LTE Accessibility
Problem Cause & Solution
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
Accessibility/SSSR(Session setup success Rate):SSSR Phase based on Counter:1. RRC Setup: Following counter are ResponsibleA> PmRrcConnEstabAtt.
B> PmRrcConnEstabAttReAtt
C> PmRrcConnEstabSucc
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.
Solution: Upgrade the LKF(License Key File) by Upgrading Software.
Eg; From L12A to L12B And L13A to L13B. L13B having License of 2000 Connected user per ENB.
License/Software upgrade activity depends as per Agreement with customer. For this Customer
pay to Ericsson.
Solution: Offload the Traffic: >>> 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.
Solution: There are many ways to Offload the Traffic: >>> 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
System Constant ulInterferenceForgettingFactor (system constant 70)
System Constant deltaPsdRs2Tx (system constant 872)
System Constant SpdcchLaGinrMargin (system constant 220)
System Constant numInitialAccessAndIncomingHo (system constant 556)
Hidden Parameter tPollRetransmitUl - DataRadioBearer
Hidden Parameter tPollRetransmitUl - SignallingRadioBearer
Hidden Parameter tPollRetransmitDl - DataRadioBearer
Hidden Parameter tPollRetransmitDl - SignallingRadioBearer
Hidden Parameter dlMaxRetxThreshold - DataRadioBearer
Hidden Parameter ulMaxRetxThreshold - DataRadioBearer
EUtranCellFDD noOfPucchCqiUsers
EUtranCellFDD noOfPucchSrUsers
EUtranCellFDD pdcchCfiMode
EUtranCellFDD ulSrsEnable
UlFss
featureStateUlFss
EUtranCellFDD pZeroNominalPucch
EUtranCellFDD pZeroNominalPusch
QciProfilePredefined schedulingAlgorithm - default
QciProfilePredefined schedulingAlgorithm - qci 1
QciProfilePredefined schedulingAlgorithm - qci 2
QciProfilePredefined schedulingAlgorithm - qci 3
QciProfilePredefined schedulingAlgorithm - qci 4
QciProfilePredefined schedulingAlgorithm - qci 5
QciProfilePredefined schedulingAlgorithm - qci 6
QciProfilePredefined schedulingAlgorithm - qci 7
QciProfilePredefined schedulingAlgorithm - qci 8
QciProfilePredefined schedulingAlgorithm - qci 9
Parameter Type
Site Level Parameter
Site Level Parameter
Site Level Parameter
Site Level Parameter
Site Level Parameter
Site Level Parameter
Site Level Parameter
Site Level Parameter
Site Level Parameter
Site Level Parameter
Sector Level Parameter
Sector Level Parameter
Sector Level Parameter
Sector Level Parameter
Site Level Parameter
Sector Level Parameter
Sector Level Parameter
Site Level Parameter
Site Level Parameter
Site Level Parameter
Site Level Parameter
Site Level Parameter
Site Level Parameter
Site Level Parameter
Site Level Parameter
Site Level Parameter
Site Level Parameter
Parameter - High Cap
Site
5
0
30
10
160
160
160
160
8
8
640
590
CF_Static_3 (3)
TRUE
1
-120
-102
RESOURCE_FAIR (0)
RESOURCE_FAIR (0)
RESOURCE_FAIR (0)
RESOURCE_FAIR (0)
RESOURCE_FAIR (0)
RESOURCE_FAIR (0)
RESOURCE_FAIR (0)
RESOURCE_FAIR (0)
RESOURCE_FAIR (0)
RESOURCE_FAIR (0)
Accessibility/SSSR(Session setup success Rate):C> pmRrcConnEstabFailOverload:The total number of failed RRC Connection
Establishments due to overload.
Solution: Same as Above.
D> pmRrcConnEstabFailActiveUserLicenseExceeded:The number of failed RRC
establishments due to more active users than what license allows.
Solution:1 Check Active user per cell through counter PmActiveUserDlSum, PmActiveUserUlsum.
Solution:2 Try to Offload traffic if possible by changing Azimuth, Tilt or Loading Hi-Cap
Parameter. Earlier we have discussed abt Hi-Cap.
Solution: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.
Solution: 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
Solution: Not included in any predefined scanner. So you have to activate Scanner.
Accessibility/SSSR(Session setup success Rate):H>pmRrcConnEstabFailLackOfResources:The number of failed RRC establishments due to lack of
resources
Solution: 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(Reset first) if required replace RRU.
Accessibility/SSSR(Session setup success Rate):2. S1-signalling Failure(PmS1SigConnEstabFail):-There is no any Specific Secondary counter was
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 S1Signalling 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).
Solution: 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).
Solution: 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.
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 Upgrade. 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 tuning these parameter.
Change dlMaxRetxTh & VULMaxRetxTh of SRB-1 (1,2,4,8,16,32)
Note: Any Suggestion/Feedback will be Highly Appreciable to Improve This Presentation.
THANK YOU