IBI Cancellation Based on Limited Channel Feedback for OFDM Systems over Channels with Large Delay Spreads

While cyclic prefix (CP) is no larger than the delay span of wireless channels in an orthogonal frequency division multiplexing (OFDM) system, inter-block interference (IBI) and inter-carrier interference (ICI) will occur and the performance of the system will be deteriorated. If OFDM is designed with long enough CP, the efficiency of OFDM modulation is significantly reduced. To effectively mitigate interference over channel with large delay spreads, pre-processing approaches at transmitters based on full channel state information (CSI) have been proposed. However, feeding full CSI back will occupy significant bandwidth and is impractical sometimes. Therefore, pre-processing optimization exploiting limited CSI feedback is investigated in this paper. An pre-processing optimization approaches for IBI and ICI mitigation has been developed and tested. Computer simulation result shows that the proposed optimization algorithm can effectively cancel IBI and ICI over channels with large delay spreads and significantly improve the performance for OFDM systems.