A Long Delay Multipath Equalization Using High Frequency Resolution Spatial Filters for SDM MIMO-OFDM Systems

Long delay multipath is a major cause of the poor reception of digital terrestrial broadcasting signals. The direct solution to this problem in orthogonal frequency division multiplexing (OFDM) system is to make the guard interval (GI) longer than the maximum channel delay. However, given the wide variety in broadcasting channel characteristics, the worst case GI may be twice the value needed which decreases the spectral efficiency and service quality. Therefore, the solution must be implemented on the receiver side. For the next generation broadcasting system, this paper proposes a space division multiplexing (SDM) multiple-input multiple-output (MIMO)-OFDM receiver for a multipath environment whose maximum delay time exceeds the GI length. The proposed system employs the high frequency resolution spatial filters that have the same configuration as the conventional one but operate at four times higher frequency resolution. Computer simulation and laboratory test results are presented to show the effectiveness of the proposed system.