To realize high-speed transmission in OFDM mobile communications, MIMO transmission scheme which spatial-multiplexes data streams by multiple antennas is investigated. Conventional MIMO-OFDM schemes remarkably suffer from both inter-symbol interference (ISI) by the adjacent OFDM symbols and inter-carrier interference (ICI) within the same symbol, when the multipath delay difference is greater than the guard interval (GI). This paper proposes a new MIMO-OFDM Turbo interference cancel equalizer (Turbo-ICE), which consists of the decision feedback equalization (DPE) to cope with ISI and the Turbo equalization to cancel ICI, and can separately detect the spatial-multiplexing data streams. Turbo-ICE can improve the transmission performance, by utilizing bit LLRs which are feedbacked from the decoding process for the equalization and the data stream separation. In addition, this paper shows a configuration of simplified Turbo-ICE which can reduce the computational complexity. Computer simulations in accordance with the wireless LAN applications enhanced to MIMO are conducted so as to verify the effectiveness of Turbo-ICE, and demonstrate that it can accomplish the good performance in multipath environments even when the excess delay is greater than GI.
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