Effective Application of Forward-Acting Error-Control Coding to Multichannel HF Data Modems

The results of a recent study to determine and evaluate effective methods of applying forward-acting error-control-coding techniques to multichannel high-frequency (HF) data modems are presented. A unique feature of this study is a conscious exploitation of the fine-grain bit-error behavior, both in time and in frequency, that is characteristic of multichannel HF data transmission systems. Attention is focused on the ability of four promising coding techniques to combat the characteristic error behavior. These techniques involve the use of bit-interleaved binary block codes, diffuse convolutional codes, block-interleaved two-stage concatenated codes with binary-coded inner stages and nonbinary-coded outer stages, and a class of two-stage binary codes with random-error-correcting inner stages and burst-error correcting outer stages.