Method and system for synchronizing a tdma communication network

Abstract

A method and a system are disclosed for synchronizing within a recurrent time frame the starting points of the transmissions from the various stations in a TDMA network wherein N stations distributed among M separate zones covered by M different down-link frequencies exchange pulse bursts through a satellite, each pulse burst being comprised of a preamble, a unique word, the transmitting station's address, and traffic data. The satellite includes a global beam antenna which covers all of the M zones and is adapted to receive M different up-link frequencies, means for converting these M up-link frequencies to M corresponding down-link frequencies, and M directional beam antennas covering the M zones, each of said M antennas being adapted to transmit the down-link frequency associated with the particular zone it covers. The bursts transmitted by the various stations are assigned a predetermined position within the frame. Each station detects whether it has received a unique word followed by the address of a given station. Upon detecting such an address, the station activates timing means which define a time interval associated with the station whose address has been detected and, at the end of that time interval, starts transmitting M successive bursts respectively destined for the M zones during predetermined time intervals within the frame. These M bursts are transmitted at different up-link frequencies so that the burst intended for a given zone will be transmitted at the up-link frequency corresponding to the down-link frequency for that zone. In accordance with an embodiment of the invention, the timing means comprise M timers respectively defining N time intervals associated with the N stations. The start of a station's transmission is determined by the timer which reaches its stopping point first.