LTE Accessibility Problem cause & solution a-z step Prepared by- Rajesh 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. RRC Phase. S1 Signaling Phase. E-RAB Phase. Definition based on Counter:- SSSR=[(PmRrcConnEstabSucc/PmRrcConnEstabAtt)*(Pms1SigConnEstabSucc/PmS1SigConnEstabAtt)*(PmErabEstabSuccInit/PmErabEstabAttInit)]*100 SSSR Phase based on Counter:- RRC Setup:-Following counter are Responsible- a> PmRrcConnEstabAtt. b> PmRrcConnEstabAttReAtt C> PmRrcConnEstabSucc

Accessibility/SSSR(Session setup success Rate):- 2.S1-Signalling Setup: Following Counter are Responsible- a> PmS1SigConnEstabAtt. b> PmS1SigConnEstabSucc. 3. E-RAB Establishment: Following Counter are Responsible- A> 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 verified- A> 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 5 deltaPsdRs2Tx (system constant 872) SpdcchLaGinrMargin (system constant 220) 30 numInitialAccessAndIncomingHo (system constant 556) 10 Hidden Parameter tPollRetransmitUl - DataRadioBearer 160 tPollRetransmitUl - SignallingRadioBearer tPollRetransmitDl - DataRadioBearer tPollRetransmitDl - SignallingRadioBearer dlMaxRetxThreshold - DataRadioBearer 8 ulMaxRetxThreshold - DataRadioBearer EUtranCellFDD noOfPucchCqiUsers Sector Level Parameter 640 noOfPucchSrUsers 590 pdcchCfiMode CF_Static_3 (3) ulSrsEnable TRUE UlFss featureStateUlFss 1 pZeroNominalPucch -120 pZeroNominalPusch -102 QciProfilePredefined schedulingAlgorithm - default RESOURCE_FAIR (0) schedulingAlgorithm - qci 1 schedulingAlgorithm - qci 2 schedulingAlgorithm - qci 3 schedulingAlgorithm - qci 4 schedulingAlgorithm - qci 5 schedulingAlgorithm - qci 6 schedulingAlgorithm - qci 7 schedulingAlgorithm - qci 8 schedulingAlgorithm - qci 9

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 Hi-Cap 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 Hi-Cap 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 E-RABs due to license rejects (Multiple Radio Bearer per user or RLC UM). Initial E-RABs 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. 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.

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