Autonomous master-slave frame synchronization among microcellular base stations

In the case of TDMA-TDD multiplexed transmission systems such as the one us ed for PHS in the microcellular mobile communication, the number of usable channels decreases due to interference by signals from nearby base stations , unless there is frame synchronization of the signal transmitted from the base station. An autonomous master-slave synchronization system is proposed which can easily cope with system modifications such as addition of base s tations. The timing difference of the transmission and reception at the bas e station is evaluated. The basic synchronization algorithm is as follows. (1) A master station is placed at a rate of one out of several hundred and the control signal of the master station is generated with accurate timing. (2) The slave stations, those not the master station, enter all-receive mo de at the synchronization control time and observe the timing of the contro l signals received. (3) After observation for a constant duration of time, the slave stations select the earliest timing in terms of frame units from the timings of the received control signals and transmit the synchronized c ontrol signal. In most cases, the timing difference of the transmission and reception obtained by this system at each station is less than twice the p ropagation time tau(w) over the effective reachable distance of the base st ation signal. (C) 1998 Scripta Technica.