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Holger Freyther holger at freyther.de> On 26. Jun 2018, at 15:27, Harald Welte <laforge at gnumonks.org> wrote: > Hey! >> In that specific case only 9/20 MS completed an Update Location within 60s. Maybe I am missing a state transition in the LUA code and don't report the success. I will need to understand this better. > > That's of course odd. But it should be rather easy to investigate if > looking at an Abis or A-interface trace? I think we recently had an > issue that we'd only use SDCCH for LU and never fall back to "bigger" > channels like TCH. Maybe that's limiting your LU rate, particularly if > you only have a SDCCH/4? Sure. But that is what we want to test as well? Immediate Assignment Rejects and back-off handling. What happens is more funny though. While looking at the RSL trace I noticed that in "CHANNEL REQUIRED" the T1, T2, T3 of consecutive requests were the same. All MS started at the _same_ second will pick the same random numbers. These are used for the RACH request and also the back-off handling. The obvious change is to go from random() to osmo_get_rand_id and indeed things are a lot better. This makes a big difference but has uncovered another issue. We have a big spread between when the LU starts and it finishes. One example is the Immediate Assignment Reject handling. IIRC Jacob implemented grouping multiple rejects into a single reject message but now we give the same "Wait Indication" in all four entries. We need to do a bit better than that. Is there a "master" bug for things to improve with many MS? The other thing I wondered about. Maybe we keep a small ring buffer of bits we have seen in channel required messages? If we see requests in near by GSM frames there is little point in answering _any_ of them. We might just create radio interference between them... cheers holger