Receivers with widely linear processing for frequency-selective channels

TitleReceivers with widely linear processing for frequency-selective channels
Publication TypeJournal Article
Year of Publication2003
AuthorsGerstacker, H., R. Schober, and A. Lampe
JournalCommunications, IEEE Transactions on
Pagination1512 - 1523
Date Publishedsep.
Keywordsadaptive filter, amplitude shift keying, amplitude-shift keying, ASK, binary minimum-shift keying, cellular radio, convolution, decision feedback equalisers, decision feedback equalization, finite impulse response filters, FIR filters, frequency-selective channels, GSM, intersymbol interference, intersymbol interference channel impulse response, ISI, least mean squares methods, minimum mean-squared error criterion, minimum shift keying, MMSE, MSK, offset quadrature amplitude modulation, QAM, quadrature amplitude modulation, radio receivers, signal processing, transient response, trellis-based detection, widely linear processing, zero-forcing criterion

We propose several equalization schemes based on widely linear processing (WLP). The received signal and its complex conjugate are separately filtered and the results are linearly combined. It is shown that WLP yields a gain in performance if the (noiseless) received signal can be interpreted as the convolution of a real-valued data sequence and an equivalent complex-valued intersymbol interference channel impulse response. Such a model applies to, e.g., amplitude-shift keying, offset quadrature amplitude modulation, and binary minimum-shift keying-type modulation. We consider receivers without and with decision feedback. Finite impulse response filters are derived for these structures, which are optimum with respect to the zero-forcing and minimum mean-squared error (MMSE) criteria, respectively. In the MMSE case, adaptive algorithms for filter adjustment are given. Infinite filter orders are investigated in order to obtain analytical performance results. Furthermore, suboptimum trellis-based detection with widely linear preprocessing is briefly discussed. It is demonstrated analytically and by numerical examples that widely linear schemes may outperform conventional schemes significantly, depending on the considered application.


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