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6 April 1995 Application of wavelet-domain adaptive filtering to spread-spectrum communications
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Frequency domain signal processing has been used for some time to suppress narrowband interference in spread spectrum signals. Essentially, narrowband interference energy appears in only a few of the transform bins whereas the wideband spread spectrum signal energy appears in most, if not all, of the bins. A simple exciser, which sets bins that are primarily interference to zero, can then remove most of the interference energy while removing only a small portion of the spread spectrum signal energy. Recently, this concept has been extended to include wavelet transform domain excision where the time-frequency localization properties of the wavelet transform are utilized to improve the effectiveness of the excision process. This paper generalizes this work by considering wavelet-based linear transforms and multirate filterbanks and replacing the simple exciser with continuously variable adaptive tap weights on each transform bin. These tap weights can be derived using a transform domain adaptive filter structure wherein the weights are adapted to optimize the detection performance in the mean- square sense, effectively producing a transform domain decision-directed equalizer. The paper presents an analytical result for bit-error-rate (BER) performance that is applicable for arbitrary linear transforms and generic multirate filterbank analysis/synthesis structures. Both adaptive weighting and simple exciser schemes are considered. Through both analytical and Monte-Carlo simulation results, the adaptive filter is shown to provide significantly better performance than the simple exciser for tone interference.
© (1995) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Michael J. Medley, Gary J. Saulnier, and Pankaj K. Das "Application of wavelet-domain adaptive filtering to spread-spectrum communications", Proc. SPIE 2491, Wavelet Applications II, (6 April 1995);


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