On suboptimum receivers for DS-CDMA with BPSK modulation

TitleOn suboptimum receivers for DS-CDMA with BPSK modulation
Publication TypeJournal Article
Year of Publication2005
AuthorsSchober, R., W. H. Gerstacker, and L. Lampe
JournalSignal Processing

In this paper, we will show that for direct-sequence code-division multiple access (DS-CDMA) with binary phase-shift keying (BPSK) modulation transmitted over complex baseband channels the real part of the matched-filter (MF) output and not the MF output itself should be used as sufficient statistics for further processing. Based on this observation, we derive novel improved linear and decision-feedback (DF) minimum mean-squared error (MMSE) receivers. We also consider improved linear and DF decorrelating (DC) receivers, which however can be viewed as a special case of the group detectors proposed in (IEEE Trans Inform; Theory IT-41 (1995) 1083). We will show that the improved suboptimum receivers significantly outperform conventional suboptimum receivers that process the complex MF output. In particular, we show that systems using the improved suboptimum receivers can support twice as many users as systems using conventional suboptimum receivers. In addition, we prove that the considered improved linear receivers are equivalent to previously reported receivers with widely linear (or conjugate linear) processing. Also a novel widely linear DF-MMSE receiver, which is equivalent to the proposed improved DF-MMSE receiver, is given and corresponding adaptive algorithms for filter adjustment are derived. (c) 2005 Elsevier B.V. All rights reserved.


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