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Reply To: T200 optimal value

#61104
Zbigniew
Guest

Hi Pix,

here is some more information.

In Siemens there are two parameters sdcchSAPI0 and sdcchSAPI3 which represent the T200. We changed them both equally in steps of 100 ms up to 1000 ms. In Nokia there is only one parameter T200S (T200F is for FACCH call setup which we don’t use) and it was incremented the same way. The range is from 145 (220) ms up to 1260 ms.

There are several counters for the SDCCH drops (i.e. Radio / BTS / Abis Failure, User Action etc). But the only counter that is decreased (if T200 is increased) is “SDCCH Radio Failure”. We guess that after (N200+1)*T200 the L2 is torn down, which will result in an “Error Indication” to L1, which will afterwards be torn down as well. Because the “SDCCH Radio Failures” are the main part in the SDCCH drops we think that this must related to bad RF conditions – but we haven’t found an exact method to make this “bullet proof”.

Why do you want to distinguish between SAPI0 and SAPI3 ?
SAPI0 = RR,MM,CC SAPI3 = SS,SMS

The T200 procedure is the same, isn’t it ?

Kind Regards

Zbigniew