Hi

I am studying the TCH channel, and read the BB source. I find that the structure of  "TCH + SACCH" is depend on ts.that is when the timeslot is even, the 12 of a TCH multiframes is SACCH,and the 25 is idle;and When the timeslot is odd, the 25 of a TCH multiframes is SACCH,and the12 is idle.

is that right?

Yes

if that`s right, why ?

To share the load. So that the BTS doesn't have to process all the SACCH of all the TCH at the same time.

I can`t find any Material about

GSM 05.02 Clause 7 Table 1 of 9, the SACCH/TF entries

Cheers,

Sylvain