Successive interference cancellation for uplink CDMA

Successive interference cancellation (SIC) is a promising technique for increasing the capacity of uplink CDMA systems due to its low complexity, allowance of strong error-correcting codes, and robustness in an asynchronous environment. Despite these attractive qualities and a decade of research, SIC has been plagued by several crucial problems that have prevented its adoption by industry. This dissertation presents effective solutions to these problems and develops a system design that increases capacity by up to an order of magnitude over that of widely used CDMA systems in a realistic wireless environment.; First, channel estimation error can easily cause catastrophic error propagation in a SIC system. An optimum power control distribution is derived that is specifically designed to mitigate estimation error. This power control formula is a general result for CDMA; previous results on CDMA power control that neglect imperfect interference cancellation are special cases. It is shown that by using this distribution, estimation error of up to 50% can be tolerated in using SIC to more than double the overall system capacity. As a side benefit of adopting this more general power control strategy, it is shown that other-cell interference and the average transmit power of each mobile node can be reduced by an order of magnitude as well, based only on path loss considerations.; Second, a non-uniform received power distribution apparently implies greater power control complexity, as all users must be kept at or near their optimum power levels, which differ based on their decoding order. Nevertheless, a simple iterative technique for achieving the optimum distribution is shown to exist. Convergence is proven mathematically for a static channel, and shown by simulation for a fast fading channel.; Finally, a multipath channel seriously hinders previous SIC systems, suggesting the need for an integrated OFDM front end. Analytical BER expressions for a novel Multicarrier-SIC (MC-SIC) system are derived in a frequency-selective fading channel, and simulation results confirmed the effectiveness of using narrowband carriers to combat multipath. There is only a small degradation relative to an AWGN channel, and it is shown that the proposed MC-SIC system design with optimal power control increases capacity by up to an order of magnitude over current industry systems.