Soft-decision COVQ for turbo-coded AWGN and Rayleigh fading channels

A robust soft-decision channel-optimized vector quantization (COVQ) scheme for Turbo-coded additive white Gaussian noise (AWGN) and Rayleigh fading ch annels is proposed. The log likelihood ratio (LLR) generated by the Turbo d ecoder is exploited via the use of a q-bit scaler soft-decision demodulator , The concatenation of the Turbo encoder, modulator, AWGN channel or Raylei gh fading channel, Turbo decoder, and q-bit soft-decision demodulator is mo deled as an expanded discrete memoryless channel (DMC), A COVQ scheme for t his expanded discrete channel is designed. Numerical results indicate subst antial performance improvements over traditional tandem coding systems, COV Q schemes designed for hard-decision demodulated Turbo-coded channels(q = 1 ), as well as performance gains over a recent soft decoding COVQ scheme by Ho.