Accessibility/SSSR(Session setup success Rate)

Report
LTE Accessibility Problem cause &
solution a-z step
Prepared byRajesh Kumar
Accessibility/SSSR(Session setup success Rate):Definition: Ability of a user to Obtain an E-RAB from the System.
Point:-Accessibility/SSSR is combination of 3 Phase.
1. RRC Phase.
2. S1 Signaling Phase.
3. E-RAB Phase.
Definition based on Counter:SSSR=[(PmRrcConnEstabSucc/PmRrcConnEstabAtt)*(Pms1SigConnEstabSucc/PmS1SigConnEsta
bAtt)*(PmErabEstabSuccInit/PmErabEstabAttInit)]*100
SSSR Phase based on Counter:1. RRC Setup:-Following counter are Responsiblea> PmRrcConnEstabAtt.
b> PmRrcConnEstabAttReAtt
C> PmRrcConnEstabSucc
Accessibility/SSSR(Session setup success Rate):-
2.S1-Signalling Setup: Following Counter are Responsiblea> PmS1SigConnEstabAtt.
b> PmS1SigConnEstabSucc.
3. E-RAB Establishment: Following Counter are ResponsibleA> PmErabEstabAttInit
B> PmErabEstabSuccInit.
C> PmErabEstabAttAdded.
D> PmErabEstabSuccAdded.
Accessibility/SSSR(Session setup success Rate):Step for Find out the Problem with Counter:1.RRC Failure(PmRrcConnEstabFail):-Following issue need to be verifiedA> pmRrcConnEstabFailLic:The total number of failed RRC Connection Establishments
due to lack of connected users license.
Soln:- Upgrade the LKF(License Key File) by Upgrading Software.Ex- From L12A to L12B
And L13A to L13B.L13B having License of 2000 Connected user per ENB.(License/Software
upgradation activity depends as per Agreement with customer).For this Customer pay to
Ericsson.
Soln:- Offload the Traffic: 1> Shared the Traffic by Changing Azimuth,By Tilt,By
Implementing Hi-Cap Parameter.If still Traffic load is more,planned new site to offload.
B>pmRrcConnEstabFailHighLoad:The total number of failed RRC Connection
Establishments due to high load.
Soln: There are many ways to Offload the Traffic: 1> Shared the Traffic by Changing
Azimuth,By Tilt,By Implementing Hi-Cap Parameter.
Following are the List of Hi-Cap Parameter which can be tune as per N/W requirement.
Accessibility/SSSR(Session setup success Rate):MOC
Parameter Name
Parameter Type
Parameter - High Cap Site
System Constant
ulInterferenceForgettingFactor (system constant 70)
Site Level Parameter
System Constant
deltaPsdRs2Tx (system constant 872)
Site Level Parameter
5
0
System Constant
SpdcchLaGinrMargin (system constant 220)
Site Level Parameter
30
System Constant
numInitialAccessAndIncomingHo (system constant 556)
Site Level Parameter
10
Hidden Parameter
tPollRetransmitUl - DataRadioBearer
Site Level Parameter
160
Hidden Parameter
tPollRetransmitUl - SignallingRadioBearer
Site Level Parameter
160
Hidden Parameter
tPollRetransmitDl - DataRadioBearer
Site Level Parameter
160
Hidden Parameter
tPollRetransmitDl - SignallingRadioBearer
Site Level Parameter
160
Hidden Parameter
dlMaxRetxThreshold - DataRadioBearer
Site Level Parameter
8
Hidden Parameter
ulMaxRetxThreshold - DataRadioBearer
Site Level Parameter
EUtranCellFDD
noOfPucchCqiUsers
Sector Level Parameter
640
EUtranCellFDD
noOfPucchSrUsers
Sector Level Parameter
590
EUtranCellFDD
pdcchCfiMode
Sector Level Parameter
CF_Static_3 (3)
EUtranCellFDD
ulSrsEnable
Sector Level Parameter
TRUE
UlFss
EUtranCellFDD
featureStateUlFss
pZeroNominalPucch
Site Level Parameter
Sector Level Parameter
-120
EUtranCellFDD
pZeroNominalPusch
Sector Level Parameter
-102
QciProfilePredefined
schedulingAlgorithm - default
Site Level Parameter
RESOURCE_FAIR (0)
QciProfilePredefined
schedulingAlgorithm - qci 1
Site Level Parameter
RESOURCE_FAIR (0)
QciProfilePredefined
schedulingAlgorithm - qci 2
Site Level Parameter
RESOURCE_FAIR (0)
QciProfilePredefined
schedulingAlgorithm - qci 3
Site Level Parameter
RESOURCE_FAIR (0)
QciProfilePredefined
schedulingAlgorithm - qci 4
Site Level Parameter
RESOURCE_FAIR (0)
QciProfilePredefined
schedulingAlgorithm - qci 5
Site Level Parameter
RESOURCE_FAIR (0)
Site Level Parameter
RESOURCE_FAIR (0)
8
1
schedulingAlgorithm - qci 6
QciProfilePredefined
QciProfilePredefined
schedulingAlgorithm - qci 7
Site Level Parameter
RESOURCE_FAIR (0)
QciProfilePredefined
schedulingAlgorithm - qci 8
Site Level Parameter
RESOURCE_FAIR (0)
QciProfilePredefined
schedulingAlgorithm - qci 9
Site Level Parameter
RESOURCE_FAIR (0)
Accessibility/SSSR(Session setup success Rate):C> pmRrcConnEstabFailOverload:The total number of failed RRC
Connection Establishments due to overload.
Soln: Same as Above.
d>> pmRrcConnEstabFailActiveUserLicenseExceeded:The number
of failed RRC establishments due to more active users than what license
allows.
Soln:1. Check Active user per cell through counter PmActiveUserDlSum,
PmActiveUserUlsum.
2. Try to Offload traffic if possible by changing Azimuth,Tilt or Loading HiCap Parameter. Earlier we have discussed abt Hi-Cap.
3.Also check distance of UE from ENB,if connected from far
distance,Can change parameter RxlevAccmin to Protect access.
Accessibility/SSSR(Session setup success Rate):.e> pmRrcConnEstabFailFailureInRadioProcedure:The number of
failed RRC establishments due to failed radio procedure.
f> pmRrcConnEstabFailBearerAdmissionRej:The total number of
failed establishment of RRC Connection due to the fact that all the UE's
bearers are rejected during bearer admission.
Soln: Implement hi-Cap Parameter to allow more user.Also PDCCH Adm
control Th can be changed.Befor change Check PDCCH CCE Utilization
by Counter- PmPdcchCceUtil
g> pmRrcConnReestFailLicMtReest:The number of RRC Connection
Reestablishments attempts that failed due to feature "Multi-Target RRC
Connection Reestablishment" not being OPERABLE
Soln: Not included in any predefined scanner.So U have to activate
Scanner.
Accessibility/SSSR(Session setup success Rate):-
h>pmRrcConnEstabFailLackOfResources:The number of failed RRC
establishments due to lack of resources
Soln: check the Utilization of Cell and try to Offload by Implementing HiCap Parameter,Shift traffic on some less utilized cell.
i> pmRrcConnEstabFailUnspecified:The number of failed RRC
establishments due to unspecified cause.
Apart from that Please check Coverage issue,UL Interference issue,Alarm
issue,H/W issue(Re-set first) if required replace RRU.
Accessibility/SSSR(Session setup success Rate):2. S1-signalling Failure(PmS1SigConnEstabFail):-There is no any
Specific Secondary counter I have found.But Following could be the
reason :
a> TN(Transport issue): Need to check Fiber issue from IPBH Team.
b> TAC Wrong Configure: Configure Correct TAC as Per Design.
c> LAC-TAC mapping: Validate the LAC-TAC mapping is correct as per
Design.
d> Message mismatch: The message flow b/w UE to MME is found any
Mismatch,will laid S1-Signalling Failure.
Accessibility/SSSR(Session setup success Rate):3. E-RAB Failure(PmErabEstabFailInit)a> pmErabEstabFailGbrDlEnb(The total number of failed E-RAB setup attempts
due to downlink GBR overload for resources common to the eNodeB).
Soln: Parameter which is Responsible:dlNonGbrRatio, dlTransNwBandwidth
b> pmErabEstabFailGbrUlEnb(The total number of failed E-RAB setup attempts
due to uplink GBR overload for resources common to the eNodeB).
Soln: Parameter Which is Responsible :ulNonGbrRatio, ,ulTransNwBandwidth
c>pmErabEstabFailAddedLic(The total number of failed establishment of added
E-RABs due to license rejects (Multiple Radio Bearer per user or RLC UM). Added
E-RABs are all E-RABs present in S1 message E-RAB Setup Request).
d>pmErabEstabFailInitLic(The total number of failed establishment of initial ERABs due to license rejects (Multiple Radio Bearer per user or RLC UM). Initial ERABs are all E-RABs present in the S1 message Initial Context Setup Request).
Accessibility/SSSR(Session setup success Rate):Apart from that Following Could be checked:
1> Security update Fail.
2> Vendor specific issue.
3> TN(Transport issue).
Note: Some case study based Problem & Solution.
1. RRC Degradation due to RRC Reject.
Parameter: no of Pucch CQI user-160
no of Pucch Sr user-160
Here RRC Conn max user is>160
Hence due to CQI resource Congestion RRC Conn was rejected.
2. SSSR degrade due to Low S1 Succ rate: Sometimes it has been Observed that S1 Succ
rate degraded due to Software upgradation.Cell KPI
Improved after DUL Restart.
Accessibility/SSSR(Session setup success Rate):-
3. SSSR Degraded due to H/W issue: Once RRU was replace SSSR
improved.
Accessibility can also be improved by tunning these parameter.
Change dlMaxRetxTh &ULMaxRetxTh of SRB-1(1,2,4,8,16,32)
Note: Any Suggestion/Feedback will be Highly Appreciable to Improve This
Presentation.
THANK YOU

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