combined CCH for GSM & GPRS

Hi Folks,

I am new to GPRS/GSM stuff,

I have one question, if we use combined CCH for both GSM and GPRS
how excatly these CCH messages are trasmitted from BSC to TRX.

In GSM we use LAPD to transfer cch
messages to TRX and from there TRX will schedule those sgs to transmit on air, what happens in
GPRS??, do we have to send RLC/MAC
blocks on LAPD(wild guess)?

And another one is, I believe that
in GSM, TRX will take care of interleaving and framming ..etc.

who does scheduling of the messaages on air In case GPRS

Thanks