Physical layer sensing using long pseudo noise codes

As research into building underwater sensor networks proceeds, researchers are focusing on using these networks to solve applicable problems. In particular we have found that underwater sensor networks are capable of performing acoustic tomography, even at very small scales. As sensor networks consist of a network of power constrained devices, researchers must also look for efficient ways to perform the required tasks. In our work we are developing an acoustic tomography system implemented in an underwater sensor network. Traditionally, acoustic signals used for tomography would be followed by acoustic signals carrying data about the previous operations. In this paper we present an acoustic network physical layer that provides for simultaneous data transmission and sensing using the same acoustic signal. By combining data and sensing transmissions we conserve energy. We describe the physical layer followed by experimental data that shows our system can perform as desired.