Reduced Complexity Adaptive MAP Receiver for Frequency-Flat, Time-Varying CDMA Channels

  • Authors:
  • Shiauhe Tsai;Wen Gao;James S. Lehnert

  • Affiliations:
  • School of Electrical and Computer Engineering, Purdue University, 1285 EE Building, West Lafayette IN 47907-1285, U.S.A.;School of Electrical and Computer Engineering, Purdue University, 1285 EE Building, West Lafayette IN 47907-1285, U.S.A.;School of Electrical and Computer Engineering, Purdue University, 1285 EE Building, West Lafayette IN 47907-1285, U.S.A.

  • Venue:
  • Wireless Personal Communications: An International Journal
  • Year:
  • 2001

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Abstract

An adaptive maximum \emph{a posteriori} (MAP) receiver withmultiple-access interference (MAI) mitigation is proposed for DS-CDMAsystems in frequency-flat, time-varying fading channels. The receiverconsists of a sequence matched filter (MF), an adaptive channelestimator, and a MAP demodulator. By oversampling the MF output, thereceiver can characterize the MAI symbol-by-symbol to suppress thestrong and time-varying MAI. Without any pilot insertion and \emph{apriori} knowledge, the channel estimator can adapt to various fadingchannels using a general, model-based approach. For practicalimplementations, a reduction in complexity is introduced and is shownto have a negligible effect on both uncoded and decoded bit errorrates (BER's).