DISCRETE WAVELET TRANSFORM BASED MULTICARRIER MODULATION OVER THE NONSELECTIVE RAYLEIGH FADING CHANNEL

Abstract

In this thesis, the performance of discrete wavelet transform based multicarrier modulation (DWT-DMT) with differential detection of binary differential phase shift keying (BDPSK) over the nonselective Rayleigh fading channel is investigated. Multicarrier modulation is implemented with cosine modulated filter banks (CMFB). The prototype filter of CMFB is optimized by using nonlinear programming algorithm. While the filter for the CMFB with many subchannels is difficult to be optimized, cubic-spline interpolation is introduced to get such filter. The orthogonal conditions which ensure zero intersymbol interference (ISI) and zero interchannel interference (ICI) for an OQAM-OFDM system are derived, and the optimal signal waveform are obtained by using nonlinear programming algorithm under the orthogonal constraints.

The fundamental approach for analyzing the BEP performance of MDPSK over the nonselective Rayleigh fading channel proposed by Kam [50] is extended to the BDPSK DWT-MCM system. The computed numerical BEP is almost same as the results in [50] for the case that the transmitted signal is a rectangular wavefonn and the receiver filter is a matched filter. The sensitivity of the BEP to the fading rate fDT is also to noted, especially in the region of small values of fDT. Now, for a data rate which is much greater than the coherent bandwidth of the fading channel, we can employ the orthogonal waveform in our DWT-MCM system, the performance will be as good as the data signal transmitted over the nonselective fading channel.