Covert Underwater Acoustic Communication without Repeating Patterns

Abstract

In this paper, a covert underwater acoustic communication scheme based on ocean ambient noise, without any repeating patterns in the transmitted signal is studied. In this scheme, ocean ambient noise is selected as the initial signal. A steganography process is performed on the initial signal to embedded the information in it. Information embedding is a multi-step process that includes time-domain symmetrical division, phase rotation, time reversal, and counterpart exchange. The Information is embedded in the steganography parameters, but not the initial signal itself. So the receiver can get the information by performing the same steganography process on the received signal without knowing any pre-knowledge of the initial signal. In this case, it is able to use different ocean ambient noise as the initial signal for each symbol. Thus, no repeating patterns are observed in the signal; this increases the covertness of this scheme. Phase rotation of the steganography process is essential to ensure optimal system performance; this paper proposes an optimal rotation phase strategy to maximize the system performance. Based on the analysis of the rotation phase, a general multiple phase shift keying receiver structure is also presented herein.