On the Performance of Chip-Level MMSE Equalization for CDMA Packet Data Networks.

MMSE equalization is a very efficient method for combatting multiple access interference (MAI) in CDMA systems. To reduce the computation cost, the MMSE equalization can be done in a reduced-rank fashion. In reduced-rank MMSE equalization only some of the coefficients of the MMSE equalizer are optimized. In an adaptive setting, reduced-rank filtering can also increase the filter convergence. In this paper, we study the system throughput of a CDMA packet data network whose receivers are equipped with MMSE equalizers (both full-rank and reduced-rank) and use automatic retransmission request (AR-Q) and packet combining. Using previous results, we derive the SINR, at the output of a reduced-rank receiver. This SINR is used to derive the expression of the system throughput as a function of the rank. We run simulations to study the impact of the filter rank on the throughput.