Mapping of logical Channels

Generally two configurations are mainly used

Separate SDCCH: FCCH + SCH + BCCH + CCCH
–Addresses a channel configuration in which no SDCCH are available on TS 0.
–In this case SDCCH sub channels are defined on TS 1
–Rest of the TS are used by Traffic channels

Combined SDCCH: FCCH + SCH + BCCH + CCCH + SDCCH/4
–Addresses a channel configuration in which all control channels are assigned to TS 0
–In this case TS1 is also available for Traffic channels

Logical channels can time-share TS 0 in different TDMA frames of 51 frame Multi frame.