Multirate CDMA system using biorthogonal coding

摘要

A modulation channelization, demodulation and error-control system based on orthogonal bipolar spreading vectors is provided that permits a variable information rate to be transmitted without inducing envelope fluctuations and which permits multiple access without requiring the transmitter amplifier to support the combined information rate of all users. The modulation system uses the Hadamard matrix vectors to form communication channels. The information rate on any channel may be doubled by using half the vector length to transmit information. The vector that is not orthogonal-in-the-half to the rate-doubled vector is deactivated. Similarly, higher information rates may be provided through truncation of the transmission vector and the elimination of the resultant non-orthogonal vectors. The system provides biorthogonal modulation in addition to multirate communication. A multi-channel receiver including a Fast Hadamard Transform structure comprised of controllable modified logic cells for performing the multi-rate communication of the present invention is illustrated.