Testing the wide-sense stationarity of bandpass signals for underwater acoustic communications

The Underwater Acoustic Communication (UAC) systems work in communication channels characterized by a large variety of multipath propagation conditions that can additionally change over time. Designing a reliable communication system requires knowledge of the transmission parameters of the channel. There is a need for the development of adaptive signaling schemes that would dynamically optimize the signal parameters of the physical layer of communication protocols. Wireless channels are often assumed to be wide sense stationary (WSS) with uncorrelated scattering (US). The WSSUS assumption allows for simultaneous modeling of time dispersion leading to the frequency selectivity of the channel, and time variability resulting in frequency dispersion. However, in the case of many underwater communication channels, especially when system terminals are in movement, the channel can be modeled as WSSUS only in restricted periods of time, and in limited frequency ranges. The paper presents a method for determining the time interval, wherein the WSS assumption is fulfilled, on the basis of a complex envelope of the received bandpass signal.