Underwater acoustic communications

In recent years, underwater acoustic (UWA) communications have received much attention as their applications are beginning to shift from military towards commercial. UWA communications are made difficult by the combined effect of multipath propagation and high temporal and spatial variability of the channel conditions. Until recently, the design of communication systems has mostly relied on the use of noncoherent modulation techniques. However, to achieve high data rates on the severely bandlimited UWA channels, bandwidth-efficient modulation techniques must be considered, together with array processing for exploitation of spatial multipath diversity. The new generation of underwater communication systems employing phase-coherent modulation techniques will achieve at least a ten fold increase in data throughput. The communication scenario in which the modern UWA systems will operate is that of an underwater network consisting of stationary and mobile nodes. Current research focuses on the development of efficient signal processing algorithms, multiuser communications in the presence of interference, and design of efficient modulation and coding schemes