Performance analysis of M-QAM with Viterbi soft-decision decoding
Manso, Rogerio C.
Ha, Tri T.
Tighe, Jan E.
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This thesis derives design tools for determining and improving performances of communication links that use M - QAM coherent demodulators associated with Viterbi soft-decision decoding (SDD) in Additive White Gaussian Noise (AWGN) and Nakagami-m channels. Performance analyses for 16-QAM, 64-QAM, QPSK and BPSK associated with up to three convolutional codes, including the one used by the IEEE 802.11a standard and the dual-k code, are presented as practical applications. The main tools relate to the analytical derivation of upper bounds of the probability of bit error (Pb) for any M -ary coherent demodulator followed by SDD, a methodology for improving an upper bound of Pb tightening it to realistic data, and the obtaining of the specific ( ) d b spectrum for any convolutional code intended to operate with a certain M-symbol modulation. All derivations involve statistical considerations over the AWGN and Nakagami-m channels, as well as in-depth analyses of modulator constellations. The tools and models developed can provide great optimization to bandwidth-limited system designs that require high data rates, especially the wireless ones. Consequently, they have great application to many fields of digital communications, such as cellular telephony, wireless networking, satellite links, ship-to-shore and ship -to-ship communications.