The design and testing of a DSP, half-duplex, vertical, DPSK communication link

Accurate in-situ studies of the oceans requires an efficient, fast and reliable method of transmitting information to and from dedicated scientific payloads. The current generation of underwater telemetry systems tend to use proven, low data rate, 'discrete-component' designs. Although these systems perform well in static environments, their performance rapidly degenerates when the environment becomes more dynamic. The next generation of underwater telemetry systems must be able to adapt automatically to the changing environment and counteract time-varying effects by means of flexible signal processing techniques and detection algorithms. This goal is hard, if not impossible, to realise using conventional 'discrete component' designs. This paper presents a vertical communication system that uses an 'Analogue Devices' digital signal processor (DSP) at its heart. This DSP controls the transmission of data and operative commands to and from a seafloor unit, using multi-phase, 2, 4 or 8, differential phase shift keying (DPSK). This system is considered to be the first step towards a completely autonomous, adaptive communications system.