FORWARD LINK CARRIER RECOVERY IN AN OCDMA SPREAD SPECTRUM COMMUNICATION SYSTEM WITHOUT A PILOT TONE

摘要

A spread spectrum CDMA communication system in which a base stationcommunicates with a plurality of subscriber terminalsand the base signal transmitted by the base station is comprised of a set ofsubstantially orthogonal functions which are overlaid with apseudo-noise (PN) sequence forming a coded spreading sequence for aninformation signal, each orthogonal function of the set carriesdata for a single user in the system. Information signals are modulated ontothe carrier to form a transmit signal and the coded spreadingsequence on the transmit signal for broadcasting, each subscriber terminalhaving a receiver (41, 50) for coherently demodulating the basestation signal. A plurality of correlators (53), each respectively tuned todifferent functions of the orthogonal signal set, are each followedby an appropriate nonlinearity (55-60) for removing the data modulation. Thesummed output of the correlators is used to improve theestimate of carrier phase over that obtained with a single correlator.