Spatial Multiplexing in Correlated Fading Via the Virtual Channel Representation


Zhihong Hong, Kei Liu, Robert W. Heath Jr, and Akbar Sayeed


Accepted to IEEE Journal on Selected Areas of Communication.


Spatial multiplexing techniques send independent data streams on different transmit antennas to maximally exploit the capacity of multiple-input multiple-output (MIMO) fading channels. Most existing multiplexing techniques are based on an idealized MIMO channel model representing a rich scattering environment. Realistic channels corresponding to scattering clusters exhibit correlated fading and can significantly compromise the performance of such techniques. In this paper, we study the design and performance of spatial multiplexing techniques based on a virtual representation of realistic MIMO fading channels. Since the non-vanishing elements of the virtual channel matrix are uncorrelated, they capture the essential degrees of freedom in the channel and provide a simple characterization of channel statistics. In particular, the pairwise error probability (PEP) analysis for correlated channels is greatly simplified in the virtual representation. Using the PEP analysis, various precoding schemes are introduced to improve performance in virtual channels. Unitary precoding is proposed to provide robustness to unknown channel statistics. Non-unitary precoding techniques are proposed to exploit channel structure when channel statistics are known at the transmitter. Numerical results are presented to illustrate the attractive performance of the precoding techniques. 


Space-time coding, spatial multiplexing, virtual channel representation, correlated channels, beamforming, diversity, precoding In this paper we propose a framework for spatial multiplexing in correlated MIMO channels using a virtual representation.

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