Channel shortening equalization for differential OFDM systems

In orthogonal frequency division multiplexing (OFDM) systems, the length of the cyclic prefix (CP) has to be greater than the length of the channel impulse response to avoid inter-symbol interference. However, a long CP costs extra bandwidth and reduces power efficiency. This paper designs a channel shortening filter for differential OFDM systems with unknown multipath channels with long delay spreads. Without introducing extra redundancy, our design shortens the length of the effective channel response and bypasses the channel estimation, thus improving bandwidth and power efficiencies. The design is easy to be implemented at both transmitter and receiver with low computational complexity. Simulation results corroborate the merits of our design.