Second-order statistics of the instantaneous mutual information in time-varying underwater particle velocity channels

Instantaneous mutual information (IMI) is the amount of information that a time-varying channel can convey for the given time instant. In this paper, second-order statistics of IMI are studied in time-varying underwater particle velocity channels. First, the autocorrelation function, correlation coefficient, level crossing rate and average outage duration of IMI are provided in a time-varying fading channel. Exact expressions are given in terms of the summation of special functions, which facilitate numerical calculations. Then accurate approximations for the autocorrelation function and correlation coefficient are presented for low and high signal-to-noise ratios (SNRs). Moreover, analytical and numerical results are provided for the correlation and level-crossing characteristics of IMI in underwater particle velocity channels. The results shed light on the dynamic behavior of mutual information in underwater particle velocity channels.