Synchronization Channel is a downlink only control channel used in GSM cellular telephone systems.It is part of the Um air interface specification.The purpose of the SCH is to allow the mobile station (handset) to quickly identify a nearby cell (a BTS) and synchronize to that BTS's TDMA structures.Each radio burst on the SCH contains: Synchronization Channel is a downlink only control channel used in GSM cellular telephone systems.It is part of the Um air interface specification.The purpose of the SCH is to allow the mobile station (handset) to quickly identify a nearby cell (a BTS) and synchronize to that BTS's TDMA structures.Each radio burst on the SCH contains: