VS.RAB.FailEstabPS.UuFail

[jeff]

Hi Experts,

What are the reasons for RAB Failures of this category? "VS.RAB.FailEstabPS.UuFail"

What could be solution(s) to resolve?

[samuraial]

Sometimes increasing RabRspTime from 5s to 10 sec helps resolving this problem.
Coverage optimization also helps(tilt optimization, overshooting analysis, pcpich optimization.
Activating SRB over HSUPA can increase this counter but usually it is about coverage problems.

Check the RNC parameters and compare them with a previous CFGMML in order to see any difference.

B/R

[jeff]

Hi Samuraial,

I didn't find RabRspTime. Did you mean RBSETUPRSPTMR?

RBSETUPRSPTMR is an RNC parameter, changing it will affect all cells in the RNC.



Sometimes increasing RabRspTime from 5s to 10 sec helps resolving this problem.
Coverage optimization also helps(tilt optimization, overshooting analysis, pcpich optimization.
Activating SRB over HSUPA can increase this counter but usually it is about coverage problems.

Check the RNC parameters and compare them with a previous CFGMML in order to see any difference.

B/R

[samuraial]

I know m8, but that is the last option but you can try the coverage optimization :).

B/R

[tharinduwije]

Best is to check the Propagation Delay (TP) Values & optimize the coverage levels.Also check RTWP levels since this can also cause poor UL performance.

[P.T.E.]

check TP to check unbalanced coverage and check DRD In and DRD out , u can optimize DRD parameters to solve RAB failure due to UuFail . for RBSETUPRSPTMR by increasing this timer PS RAB SSR will improved and PS RAB failure due to Uu no reply wil decrease greatly.

BR,

[gunpowder]

what is the best moderate value for RBSETUPRSPTMR ?

[samuraial]

Mostly of Huawei documents suggest it to be 10000(10s).

B/R

[paulus]

Hi Jeff,

If this cell has 2nd or 3rd carrier, try to disable BlindHO for this cell (neighbor interfre rellation to this cell)

BlindHO condition can trigger this issue due to HO based on non coveragemeasurement.

Thanks
BR//Paul

[mounir34]

dear
i am already facing a lot of case like this,please download the PCHR and use the FMA to analyse the Data , you will found PS RAB SR degradation due to “IMCOMPATIBLE_SIM_RECFG” with one user or more users ,
the solution :
added these users on black list

thank you

[awa_207]

Hi mounir34,
What's root cause of this issue?

Tks!

[Vladislav]

Hi Jeff,
A lot of things already answered in previous posts, but I want to make small summary:
VS.RAB.FailEstabPS.UuFail has 2 main reasons - UE no response and UE returns a failure message
1) UE no response, here you can check if there is a problem with Radio bearer setup. If radio bearer setup failed (VS.FailRBSetup.NoReply) in same trend as RAB setup it means that you have coverage issue. Also you can correlate with number of RAB abnormal releases and RRC failures due to UE no reply.
2) UE returns a failure message - here as mounir34 mentioned, there can be a problem with some particular UE or subscriber. For counter you can check also radio bearer setup group: VS.FailRBSetup.CfgUnsup, VS.FailRBSetup.PhyChFail, VS.FailRBSetup.IncCfg. Or better make PCHR analyses with FMA. Sometimes this can be a problem with inconsistent NodeB config or just some NodeB bug - better to reboot it first.
Also important question if you have this problem in just few cells or for entire network. If second - it is better to escalate the issue ;-)

Best regards!

[Vladislav]

Hi Paulus,
Just want to add that next actions can help to check if it is a DRD issue:
check the counters
Source cell:
VS.DRD.RBSetup.AttOut
VS.DRD.RBSetup.SuccOut
Target cell:
VS.DRD.RBSetup.AttIn
VS.DRD.RBSetup.SuccIn
It success rate is high - problem is not with DRD and blind handovers.

Best regards!

[sade]

Since your problem is related to PS RAB's you can check and adjust the criteria for initial TTI selection - if the great majority of users on cell level is using 2ms TTI, and you have a lot of failures - maybe you are trying to establish 2ms TTI in radio conditions which are inadequate for establishing 2ms TTI.
what are you settings of parameters:
BeThd6A1
BeThd6B1
BeThd6A2
BeThd6B2
EcN0ThsFor2msTo10ms
Those settings are RNC level - so change would impact all cells under RNC, but if done properly it can improve your KPI's and reduce UuFails