Covert underwater acoustic communications

Jun Ling, Hao He, Jian Li, William Roberts, Petre Stoica
2010 Journal of the Acoustical Society of America  
Low probability of detection ͑LPD͒ communications are conducted at a low received signal-to-noise ratio ͑SNR͒ to deter eavesdroppers to sense the presence of the transmitted signal. Successful detection at intended receiver heavily relies on the processing gain achieved by employing the direct-sequence spread-spectrum ͑DSSS͒ technique. For scenarios that lack a sufficiently low SNR to maintain LPD, another metric, referred to as low probability of interception ͑LPI͒, is of interest to protect
more » ... e privacy of the transmitted information. If covert communications take place in underwater acoustic ͑UWA͒ environments, then additional challenges are present. The time-varying nature of the UWA channel prevents the employment of a long spreading waveform. Furthermore, UWA environments are frequency-selective channels with long memory, which imposes challenges to the design of the spreading waveform. In this paper, a covert UWA communication system that adopts the DSSS technique and a coherent RAKE receiver is investigated. Emphasis is placed on the design of a spreading waveform that not only accounts for the transceiver structure and frequency-selective nature of the UWA channel, but also possesses a superior LPI. The proposed techniques are evaluated using both simulated and SPACE'08 in-water experimental data.
doi:10.1121/1.3493454 pmid:21110585 fatcat:mjuywxav25fp7kdbkwoo6ea26q