The Performance of Coded Diversity Systems on a Slowly Fading Rayleigh Channel

A new diversity technique has been developed that uses message waveforms consisting of a sequence of RF bursts at a number of different frequencies. Furthermore, the ensemble of message sequences is a code with large minimum Hamming distance. Hence, reliable communications are possible in spite of channel fading and additive noise. The new diversity technique has been integrated into a troposcatter communication system that was first tested in 1967. The new technique is illustrated and its performance predicted assuming both correlated and uncorrelated fading between the RF frequencies. A particular code is presented that achieves a 4-dB coding improvement beyond that generally obtained using binary modulation and frequency diversity techniques of the same order. Theoretical predictions of system performance and actual empirical data taken on two operational links agree very closely.