Low-Complex ICI Cancellation for Improving Doppler Performance in OFDM Systems

A combination of receiver windowing and inter-carrier interference (ICI) canceling is proposed for improving the Doppler performance of orthogonal frequency division multiplex (OFDM) systems. The windowing reduces the ICI, and also reduces the required number of canceled bins. The effect of windowing is analytically derived, and bounds are given on the possible gain that can be obtained. Since successful ICI cancellation relies on that the channel can be accurately estimated, the paper also give examples for how different one-dimensional and two-dimensional channel estimators can be expected to work for various Doppler spread and delay spread of the channel. To verify that the proposed approach for ICI canceling works, as well as studying the impact of channel estimation errors, simulations are performed using the key parameters of DVB-H. As a result it is found that with proper channel estimation, windowing but no ICI cancellation can increase the allowed Doppler by 20%, ICI cancellation but no windowing can also increase the allowed Doppler by 20%, and if both windowing and ICI cancellation are used, the allowed Doppler can increase by more than 40%.