Investigation of adaptive beamformer performance and experimental verification of applications in high data rate digital underwater communications

To use a remote operated vehicle (ROV) for high speed underwater data transmission (e.g. video) requires the establishment of a reliable acoustical communication link. The most difficult effect to overcome in a time varying underwater channel is multipath. An adaptive beamformer uses an adaptive algorithm to maximise the signal strength received from a desired direction while simultaneously inserting nulls in directions of interferers. Both the Frost (1972) and LMS algorithms are being investigated at Newcastle University, and an objective comparison is made of their performance using synthetic and real data. A flexible and powerful state of the art multichannel data acquisition system, based around the TMS320C40 DSP, has been designed and commissioned. This system is being used to capture and store large volumes of data generated during sea trials. The data acquired is analysed off-line to allow the investigation of various phenomena affecting underwater communications (e.g. multipath), and to provide a realistic method of comparing the performance of a variety of different modulation techniques