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为实现压缩语音在有多径衰落和多用户干扰的无线信道中的可靠传输,提出利用语音码流残留冗余的低密度奇偶校验码(LDPC)译码算法。因信源统计规律的时变性及信源编码复杂度和延时的限制,语音编码输出码流中还存在残留冗余,在信道译码时利用这些冗余可有效增强LDPC迭代译码的纠错能力。仿真结果表明:通过利用语音码流中的残留冗余,能有效提高LDPC码的纠错性能,减少平均迭代次数,明显降低译码运算量,改善合成语音质量。特别在信噪比较低时,效果更加显著,平均迭代译码次数下降30%~50%,合成语音平均谱失真下降0.3~0.8 dB。
In order to realize the reliable transmission of compressed speech in wireless channel with multipath fading and multi-user interference, a low density parity check code (LDPC) decoding algorithm using residual redundant voice stream is proposed. Due to the time-varying statistic rules of source and the limitation of source coding complexity and delay, residual redundancy exists in the output stream of speech coding, and these redundancies can effectively enhance the performance of LDPC iterative decoding in channel decoding Wrong ability. The simulation results show that by using the residual redundancy in the speech code stream, the error correction performance of the LDPC code can be effectively improved, the average number of iterations can be reduced, the decoding operation amount can be obviously reduced, and the synthesized speech quality can be improved. Especially when the signal-to-noise ratio is low, the effect is more remarkable. The average number of iterative decoding decreases by 30% -50%, and the mean spectral distortion of synthesized speech decreases by 0.3-0.8 dB.