Delay spread and time dispersion estimation for adaptive OFDM systems

Time dispersion is one of the most important characteristics of the wireless channel. The knowledge about the time dispersion of a channel can be used for designing better systems which can adapt themselves to the changing nature of the transmission medium. In this paper, algorithms for estimating the time dispersion (frequency selectivity) of the channel, which use the frequency domain channel estimates or the frequency domain received signal, are proposed. The proposed algorithms first estimate the power delay profile (PDP) from which the two important dispersion parameters, namely root-mean-squared (RMS) delay spread and maximum excess delay of the channel, are estimated. It is shown that synchronization errors bias the performance of the estimators based on the channel correlation, and this bias is removed by obtaining the PDP using the magnitude of the channel estimates. The performances of the proposed algorithms are evaluated using computer simulations