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Due to the ongoing miniaturization of electronic devices and due to a multitude of applications, wireless body area networks (WBANs) have gained much interest recently. Ultra wideband (UWB) communication is one promising transmission technology for WBANs due to reduced hardware complexity. To optimize receiver structures and antennas for UWB WBANs it is necessary to know the propagation mechanisms at the human body. In this paper, we focus on transmission at the head and consider direct transmission, surface waves, reflections, and diffraction as possible propagation mechanisms in the frequency range between 1.5-8 GHz. We show theoretically and by measurement results that the direct path is attenuated such that direct transmission through the head is negligible. Based on measurements we conclude by process of elimination that diffraction is the main propagation mechanism around the human body and that surface waves and reflections are negligible. Finally, we discuss the impact of the propagation mechanisms on the UWB WBAN communication system.

We introduce geo-regioning as a method to achieve rough localization in asynchronous UWB networks. The approach is to localize the transmitter position by means of the multipath components in the received channel impulse response (signature). To show the principle feasibility of this approach a first regioning algorithm is introduced and tested with measured data. Therefore, a measurement campaign in a rich multipath environment has been performed. A high number of signatures originating from different regions in a room have been collected. The regioning algorithm presented here is based on the a priori knowledge of the average power delay profiles of the different regions. The performance results show that almost all regions can be localized at reasonable SNR and error probability. We conclude that the geo-regioning approach is a promising alternative or supplement to classical time of arrival based approaches in UWB networks.

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