Performance of a low complexity CELP speech coder under mobile channel fading conditions

The authors report on the simulation of a voice codec intended for the terrestrial and satellite radio environments. The coder is based on a complexity reduced version of code-excited linear prediction (CELP). The codebook search complexity has been reduced to only 0.5 MFLOPS (million floating point operations per second) while maintaining excellent speech quality. Novel methods to quantize the residual and the long- and short-term model filters are presented. Due to its inherent simplicity, the codec can be easily realized in VLSI form or implemented on a dedicated single-chip digital signal processor. The coder has been tested under simulated channel conditions. Different block coding and convolutional coding techniques have been applied to improve the performance of the coder in the presence of burst errors.<
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