A general model for multiple access communications

A general model for multiple access methods (FDMA, TDMA and CDMA) is given. We point out that if orthogonality is determined by transmitter and receiver jointly, better performance can be obtained. Using some reasonable assumptions on the channel in the model, we deduce the Lagrange/Vandermonde system where orthogonality is determined by transmitter and receiver jointly and its BER performance is much better than that of a conventional CDMA system using Gold codes, while the time-varying multipath channel adopted here is different from that in Scaglione et al., 1997.