Error correction of low rate speech in jammed HF ECCM

The authors describe the application of error detection and correction (edac) coding to linear predictive coding based voice coders at 600, 800, and 1200 b/s. In all cases, the transmitted information rate is 2400 b/s, which means that rate 1/4, 1/3, and 1/2 codes are used. The candidate baseline voice coding schemes are described. Several candidate edac codes, both block and convolutional, are discussed, and comparative results from simulations are presented. It is demonstrated that reasonable speech intelligibility can be maintained on jammed frequency-hop low-rate speech systems when appropriately chosen error correction techniques are applied to the speech bit stream. Reed-Solomon (RS) edac performs more robustly than alternative schemes, especially as it inherently allows erasure processing. When a random channel bit error rate of several percent was added to hop jamming, smaller symbol size RS codes are found to operate best