RS Forward Error Correction for Variable-Length Frames

A method of forward error correction by Reed-Solomon (RS) coding has been devised to increase the link margins of data-communication systems that must handle variable-length frames or packets of data. Heretofore, RS coding has involved fixed-length blocks: In order to encode variable-length frames, it has been necessary to (a) choose a fixed block length equal to a multiple of some given block length and greater than or equal to the length of the longest variable-length frame and (b) in the case of a frame shorter than the fixed block length, pad or fill the remainder of the block with extra bytes. This is very inefficient because the fill conveys no useful information, and any errors in the fill diminish the overall coding gain by using up some or all of the available error-correction capacity.