameter defines the transport
format dependent offset in power
control for PUCCH format 1.
Ranges
and
Steps
-127...-96
dBm, step
1 dBm
Impact
Aggressive
parameter setting
can impact the
QCI drop ratio
0 (1)/ 0(1)
0: -2
1: 0
2: 2
Increase value in
case of poor
robustness of
PUCCH format 1.
Negative value to
be considered in
the case of high
PUCCH
interference
dFpucchF1b
(DeltaF PUCCH
format 1b)
The parameter defines the transport
format dependent offset in power
control for PUCCH format 1b.
1(0)/ 3(1)
0: 1
1: 3
2: 5
The increase of
this parameter
value shall be
considered in
case
of poorof
robustness
PUCCH format 1.
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Troubleshooting, Continued
Uplink
Throughput,
continued
Parameter
Name
dFpucchF2
(DeltaF PUCCH
format 2)
Description
The parameter defines the transport
format dependent offset in power
control for PUCCH format 2.
Default
Value/
Verizon
GPL
0(1)/ 0(1)
Ranges
and
Steps
0: -2
1: 0
2: 1
3: 2
dFpucchF2a
(DeltaF PUCCH
format 2a)
The parameter defines the transport
format dependent offset in power
control for PUCCH format 2a.
0(1)/ 0(1)
0: -2
1: 0
2: 2
Impact
Increase value in
case of poor
robustness of
PUCCH format 2.
Negative value to
be considered in
the case of high
PUCCH
interference
Increase value in
case of poor
robustness of
PUCCH format
2a.
Negative value to
be considered in
the case of high
PUCCH
interference
Continued on next page
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Troubleshooting, Continued
Uplink
Throughput,
continued
Parameter
Name
dFpucchF2b
(DeltaF PUCCH
format 2b)
Description
The parameter defines the transport
format dependent offset in power
control for PUCCH format 2b.
Default
Value/
Verizon
GPL
0(1)/ 0(1)
Ranges
and
Steps
0: -2
Impact
Increase value in
case of poor
robustness of
1: 0
2: 2
PUCCH format
2b.
Negative value to
be considered in
the case of high
PUCCH
interference
ulpcAlpha (Alpha)
Used as a fractional path loss
compensation factor: alpha. It controls
received SNR variance (fairness) for
user data and sounding reference
symbol.
Alpha can't control the fractional
fractional
pathloss compensation for the sounding
in the case PUSCH masking is
activated (actPuschMask equal to 'true')
as SRS is disabled in this case.
Recommended default values are
- for FDD cell: 'alpha 1'
- for TDD cell: 'alpha 0.8'.
alpha 1 (7)/
alpha 1 (7)
0: alpha 0
1: alpha
0.4
Low load
scenario: alpha =
1
Medium/high load
scenario: alpha <
1
2: alpha
0.5
3: alpha
0.6
4: alpha
0.7
5: alpha
0.8
6: alpha
0.9
7: alpha 1
Continued on next page
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Troubleshooting, Continued
Uplink
Throughput,
continued
Parameter
Name
ulpcAlpha (Alpha)
Description
Used as a fractional path loss
compensation factor: alpha. It
controls received SNR variance
Default
Value/
Verizon
GPL
alpha 1 (7)/
alpha 1 (7)
Ranges and
Steps
0: alpha 0
1: alpha 0.4
2: alpha 0.5
(fairness) for user data and
sounding reference symbol.
3: alpha 0.6
4: alpha 0.7
Alpha can't control the fractional
fractional
pathloss compensation for the
sounding in the case PUSCH
masking is activated (actPuschMask
equal to 'true') as SRS is disabled in
this case.
Impact
Low load
scenario: alpha =
1
Medium/high load
scenario: alpha <
1
5: alpha 0.8
6: alpha 0.9
7: alpha 1
Recommended default values are
- for FDD cell: 'alpha 1'
- for TDD cell: 'alpha 0.8'.
deltaTfEnabled
(Enabled TB size
impact to UE
PUSCH power
Enabling/disabling of the transport
format dependent offset on a per
UE basis. If this parameter is "true",
PUSCH power calculation in UE
calculation)
uplink power control equation (P1)
takes the Transport Block size in
account during the power
calculation.
0 (false)/ 0
(false)
0 (false), 1
(true)
Should be
switched on, only
for special cases,
e.g. when UL
AMC is disabled,
and there s no
other way to
perform link
adaptation
’
Continued on next page
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Troubleshooting, Continued
Uplink
Throughput,
continued
Parameter
Name
actUlpcMethod
(Method for UL
power control)
Description
Selects a working mode for UL
power control. Offers various
combinations between openloop and closed-loop control for
PUCCH and PUSCH/SRS
power.
Default
Value/
Verizon GPL
Ranges and
Steps
PuschOLPucc
hOL (0)/
PuschCLPucc
hCL (3)
0: PuschOLPucchOL
Impact
1: PuschOLPucchCL
2: PuschCLPucchOL
3: PuschCLPucchCL
4:
PuschCLSrsPucchOL
5:
PuschCLSrsPucchCL
6: PuschIAwPucchOL
7: PuschIAwPucchCL
p0NomPusch
(Nominal power
for UE PUSCH
or NPUSCH TX
power
calculation)
This parameter defines the cell
specific nominal power for the
PUSCH or NPUSCH. Used for
P0_PUSCH calculation in UE
uplink power control equation
(P1) for controlling the mean
received SNR for user data
during (re)transmission
corresponding to a received
-80 dBm / -106
dBm
-126...24 dBm, step 1
dBm
Decreasing the
Power allows
maximum
users to
transmit
PDCCH with DCI format 0
associated with a new packet
transmission. This parameter is
used to control mean received
SNR for user data.
Continued on next page
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Troubleshooting, Continued
Uplink
Throughput,
continued
Parameter
Name
actModulationS
chemeUL
(Activate
modulation
scheme UL)
Description
The parameter selects the
highest order modulation
scheme which is supported in
the cell for UL transmissions.
Default
Value/
Verizon GPL
QPSK (0)/
16QAMHighM
CS (2)
Ranges and
Steps
0: QPSK
1: 16QAM
2: 16QAMHighMCS
Impact
Increasing the
value will
provide higher
throughput
3: 64QAM
Depending
on the settingthe
of
actModulationSchemeUl
supported MCS range is
determined for the UEs in the
cell.
•
•
•
•
4:
64QAMand16QAMHi
ghMCS
QPSK: supported MCS range
is from MCS0 to MCS10 for all
UEs
16QAM: supported MCS
range is from MCS0 to
MCS20 for all UEs
16QAMHighMCS: supported
MCS range is from MCS0 to
MCS24 for all UEs
64QAM: supported MCS
range is from MCS0 to
MCS28 for UEs with 64QAM
capability and from MCS0 to
MCS20 for UEs without
64QAM capability
•
64QAMand16QAMHighMCS:
supported MCS range is from
MCS0 to MCS28 for UEs with
64QAM capability and from
MCS0 to MCS24 for UEs
without 64QAM capability.
Continued on next page
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Troubleshooting, Continued
Uplink
Throughput,
continued
Parameter
Name
actUlLnkAdp
(Activate uplink
link adaptation)
Description
Default
Value/
Verizon GPL
Activates Uplink Link Adaptation
Adaptation
and defines Link Adaptation
mode
eUlLa (5)/-
‘
Ranges and
Steps
Impact
0: off
4: slowAmcOllaATB
s lowAmcOllaATB
5: eUlLa
’
When set to off no Uplink link
6: fUlLa
Adaptation function is
is active at
all.
‘
’
When set to eUlLa the
extended Uplink Link Adaptation
function is activated.
‘
’
When set to fUlLa the new Fast
Uplink Link Adaptation function
is activated.
The other choice
slowAmcOllaATB allows to set
to active all the 3 old
components of the UL LA
function as it was up to RL20.
‘
iniMcsUl (Initial
MCS in uplink)
’
The parameter defines an initial
Modulation and Coding Scheme
5/1
0...28, step 1
Higher values
can lead to
(MCS) to be used on PUSCH for
other use than random access
message 3.
ulsSchedMetho
d (Scheduling
method of the
UL scheduler)
Defines the scheduling method
which shall be applied in the cell
for the UL branch.
Selects the method for the
scheduling of the UEs in UL.
lower HO
success rate.
channel
unaware (0)
(MINT)
0: channel unaware
1: channel aware
2: interference aware
Continued on next page
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Troubleshooting, Continued
Latency
This section covers the parameters and counters for latency.
The following counters depict the delay for non GBR:
•
Average Burst Initial Scheduler Delay = PDCP_RE
PDCP_RET_DL_DEL_MEAN_Q
T_DL_DEL_MEAN_QCI_X,
CI_X, where X can
be 6,7,8,9
M8001C310...313
•
PDCP_PDU_Delay_PerLstTT
PDCP_PDU_Delay_PerLstTTI_V1
I_V1 (ms) = ∑PDCP_RET_DL_DEL_M
PDCP_RET_DL_DEL_MEAN_QCI_X
EAN_QCI_X /
∑PDCP_SDU_DL_QCI_X
PDCP_SDU_DL_QCI_X,, where X can be 6
6,7,8,9
,7,8,9
NOTE:: High value of DL latency(>9ms) would impact DL throughput
NOTE
Table: Parameters to improve Latency
Parameter
Name
ilReacTimerUl
(Uplink improved
latency reaction
timer)
Description
Default
Value/Verizon
GPL
Ranges
and Steps
Improved latency reaction timer
in uplink defines the time in
which the UE must send useful
data after either the initial
dummy grant or a previous
reception of useful data. If the
timer expires the, UE will not get
dummy grant anymore.
0ms/ 0ms
0...2000 ms,
step 5 ms
Impact
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IEH 550, Section 006
October 11, 2017
VoLTE
BBU Swap Validation & Troubleshooting for Verizon
Contents
Introduction..................................................................................................................... 3
Overview ..........................................................................................................
....................................................................................................................
.......... 3
Network Architecture ..................................................................................................
........................... ....................................................................... 3
VolTE Call Flow .............................................................................................................. 4
Call Flow - Initial Registration ..................................................................................... 4
Call Flow – Registration .............................................................................................. 4
Call Flow – UE to UE................................................................................................... 6
High Level End to End Call Flow................................................................................. 8
VoLTE Voice Quality ......................................................................................................
.................................... .................................................................. 9
Overview .................................................................................................................... 9
Voice Quality Over a VoLTE Call ................................................................................ 9
MOS (Mean Opinion Score)........................................................................................ 9
Jitter ...........................................................................................................................
................................................................................... ........................................ 9
Packet Loss ................................................................................................................ 9
VoLTE Accessibility ...................................................................................................... 10
Overview .................................................................................................................. 10
Flow Chart ................................................................................................................ 10
VoLTE Accessibility Failures......................................................................................... 11
Overview .................................................................................................................. 11
Attach Failures.......................................................................................................... 11
Authentication Failures ............................................................................................. 11
Default Bearer Setup Failures ................................................................................... 11
IMS Registration Failures.......................................................................................... 12
Failure due to Non-Establishment of QCI 1 ............................................................... 12
Failure due to Non-Establishment of QCI 5 ............................................................... 12
Failure Due to Handover in Progress ........................................................................ 12
X2 and TAU Collision ................................................................................................ 12
VoLTE Mobility ............................................................................................................. 13
Overview .................................................................................................................. 13
Flowchart .................................................................................................................. 13
VoLTE Mobility Failures ................................................................................................ 14
Overview .................................................................................................................. 14
HO Failures .............................................................................................................. 14
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HO Execution Failure................................................................................................ 14
Swapped Sectors ...............................................................
.....................................................................................................
...................................... 14
VoLTE Mobility Parameters .......................................................................................... 15
Overview .................................................................................................................. 15
VoLTE Retainability ...................................................................................................... 20
Overview .................................................................................................................. 20
Retainability KPI Information..................................................................................... 20
Flow Chart ................................................................................................................ 21
VoLTE Retainability Issues ........................................................................................... 22
Overview .................................................................................................................. 22
Duplicated S1 Connection ........................................................................................ 22
Physical Layer Failure T310 & T311 ......................................................................... 23
RLF detected by UE(LTE1569)................................................................................. 23
RLF detected by eNB (LTE2206) .............................................................................. 24
Radio Conditions ...................................................................................................... 24
VoLTE Retainability Parameters ................................................................................... 26
Overview .................................................................................................................. 26
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Introduction
Overview
VoLTE stands for voice over LTE, which is an all IP multimedia subsystem (IMS). With
additional new radio access features to ensure low latency, improved error correction in fringe
areas and other features that guarantee voice services
se rvices as good as or better than any we’ve
had.
4G LTE provides seamless IP connectivity between the subscribers UE and the packet data
networks(PDNs) that are delivered through the IP multimedia subsystem(IMS).
When a subscriber leaves LTE
L TE coverage:
•
•
Voice would normally drop because most circuit switched networks
networks do not support VoIP, the
call would have to convert to circuit switched
SRVCC
The important goal of VoLTE is to deliver ‘carrier grade’ voice services that are perceived by
subscribers to be as good as, if not better than legacy circuit switched voice services. This
concept differentiates VoLTE from other VoIP services. Deploying IMS and SIP provide VoIP
services in LTE network, but VoLTE raises the bar
b ar to provide “carrier-grade” voice services
that is the vital objective of LTE networks and operators.
Network
Ar ch it ect ur e
Below pictures shows the complete network architecture of VoLTE including the core network.
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VolTE Call Flow
Call
Call Flow Initial
Registration
Below points summarize the call flow using SIP signalling procedure initial registration.
•
•
•
•
Initial registration procedure consists of UE sending an unprotected REGISTER
REGISTER request to
S-CSCF (via P-CSCF)
UE can register a public user identity with any of its contact addresses at any time after it
has acquired an IP address, discovered a P-CSCF, and established an IP-CAN bearer that
can be used for SIP signalling
UE shall only initiate a new registration procedure when it has received a final response from
the registrar for the ongoing registration, or the previous REGISTER request has timed out
Authentication is performed during initial regi
registration.
stration. S-CSCF acquires user authentication
information from HSS
•
UE will receive a 401 (Unauth
(Unauthorized)
orized) response to the REGI
REGISTER
STER request
•
UE calculates the response and sends it to S-CSCF in REGIS
REGISTER
TER message
S-CSCF downloads and stores service control information from HSS and notifies to the UE
about completed registration
Call
Call Flow –
Registration
Below points summarize the call flow registration:
•
UE Attaches to the network, the PG
PGW
W assigns IP address and identifies P-CSCF to the
terminal.
•
Terminal sets the IMEI and IM
IMS
S communication identifier ICSI
ICSI value
•
UE sends Registration Request to S-CSCF (via P-CSCF) in RE
REGISTER
GISTER message
•
S-CSCF performs registrat
registration
ion procedures with HSS and acquires
acquires user authentication
information
•
S-CSCF sends UE a challe
challenge
nge in 401 Unauthorized messag
message
e
•
UE calculates the response and sends it to S-CSCF in REGIS
REGISTER
TER message
•
•
After the authenticat
authentication
ion has succeeded the S-CSCF downloads and stores service control
information from HSS
S-CSCF notifies the terminal about complet
completed
ed registration
Continued on next page
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VolTE Call Flow, Continued
Call
Call Flow –
Registration ,
continued
Below diagram summarizes the call flow registration from the points mentioned above:
Continued on next page
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VolTE Call Flow, Continued
Call
Call Flow – UE
to UE
Below points explain the process of VoLTE call from between two UEs:
•
•
•
•
•
•
•
•
•
MO UE generates an INVITE request, which is sent to the IIMS
MS
The P-CSCF acknowledges the INVITE tto
o the MO UE with "100 Trying” message indicating
that the call setup is in progress
The SIP method OPTIO
OPTIONS
NS allows a IMS to query another UA or a proxy server as to its
capabilities. This allows a client to discover information about the supported methods,
content types, extensions, codecs, etc
At MT UE the INVITE message contains: Session Description Protocol (SDP) paramet
parameters:
ers:
declaration for using precondition, type of media, codec to use and the protocol for
transporting the media
When precondition mechanism iis
s supported P-CSCF would send 183 Session Progress to
originating UE which then compares the terminating UE capabilities with its own and
determines the codec to be used
Originating UE notifies the terminating UE using PRACK the selected codec. OK 200 is
received from terminating UE. EPS Bearer Activation follows for both UEs
UPDATE message contains an updated current status attribute
attribute for this particular media
stream
Both terminals confirm the setup of bearer with QoS according
according to UPDATE & 200 OK
message, terminating UE start ringing
Once both UEs receive 200 OK, they ACK it and the SIP session
session is established - voice
communication starts
•
MT or MO can release tthe
he voice communication by sendi
sending
ng BYE message
•
This is the acknowledge message to BYE from ter
terminating
minating UE
Continued on next page
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VolTE Call Flow, Continued
Call Flow – UE
to UE, continued
Below diagram summarizes the call flow from the points mentioned above:
Continued on next page
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VolTE Call Flow, Continued
High Level End
to End Call
Flow
The steps listed below depicts the complete end to end VoLTE call flow:
1. Turn
Turn the phone on
2. Attach
−
Primary Default Bearer attach (IMS APN)
−
SIP REGISTER
−
Secondary Default Bearer attach (DATA APN)
3. Making call
−
SIP INVITE
−
Dedicated Bearer activation
−
Start conversation
4. Call Release
−
−
SIP BYE
Dedicated Bearer deactivation
Below diagram depicts the points listed above:
© Nokia 2017
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VoLTE Voice Quality
Overview
Voice Quality
Over a VoLTE
Call
MOS (Mean
Opinion Scor e)
Jitter
The parameters related to VoLTE are mainly focused on the voice quality in which the RF
quality plays an important role. VoLTE requires more keen metrics than other packet
packe t switching
services used in LTE. RF quality is measured based on below metrics:
•
RSSI
•
RSRP
•
RSRQ
•
SINR
•
BLER
•
Latency
Voice quality over a VoLTE call is measured based on the below measurement metrics:
•
•
MOS (M
(Mean
ean Opinion S
Score)
core)
Jitter
•
Packet Loss
MOS is the nearest representation of the voice quality over a VoLTE call.
•
The range is given fr
from
om o to 5
•
The MOS depends on latency and jitter i.e. the variable laten
latency,
cy, mouth to ear delay
•
The MOS decreased as the pa
path
th loss increases
•
The counter associated with MOS is ‘S1U_RTP_Avg_MOS’
Deviation of the difference in packet spacing at the receiver compared to the sender, for a pair
of packets which refers to inter-packet delay variation (IPDV).
•
Jitter 20-30ms  tolerance range
Jitter <5ms  recommended
•
The counter associated with Jitter is ‘S1U_RTP_AvgRTP_Jitter’ [ms]
•
Pa
Packet
cket Loss
Acceptable packet losses are in below range
•
Packet loss <1% is ac
acceptable
ceptable
•
Packet loss >3% leads to quali
quality
ty degradation
•
The counter associated with packet lloss
oss is ‘S1U_RTP_TotalPacketsLost’ [%]
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VoLTE Accessibility
Overview
Flow Chart
Accessibility KPIs are used
used to measure the probability whether services requested by a user
can be accessed. MOS (Mean opinion score) plays an important role in measuring the voice
quality of the VoLTE call.
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VoLTE Accessibility Failures
Overview
VoLTE failures can be associated with any one of the below reasons:
•
Attach failures
•
Authentication failures
•
Default bearer setup failure
•
IMS registration failures
•
Failure due to non-establishment of QCI-1
•
Failure due to non-establishment of QCI-5
•
Failure due to handover in progress
•
Failure in poor coverage
•
X2 & TAU collision
Attac
At tac h F
Fail
ail ur es
Attach failures are mainly
mainly associated with SIP registration failures.
Au th ent ic ati on
Auth
Failures
If any one of the below mentioned parameters are not optimally set, authentication can fail:
Default Bearer
Se
Setup
tup Failur
Failur es
•
Invalid M
MAC
AC code
•
Invalid separat
separation
ion bit
•
Synch failure
Activate Default EPS
EPS Bearer Request is sent by the MME to
to the UE together w
with
ith Attach
Accept. While Attach
Attach Accept is a mobilit
mobility
y management (EMM
(EMM)) message, Activate Default
Default EPS
Bearer Request belongs to the category of session management (ESM) messages. If for some
reason the UE is not able to confirm the successful activation of the default EPS bearer it will
respond with an activate default EPS bearer failure message. As a result, the UE will remain
attached to the network (NAS state: EMM Registered) while it does not have an active bearer
(NAS state in UE: ESM Bearer Context Inactive).
The reaction of the MME when receiving Activate Default EPS Bearer Failure is to repeat
sending Activate Default EPS Bearer Request for a maximum of four times. If this does not
help to activate the bearer context on the UE side, the MME may detach the UE so that a new
initial registration to the network is required.
Continued on next page
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VoLTE Accessibility Failures, Continued
IMS
Registration
Failures
Failure
Failure du e to
NonEstablishment
of QCI 1
During the IMS registration these errors can occur:
•
305 Use Proxy
•
408 Request Timeout
•
423 Interval Too Brief
•
500 Internal Server Err
Error
or
•
504 Server Timeout
QCI1 is the dedicated bearer for speech. W hen the QCI1 bearer is to be established the same
s ame
thresholds are checked against the request for a new bearer i.e. number of active users and
number of DRBs and additional thresholds which controls the number
n umber of QCI1 bearers in the
cell.
•
•
•
Admission control is one of the reasons for QCI1 e
establishment
stablishment failure
The QCI1 bearer limit should be set so that it is always bigger than the GBR limit
limit received
from the MME (S1), if not ERAB setup would be rejected
If QCI1 bearer limit is set too large then admission control would ttry
ry to reserve large
amounts of resources for the Ue hence Admission Control could again reject the ERAB
setup
Failure
Failure du e to
NonEstablishment
of QCI 5
QCI5 is used for IMS signalling.
Failure
Failure Due to
Handover
Handover in
If a handover becomes necessary during
dur ing E-RAB Setup, the eNB may interrupt the ongoing ERAB Setup procedure and initiate the Handover.
Progress
The eNB shall send the E-RAB SETUP RESPONSE message in which the eNB shall indicate,
if necessary all the E-RABs fail with an appropriate cause value, e.g., ‘S1 intra system
Handover triggered’, ‘S1 inter system Handover triggered’ or ‘X2 Handover triggered’
X2 and TAU
Collision
The collision between X2 and TAU can happen due
d ue to the following reasons:
The failures of QCI5 are mostly IMS signalling related failures.
•
Collision between T
TAU
AU and X2 Handoff procedures
•
Combined Attach followed by TA
TAU
U in progress (TAU accept is not sent) and received X2 HO
•
TAU and X2 hand-off should run parallel only after TAU accept is sent and waiting\
waiting\ for TAU
complete
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VoLTE Mobility
Overview
Flowchart
VoLTE mobility refers to a state of the UE where in the call continuity does not get effected
even when the UE is moving from one location to another by the handover procedure. It c
can
an
be in connected mode or in idle mode.
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VoLTE Mobility Failures
Overview
HO Failures
Mobility failures in VoLTE can happen due to one of the following reasons:
•
HO failures
•
SRVCC failures
•
HO executio
execution
n failure
•
Swapped sectors
Ho failures are the most recurring events in mobility. The reasons for HO failures can be any
of the following:
•
Poor coverage
•
Neighbors not defined
•
ANR not activated
•
Admission reject
•
UL noise
Failures can be optimized by 2 methods:
HO Executio
Executio n
Failure
Swapped
Sectors
•
Physical optimization
•
Parameters associated with th
the
e HO thresholds have to be set ideally
HO execution failure can be associated with poor coverage, high UL interference on target
cell, wrong neighbor relation, alarms on the target cell. The neighbor relations have to be
redefined, ANR parameter has to be set ideally, alarms on the target cell have to be looked
upon.
Swapped sectors are related to HW issues. Any swap on the source or target cell can lead to
HO failures. Below methods can be used to check
c heck a swap on the s
site:
ite:
•
Drive test around the site to check the serving PCI in front of the sector
•
Check for the mobility K
KPIs
PIs on the site
•
Physical check on the site ffor
or swapped antenna cables
If swap is detected the antenna cables have to be physically inspected on the field and they
should be re connected to the right sectors.
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VoLTE Mobility Parameters
Overview
Parameter
The parameters which affect the VoLTE mobility are listed below along with the ranges and
impacts.
Description
Default Value/
Ranges
VZ GPL
and Steps
Threshold for RSRP of
serving cell for start of
WCDMA Measurements
when UE has QCI1 bearer
-113 dBm (MINT)
-140...-43
dBm, step 1
dBm
Threshold for RSRP of
serving cell when UE has
QCI1 bearer.
NA
-140...-43
dBm, step 1
dBm
Should be set greater
than
b2Threshold1Utra for
SRVCC to trigger 23dB earlier than PS
handover to maintain
voice service quality
perceived by end
users
This parameter enables and
disables A2 based
redirection for VoLTE calls
when UE has QCI1 bearer.
enabled (1) /
disabled (0)
disabled (0),
enabled (1)
If enabled A2based
redirection will be
triggered, if disabled it
will not be triggered.
Threshold for RSRP of
serving cell for start of inter
frequency measurements
when UE has QCI1 bearer
-105 dBm / -
-140...-43
dBm, step 1
dBm
Higher the value,
measurements start
earlier before A3
criteria is met.
This parameter activates the
functionality to keep the UE
in RRC connected mode
even if there is no activity
until QCI1 establishment
triggered protection timer
expiry.
0, False
0 (false), 1
(true)
If activated UE will be
in RRC connected
mode till QCI1 timer
expiry.
Name
threshold2Wcdm
aQci1
Threshold th2
WCDMA for RSRP
during QCI1
b2Threshold1Utr
aQci1
Threshold1 UTRA
for RSRP of
serving cell during
QCI1
a2RedirectQci1
A2 based redirect
for VoLTE calls
threshold2InterFr
eqQci1
Threshold Th2
InterFreq for
RSRP during
QCI1
actRrcConnNoAc
tivity
Activate RRC
connected mode
while no activity
Impact
Higher the value,
VoLTE user’s
measurements starts
earlier than nonVoLTE user.
Continued on next page
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VoLTE Mobility Parameters, Continued
Overview,
continued
Parameter
Description
Name
qci1ProtectionTi
mer
QCI1 protection
timer
The timer determines the
maximum time between QCI1
bearer establishment and the
release of the UE to RRC idle
Default
Ranges
Value/
and
VZ GPL
Steps
40s, 2s
2...180 s,
step 1 s
mode.
freqLayListServic
eBasedHo
Frequency layer
list for VoLTE
service based HO
freqLayListDedV
oLteHo
Frequency layer
list for ded. VoLTE
inter-frequency
HO
maxNumQci1Drb
Max number QCI1
DRBs (GBRs)
Specifies the frequency layers
that are preferred for service
based handover (LTE1127) or
redirected VoLTE call setup
(LTE2108).
NA
Specifies the dedicated target
frequency layers for interfrequency mobility during VoLTE
calls. The configured values are
only applicable if feature
LTE1942 "Dedicated VoLTE IF
frequency layers" is activated,
NA
Threshold for the maximum
number of established QCI1GBR-DRBs in the cell.
100, 200
for
10/15/20
MHz
Add number QCI1
DRB for
radioReasHo
Additional margin for the
the
maximum number of active
GBRs in the cell accessing the
cell via hand over with HOcause: "HO desirable for radio
reasons".
If timer is set to higher value,
the time available between
QCI1 bearer establishment
to the UE moving to Idle
mode will be high.
0...262143,
step 1
0...600,
step 1
If the value is higher, then
more number of
simultaneous voice calls with
QCI1 data radio bearer per
cell will be allowed.
0...600,
step 1
Decreasing
addNumQci1DrbRadioReas
Ho will alleviate Admission
control.
50 for 5
MHz
addNumQci1Drb
RadioReasHo
Impact
15
(MINT)
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VoLTE Mobility Parameters, Continued
Overview,
continued
Parameter
Description
Name
addNumQci1Drb
TimeCriticalHo
VZ GPL
Steps
0 (MINT)
0 (false), 1
(true)
When activated this feature
improves admission control
issues.
Maximum radio resource
consumption (PRBs) for GBR
traffic in UL and DL
0.75
(MINT)
30...90 %,
step 5 %
Higher the limit, more
number of PRBs are
allocated for GBR users.
Add GBR-DRB traffic
traffic for radio
reason handover
0.05
(MINT)
0...30 %,
step 5 %
Higher the value, higher
margin of PRBs will be
allocated for radio HO users
over and above
maxGbrTrafficLimit
cause: "Time Critical HO".
actEnhAcAndGbr
Services
This parameter activates
support of the following features
•
•
•
addGbrTrafficRr
Ho
and
Decreasing
addNumQci1DrbTimeCritic
alHo will alleviate Admission
control
timeCriticalHo
Maximum GBRDRB Traffic Limit
Value/
Impact
0...600,
step 1
Add number QCI1
DRB for
maxGbrTrafficLi
mit
Ranges
20
(MINT)
Additional margin for the
the
maximum number of active
GBRs in the cell accessing the
cell via hand over with HO-
Activate enhanced
AC and GBR
services
Default
ARP based Admission Contr
Control
ol
Smart Ad
Admission
mission Contro
Control,
l,
comprising RAC and TAC
EPS bearers wit
with
h QCI 2, 3
and 4
Add GBR-DRB
Traffic for Radio
Reason Handover
Limit.
addGbrTrafficTc
Ho
Add GBR-DRB
Traffic for Time
Critical Reason
Handover
Add GBR-DRB traffic
traffic for time
critical reason handover
0.1
(MINT)
0...30 %,
step 5 %
Higher the value, higher
margin of PRBs will be
allocated for time critical
reason HO users over and
above maxGbrTrafficLimit
Limit.
Continued on next page
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VoLTE Mobility Parameters, Continued
Overview,
continued
Parameter
Description
Name
tacLimitGbrNorm
al
Default
Ranges
Value/
and
VZ GPL
Steps
Impact
This parameter specifies the
maximum permitted aggregate
guaranteed transport bit rate for
normal GBR connections.
NA
0...100000
0 kb/s,
step 100
kb/s
Threshold for RSRP of serving
cell for start of GERAN
Measurements when UE has
QCI1 bearer
-115
dBm
(MINT)
-140...-43
dBm, step
1 dBm
Higher threshold values will
delay the trigger
measurements
Handover Margin for Better Cell
Handover when UE has QCI1
bearer
1 dB
(MINT)
-15...15
dB, step
0.5 dB
Higher threshold values will
delay the HO
threshold3InterFr
Threshold for RSRP of serving
-120
-140...-43
Low values: allow the UE to
eqQci1
Threshold Th3 For
RSRP inter
frequency during
QCI1
cell when UE has QCI1 bearer.
dBm
(MINT)
dBm, step
1 dBm
handover earlier
High values: delays the
handover
threshold3aInter
FreqQci1
Threshold for RSRP of neighbor
cell when UE has QCI1 bearer.
-110
dBm
(MINT)
-140...-43
dBm, step
1 dBm
Low values: allow the UE to
handover earlier
TAC Limit GBR
Normal
threshold2GERA
NQci1
Threshold th2
GERAN for RSRP
during QCI1
a3OffsetRsrpInte
rFreqQci1
A3 Offset RSRP
Inter Frequency
during QCI1
Threshold Th3a
For RSRP inter
frequency during
QCI1
High values: delays the
handover
Continued on next page
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VoLTE Mobility Parameters, Continued
Overview,
continued
Parameter
Description
Name
b2Threshold2Utr
aRscpQci1
Threshold2 UTRA
for RSCP
Threshold for UTRA neighbour
cell on the current frequency
when UE has a QCI1 bearer,
such that it is good and reported
neighbour cell
during QCI1
in the measurement result of B2
event.
b2Threshold2Utr
aEcn0Qci1
Threshold for UTRA neighbour
cell on the current frequency
when UE has a QCI1 bearer,
such that it is good and reported
in the measurement result of B2
event.
Threshold2 UTRA
for ecNo
neighbour cell
during QCI1
Default
Ranges
Value/
and
VZ GPL
Steps
NA
-120...-24
dBm, step
1 dBm
Impact
Low values: introduces pingpong phenomenon during
HO operation
High values: Delays the HO
and increases possibility of
losing the active connection
on the serving cell
NA
-24...0.5
dB, step
0.5 dB
Low values: introduces pingpong phenomenon during
HO operation
High values: Delays the HO
and increases possibility of
losing the active connection
on the serving cell
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VoLTE Retainability
Overview
Retainability KPIs are used to evaluate network capability to retain services requested by a
user for a desired duration after the user is connected to the services. These counters can be
calculated per cell or per cluster.
c luster. The KPIs at the cluster level can be calculated by
aggregating all the cell counters. Retainability KPIs are important in evaluating whether the
system can maintain the service quality at certain level.
The two most important KPIs are:
Retainability
KPI Information
•
Call Drop Rate
•
Call Setup Complete Ra
Rate
te
Analysis for the retainability
retainability KPIs can be done by following the steps below:
below:
Step
Action
1
Open current PNM BTS Report
2
Check VoLTEERABDropRate tabs for retainability issues
Continued on next page
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VoLTE Retainability, Continued
Flow Chart
© Nokia 2017
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VoLTE Retainability Issues
Overview
The issues related to retainability can be classified as voice related and data related:
Voice related retainability issues are as listed below:
•
Duplicated S
S1
1 Conne
Connection
ction
•
Physical Layer Failure T310 & T311
•
RLF detected by UE(LTE
UE(LTE1569)
1569)
•
CQI Failure(LTE2206)
•
Radio Conditions
Data related retainability issues are as listed below:
Duplicated S1
Connection
•
Out of sync detected
•
DL HARQ failure detected
•
Maximum numb
number
er of R
RLC
LC
•
Retransmissions
•
GTP-U ffailure
ailure at eNB
•
S1-Reset
Duplicated S1 connection occurs when the UE tries to make HO from eNB-A cell to eNB-B cell
but the HO fails and the following RRC connection
co nnection re-establishment fails and therefore,
•
•
UE makes new RRC setup attempt in eNB-B cell which causes new (duplicated) S1
connection establishment towards the MME
The MME notices that there are two S1 connections for the U
UE
E and releases the old one
(eNB-A). This release can be done with cause: NORMAL release or RADIO, and the drop
call is counted, (EPC initiated E-RAB release due RNL)
Continued on next page
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VoLTE Retainability Issues, Continued
Duplicated S1
Connection ,
continued
Coun ter: M8006C
M8006C314:
314: ERAB_REL_DOU
ERAB_REL_DOUBLE_S1
BLE_S1 is associated with the double S1
•
•
•
Physical Layer
Failure T310 &
This counter provides the number of E-RAB releases initiated by the MM
MME
E in a double S1
scenario
This counter is updated when the eNB detects a double S1 scenario for a UE with the
number of released E-RABs.
The reception of an S1AP: UE CONT
CONTEXT
EXT RELEASE COM
COMMAND
MAND message sent by the
MME to the eNB due to ‘Radio Connection With UE Lost’ without previous S1: UE
CONTEXT RELEASE REQUEST message sent from the eNB to the MME
Timer T310 supervises re-establishment. the recovery from physical layer problems
pro blems and Timer
T311 supervises the RRC connection.
T311
Solution for physical layer failure is to tune the T310 and T311 timers.
RLF detected
by
UE(LTE1569)
•
•
•
•
The RLF and re-establishment procedure are controlled by parameters (N310 and T310)
common for all Ues
There is no VoLTE (QCI1) UE specific parameters for detecti
detection
on of RLF, triggering of RRC
Connection Re-establishment procedure is common for all UEs
Low value of N310 and T310 causes earlier RLF detection by all UEs -> earlier triggering of
re-establishment for all UEs (high C-plane load)
From VoLTE point of view - possible end user ex
experience
perience degradation and call drops
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VoLTE Retainability Issues, Continued
RLF detected
by
UE(LTE1569) ,
continued
Solution for RLF failure detected by LTE1569:
•
•
•
N310 and T310 can be config
configured
ured using VoLTE user’s specific values
VoLTE dedicated T310 and N310 values allows VoLTE users to detect RLF at d
different
ifferent
conditions in comparison to non-VoLTE users
It allows the UE to perform re-establishment in poor RF conditions earlier for QCI1 calls,
hence helping to reduce probability of end user experience degradation and RF loss
detection at the eNB
The timers associated with RLF must be fine-tuned to allow an ideal time before the UE
declares RLF.
RLF detected
by eNB
(LTE2206)
LTE2206 feature allows tuning RLF detection sensitivity at eNB in order to keep
k eep UEs longer in
RRC connection state.
•
It applies to cases the eNB indicates RLF due to CQI
CQI DTX.
•
The tuning is possible by setting LNBTS:nCqiDtx and LNBT
LNBTS:nCqiRec
S:nCqiRec parameters.
•
LTE2206 does not change RLF detection functionality, sensitivity
sensitivity RLF indication is issued
The timers associated with RLF must be fine-tuned to allow an ideal time before the eNB
declares RLF
Radio
Conditions
Ensuring good radio conditions is a pre-requisite for VoLTE Services:
•
VoLTE is a GBR (Guaranteed Bit Rate) service. In poor radio conditions,
conditions, a VoLTE call might
not be established if the bit rate cannot
c annot be guaranteed.
•
•
•
•
Under poor radio conditions, tthe
he average coding rate is low and e
each
ach new bearer requires
more resources.
Smart Scheduler (RL40) introduces a limit to the amount
amount of resources available for GBR
traffic (maxGbrTrafficLimit
(maxGbrTrafficLimit , %) to ensure air interface resources are left for the lower
priority non-GBR traffic. If adding the new GBR bearer implies going over that thre
threshold
shold
then it is rejected.
Usually Voice bearer has typically w
worse
orse retainability due to longer call sessions compared
with non-GBR data traffic. Poor radio conditions accentuate the low retainability (VoLTE call
drops).
Voice bearer is also more sensitive to HO failures than non-GBR bearer due to longer time
in connected mode.
AMR codec bit rate (VoLTE
(VoLTE quality) is bett
better
er under good RF conditions
Continued on next page
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VoLTE Retainability Issues, Continued
Radio
Conditions ,
continued
•
Potential contributors to poor radio conditions are:
−
No clear dominance
−
Frequent handovers
−
Overshooting eNodeBs
−
Excessive handover attempts
−
High RRC attempts to distant eNodeB
−
Missing neighbors
−
eNodeB, MME and other Network Parameters not set correctly
Physical optimization is the solution to improve radio conditions.
© Nokia 2017
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VoLTE Retainability Parameters
Overview
Paramet
The below listed parameters can be tuned to improve retainability in VoLTE.
Description
er Name
nCqiDtx
(Radio
problem
indication
based on
CQI DTX)
nCqiRec
(Radio
problem
recovery
based on
CQI DTX)
The parameter defines the number of
consecutive CQI DTX detections
causing radio link failure indication.
Special value 0 means that the
feature is disabled.
Default Value/
Ranges
Verizon GPL
and Steps
100 / 0
0...100, step
1
Impact
•
•
The parameter defines number of
consecutive CQI non-DTX detections
causing radio link failure recovery
indication.
2/2
1...8, step 1
•
•
t310Qci1
(T310 for
QCI1)
Timer t310Qci1 supervises the
recovery from physical layer
problems for UE with established
QCI1 bearer.
With feature LTE1569 for UEs with
established QCI1, settings of
t310Qci1 will be configured in RRC
Connected mode (overwriting SIB2
T310 value) via RRC Connection
Reconfiguration message.
2000ms (MINT)
0ms (0),
50ms (50),
100ms
(100),
200ms
(200),
500ms
(500),
1000ms
(1000),
2000ms
(2000)
•
Lower the value of
this parameter,
faster RLF
indication would be
triggered.
Higher the value of
this parameter,
slower RLF
indication
Lower the value of
this parameter,
faster the recovery
from the RLF state.
Values higher than
1 and lower than 4
are recommended
Higher the value of
this parameter,
slower recovery
from the RLF state
Increasing tthe
he value
will increase the
window hence
reduce the chance
of call drops.
However, this will
also increase the
usage of network
resources.
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VoLTE Retainability Parameters, Continued
Overview,
continued
Parameter
Description
Default
Ranges
Value/
and Steps
Name
Impact
Verizon GPL
N310Qci1
(N310 for
QCI1)
Constant n310Qci1 is the
maximum number of
consecutive "out of sync"
indications received from lower
NA
n1 (1), n2
(2), n3 (3),
n4 (4), n6
(6), n8 (8),
Increasing the value will
improve the call drop
rate. However, this will
also increase the usage
of network resource
n10 (10),
n20 (20)
layers for UE with established
QCI1 bearer.
.
T311
(Timer 311)
n311
(Maximum
number of insync
indications)
maxGbrTraffic
Limit
(Maximum
GBR-DRB
Traffic Limit)
Timer T311 supervises the RRC
connection re-establishment.
3000 ms (1) /
5000 ms
1000ms (0),
3000ms (1),
5000ms (2),
10000ms
(3),
15000ms
(4),
20000ms
(5),
30000ms (6)
Maximum number of
consecutive "in-sync" indications
received from lower layers.
n1 (0) / n1
n1 (0), n2
(1), n3 (2),
n4 (3), n5
(4), n6 (5),
n8 (6), n10
(7)
0.75 /
30...90 %,
step 5 %
n1 corresponds to 1 and so on.
Maximum radio resource
consumption (PRBs) for GBR
traffic in UL and DL
The amount of radio resources
(PRBs) is calculated in % of the
available PRBs depending on
the system.
Increasing the value will
increase the window
hence reduce the chance
of call drops. However,
this will also increase the
usage of network
resources.
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IEH 550, Section 007
October 11, 2017
Appendix
BBU Swap Validation & Troubleshooting for Verizon
Contents
Appendix ........................................................................................................................ 2
Appendix
LTE1541: Advanced SCell measurement
measurement handling ..................................................... 2
LTE 2733: Baseband
Baseband Pooling ..................................................................................... 2
LTE1406: Extended VoLTE Talk Time ........................................................................ 3
LTE 2664: Load Based PUCCH region ....................................................................... 4
MIMO.......................................................................................................................... 4
LTE 44: 64 QAM Modulation
Modulation Scheme......................................................................... 5
LTE 571: Packet Segmentation
Segmentation .................................................................................. 6
LTE11: RoHC(Robust Header Compression) ............................................................. 7
LTE907: TTI Bundling................................................................................................. 8
LTE2098: VoLTE Uplink Coverage Boosting .............................................................. 9
Call Admission Control ............................................................................................. 10
CAC Optimization for number of RRC connections ................................................... 10
CAC Optimization for number of Active users ........................................................... 11
October 11, 2017 – IEH 550, Section 007
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Appendix
LTE1541:
Ad van ced SCell
measurement
handling
It supports feature LTE1541 (Advanced SCell measurement handling)
Below are the specific functionalities of feature LTE1541:
•
New triggers added for SCell
SCell deactivation and deconfiguration
•
Decision to release SCell is based
based on the reported channel quality indicator
indicator for this SCell
Below are the counters for SCell swap:
•
Scell_Swap_Intra_Freq | M8011C165
•
Scell_Swap_Inter_Freq_A6
Scell_Swap_Inter_Freq_A6 | M8011C168
•
Scell_Swap_Inter_Freq_NA6
Scell_Swap_Inter_Freq_NA6 | M8011C169
M8011C169
The Flexi Multiradio BTS supports the following improvements for SCell handling:
•
SCell release when undetected
undetected by the UE
•
SCell deactivation
deactivation because of poor cchannel
hannel quality
SCell deconfiguration because
because of inact
inactivity
ivity
SCell configuration and activation control
•
LTE 2733:
Baseband
Pooling
Highlights of LTE 2733 are:
•
This feature is activated
activated on eNB level
•
This feature introduces two identical
identical Baseband (BB) pools within
within every ABIA
•
One BB pool can host
host a pool of up to
to 8 cells
•
Cells are allocated to
to BB pools on eNB start-up
•
BB resources (U-Plane) from a BB pool are dynamically
dynamically shared among all cells
cells allocated to
that BB pool
This feature provides the following benefits:
•
This feature increases the ABIA
ABIA baseband capacity in terms
terms of:
−
Cells
−
RRC Connections per cell
−
GBRs per cell
−
scheduled UEs/TTI per cell
•
RRC
Connections,
GBRsload
and scheduled
scheduled UEs/TTI are dynam
dynamically
ically distributed among cel
cells
ls
depending
on live traffic
Continued on next page
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Appendix, Continued
LTE1406:
Extended
VoLTE Talk
Time
One of the most important aspects for LTE users is battery consumption:
•
If UE does not check PDCCH continuously (only during DRX ACTIVE state) energy savings
savings
can be achieved.
LTE42 DRX in RRC Connected Mode feature introduces
introduces several DRX profiles. One
One of them
is DRX Profile 2 which is optimized for VoIP traffic.
Features gained from DRX are improved by LTE 1406 introducing:
•
•
Alignment of the Scheduling Request
Request (SR) timing with the DRX 'ON' timing
•
Adjustment of SR Periodicity
Periodicity to DRX Long Cycle length
Dedicated BLER target and number of HARQ
HARQ retransmissions for VoLTE
VoLTE UEs
LTE1406 can be applied only for the UEs with QCI1 bearer
•
•
Alignment of the Scheduling Request (SR) timing with the DRX 'ON' timing
−
•
Scheduling Request is allocated 3 TTIs before periodic CQI (pCQI). As a result, UL Grant
on PDCCH can be provided at earliest 1ms after pCQI (SR, 4ms) - UE is already in DRX
Active state when
when it sends pCQ
pCQII then additional DRX Active stat
state
e caused by s
sending
ending
Scheduling Request is avoided
Adjustment of Scheduling
Scheduling Request periodicity to Long DRX Cycle for the UEs with QCI1
bearer drxProfile2: drxLongCycle (40ms)
Lower number of HARQ Retransmissions increases gains from the DRX:
•
•
According to the 3GPP, UE must
must be in DRX Active stat
state
e when an uplink grant for a pending
HARQ retransmission can occur, i.e. Ue will read PDCCH harqMaxTrUl -1 times after
a fter initial
transmission.
Maximum number of HARQ transmissions
transmissions in UL and DL, for the UEs with
with eVTT profile, is
controlled by means of dedicated parameters qci1HarqMaxTrUl and qci1HarqMaxTrDl
Continued on next page
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Appendix, Continued
LTE 2664:
2664: Lo ad
Based PUCCH
region
Load based PUCCH Region introduces allocation of PRBs for PUCCH based on current cell
load
In LTE2664 PUCCH size can be:
−
expanded , when cell load is rising to avoid rejection of UEs, which try to access the cell
−
compressed, when cell load is low to improve UL throughput
Starting PUCCH size is set to minimum value, whereas LTE1130 Dynamic PUCCH allocation
defines maximum number of PUCCH resources − PUCCH expansion above this configuration
is not possible.
MIMO
Commonly used MIMO techniques are:
MIMO Techniques
Transmit Diversity
Features
•
•
Spatial Multiplexing (SM)- SU-MIMO
•
•
Improves reliability
reliability/coverage
/coverage on a single
data stream
Fall back schem
scheme
e if channel cconditions
onditions do
not allow SM; useful to improve reliability
on common control channels
Multiple data strea
streams
ms sent to tthe
he same
user
Significant throughput gains for users in
high SINR conditions
Continued on next page
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Appendix, Continued
LTE 44: 64
QAM
Modulation
Scheme
Feature LTE44 introduces 64 QAM modulation scheme in UL increasing maximum achievable
UE uplink throughput in a very good radio conditions and improving average cell capacity
Higher peak UL throughputs can be achieved due to the support of higher Modulation and
Coding Schemes (MCSs) -> MCS 21 – MCS 28
•
Possibility of using
using higher order modulation (64 QAM) in UL may lead to the UL av
average
erage
throughput increase, especially when many 64 QAM capable UEs (3GPP UE Cat. 5, Cat. 8
and Cat. 13) are in a very good radio conditions in the cell.
−
•
•
•
NOTE: such effect can be expected only if the offered traffic is high enough -> for low
offered traffic high MCSs will not be used causing no impact on the UL throughput
It is also expected to observe
observe UL Max throughput increase for UE
UEss using the highest MCSs.
Possibility of UL PRB utiliz
utilization
ation decreas
decrease
e due to
to the usage of higher order modulatio
modulation
n (64
QAM) the same data volume can be sent with less PRBs used as the single modulation
symbol carries 1.5 times more information than in case of 16 QAM modulation
In case of high number of 64QAM in UL supported
supported UEs and good radio conditions for those
those
UEs, average used MCS for PUSCH transmission is expected to increase.
Continued on next page
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Appendix, Continued
LTE 571:
Packet
Segmentation
Packet Segmentation algorithm is used as an extension to the uplink link adaptation to
improve the UL cell edge performance.
•
•
•
In worsening radio conditions scheduler
scheduler performs packet segmentation
segmentation on Layer 2, to use
more robust MCS and transmits the packet over multiple TTIs.
Since RLC/MAC overhead is transmitted
transmitted more than once, more
more resources are consumed to
transmit the same amount of user data.
As number of transmitted packets
packets increases, more
more resources on PDCCH are utilized and on
PHICH due to transmission of ACKs/NACKs for HARQ purposes.
NOTE: Packet segmentation is not an event-triggered mechanism, it is done automatically and
only for UEs with poor radio channel.
Controlled Packet Segmentation:
Controlled UL packet segmentation means that the extent of segmentation can be configured
with the following parameters:
•
•
amount of data a UE can send in a TTI. The lower this
ulsMinTbs defines the minimum amount
setting is, the higher the number of segments a packet can be divided in. This will increase
user robustness by increasing the energy per packet, but more radio resources are
consumed due to increased RLC/MAC overhead
ulsMinRbPerUe
defines the
number
of PRBs
be occupied
power
limited. It prevents
theminimum
UE of being
allocated
a toothat
lowcan
number
of PRBsby UE which is
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Appendix, Continued
LTE11:
RoHC(Robust
Header
Compression)
This feature compresses the header of IP/UDP/RTP packet
packetss for the EPS bearer with QCI1 to
avoid transferring high overheads across the air-interface.
•
IP/UDP/RTP headers size
size can be either 40 bytes for IPv4 or ev
even
en 60 bytes for IPv6.
•
PDCP layer can compress the RTP/UDP/IP headers.
•
•
•
•
RoHC improves uplink link budget due to less
less bandwidth needed per user (i.e. lower MCS
can be used) which translates to greater cell range.
Throughput requirement is reduced and thus, more VoLTE users can be scheduled or better
better
voice codecs can be used.
RTP/UDP/IP headers of 40 Bytes are compressed to typicall
typically
y 3 Bytes with RoHC (Robust
Header Compression)
RoHC results in ~ 50% reduction of data volume
volume at the air interface, i.e. 100% capacity
improvement and/or ~3 dB gain in link budget @ NB-AMR
VoLTE/No RoHC
VoLTE + RoHC
Bit Rate
Voice packet size
12.2 kbps
244 bits
12.2 kbps
244 bits
RTP/UDP/IP headers
320 bits
24 bits
VoIP overhead
57%
9%
NOTE: VoLTE: RoHC is activated by default at QCI1 bearer establishment RoHC usage is
controlled by operator settings
Continued on next page
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Appendix, Continued
LTE907: TTI
Bundling
TTI bundling is specified in 3GPP (TS 36.213, 36.321) to allow the improved uplink
performance for cell border UEs (which
( which often hit the maximum transmission power) and for
reduced PDCCH load.
TTI bundling allows for transmitting the same transport block in 4 consecutive UL subframes
(also known as bundle size), which leads to increased energy per transmitted bit and therefore
improved uplink link budget.
When BLER increases and Link Adaptation has no more options for MCS/PRB reduction while
radio conditions for handover are not fulfilled, TTI Bundling can be triggered to sustain the
voice call quality before UE will either change the cell or RF conditions becomes better.
NOTE: TTI Bundling mode is also maintained during the handover (if target cell supports TTI
Bundling).
Transmission
Tra
nsmission Cha
Characteristics:
racteristics:
A single transport block is enc
encoded
oded and transmitted with different redundancy versions in fo
four
ur
(4) consecutive UL subframes, i.e. within a bundle.
•
•
A single UL grant on PDCCH is used for
for each bundle.
HARQ feedback is only received
received (and transmitted) for the last subframe
subframe of a bundle. HARQ
process ID is same for each of the bundled subframes.
HARQ retransmission of a TTI bundle, which is also transmitted as a bundle, occurs 16 TTIs
after previous (re)transmission in order to be synchronized with normal (non-bundled) LTE
HARQ retransmissions (8 TTIs)
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Appendix, Continued
LTE2098:
VoLTE Uplink
Uplink
Coverage
Boosting
Feature LTE2098 introduced in FL16/TL16 release aims at improving UL coverage for VoLTE
UEs i.e. the ones with QCI1 bearer established.
•
•
The feature is activated on the LNCEL
LNCEL level by means of dedicated feature
feature activation flag
namely actVoipCovBoost
Feature LTE2098 provides better UL coverage
coverage for the UEs with QCI1 bearer established
established by
introduction of:
−
−
−
•
Sensitivity based UL Resource Allocation (RA): Sensitivity based selection of #PRB and
MCS if UE enters power limitation (PHR<0)
Reduction of aperiodic CQI reporting: Aperiodic CQI reports are requested only for initial
transmissions of 1st fragment of regular transmissions or 1st TTI of a TTI Bundling
transmission
Improved UL receiver: more robust Channel Estimation (CE), improved Noise Power
Estimation algorithm
VoLTE UL Coverage Boosting feature
feature brings up to about 1.24 dB gain on cell edge over
regular deployment (without TTI Bundling activated) and up to about 2.5 dB gain in
scenarios with TTI Bundling activated
UL VoLTE coverage can be enhanced up to even 5 dB when
when both TTI Bundling and VoLTE
UL Coverage Boosting are in use
General assumptions
•
•
Operating band: 2600 MHz
•
Channel bandwidth: 10 MHz
•
Antenna gain:
•
eNB: 22 dBi
•
UE: 0 dBi
•
eNB configuration:
•
DL: 2Tx-2Rx
•
UL: 1Tx-2Rx
•
Service: AMR-NB 12.2
•
Clutter type: Urban
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Appendix, Continued
Call Admission
Control
Radio Admission Control is responsible for admitting or rejecting requests for new RRC
connections and new radio bearers.
The optimization of Admission Control should ensure that RRC connections and data radio
bearers are always admitted.
Optimization can have two targets:
CAC
Optimization
for number of
RRC
connections
•
Procedure for the number of RRC connections
connections
•
Procedure for the number of active users
users
This procedure is triggered when either Admission Control blocking issue or the counters
quantifying the maximum number of RRC connections issue.
Follow the below steps for optimization if above issues found.
Step
Action
1
Check the counter which determine the maximum number of RRC connections
within the cell is reaching the Admission Control threshold defined by the
eNodeB databuild.
2
Check the number of resource blocks allocated to PUCCH to ensure sufficient
resources to support the maximum number of RRC connections
3
Check the Admission Control threshold values to be configured maximum
values, if not increase the threshold value.
NOTE:
Threshold values should be increased by looking impact of PUCCH resource
allocation.
4
Need to check whether PUCCH re-dimensioning is required by checking
PUCCH Resource Block requirement. Follow step 8 & 9 for PUCCH redimensioning.
5
Enable Parameter actHighRrc to increase the maximum number of RRC
connections.
NOTE:
•
•
•
This parameter can be enabled for FSMF3
FSMF3 when using 15Mhz or 20 Mhz
channel bandwidth.
This parameter cannot
cannot be set enabled if Parameter actFlexBbUsage is
enabled.
Step 1-4 provides to set cell maximum
maximum capacity.
capacity.
Continued on next page
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Appendix, Continued
CAC
Optimization
for number of
RRC
connections,
Step
6
continued
7
Action
Evaluate the parameter changes if above steps are not solving Admission
blocking issue.
•
Enable Traffic balancing featur
features
es
•
Change the prioritization
prioritization of net
network
work layers
•
Check the RRC inactivity timer
Evaluate Hardware changes if above steps are not solving Admission blocking
issue.
Hardware changes can be introduced by:
New RF Carrier
•
CAC
Optimization
for number of
Ac ti ve u ser s
•
Sectorization
•
Adding new sit
site
e
8
Re-dimension the PUCCH with existing parameter set to ensure PUCCH is
allocated to sufficient resource blocks.
9
Change the PUCCH parameter to reduce PUCCH resource block requirement.
For example: increase CQI reporting period (cqiPerNp ) from 20ms to 40ms
The optimization of Admission Control should also ensure that the number of active users do
not cause blocking. An active user is a user with one or more Data Radio Bearers (DRB)
The procedure is triggered when either Admission Control blocking issue or the counters
quantifying the maximum number of active users indicates that the cell load is approaching its
upper limit.
Follow below optimization steps if above issues found:
Step
Action
1
Compare the parameters maxNumRRC and maxNumActUE
2
Set the both parameter value equal if value found not equal.
3
Follow optimization procedure of RRC Connection if value found equal
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