UNDERWATER COMMUNICATIONS WITH ACOUSTIC STEGANOGRAPHY: RECOVERY ANALYSIS AND MODELING

In the modern warfare environment, communication is a cornerstone of combat competence. However, the increasing threat of communications-denied environments highlights the need for communications systems with low probability of intercept and detection. This is doubly true in the subsurface environment, where communications and sonar systems can reveal the tactical location of platforms and capabilities, subverting their covert mission set. A steganographic communication scheme that leverages existing technologies and unexpected data carriers is a feasible means of increasing assurance of communications, even in denied environments. This research works toward a covert communication system by determining and comparing novel symbol recovery schemes to extract data from a signal transmitted under a steganographic technique and interfered with by a simulated underwater acoustic channel. We apply techniques for reliably extracting imperceptible information from unremarkable acoustic events robust to the variability of the hostile operating environment. The system is evaluated based on performance metrics, such as transmission rate and bit error rate, and we show that our scheme is sufficient to conduct covert communications through acoustic transmissions, though we do not solve the problems of synchronization or equalization.Lieutenant, United States NavyApproved for public release. Distribution is unlimited

Numerical indefinite integration by double exponential sinc method

Sinc関数とはsinc(x)=sin(π　x)/(π　x)で定義される関数であり、関数系{sinc(x/h-k)}（hは正の実数、kは整数）を用いた近似手法が、ここ三十数年ほど様々な数値解析の分野において研究されてきた。一方、1974年に高橋・森により、高精度の定積分公式を作ることを目的として二重指数関数型変換（以下DE変換）と呼ばれる変換が考案された。そこで本論文では、Sinc関数系とDE変換を併せ用いた、従来より高精度な数値不定積分公式を確立した