Paper 1, Section I, 3G3 G

Coding and Cryptography
Part II, 2015

Let A\mathcal{A} be a finite alphabet. Explain what is meant by saying that a binary code c:A{0,1}c: \mathcal{A} \rightarrow\{0,1\}^{*} has minimum distance δ\delta. If cc is such a binary code with minimum distance δ\delta, show that cc is δ1\delta-1 error-detecting and 12(δ1)\left\lfloor\frac{1}{2}(\delta-1)\right\rfloor error-correcting.

Show that it is possible to construct a code that has minimum distance δ\delta for any integer δ>0\delta>0.