Characterization of WSSUS channels: normalized mean square covariance

A set of second-order statistics collectively called normalized mean square covariance (NMSV) are defined to characterize the frequency and/or the time selectivity of wide-sense stationary uncorrelated scattering (WSSUS) channels. Normalized frequency mean square covariance (NFMSV) quantifies the frequency selectivity, while normalized time mean square covariance (NTMSV) characterizes the time selectivity. Normalized frequency-time mean square covariance is defined to characterize the combined effect of frequency and time selectivities. The NMSVs of a WSSUS channel can be computed easily from the scattering function. We show that there is a very close relationship between the NMSV of a WSSUS channel and the performance of various diversity combing schemes. Also we discuss, with practical system design problems, how useful the parameters are for efficient system design.