Error coding strategies for MELP vocoder in wireless and ATM environments

The U.S. Government has developed a new military standard (U.S. MilStd3005) 2400 bps voice coding algorithm known as MELP (mixed excitation linear prediction). This vocoder has quite acceptable voice quality and intelligibility under benign error channel conditions. However, when it is subjected to high error rates (due to noise and fading) as may be experienced in tactical wireless operations, amelioration techniques can be utilized which take advantage of the underlying inter-frame residual redundancy statistics of the specific MELP parameters. In wireless ATM system implementations, the vocoder error correction and amelioration technique must deal with the potential loss of ATM cells (in addition to the traditional RF impairments). This paper describes simulation experiments conducted on the MELP vocoding algorithm in both scenarios and notes that optimization strategies are highly dependent on both the error coding overhead allowed and the expected nature of the bitstream error and loss statistics.