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Channel Prediction of Wideband OFDM Systems in a Millimeter-Wave Band Using Delay-Domain Multipath Detection

In multi-user MIMO systems, we can achieve high-capacity downlink transmission without interferences using precoding at a base station. We need, however, accurate channel state information (CSI). In time-varying environments, the CSI may be outdated at the actual transmission time. Frequent pilot symbol transmission decreases the communication efficiency. One of the solutions to this challenging issue is channel prediction, that is, we predict future channels from observed past channels. This paper presents a channel prediction method for wideband OFDM systems. The method detects multipath components in a delay domain using fast iterative shrinkage-thresholding algorithm (FISTA). We evaluate the prediction performance, and compare it with that using IDFT. It has been shown that the proposed method using FISTA is excellent in terms of prediction accuracy in a sparse propagation environment. In an environment where we have densely located multipath components around clusters, the performance degrades and is almost the same as that of the method using IDFT.