Universal properties of the channel Q function: Applications to underwater acoustic communications

Channel Q function is, for a time‐invariant channel, the sum of autocorrelation functions of the channel impulse response functions over multiple receivers [T. C. Yang, IEEE J. Oceanic Eng. 28, 229–245 (2003)]. It can be used to characterize the performance (output SNR) of acoustic communications using either passive‐phase conjugation or decision feedback equalizer [T. C. Yang, IEEE J. Oceanic Eng. 29, 472–487 (2004)]. Channel Q function also determines the channel capacity for a single source and multiple receivers (SIMO). We analyze in this paper the properties of the channel Q function and show that it possesses universal and stable properties for underwater acoustic waveguides, irrespective of the channel sound‐speed profiles, source and receiver range/depths. This property is examined with real data collected in various oceans with significant temporal variations in the propagation conditions and/or source‐receiver range. Applications to underwater acoustic communications are discussed. [Work support...