Recently, for the realization of wideband and spectrally efficient wireless links, MIMO-OFDM systems combining MIMO (Multiple Input/Multiple Output) and OFDM (Orthogonal Frequency Division Multiplexing) have attracted attention. MIMO-OFDM systems transmit several data streams in parallel, over several transmit antennas in the space dimension, and over several subcarriers in the frequency domain. MIMO-OFDM systems have the advantage that for wideband wireless channels, multi-stream detection can be performed over each subcarrier separately. In this paper, ordered successive MMSE detection (OSD) and sphere decoding are considered for multi-stream detection. First, the performances of both schemes are compared for several constellation sizes and with imperfect channel estimates using computer simulations. Then, two approaches are introduced to OSD in order to compensate for the large performance degradation due to channel estimation errors.
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