UL TBF Access Fail

[TelecomEng1983]

Hello engineers,

I am facing TBF UL Access Fail in both technologies H... and E// in two unrelated cells.
I checked alarms/Trnasmission/possible neighbours same scenario... nothing came up. I also checked PDTCH availability/channel mapping, configuration GTRX or TG in E//
does anyone here haveorhad the same issue and if so please share a troublshooting method with all my gratitude

[subway]

And you are sure you dont have a UL TBF exhaust scenario? Lately with a lot of networks removing 3G and shrinking 2G capacities, on GPRS/EDGE you will see UL TBF exhaust scenarios, even when the traffic volume does not grant for it. You can also check if you have no antenna issues: check the TA on the two affected cells to see if it is not tilted accidentally and you have not run into an issue where your coverage area increased quite a bit. I have seen this a couple years ago.

[TelecomEng1983]

Hello,
Please can anyone tell me how to look at OMC Huwaei counters for UL TBF fails details?!

[TelecomEng1983]

Thanx a lot for your reply, for the exhaust scenario, does it mean exhausting 2G ressources? If so I have not a high PDTCH usage nor congestion

[subway]

No. If you have UL TBF issues, that is not necessarily related to PDTCH issues. A single timeslot can be divided into 8 times max if my memory servers me good enough. If you have more UL TBF requests than that, you have a UL TBF exhaust situation. You can imagine how shitty the user experience can be if you already split up a TS 8 times, but with mostly IoT that can happen if they are "pinging" or do keepalive often. I can't give you an exact KPI name, but you should be able to see UL TBF related data with both vendors.

[TelecomEng1983]

So even with PDTCH low usage percentage if i have more UL TBF requests (which during the degradation has increased) than 8 sub-timeslot i'll have them blocked! but with counters available in my hand I don't see rejects due to ressources but mostly due to "Immediat Assignement reject" with causes "Other".

[subway]

So even with PDTCH low usage percentage if i have more UL TBF requests (which during the degradation has increased) than 8 sub-timeslot i'll have them blocked!

Yes. A single uplink timeslot can only be split 8 times, and this is not going to be shown as a PDTCH issue. You should have KPI(s) for UL TBF separately. The "other" casue is not very helpful for sure... :-)