Abstract
We investigate the optimal design of uniform rectangular arrays (URAs) employed in multiple-input multiple-output communications, where a strong line-of-sight (LOS) component is present. A general geometrical model is introduced to model the LOS component, which allows for any orientation of the transmit and receive arrays, and incorporates the uniform linear array as a special case of the URA. A spherical wave propagation model is used. Based on this model, we derive the optimal array design equations with respect to mutual information, resulting in orthogonal LOS subchannels. The equations reveal that it is the distance between the antennas projected onto the plane perpendicular to the transmission direction that is of importance with respect to design. Further, we investigate the influence of nonoptimal design, and derive analytical expressions for the singular values of the LOS matrix as a function of the quality of the array design. To evaluate a more realistic channel, the LOS channel matrix is employed in a Ricean channel model. Performance results show that even with some deviation from the optimal design, we get better performance than in the case of uncorrelated Rayleigh subchannels.
Highlights
Multiple-input multiple-output (MIMO) technology is a promising tool for enabling spectrally efficient future wireless applications
The authors of the present paper have previously studied the optimal design of uniform linear arrays (ULAs) with respect to mutual information (MI) [8, 9], and have given a simple equation for the optimal design
We introduce a new general geometrical model that can describe any orientation of the transmit (Tx), receive (Rx) uniform rectangular arrays (URAs), and incorporate ULAs as a special case
Summary
Multiple-input multiple-output (MIMO) technology is a promising tool for enabling spectrally efficient future wireless applications. Introducing a strong line-of-sight (LOS) component for such systems is positive in the sense that it boosts the signal-to-noise ratio (SNR) It will have a negative impact on MIMO performance as it increases the correlation between the subchannels [6]. Some work on the design of uniform rectangular arrays (URAs) for MIMO systems is presented in [10], where the optimal design for the special case of two broadside URAs is found, and the optimal throughput performance was identified to be identical to the optimal Hadamard bound. It should be noted that a spherical wave propagation model is employed, in contrast to the more commonly applied approximate plane-wave model This model is used to derive new equations for the EURASIP Journal on Wireless Communications and Networking optimal design of the URAs with respect to MI.
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