MMSE channel shortening equalization for OFDM systems with unequal subcarrier powers

In severe time dispersive channel, channel shortening equalization enables short cyclic prefix to effectively combat the inter-symbol interference, thus improving the bandwidth efficiency of OFDM system. However, for practical OFDM systems, the transmission powers of all the subcarriers may be different due to either transmission arrangement or power allocation scheme. We propose a new MMSE channel shortening equalization algorithm applicable to all the OFDM/OFDMA systems with equal or unequal subcarrier powers. It is a generalization of the existing channel shortening equalization algorithms. The expressions of correlation matrices of signals are restudied and the optimal coefficients of equalizer are derived. Simulation results validate the positive impact of channel shortening equalization on both error performance and bandwidth efficiency of the system.