Space-frequency precoding for an OFDM based system exploiting spatial and path correlation

We investigate the capacity behavior of an OFDM wireless link for the frequency selective MIMO channel with correlated paths. The derivation is based on a particular channel model that characterizes path correlation as well as spatial correlation. As in the case of spatial correlation, path correlation can reduce capacity. If there is no channel knowledge at the transmitter, the capacity reduction of an OFDM based system due to path correlation can be explained in terms of the effective SNR at each tone. With spatial and path correlation information at the transmitter, we derive the optimal space-frequency precoder at every tone by numerical optimization techniques. We propose a sub-optimal precoding scheme with lower complexity which leads to a tight lower bound of the capacity of the OFDM system.

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