To shorten the initial synchronization of a moble station, time requiring the judgement of existence in a range and long code synchronous acquisition time in a cellular system using a CDMA(code division multipler access)/TDD (time division duplex) system.

A receiving base band processing part 27 reproduces the data of a perch channel from a received signal by using symbol timing obtained from a synchronizing circuit 28. The circuit 28 detects a unique word from the data of the perch channel and executes slot synchronous acquisition. A receiving level detection circuit 29 judges a base station using a short code having the highest receiving level out of obtained receiving levels as the nearest base station. The base station inserts information related to frame timing and information related to a long code sort used for an outgoing communication channel into the perch channel and transmits these information and the circuit 28 receives the transmitted information, acquires frame synchronization and acquires long code synchronization by using the long code sort.