Information-theoretic sum capacity of reverse link CDMA systems

The information-theoretic sum capacity of reverse link CDMA systems is investigated in this paper. As the reverse link CDMA systems are interference-limited, for given channel and noise conditions, the information-theoretic system capacity can be achieved by optimally managing the interference from mobile stations. Optimal interference management means optimal allocation of the transmit powers of the mobile stations. The exhaustive search of the optimal power allocation policy that maximizes the aggregate system capacity, requires O(N^M) computations, where M is the number of the mobile station in the system and N is the granularity of the transmit power of a mobile station. In this paper, we prove that for a single cell, the number of computations to find the optimal power allocation solution can be reduced to O(NM), without sacrificing the optimality. We also show that an upper and a lower bound can be computed with O(M) computations, and the bounds are tight for small signal to noise ratio.