On coding for block fading channels

This work considers the achievable performance for coded systems adapted to a multipath block–fading channel model. This is a particularly useful model for analysing mobile–radio systems which employ techniques such as slow frequency–hopping under stringent time–delay or bandwidth constraints for slowly time–varying channels. In such systems, coded information is transmitted over a small number of fading channels in order to achieve diversity. The separation between the diversity effects of multipath resolution and coding are studied. Bounds on the achievable performance due to coding are derived using information–theoretic techniques. It is shown that high diversity can be achieved using relatively simple codes as long as very high spectral–efficiency is not required. Examples of simple block codes and carefully chosen trellis codes are given which yield, in some cases, performances approaching the information–theoretic bounds.