Abstract: The present invention describes a communications system that utilizes frequency division multiple access (FDMA), code division multiple access (CDMA), and time division multiple access (TDMA) techniques for providing efficient use of frequency spectrum while supporting a large number of transmitters/users (2-6). Many users of the communications system share a common frequency band, but each transmit their respective message bursts (50) at different and specific times via a TDMA technique. To facilitate synchronization of the TDMA technique, each transmitter of the system is synchronized to a common timing reference (1) thereby abating the need to maintain synchronization between the transmitters (2-6) and receivers (8-12) of the system.

Abstract: An asynchronous communications receiver rapidly despreads and demodulating a short, low duty cycle CDMA burst signal. The receiver includes a multichannel despreader (20) for generating a plurality of despread signals (21) corresponding to timing offsets of a spreading code. The plurality of despread signals are respectively supplied to a plurality of demodulators (22) for demodulating each despread signal and for respectively generating a plurality of soft decisions for each demodulated bit values whereby each soft decision is proportional to the quality of the received signal. The plurality of soft decisions are supplied to both a first input of a plurality of multipliers (23) and to a plurality of inputs of a selector (28). The selector processes the soft decisions from each of the demodulators and generates a message indicator (29) when a message is present.