On the problems of symbol‐spaced tapped‐delay‐line models for WSSUS channels

This paper analyzes the validity and statistical behavior of symbol‐spaced tapped‐delay‐line (SSTDL) models for wide‐sense stationary uncorrelated scattering (WSSUS) mobile radio channels. SSTDL models are obtained by sampling the channel impulse response (CIR) in delay domain at a rate equal to the reciprocal of the symbol duration. They were proposed more than four decades ago as canonical channel models for band‐limited time‐variant linear (TVL) systems, and are nowadays widely in use for assessing the performance of several wireless communication systems. The applicability of these tapped‐delay‐line (TDL) models seems to be unquestionable, as they were developed in the framework of the sampling theorem. Nonetheless, we show here that SSTDL models should be used with care to model WSSUS channels, because the channel's uncorrelated scattering (US) condition might easily be violated. Furthermore, we show that SSTDL models suffer from strong limitations in emulating the channel frequency correlation function (FCF). This drawback leads to an inaccurate performance evaluation of wireless communication systems sensitive to the FCF. To cope with this problem, we present a simple solution by doubling the channel's sampling rate. The benefits of this solution are demonstrated with some exemplary simulation results. Copyright © 2008 John Wiley & Sons, Ltd.