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Reply To: T200 optimal value



The Qos Stats show a clear & strong corelation between the KPI and the parameter T200. That’s amazing !

Regarding the Ack from the BTS, I’m not sure (and I’m tired to look in the 3GPP specs 🙂 ). Take the subchannel “0” from the SDCCH ts.

in DL : the BTS sends SDCCH/0 on burst 0, 1, 2, 3 and the SACCH/0 on burst 32, 33, 34, 35

in UL : th MS sends SDCCH/0 on burst 15, 16, 17, 18
and the SACCH/0 on 47, 48, 49, 50

And I ***believe*** that the Lapdm acknowledgments can be sent on either the SACCH or the SDCCH, since both of them are sent over the same LapDm link. I’m not sure at all about this though, but it sounds logical.

The value of the SDCCH Drop due to Radio failures (in ALU) is usually around 1% in a fairly good network. The SDCCH Drop due to Radio Failures is a counter that encompasses both the Radio Link Timeout and the “T200*N200+1 times” failures.

I am not able to test your changes because I am not working on a live network (i am a gsm trainer, living in a world of theory…)

T200 = 220ms for sDCCH SAPI0
= 450ms for SDCCH SAPI3
= 900ms for SACCH associated to SDCCH

Looking at those timers, I fear that the LapDm link for SDCCH is different than the LapDm link for the SACCH of the SDCCH… I’ll let you look it up though 🙂