Chip-level MMSE equalization for high-speed synchronous CDMA in frequency-selective multipath

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Abstract
This work deals with synchronous CDMA transmission using orthogonal channel codes in frequency selective multipath. The motivating application is the Forward Link in 3G CDMA Cellular Systems. In saturated systems, the intra-cell Multi-user Access Interference created by the multipath causes the RAKE receiver to yield extremely poor performance. The chip-level MMSE estimate of the (multi- user) synchronous sum signal transmitted from the base followed by a correlate and sum with the desired user's spreading code, Walsh-Hadamard channel code multiplied by appropriate portion of long code, has been shown to yield superior performance to the RAKE receiver. This work considers reduced-rank, chip-level MMSE estimation based on the Multi-Stage Nested Weiner Filter (MSNWF) of Goldstein and Reed. It is shown that only a small number of stages of the MSNWF are needed in order to achieve near full-rank MMSE performance over a practical SNR range. This implies rapid adaptation in the case where the chip-level MMSE equalizer is adapted based on the pilot channel.© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

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