thanks PIX for your reply. one more question it is said that one SDCCH/8 logical channel can serve 8 MS. while one SDCCH/4 can do it for 4 MS. How is it calculated? I mean at any instance (live time) the SDCCH will be serving one MS only and after that it will become free and can be used by other MS and so on(pl correct if not so). So does that means if we consider a 51-TDMA frame structure plus assuming that none of the frame will go idle 50/8=6 frames are required by a MS for completing the signalling work.