Coding strategies for CDMA packet data networks with reduced rank multiuser detection, ARQ and Packet Combining

Reduced-rank code division multiple access (CDMA) multi-user detection has received a lot of attention recently. The output SINR provided by a reduced-rank receiver depends on the filter rank and is confined between the SINRs of the single user matched filter (SUMF) and the minimum mean squared error (MMSE) receiver. In packet CDMA data networks like HSDPA, the measure of performance is the throughput. Thus, previous results on reduced-rank MMSE receivers SINR cannot be used directly. In this paper, we study the throughput of CDMA data networks using reduced-rank MMSE receivers, automatic retransmission request (ARQ) and packet combining. We derive the expression of the system throughput as the function of the filter rank, the coding rate and the number of retransmissions. We present simulation results to highlight the behavior of the maximum throughput as a function of the filter rank and the coding rate. We then conclude on coding strategies to adopt depending on the signal to noise ratio and the receiver rank in order to maximize the system throughput.