Martin Nesenbergs

Abstract: A U.S. Postal Service (USPS) electronic message system could incorporate many types of error control coding, or no coding at all. This report reviews a variety of possible codes, lists their advantages and disadvantages, and selects a preferred alternative. It turns out to be a concatenation of an inner convolutional (rate 1/2 to rate 3/4) code with Viterbi decoding, and an outer long block, high efficiency code. The two codes have separate functions, in the sense that the inner code performs forward error correction and the outer code does error detection only. The report describes the structures, properties, and implementations of the coding hybrid. After that, the performance of the preferred coding scheme is estimated. The resultant error probability gains, which are shown to be considerable, are balanced against system slowdown and bandwidth expansion.

Keywords: FEC; ARQ; coding gains; concatenated codes; error probability; hybrid operation; modem losses; throughput; Viterbi decoding

Disclaimer: Certain commercial equipment, components, and software may be identified in this report to specify adequately the technical aspects of the reported results. In no case does such identification imply recommendation or endorsement by the National Telecommunications and Information Administration, nor does it imply that the equipment or software identified is necessarily the best available for the particular application or uses.

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