how to know GPRS channel coding

Hi all, I want to know how to know GPRS channel coding. GPRS using PDCH, both MAC/RLC data block and MAC/RLC control block is transmitted on PDCH, although there is PACCH, PTCH, PTCCH and so on it still PDCH. then the MAC/RLC control block is coded with cs-1 channel coding scheme and MAC/RLC data block may be coded with other channel coding scheme. so when received a burst how to know what kind of MAC/RLC block it belong to and which channel coding scheme it used? Thanks!