Generalised differential encoding for underwater acoustic communication

We study the efficacy of a generalised form of differential encoding of binary phase shift keyed (BPSK) signals transmitted through a shallow underwater acoustic communication channel. Using simulations involving a fixed source and a receiver moving about with the surface waves, we show that no advantage arises from using the generalised differential encoding methods. On the contrary, the best results in our study arise from simple secondorder differential BPSK (DBPSK) signalling. This is in contrast to an earlier study that showed the promise of the generalised differential encoding methods via simulations. The previous study did not address the issue of intersymbol interference (ISI), whereas we include ISI. It appears that the added complication of removing ISI significantly reduces the benefits of generalised differential encoding.