Underwater communication via frequency shift keying in particle velocity channels: Experimental results

The commonly-used underwater communication channel is the acoustic pressure channel, which is the scalar component of the acoustic field. In this paper acoustic particle velocity channels, which are vector components of the acoustic field, are used together with the acoustic pressure channel, to increase the transmission rate and also improve the signal-to-noise ratio. The goal of this paper is to provide experimental results on underwater communication via particle velocity channels. Acoustic vector transducers, devices that can excite or measure the vector and scalar components of the acoustic field, are used in our experiments. Here we show how a compact vector transducer can be used either as a multichannel transmitter or a multichannel receiver for underwater communication. Without loss of generality, we have used frequency shift keying as a simple modulation scheme to demonstrate the feasibility of underwater communication in particle velocity channels via vector transducers. We present experimental results on two vector communication system configurations. In the first configuration a compact vector transmitter that excites two particle velocity channels and the pressure channel is used, to triple the transmission rate. One advantage of this setup compared to a fully scalar system which uses an array of three spatially-separated scalar transmitters for tripling the transmission rate is the small size of the vector transmitter. In the second configuration, a compact vector receiver that measures two particle velocity channels and the pressure channel is utilized, to increase the signal-to-noise ratio. Compared to a fully scalar system which uses an array of three spatially-separated scalar receivers, signal-to-noise ratio is significantly increased using a small vector receiver. Overall, our experimental results show the usefulness of particle velocity and vector transducers for underwater communication.