Spreading sequence adaptation in multicode CDMA systems

The problem of adapting the spreading sequences and the transmission powers of different users in a multicode direct-sequence code division multiple access (DS-CDMA) system is considered. Particular attention is given to a distributed algorithm which updates each pair of transmitter and receiver without information from other users. The sequence adaptation problem and the algorithm are studied from from the viewpoint of a single user as well as the viewpoint of the whole system. The algorithm is shown to give either the optimal sequences or sequences that are close to the optimal ones. The effect of restricting the choice of sequences to polyphase sequences is also considered