Comparison of two speech coders for digital mobile radio applications

This paper attempts to compare the performance of two popular speech coders, namely regular pulse excitation with long-term predictor (RPE-LTP) and code-excited linear prediction (CELP), in both random and burst error environments. In simulation, the bit stream generated by each coder is corrupted with error patterns obtained from the burst error model. The burst error model consists of two parts: a Rayleigh fading envelope generator and an M-ary differential phase shift keying receiver model in which the signal level is varied according to the Rayleigh fading envelope. The performance of each coder is evaluated both objectively and subjectively. The simulation results indicate that the RPE-LTP coder provides more consistent performance in the burst error environment. This paper also discusses the comparison of four channel coding techniques designed for the CELP coder.