Carrier recovery, the forward link in a ocdma without pilot tone, the expander band - communication system

摘要

A spread spectrum CDMA communication system in which a base station communicates with a plurality of subscriber terminals and the base signal transmitted by the base station is comprised of a set of substantially orthogonal functions which are overlaid with a pseudo-noise (PN) sequence forming a coded spreading sequence for an information signal, each orthogonal function of the set carries data for a single user in the system. Information signals are modulated onto the carrier to form a transmit signal and the coded spreading sequence on the transmit signal for broadcasting, each subscriber terminal having a receiver (41, 50) for coherently demodulating the base station signal. A plurality of correlators (53), each respectively tuned to different functions of the orthogonal signal set, are each followed by an appropriate nonlinearity (55-60) for removing the data modulation. The summed output of the correlators is used to improve the estimate of carrier phase over that obtained with a single correlator.