Study of adaptive filtering technique for fading channels

Pao Yue-kong Library Electronic Theses Database

Study of adaptive filtering technique for fading channels


Author: Tam, Chi-hong
Title: Study of adaptive filtering technique for fading channels
Degree: M.Sc.
Year: 1997
Subject: Adaptive filters
Adaptive signal processing
Hong Kong Polytechnic University -- Dissertations
Department: Multi-disciplinary Studies
Pages: ix, 83 leaves : ill. ; 30 cm
Language: English
InnoPac Record:
Abstract: Radio signal fading caused by multipath can be a major problem in communication systems. Wideband signals are subject to frequency-selective fading. Adaptive filtering is discovered to provide a good technique for frequency-selective fading. In fact, the goals of our work are to present fading channel simulator and the proposed system model for an adaptive filtering in Kowloon Canton Railway Corporation (KCRC) environment. The radio channel of base stations and KCRC trains between Kowloon and Lo Wu Station are measured and a theoretical model developed. The measurement data are used to develop a computer model for frequency-selective fading channel in computer aided modeling of communication systems under fading conditions and predicting the performance in terms of bit error rate. Using the model obtained, we demonstrate that a properly designed adaptive equalizer provides performance improvement for binary phase shift keying (BPSK) modulation. The BPSK modulation with an adaptive equalizer simulated operates over a fading (4.25-Hz Doppler) mobile channel at bit rate of 1.7 and 3.4 kbit/s using 153-MHz carrier. The bit error rate for theoretical and simulated BPSK modulation in simulated Rayleigh fading channels with an adaptive equalizer have been thoroughly examined. The resulting bit error rate is quantified for various numbers of taps and alpha in our design. The adaptive equalizer with more taps produces less mean-squared error. However, it is found that the use of up to 12 taps in the adaptive equalizer can provide more dB improvement in bit error rate under fading KCRC environments. Adding taps beyond this number adds to the receiver complexity, while the performance benefit is either marginal or a degradation results. BPSK modulation with an adaptive equalizer can reduce the error propagation and suitable for KCRC fading environments. It is shown that BPSK modulation with an adaptive equalizer has smaller bit error rate.

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