Capacity Management
Admission Control & Congestion Control
Capacity
management
Capacity >> LIMITED RESOURSES
DL Ch Codes
UL & DL HW
(Channel Elements)
• There is one code tree for each cell and each
carrier
• Depends on installed capacity (UL CEs depend on
RAX boards and DL CEs depend on TX boards)
DL Transmitted Carrier
• Depends on the PA
Power
UL
RTWP
UL & DL
Spreading Factor (SF)
UL & DL
ASE
• Radio conditions and traffic load
• Also limited by the code tree and settable by
parameters
• Load measured in Air Speech Equivalents
Capacity >> LIMITED RESOURSES
# HSDPA users
• Depends on the license level and it is adjustable through
parameters
# EUL & 2ms EUL
• Depends on the license level and it is adjustable through
parameters
# EUL
non-serving)
• Depends on the license level and it is adjustable through
parameters
Transmission Bandwidth
EUL
Scheduled rate
# RLs in Compressed
Mode
RRC Reject
Ratio
• Depends on installed capacity
• Average rate of unhappy non-guaranteed users configured on
EUL in one cell
• The number of Radio Links in Compressed Mode
• Monitoring is done during a fix time interval. At the end of every time interval
the RRC Rejection Ratio is calculated from the number of admission requests
and the number of admission confirm messages sent.
Capacity Management
Admission Control
• accept/refuse new calls
Congestion Control
• detect and resolve overload situations
Dedicated Monitored
Resource Handling
• monitoring resources utilization
ADMISSION
CONTROL
ADMISSION Control POLICIES
BLOCKED
CONDITIONALLY BLOCKED
ADMITTED
Between
the admission
If the resource
is: and maximum level, (guaranteed, non-handover) or (nonguaranteed, non-handover/handover)BLOCKED
requests are not admitted unless RN Soft Congestion
actions
canthe
findadmission
the required level,
resources
release. is admitted.
• Up till
thetorequest
Admission Request Attributes
Request Type
• indicating whether the request for resources concerns a
handover of a connection or not (used in the
evaluation of admission policies).
Request Class
• indicating whether the request for resources concerns
a request for guaranteed rate connection parts or
non-guaranteed connection parts (used in the
evaluation of admission policies).
Preemption
Capacity
• indicating whether this request can preempt a lower
priority (part of a) radio connection in case of resource
shortage.
Priority of the
request
• (1..15)
Indication of additional resources required, including additional UL/DL
channelization codes, UL/DL ASE, and so on
RAB ASSIGNMENT REQUEST message
RAB Assignment Request message IEs
Information Elements
IE/Group Name
Message Type
RABs To Be Setup Or
Modified List
>RABs To Be Setup
Or Modified Item IEs
>>First Setup Or
Modify Item
Presence
Range
M
O
IE type and
reference
9.2.1.1
Semantics
description
RAB Parameters
IE/Group Name
RAB parameters
Class
Criticality>Traffic
Assigned
Criticality
>RAB
Asymmetry Indicator
YES
reject
YES
1 to
<maxnoofRABs>
M
>>>RAB ID
M
9.2.1.2
>>>NAS
Synchronisation
Indicator
>>>RAB
Parameters
O
9.2.3.18
O
9.2.1.3
3GPP
25.413 RANAP
Grouping
reason:
same
criticality
The same
RAB ID must
only be
present in
one group.
EACH
-
-
Includes all
necessary
parameters
for RABs
(both for
MSC and
SGSN)
including
QoS.
ignore
>Maximum Bit Rate
>Guaranteed
Bit Rate
reject
>Delivery Order
>Maximum SDU Size
>SDU parameters
>Transfer Delay
>Traffic Handling Priority
-
>Allocation/Retention priority
>Source Statistics Descriptor
>Relocation Requirement
>Signalling Indication
>Extended Maximum Bit Rate
SOFT CONGESTION
What?
• Increase accessibility in case of
resource shortage
How?
• By admitting users in a cell in
case of resource shortage, if a
low priority user can lower its
rate or be preempted
SOFT CONGESTION ALGORITHM
Non-guaranteed requests can reduce the rate of
other lower priority, non-guaranteed connection parts
in steps. Example: from interactive PS 384/64 to
interactive PS 128/64, down to their lowest retainable
rate
Guaranteed requests can reduce the rate of
any priority, non-guaranteed connection parts in
steps down to their lowest retainable rate
If that is not sufficient, RN Soft Congestion can preempt
existing guaranteed RABs of lower priority, or nonguaranteed RABs at the lowest retainable rate if request is
preemption capable and connection part targeted is
preemption vulnerable
RN Soft Congestion will not target users that have already ongoing HO
attempts, or that have been triggered (but not finished) to do soft congestion
actions by earlier admission requests.
SOFT CONGESTION ilustration
New User requesting New
PS RAB
64/HS
128/HS
UL CE Admision
Limit Exceeded
64/HS
Downgrade
DOWnlink
channelization
Codes
Downlink Channelization codes
SF 1
SF 2
SF 4
SF 8
SF 16
SF 32
SF 64
SF 128
SF 256
Channels
CPICH
BCH
AICH
FACH
Spread Factor
256
256
256
64
Channels
PCH
PICH
HS-SCCH
Speech
Spread Factor
256
256
128
128
Channels
Spread Factor
HSDPA
PS 64/64
PS 64/128
PS 64/384
16
32
16
8
SF 1
SF 1
SF 2
SF 2
SF 4
SF 4
SF 8
SF 16
SF 32
SF 64
SF 128
SF 256
SF 8
SF 16
SF 32
SF 64
10 HSDPA codes
1 user – R99
PS64/384 – SF 8
3 HS-SCCH
26 Hs users
– A-DCH
FACH
2 users – R99
PS64/128 – SF 16
08
Speech
users –
4 users – R99
PS64/64 – SF 32
SF 128
SF 64
CPICH
BCH
AICH
PCH
PICH
Downlink Channelization
› The admission request can be granted if the resource usage plus the
additional SF is below the admission level dlCodeAdm.
› Admission limit (dlCodeAdm) is set to 90% (reserving 10% of the code
tree for new handover legs).
PS R99, HS,
Voice,VT - Setup
Voice,VT - HO
0%
Granted
Conditionally
Blocked
Soft Congestion
Blocked
Granted
Granted
Blocked
dlCodeAdm
90%
100%
Downlink Code Usage %
+ Additional Request
Downlink Channelization
BLOCKED
CONDITIONALLY
BLOCKED
ADMITTED
DOWnlink
Transmitted
carrier power
DOWnlink Tx carrier power
100% (MaxTransmissionPower = MaxDlPowerCapability)
Congestion Control
99% (PowerOffset = 14)
Admission Control
85% (PowerAdm = 85)
User Traffic
20%
Common Channels
8 ~ 10%
CPICH
DOWnlink Tx carrier power
DOWnlink Tx carrier power
› The admission request can be granted if the resource usage plus the
additional DL transmitted carrier power is below the admission level
pwrAdm.
› Admission limit (pwrAdm) is currently set to 85%.
› Monitored Dl Transmitted carrier power is considered for R99 traffic ( No
HSDPA Power)
PS R99, HS,
Voice, VT- Setup
Granted
Conditionally
Blocked
Soft Congestion
Granted
Granted
Voice, VT- HO
0%
PwrAdm
85%
Blocked
Blocked
100%
Downlink Pwr Usage %
+ Additional Request
DOWnlink Tx carrier power
BLOCKED
CONDITIONALLY
BLOCKED
ADMITTED
DL & UL
Spreading
FActors
DL & UL Spreading FActors
›
New Requests with SFXX, are denied if number of
connections exceed sfXXAdm
› UL SF Histogram Admission Policy
– sf4AdmUl, sf8AdmUl, sf16AdmUl, sf8gAdmUl
› DL SF Histogram Monitor Admission Policy
– sf8Adm, sf16Adm, sf32Adm, sf16gAdm
›
Actual configuration
sf4AdmUl = 3
sf8AdmUl= 6
sf16AdmUl = 50
sf8gAdmUl = 6
Actual configuration
sf8Adm = 3
sf16Adm = 6
sf32Adm = 12
sf16gAdm = 6
DL & UL Spreading FActors
Uplink Channel
Element Consumption
Downlink Channel
Element Consumption
UL & DL HW
(Channel Elements)
UL & DL HW
Definition of CE
• CE is a measure of board capacity and radio bearer (RB)
capacity cost
Normalization of 1 CE
• Downlink (DL): One AMR 12.2 kbps with SF=128
• Uplink (UL): One AMR 12.2 kbps with SF=64
Different Services
• Different services have different HW consumption
(different Channel Elements consumption)
Hardware Consumption
• Hardware consumption is related with the Symbol Rate >>
Inversely proportional to Spreading Factor (SF)
Spreading Factor is
double in UL than in DL
• due to different modulation scheme: QPSK (Downlink)
and BPSK (Uplink)
• BSPK (1bit per symbol). QPSK (2bits per symbol)
UL & DL HW
› The admission request can be granted if the resource usage plus the
additional DL/UL Hardware is below the admission level dlHwAdm/
ulHwAdm.
› Admission limit dlHwAdm=100% (disabled) and ulHwAdm=90%.
PS R99, HS,
Voice, VT- Setup
Granted
Conditionally
Blocked
Soft Congestion
Granted
Granted
Voice, VT- HO
0%
ulHwAdm
90%
Blocked
Blocked
100%
UL HW Usage% +
Additional Request
Other Admission
Policies
ASE Admision Policy
›
›
›
›
Same behavior for Downlink and Uplink ASE
ASE: Air Interface Speech Equivalents (ASE) in uplink and downlink
This monitor accounts for the air interface resources usage in a cell.
Currently DISABLED: ( No blocks due to UL/DL Ase)
– aseDlAdm=500 (MAX VALUE)
– aseUlAdm=500 (MAX VALUE)
PS R99, HS,
Voice, VT - Setup
Voice, VT - HO
Granted
Granted
0%
aseDlAdm=500
aseUlAdm=500
Other Admission Policies
Compressed Mode Admission Policy
The policy aims to control the number of RLs allowed in compressed mode on cell level, in
order to limit the amount of DL power peaks caused by SF/2 compressed mode operation.
Serving HS-DSCH Admission Policy
By means of this policy it is possible to limit the number of simultaneous DL scheduled users
in a cell, preventing that many users have to share the available resources and get too low
throughput. hsdpaUsersAdm, maxNumHsdpaUser.
HS Setup
Granted
Blocked
Blocked
HS HO
Granted
Granted
Blocked
0 Users
hsdpaUsersAdm=52
maxNumHsdpaUsers=64
Number of HS
Users
Other Admission Policies
Serving and Non-serving EUL Admission Policy
RN Admission Control must reject an EUL user, requesting the cell as serving cell if the total
number of serving cell EUL users including the requested is above eulServingCellUsersAdm
parameter.
EUL users can be in soft/softer handover. It is also possible to be able to limit the EUL users
having the cell as non-serving cell. This is to be able to limit the amount of UL hardware
reserved for the non-serving connections.
•eulServingCellUsersAdm, eulNonServingCellUsersAdm.
Congestion
Control
Congestion Control
› Detects and Resolves the following types of overload
UL RTWP
DL Cell Congestion
DL HSDPA Pwr
overload
Congestion
Detection
UL RTWP CELL CONGESTION
Actually disabled
iFCong = 621= -49.9 dBm
iFHyst = 6000 = 60000ms
=6s
= 621
No congestion
Congestion
Congestion
solved
UL RSSI EXAMPLE IN HIGH TRAFFIC CELL
DL Cell Congestion
Actual configuration
pwrAdm = 85%
pwrOffset = 14%
No congestion
Congestion
Congestion
solved
DL CELL CONGESTION EXAMPLE
DL HSDPA Congestion Detection
No congestion
Actual configuration
maxPowerOverloadHystTime = 10 s
Congestion
Congestion
solved
Congestion
Resolve
HAndling
UL RTWP CELL Congestion
Resolve Handling
UL RTWP
CELL
CONGESTION
• Blocking all non handover
requests until UL
congestion is resolved.
DL Cell and DL HSDPA Congestion
Resolve Handling
DL Cell &
DL HSDPA
Congestion
• Blocking all non handover requests
until UL congestion is resolved
• RN Congestion Control starts
congestion resolve actions in the
cell.
Congestion Control Resolve Actions
Pace
• The interval between periodic congestion
resolve actions. The congestion resolve
actions are periodic from the start of DL
congestion until the DL cell congestion
situation is resolved.
Strength
• The amount of ASE in DL to be released
each congestion resolve action
CONGESTION CONTROL RESOLVE
=3s
= 1 ASE
= 3 ASE
= 0.8 s
=2s
Non-guaranteed RABs on dedicated, non-shared radio
channels are reduced to their lowest retainable rate in the
current radio configuration
Guaranteed RABs and non-guaranteed RABs
(remaining after step 1 and not on 0 kbps or on
common radio channels) on dedicated, non-shared
radio channels are released
Practical
examples
Spotting blocking in SMART
How to check
is there is
blocking?
• Check your RNCs RAB and RRC blocking counters
• The set of counters available in SMART is not
comprehensive, but it is useful to spot some types of
blocking such as: DL Ch Codes blocking, DL Tx Power
Blocking, UL & DL HS (CEs)
How to solve
this cases?
• Analyze each case and check if there is room for
parameter optimization or coverage reduction
I it solved
now?
• After applying the changes it is necessary to go back
to SMART and check if the statistics have improved
DF0586 RAB Blocking EXAMPLE
due to DL CH Codes & DL Tx Pwr
CR to clear
blocking
W implementation of HSDPA+
rollback to default parameters
New CR to reduce blocking
IF you have a CSSR degradation
CSSR
degradation
• If the CSSR is degraded and after
discarding alarms/unavailability of the site or
surrounding sites
WHAT to look for?
RRC
Blocking
• In SMART you can easily isolate DL Ch Code and DL
Tx Pwr blocking
RAB
Blocking
• In SMART you can easily isolate DL Ch Code, DL Tx
Pwr blocking, UL and DL HW, TN (transport network),
NB Speech, NB HS, UL and DL ASE, UL and DL SF
Congestion
• In SMART you can check if there is time spent in
congestion state
RRC Blocking
RAB Blocking
Congestion
How to solve it with parametrization?
examples for some common issues
DL Ch Codes
Blocking
• Check is the sector does not have exceeded coverage
• Check the threshold dlCodeAdm (you can raise it by
steps upto 95%)
• Change the parameter numHsPdschCodes from the
default 5 to 3 or even 1
DL TX Pwr
• Check is the sector does not have exceeded coverage
• Check the parameters pwrAdm and pwrOffset, increase
pwrAdm as much as possible taking into account that
pwrAdm + pwrOffset < 99%
• Check if it is possible to decrease primaryCpichPower
UL HW
• Check is the sector does not have exceeded coverage
• Check if the site has maximum RAX board cofiguration
Additional
documents
Additional INFORMATION
› Presentation from previous workshops
› Ericsson document