Performance Evaluation of Multi-Pulse Based Code Excited Linear Predictive Speech Coder with Bitrate Scalable Tool over Additive White Gaussian Noise and Rayleigh Fading Channels

Problem statement: In the modern speech communication technology, the speech coding with bitrate scalability was needed. However, various types of noises in the communication channels cause damages in the transmitted information especially speech data. Tonal-language speech was also affected by this situation. Approach: Based on the high pitch delay resolution technique, the MPCELP speech coding was proposed over the environment with CDMA AWGN and Rayleigh fading channels for tonal language. The proposed coder supports multiple bitrates and also has the functionality of bitrate scalability. Results: Through performance analysis and computer simulation, the quality of the proposed coding was presented with an improvement from conventional scalable MP-CELP in the specific-noise environments. The HPDR technique was applied to the MP-CELP to use for tonal language, meanwhile it can support the core coding rate of 5.6, 8.2, 12.2 kbps and additional scaled bitrates. Conclusion: By applying the high pitch delay resolution technique with the MP-CELP speech coding, we can improve the quality of tonal encoded speech. Moreover, the coding quality of the proposed coder was better than the conventional coder for Thai language over both AWGN channel and Rayleigh fading channel.