Abstract
This paper considers spatial multiplexing (SM) systems with preceding. The precoder is derived from the singular value decomposition (SVD) of the available channel state information at the transmitter (CSIT) and the receiver is a function of the precoder and the current channel. With perfect CSIT, the M <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">R</sub> xM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</sub> flat-fading MIMO channel can be decomposed into mm(M <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</sub> ,M <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">R</sub> ) parallel spatial subchannels. However in practice, the available CSIT suffers from delay-induced error due to the channel temporal variations. Using this outdated CSIT for precoding in SM systems causes interference among the subchannels. Performance of the decorrelator, minimum mean squared error (MMSE) and successive interference cancelation (SIC) receivers is analyzed as the reliability of the available CSIT varies. Explicit expressions for the signal to interference-plus-noise ratio (SINR) and the mean squared error (MSE) are derived. Simulation results are provided to illustrate the significant performance gain achieved by precoding even with a moderate amount of correlation between the available outdated channel estimate and the current channel.
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