CDMA/TDD mobile communication system and method

A mobile station apparatus in a CDMA/TDD mobile communication system that employs a communication frame comprising a plurality of time slots each assigned one of a forward link and a reverse link, the CDMA/TDD mobile communication system comprising a base station apparatus that assigns a synchronization control signal to position fixed forward link time slots disposed at regular intervals among the plurality of time slots and that divides time slots other than the position fixed forward link time slots into time slots for a reverse link user information channel and time slots for a forward link user information channel according to an amount of information on the reverse and forward link user information channels, the mobile station apparatus comprising:

• a receiver that receives the synchronization control signal included in the position fixed forward link time slots and a signal of the time slots for the forward link user information channel;
• a correlation detector that performs correlation detection of the synchronization control signal per sample timing of a reception signal;
• an integrator that integrates a correlation detection result acquired per sample timing in an integration cycle corresponding to a length of the intervals at which said position fixed forward link time slots are disposed;
• and
• a synchronizer that determines that a sample timing at which an integrated value of the correlation detection result is largest in the integration cycle includes the synchronization control signal, and acquires synchronization with the base station apparatus based upon the largest integrated value.