Abstract
The construction of high-rate codes is far from obvious, as table look-up for encoding and decoding is an engineering impracticality. The usual approach is to supplement the p source bits with m=q-p bits. Under certain, usually simple, rules the source word is modified in such a way that the modified word plus supplement bits comply with the constraints. The information that certain modifications have been made is carried by the m supplement bits. The receiver, on reception of the word, will undo the modifications. In order to reduce complexity and error propagation, the number of bits affected by a modification should be as small as possible. We will survey some examples of code constructions.
