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International Journal of Antennas and Propagation
Volume 2012, Article ID 413683, 13 pages
http://dx.doi.org/10.1155/2012/413683
Research Article

Indoor Off-Body Wireless Communication: Static Beamforming versus Space-Time Coding

1Department of Information Technology (INTEC), Ghent University, St. Pietersnieuwstraat 41, 9000 Ghent, Belgium
2Faculty of Applied Engineering Sciences (INWE), University College Ghent, Valentin Vaerwyckweg 1, 9000 Gent, Belgium
3Department of Telecommunications and Information Processing (TELIN), Ghent University, St. Pietersnieuwstraat 41, 9000 Ghent, Belgium

Received 25 July 2011; Revised 20 October 2011; Accepted 22 October 2011

Academic Editor: Yan Zhang

Copyright © 2012 Patrick Van Torre et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

The performance of beamforming versus space-time coding using a body-worn textile antenna array is experimentally evaluated for an indoor environment, where a walking rescue worker transmits data in the 2.45 GHz ISM band, relying on a vertical textile four-antenna array integrated into his garment. The two transmission scenarios considered are static beamforming at low-elevation angles and space-time code based transmit diversity. Signals are received by a base station equipped with a horizontal array of four dipole antennas providing spatial receive diversity through maximum-ratio combining. Signal-to-noise ratios, bit error rate characteristics, and signal correlation properties are assessed for both off-body transmission scenarios. Without receiver diversity, the performance of space-time coding is generally better. In case of fourth-order receiver diversity, beamforming is superior in line-of-sight conditions. For non-line-of-sight propagation, the space-time codes perform better as soon as bit error rates are low enough for a reliable data link.