IS-96 describes a variable rate code-excited linear prediction (CELP) speech coder in code division multiple access (CDMA) digital cellular environment. In this work we focus on the study of the error protection methods in CDMA cellular environments. We find that although the error protection technique described in IS-96 can improve the speech quality in noisy channels considerably, the error concealment effect in IS-96 can be further improved by a better bit protection pattern without increasing the processing complexity.

A combination of trellis coded quantization (TCQ) and its vector alphabet generalization TCVQ is used to code the coefficients resulting from a biorthogonal wavelet transform in an image. TCVQ is a vector trellis coder with fixed rate, very good rate-distortion performance, and yet reasonable implementation complexity. The experimental results show that the Lena image can be coded by this coding system at the rate of 0.265 bpp to yield a peak signal-to-noise ratio (PSNR) of about 29 dB. This PSNR is about 3 dB larger than that obtained by a coding system of the same rate that uses VQ to obtain the wavelet transform coefficients. Naturally, the performance of the TCQ/TCVQ wavelet transform coder can be improved if entropy-coded TCQ and TCVQ coders are employed.>

A vector generalization of trellis coded quantization (TCQ), called trellis coded vector quantization (TCVQ), and experimental results showing its performance for an i.i.d. Gaussian source are presented. For a given rate, TCVQ yields a lower distortion that TCQ at the cost of an increase in implementation complexity. In addition, TCVQ allows fractional rates, which TCQ does not.>