Digital communications using soft-decision detection techniques

The history of soft-decision techniques is briefly reviewed and the potential advantages of using such techniques are outlined. The experimental implementations of soft-decision schemes are described and evaluated. The results of some studies of quite simple block soft-decision decoding schemes are presented. Then a practical implementation of a data transmission system incorporating full minimum-distance soft-decision decoding is described. The system is based on a transparent product block code, with interleaving; and is suitable for use of HF, VHF and UHF channels. The results of tests on simulated and real channels are presented and commented on. It was concluded that efficient operation of data transmission systems with channel (redundant) coding is impossible without soft-decision detection, particularly in non-Gaussian environments.