Morozov Andrey K, Colosi John A
Department of Applied Ocean Physics and Engineering, Woods Hole Oceanographic Institution, MS# 09, Woods Hole, Massachusetts 02543, USA.
Department of Oceanography Graduate School of Engineering and Applied Sciences, Naval Postgraduate School, 833 Dyer Road, Monterey, California 93943, USA.
J Acoust Soc Am. 2015 Sep;138(3):1353-64. doi: 10.1121/1.4928617.
The reduction of information capacity of the ocean sound channel due to scattering by internal waves is a potential problem for acoustic communication, navigation, and remote sensing over long ranges. In spite of recent progress in research on acoustic signal scattering by random internal waves and the fact that random internal waves are ubiquitous in the world oceans, there is no clear understanding of how these waves influence data communication performance. The entropy decrease resulting from scattering by internal waves is an important measure of information loss. Here a rigorous calculation of the entropy is carried out using second moment transport theory equations with random sound-speed perturbations obeying the Garrett-Munk internal-wave model. It is shown that full-wave rate of entropy is of the same order of magnitude as the Kolmogorov-Sinai entropy and Lyapunov exponents for the relevant ray trajectories. The correspondence between full-wave and ray entropies suggests a correspondence between full-wave scattering and ray chaos near statistical saturation. The relatively small level of entropy rate during propagation through the random internal-wave field shows that scattering by internal waves is likely not an essential limitation for data rate and channel capacity.
内波散射导致海洋声道信息容量降低，这对于长距离声学通信、导航和遥感来说是一个潜在问题。尽管最近在随机内波引起的声信号散射研究方面取得了进展，而且随机内波在世界海洋中普遍存在，但对于这些波如何影响数据通信性能仍缺乏清晰认识。内波散射导致的熵减少是信息损失的一个重要度量。在此，利用服从加勒特 - 蒙克内波模型的随机声速扰动的二阶矩传输理论方程，对熵进行了严格计算。结果表明，全波熵率与相关射线轨迹的柯尔莫哥洛夫 - Sinai 熵和李雅普诺夫指数具有相同的量级。全波熵与射线熵之间的对应关系表明，在统计饱和附近全波散射与射线混沌之间存在对应关系。在通过随机内波场传播过程中相对较低的熵率水平表明，内波散射可能并非数据速率和信道容量的本质限制因素。
