Hi Assia
The assumption of 1 TRX with 4 voices of 16kbits/s is incorrect 1 TRX is 8 channels of 16kbits/sec so 1 TRX takes 2.25 TS of the E1, so 12 trx = 27 TS + 1 ts for omu + 3 ts for rsl (i.e for 3 cells + the first ts of e1 is not usable for tch) so practically 1 e1=12 trx