Error Correction Code Performance on HF, Troposcatter, and Satellite Channels

Four forward error correction techniques are examined and their performance compared on several real channels. Techniques of both adaptive and nonadaptive block and convolutional coding are examined. The Golay code is considered in a randomerror correcting mode and in an adaptive burst-random modes. Both versions employ interleaving as an added error correction aid. The adaptive convolutional code is a diffuse threshold-decoded Gallager code requiring a variable guard space, while the nonadaptive is a Massey code. The codes are commonly used rate 1/2 codes. The codes are evaluated and compared on three channels: a transcontinental HF 4800 bit/s channel between San Diego, Calif., and Bedford, Mass.; a mixed wireline microwave troposcatter 2400 bit/s channel dominated by a 583-mi troposcatter hop; and a 2400 bit/s satellite communications circuit from Ascension Island to Andover, Me., with wireline transmission from Andover, Me., to Greenbelt, Md. All three channels exhibit burst errors with the error rate decreasing and the burst error density increasing in the order in which channels were identified. The adaptive codes are shown to perform better than nonadaptive codes, although the difference is less significant for convolutional codes. Furthermore, the convolutional codes give better performance than nonconcatenated block codes.