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Performance of multi-antenna signaling strategies using dual-polarized antennas: Measurement results and analysis

Authors

Rohit U. Nabar, Vinko Erceg, Helmut Bölcskei, and Arogyaswami J. Paulraj

Reference

International Symposium on Wireless Personal Multimedia Communications (WPMC), Aalborg, Denmark, pp. 175-180, Sept. 2001, (invited paper).

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Abstract

Multiple-input multiple-output (MIMO) wireless systems employ spatial multiplexing to increase spectral efficiency or transmit diversity techniques to improve link reliability. The performance of these signaling techniques is highly dependent on channel characteristics which in turn depend on antenna spacing and richness of scattering. The use of dual-polarized antennas is a cost and space effective alternative where two spatially separated antennas can be replaced by orthogonally polarized antenna elements. In this paper, we use fixed-wireless experimental data collected in a typical suburban environment at 2.5 GHz to investigate the performance of spatial multiplexing and transmit diversity (Alamouti scheme) for a dual-polarized antenna setup. Channel measurements were conducted over a cell of radius 7 km and channel statistics such as K-factor, cross-polarization discrimination (XPD) and fading signal correlation were extracted from the gathered data. At each location, different combinations of these parameters yield different performance of spatial multiplexing and the Alamouti scheme. We evaluate the performance of the two transmission techniques in terms of average bit error rate for a fixed data rate and signal to noise ratio as a function of distance from the base-station using previously developed performance analysis techniques for narrow-band polarization diversity based MIMO links. The results indicate that proper selection of the transmission mode through feedback, if possible, can reduce the bit error rate by several orders of magnitude. Furthermore, the results hint to the existence of a preferred-mode switching distance within a cell -- above/below which one mode of transmission is generally preferred.

Keywords

MIMO wireless, channel measurements, polarization diversity, spatial multiplexing, Alamouti scheme, preferred-mode switching distance

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