A Frequency Domain Approach to Channel Shortening in OFDM Systems

Abstract

Channel shortening filters are used in OFDM systems to reduce the overall duration of channel response. The effective channel response length is required to be shorter than the cyclic prefix inserted between OFDM symbols to reduce inter-symbol interference. Various optimum/suboptimum techniques have been explored in literature to determine the channel shortening filter response, which is also referred to as the time domain equalizer (TEQ). In this paper, we propose a novel frequency domain approach to the problem of estimating the TEQ response, when the channel characteristics are unknown. This iterative approach provides faster and better convergence as well as better control over effective sub-channel response compared to its time domain counterpart, at a relatively low computational cost. The simulation results are shown as applied to wired communication systems but could be easily extended for any OFDM based system.