CI/DS-CDMA scheme for autonomous underwater vehicle communication

Autonomous underwater vehicles (AUVs) are deployed in search and rescue operations where it is difficult for divers to reach. During the operation a fleet of AUVs communicate among themselves and exchange two type of information. The first includes control signal which has a low-data rate but has a very stringent bit error rate (BER) requirement and the second being the data collected by the AUVs in the form of high resolution video, pictures and important sensor observations, which has a high-data rate but a little relaxed BER constraint. This paper proposes an efficient two-rate data transmission scheme for AUV communication using carrier interferometry (CI) coded direct sequence code-division multiple access (CI/DS-CDMA). The BER performance of the proposed scheme is compared with that of the conventional Walsh Hadamard (WH) coded DS-CDMA in underwater channel and is shown to ensure improved BER performance. For two-rate communication we assume a basic low-data rate (LDR) “R” and a high-data rate (HDR) as “2R” and we further presume that the acceptable BER of LDR is atleast an order of magnitude less than that of the HDR. Simulation results show that with CI/DS-CDMA scheme, the high-data rate communication achieves a BER of 3×10⁻⁴ at 20 dB whereas the low data rate communication reach a BER of 1.76×10⁻⁵ at 16 dB for a typical underwater channel. The results justify CI/DS-CDMA scheme as a deserving candidate for single rate as well as two-rate underwater acoustic communication.