LTE EVENTS & Mobility KPI
Optimization
LTE Events?
What is Mobility/Handover ?
What are the type of Mobility/Handover ?
Reason for Failures
Solutions
LTE Events
L
T
E
IR
A
T
Event
A1
A2
Triggering Condition
is triggered when the serving cell becomes better than a threshold.
is triggered when the serving cell becomes worse than a threshold.
A3
is triggered when a neighboring cell becomes better than the serving
cell by an offset.
A4
is triggered when a neighboring cell becomes better than a threshold.
A5
is triggered when the serving cell becomes worse than hreshold-1 and
neighboring cell becomes better than threshold-2.
B1
is triggered when a neighboring inter-RAT cell becomes better than a
threshold.
B2
is triggered when the serving cell becomes worse than threshold-1 and
neighboring inter-RAT cell becomes better than threshold-2.
LTE EVENT A1
Triggered when the serving cell becomes better than a threshold. Good Coverage. This type of event
mainly used to stop the measurement in good radio condition. Based on either RSRP or RSRQ which
decided by operator.
There are two parameter which mainly defined for Event A1:
Threshold2a= -108dBm (-140…-43dbm)
Hysthreshold2a= 1(0…..15db)
LTE EVENT A2
Triggered when the serving cell becomes worse than a threshold. Poor coverage.
This even mainly used to start the measurement in bad radio condition. Based on either RSRP or RSRQ
Below parameters are defined for Event A2:
threshold2InterFreq= -110dBm(-140….-43dBm)
hysThreshold2a= 1(0….15dB)
hysThreshold2GERAN=1 (0…15dB)
hysTheshold2Wcdma=1(0…15dB)
LTE EVENT A3
Triggered when a neighbouring cell becomes better than the serving cell by an offset.
EVENT A3
Parameters:
triggerQuantityA3(RSRP-0,RSRQ1)
a3Offset 30(3dB Default Value)
hysteresisA3 (0….15dB)
timeToTriggerA3 320 ms Default(0,40,60,80,100,160,256,320…5120ms)
LTE EVENT A4
Event A4 trigger when neighbour cell becomes better than threshold.
It is similar to Event A1.
It hold the cell in good coverage area under neighbour.
LTE EVENT A5
Triggered when serving cell becomes worse than Threshold 1 and Neighbour Cell Becomes
better than Threshold 2.
EVENT A5
triggerQuantityA5(RSRP 0,RSRQ 1)
timeToTriggerA5 256ms default(0,40,64,80,100,128,160,256….5120)
hysteresisA5 10dB default(0…150)
a5Threshold1Rsrp -44 default(-140..-44dBm)
a5Threshold2Rsrp -44 default(-140..-44dBm)
reportIntervalA5
LTE EVENT B1 & B2
EVENT B1: This event is triggered when a neighboring interRAT cell becomes better than a threshold.
EVENT B2: is triggered when the serving cell becomes
worse than threshold-1 and neighboring inter-RAT cell
becomes better than threshold-2.
EVENT B1 PARAMETER
EVENT B2 PARAMETER
b1ThresholdGeran
b2Threshold1Rsrp
hysteresisB1
timeToTriggerB2
timeToTriggerB1
triggerQuantityB2
b1ThresholdEcNoUtra
b2Threshold2Geran
utranB1ThresholdRscp
hysteresisB2
b1ThresholdRscpUtra
b2Threshold2RscpUtra
LTE/VoLTE Mobility KPI Optimization
Mobility is the key procedure
for ensuring that users can
move freely within a network.
LTE/VoLTE
Mobility (HO)
LTE/VoLTE Mobility KPI Optimization
Mobility is the key procedure
for ensuring that users can
move freely within a network.
LTE/VoLTE
Mobility (HO)
LTE Handover
(Intra/Inter
Frequency)
IRAT Hanover
(Inter Radio
System
Technology)
LTE/VoLTE Mobility KPI Optimization
Mobility is the key procedure
for ensuring that users can
move freely within a network.
LTE/VoLTE
Mobility (HO)
IRAT Hanover
(Inter Radio
System
Technology)
LTE Handover
(Intra/Inter
Frequency)
 Intra-Frequency Handover: within same LTE frequency
(Event A3-is triggered when a neighboring cell
becomes better than the serving cell by an offset)
 Inter-Frequency Handover: different LTE frequencies
(Event A5-is triggered when a neighboring cell
becomes better than a threshold)
 IRAT Handover: between different Radio system technology like LTE to 3G or
2G (Event B1 & B2).
LTE/VoLTE Mobility KPI Optimization
LTE handover have two versions: X2‐based and S1‐based
X2 Based: When source and target eNB are served within the same MME pool.
LTE Handover
(Intra/Inter
Frequency)
LTE/VoLTE Mobility KPI Optimization
LTE handover have two versions: X2‐based and S1‐based
X2 Based: When source and target eNB are served within the same MME pool.
S1 Based: When source and target eNB are served in different MME pool.
LTE Handover
(Intra/Inter
Frequency)
MME
LTE/VoLTE Mobility KPI Optimization
LTE handover have two versions: X2‐based and S1‐based
X2 Based: When source and target eNB are served within the same MME pool.
S1 Based: When source and target eNB are served in different MME pool.
MME
LTE Handover
(Intra/Inter
Frequency)
Intra eNB Handover-HO between two cells of same eNB (S1 or X2 HO is not required)
LTE/VoLTE Mobility KPI Optimization
LTE/VoLTE Mobility
(HO)
LTE Handover
(Intra/Inter
Frequency)
IRAT Hanover (Inter
Radio System
Technology)
LTE/VoLTE Mobility KPI Optimization
LTE/VoLTE Mobility
(HO)
LTE Handover
(Intra/Inter
Frequency)
Preparation
Phase
IRAT Hanover (Inter
Radio System
Technology)
Execution
Phase
Formula
Mobility Success Rate [%]:
LTE/VoLTE Mobility KPI Optimization
Preparation Phase:
The phase when the source RAN request the target RAN to
prepare to accommodate the UE. The target RAN performs
admission control and reserves cell resources required for the
UE and prepares the UE access and sends the needed access
information in a container sent transparent through the source
RAN to the UE.
Execution Phase:
The handover execution phase starts with the source RAN
command the UE to make a handover. The source RAN
performs packet forwarding to target RAN during the execution
phase. The phase ends when the UE access the target RAN
and confirm the new connection in the target cell.
LTE/VoLTE Mobility KPI Optimization
LTE/VoLTE Mobility
(HO)
LTE Handover
(Intra/Inter
Frequency)
Preparation
Phase Fail
•
•
•
•
•
•
•
•
Neighbor Cell Load Issue
Check Feature & One Way
NBR Relation
TAC Issue
X2 Link or S1 Link Failure
Configuration Issue
Late HO+Early/Ping Pong
Cell Downtime & MME Pool
HW Issue
IRAT Hanover (Inter
Radio System
Technology)
Execution
Phase Fail
LTE/VoLTE Mobility KPI Optimization
LTE/VoLTE Mobility
(HO)
LTE Handover
(Intra/Inter
Frequency)
Preparation
Phase Fail
•
•
•
•
•
•
•
•
Neighbor Cell Load Issue
Check Feature & One Way
NBR Relation
TAC Issue
X2 Link or S1 Link Failure
Configuration Issue
Late HO+Early/Ping Pong
Cell Downtime & MME Pool
HW Issue
IRAT Hanover (Inter
Radio System
Technology)
Execution
Phase Fail
•
•
•
•
•
•
•
•
Coverage Issue
OverShooting
Poor SINR (CQI)
Interference
PCI Collision
Target Cell Range Issue
Poor RF Condition
HW Issue & Alarms
LTE/VoLTE Mobility KPI Optimization
Neighbor Cell Load Issue
Check PmHoPrepRejInHighLoad, PmHoPrepRejInOverload, if these counters are pegging we need offload the target cell by changing
layer management parameters and load balancing parameters.
Check Feature and One way neighbour cell relation or Missing Neighbour relation
Check IntraLTEHandover feature. Check cell relation who has most failure and if it define one way the define it to both way. Identify
missing cell relation and create manually, sometime ANR did not create the relation.
TAC Issue
Preparation
Phase Fail
Wrong TAC defined. Solution-Correct from the planning database.
X2 link or S1 link Failure
Delete relation and ANR will add
Configuration Issue
Check ExternalEUtranCellFDD, EUtranCellRelatioin, TermPointToENB, TemPointToMME MO.
Late HO + Early and Ping Pong
•
•
In this scenario we optimize the cell Individual Offset(CIO). If Late HO then set CIO i +ve side •
and if early handover the need to set CIO in negative side.Ping-pong of cell lead overshooting. •
•
If 100% failure then block the cell relation.
•
Cell Downtime & MME Pool issue
•
If HO-Preparation fail = 100%, it might be due to MME pool different at source and target end. •
Check source and target cell Cell Downtime auto and manually.
HW Issue
Neighbor Cell Load Issue
Check Feature & One Way
NBR Relation
TAC Issue
X2 Link or S1 Link Failure
Configuration Issue
Late HO+Early/Ping Pong
Cell Downtime & MME Pool
HW Issue
LTE/VoLTE Mobility KPI Optimization
PCI Conflict
PCI Collision lead high number of execution failure. If source and target is having same PCI then we need to replan the PCI.
OverShooting
Execution
Phase Fail
Some times HO failures due to far away sites. In this scenario we need to block the cell relation using
Isremovedallowed and ishoallwoed to be false. We can recommend CIO also. Over shooting cause POOR sinR
If there is POOR sinR we need to do physical optimization the site, check LM parameters.
High UL RSSI
Check for Loose Connectors,Faulty Antenna(Tx & Rx antenna ports),VSWR alarms,Faulty External
interference (cable tv , repeaters (due to power leak issues)
Target is Sleeping Cell
The target cell is sleeping, need fixed sleeping on daily basis.
Cell Range Issue
•
•
•
•
•
•
•
PCI Conflict
OverShooting
High UL RSSI
Target is Sleeping Cell
Cell Range Issue
Poor RF Condition
HW Issue & Alarms
Incorrect cell range setting between source and target , it will impact specific
Nbr not all nbrs relation, check HO per Nbrs.
The target cell is more than 15km from the UE (or the current cell range setting). In that case Ho-Exec fail occur. Need to
change cell range or cellindividualoffset b/w relation (as per required)
Poor RF Condition
HW Issue and Alarms
Quick Checks For Handover Optimization:
Check which relation are having most failures.
Changes like Cellindividualoffset, Blacklisting relation, Delete and recreate relation can be given as per the requirement.
PCI conflict needs to be check
Check the KPI for nearby site if issue is severe, any prelaunch site nearby.
Alarms like S1, X2 can be the issue.
If issue happening in Prepration phase then check for relation availability, PCI conflict.
Check for Swap sector if issue started after integration
freq defination check
LM parameter check & GS Alignment
Most Commonly Used Parameter to Optimize Handover
For Intra Freq Handover:
cellIndividualOffsetEUtran; a3offset; hsyteresisA3; timeTotriggerA3,
isHoAllowed, isRemovedAllowed, fliterCoefficientEUtraRsrp,sMeasure.
For Inter Freq Handover:
cellIndividualOffsetEUtran, a5Threshold1RSRP,
a5Threshold2RSRP,hysteresisA5, timeTotriggerA5, a2ThresholdRsrpPrim,
timeTotriggerA2Prim, hysteresisA2Prim
LTE/VoLTE Mobility KPI Optimization
LTE/VoLTE Mobility
(HO)
LTE Handover
(Intra/Inter
Frequency)
•
•
•
•
•
•
IRAT Hanover (Inter
Radio System
Technology)
SRVCC Settings (enable SRVCC, RSRP trigger threshold) only for VoLTE/QCI1
PSC/BCCH Collision
Congestion (Balanced traffic between UMTS carriers, offload with NBRs)
Missing Target NBR/Carriers for GSM/WCDMA
B2 event setting (b2threshold2UtraEcno/RSRP, offset & hysteresis etc.)
Redirection settings towards LTE to UMTS/GSM like voice prio or connectedmode
Thank You