Ultra Wideband Wireless Body Area Network Research Articles

UWB signal propagation at the human head

Among different wireless solutions, ultra-wideband (UWB) communication is one promising transmission technology for wireless body area networks (WBANs). To optimize receiver structures and antennas for UWB WBANs with respect to energy efficiency and complexity, the distinct features of the body area network channel have to be considered. Thus, it is necessary to know the propagation mechanisms in the proximity of the human body. In this paper, we limit ourselves to transmission at the head, since the most important human communication organs, such as the mouth, eyes, and ears, are located there. We especially focus on the link between both ears and consider direct transmission, surface waves, reflections, and diffraction as possible propagation mechanisms. We show theoretically and by measurements, which were performed in the frequency range between 1.5-8 GHz, that direct transmission through the head is negligible due to the strong attenuation. We conclude by process of elimination that diffraction is the main propagation mechanism around the human body and verify these conclusions using a finite-difference time-domain simulation. Based on a second measurement campaign, we derive an approximation of the average power delay profile for the ear-to-ear link and calculate values for mean excess delay and delay spread. Finally, we briefly discuss the impact of the distinct ear-to-ear channel characteristic on the design of a WBAN communication system.

A Novel Small-Size Printed Tapered Monopole Antenna for UWB WBAN

In this letter, a novel antenna topology based on the printed tapered monopole antenna (PTMA) is investigated in view of ultra-wideband (UWB) wireless body area network (WBAN) applications. First, the bandwidth in the presence of a human arm is studied. Second, the pulse distortion of a modulated Gaussian pulse is investigated, based on measured $ S_21$-parameters. We observe that there is a small acceptable influence on the matching of the antenna and that the pulse distortion is low. The main conclusion is that this modified PTMA is a very good candidate for WBAN UWB applications.