chapter  4
24 Pages

Block codes – some constraints and some geometry

ByJohn Baylis

We saw in Chapter 1 how the 3-fold repetition code would drastically reduce the probability of messages being wrongly decoded, and discussed the price which this entailed. Then in Chapter 2 we saw how the Hamming code solved the same problem of guaranteeing to correct every instance of a single error per codeword at much less cost. The way in which it achieved its impressive performance was by ensuring that amongst the 16 7-bit codewords, no pair of them was separated by a Hamming distance less than 3. We also developed general results, Theorems 2.1 and 2.2, to connect the minimum distance of the code with its error detecting and correcting potential.