Adaptive multicode CDMA for uplink throughput maximization

We determine the optimal adaptive rate and power control strategies to maximize the total average throughput in a multicode CDMA system. Peak power and instantaneous bit error rate (BER) constraints are assumed at the transmitter with matched filter detection at the receiver. We first obtain results for the case where the codes available to each user are unrestricted, and we then consider the more practical scenario where each user has a finite discrete set of codes. An upper bound for the maximum average throughput is obtained and evaluated for Rayleigh fading. Sub-optimal low-complexity schemes are considered to illustrate the performance tradeoffs between optimality and complexity. We also show that the optimum rate and power adaptation scheme with unconstrained rates is in fact just a rate adaptation scheme with fixed transmit powers, and it performs significantly better than adapting just power alone.