GSM Combined Channel Configuration

This page describes the GSM combined channel configuration for Time Slot 0 (TS0). It covers the 51-frame multiframe structure, mentioning the mapping of FCCH, SCH, BCCH, CCCH, SDCCH, and SACCH channels on TS0 for both downlink and uplink.

Signaling channels (SDCCH) are combined with (FCCH+SCH+BCCH+CCCH) on time slot TS0. In this configuration, the position of FCCH+SCH+BCCH remains unchanged, but the CCCH capacity is reduced from 9 blocks to just 3 blocks.

These 6 blocks are reallocated: 4 blocks are used by SDCCH, and 2 blocks are used by SACCH.

In the downlink, the CCCH provides a pathway for signaling channels (SDCCH/SACCH). Similarly, in the uplink, RACH gives a way for these signaling channels, as illustrated in the figure above.