Addressing L.E-RAB.FailEst.NoRadioRes

4G LTE
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1

Hi everyone,

Hope all is well.

I’m severe degradation of E-RAB Success Rate, mainly due to L.E-RAB.FailEst.NoRadioRes. I’m aware that these failures mainly due to insufficient license (which is the case, here I have 400 as allocated RRC Connected Users License (FDD) and the actual values are exceeding this). Things got relatively better after performing down E-tilt.

E-RAB SR
E-RAB SR723×339 41 KB

But my concern is, why Cell A and Cell C are impacted the most while B (which has much higher users) is less impacted? Isn’t the license equally distributed between cells at eNodeB level?

L.Traffic.User.Max

L.E-RAB.FailEst.NoRadioRes

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License number of RRC users is managed at enodeb level, not cell level.
Enb count current RRC connected UE inside it, if higher than license + 10%, new erab setup request will be rejected.
However, counter no of rrc users at enb is not sum of counter in all cells.
And cause no radio resource not onky include license limit but also, srs, pucch, synch ue congested

1 Like
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Hello @Hainm ,

Thanks for the feedback.

I have checked the related counters and it turns out that it’s a license issue indeed. Since license expansion is out of the table right now, I reduced UE Inactivity to 2s (combined with downtilting and traffic shift to UMTS) and almost nulled these failures.

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Inactivity timer 2s is very low, it can reduce number of RRC connected users but user experience reduce, setup time increase, uplink interference increase, CPU load increase, csfb call failure may increase also.

2 Likes
5

Yes, you’re right. The average CPU load was 9%, now it’s 12%. The number of users reduced by almost 32%. Other KPIs remained stable.

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Is there any observed problem with such low inactivity timer at the core side?

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I haven’t done a relevant trace from core side nor an issue rose to the surface (at least until now).