Spectrum-efficient cognitive radio transceiver using multiwavelet filters
ISRN Communications and Networking
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The bandwidth efficiency and ability to combat the effectsof frequency selective channels are critical issuesin the design of new digital modulation schemes. To improvethe bandwidth utilization and to avoid the inter symbolinterference (ISI) caused by the time dispersion in thechannel, a new multi-wavelet packets modulation (MWPM)scheme is proposed in this paper. The MWPM is based onthe orthogonal multi-wavelet packets (MWP). In particular,the orthogonality in MWP is exploited to guarantee the demodulationof the overlapped MWP coded signals in timeand frequency domains. A practical implementation of theMWPM transceiver is proposed by employing the matrix filterbanks. The bandwidth efficiency is increased r times forMWP with multiplicity r compared to the scalar waveletpacket modulation or the conventional fast Fourier transform(FFT) based orthogonal frequency division multiplexing(OFDM) system. Similarly, as these prototype schemes,the MWPM is implementable either as a binary or a multilevelscheme. As a multi-carrier modulation, MWPM canmitigate the time dispersiveness in the channel effectivelybecause the symbol duration can be extended as requiredby the flexible structure of MWPM.Using two orthogonal MWP introduced in [8] and [3]which are referred to in this paper after their inventorsý initialsas GHM and CL MWP, respectively, the correspondingMWPM are constructed. The performance for theseMWPM in additive white Gaussian noise (AWGN) and flatRayleigh fading channels is analyzed and simulated usingMonte Carlo methods, where the binary phase shift keying(BPSK) is used in each subcarrier. The simulation resultsdemonstrate the effectiveness of the proposed MWPMscheme.