Coherent path measurement for characterization of the underwater acoustic channel

A novel method of underwater acoustic communication is being developed that does not rely on single or multichannel adaptive equalization methods which degrade in the presence of severe time varying multipath. The new method, called the coherent path beamforming (CPB) method uses eigen vectors for characterizing the underwater acoustic communication channel. In the output of the CPB, each of the many channels represents a vertical beam that is focused in the direction of correlated acoustic energy arriving at the array of vertically spaced sonar elements. Within each of the CPB principal beams, nulls are formed in the direction of the remaining acoustic paths thereby canceling interference. A vertical array of 64 elements operating at 245 kHz has been used in shallow water experiments to evaluate performance under various conditions. The experiments were performed in shallow water high multipath conditions off Boca Raton. Results are presented for fixed platform communication