Software Acoustic Modems for Short Range Mote-based Underwater Sensor Networks

Most recent work in underwater network development has relied on using expensive commercial acoustic modems or on building custom transceivers for each application to establish acoustic communication links among the sensors. Using commercial modems or designing custom hardware may require prohibitive monetary or time investment for many applications. Our work proposes the design of software acoustic modems that can utilize built-in microphones and speakers on the relatively cheap Tmote Invent platforms. The built-in Tmote hardware and the software modem enable acoustic communication in a short range shallow water network. In this paper, we present the initial design and architecture of our acoustic communication system which targets environmental monitoring applications. Our experiments with generic acoustic hardware to profile this underwater communication channel reveal that the channel favors frequencies below 3 Khz, a result which guides the design choices for our FSK software modem. We perform experiments with our software modem/generic hardware system to explore the system´s data transfer capability. The data communications experiments confirm the system´s capability of transferring information in the order of tens of bits per second for a communications range of up to 10 meters.