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本文用计算机模拟,以实际话音信号输入对三种有代表性的自适性增量调制系统进行了比较研究。这三种系统是连续可变斜率增量调制(CVSD),固定系数增量调制(CFDM),和改进的混合压扩增量调制(HCDM)。三种系统中,不管信道误码情况如何,HCDM所得到的信号量化噪声比与动态范围性能都最好。在理想信道情况下,CVSD和CFDM上比较,最大信号量化噪声比几乎相同,但CFDM的动态范围要显著大于CVSD系统。在噪声信道中,随着误码率增大,CFDM系统的性能劣化比其他两种系统更为迅速。对于误码率在10~-3以上的信道,传输码率低于 16kb/s时CFDM就无法使用了,但用HCDM或CVSD,甚至误码率高到10~-1还可以作到可懂话音传输。
In this paper, computer simulation is used to compare three representative adaptive incremental modulation systems with actual voice signal input. The three systems are CVSD, CFDM, and HCDM. In all three systems, HCDM achieves the best signal-to-noise and dynamic range performance regardless of channel error conditions. In ideal channel conditions, the maximum signal-to-noise ratio for CVSD and CFDM is almost the same, but the dynamic range of CFDM is significantly greater than for CVSD systems. In the noise channel, as the bit error rate increases, the performance degradation of the CFDM system is more rapid than that of the other two systems. For channels with bit error rate above 10 ~ 3, CFDM can not be used when the transmission bit rate is lower than 16kb / s, but even using HCDM or CVSD, even the bit error rate of 10 ~ -1 can be understood Voice transmission.