Pre-processing optimization for IBI mitigation in an OFDM system over channels with large delay spreads

When the cyclic prefix (CP) in an orthogonal frequency division multiplexing (OFDM) system is shorter than the delay span of wireless channels, inter-block interference (IBI) and inter-carrier interference (ICI) will occur. To effectively mitigate interference in this case, 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, a pre-processing optimization exploiting limited CSI is investigated in this paper; several pre-processing optimization approaches have been developed. Simulation results show that the proposed algorithms can effectively cancel the IBI and ICI and significantly improve the performance in OFDM systems.