Abstract-Body-coupled communications (BCC), in which the human body is used as a communications channel, has been shown to be a promising solution for wireless body-area networks (WBANs). For successful deployment of these BCC-based WBANs, it is necessary to develop a clear understanding of the channel behavior. Therefore, this paper presents the key characteristics of the capacitively-coupled on-body channel used for BCC. This is based on an experimental study, which was carried out with a specifically designed measurement system. The goal of the study was to reveal the influence of electrode design, electrode position and body motion on the propagation loss and to characterize the experienced interference. It is concluded that the maximum propagation loss for the whole body channel is below 80 dB. Moreover, the frequency dispersion and the influence of body movement on channel attenuation are shown to be much smaller than for radio frequency (RF) WBAN channels. From the results we conclude that BCC can result in a simpler, more robust, and lower-power WBAN than what is achievable with traditional RF solutions.

The use of duty-cycled ultra-low power wake-up receivers (WRxs) can significantly extend a node life time in low-power sensor network applications. In the WRx design, both low-power operation of the WRx and wake-up beacon (WB) detection performance are of importance. We present a systemlevel analysis of a duty-cycled WRx design, including analog front-end, digital base-band, WB structure, and the resulting WB detection and false alarm probabilities. We select a low-power WRx design, with about two orders of magnitude lower power consumption than the main receiver. The associated cost is an increase in raw bit-error rate (BER), as compared to the main receiver, at the same received power level. To compensate, we use a WB structure that employs spreading. The WB structure leads us to an architecture for the digital base-band with a high address-space scalability. We calculate closed form expressions for detection and false alarm probabilities. Using these we analyze the impact of design parameters. The analytical framework is exemplified by minimization of WB transmit energy. For this particular optimization, we also show that the obtained results are valid for all transmission schemes with an exponential relationship between signal-to-noise ratio and bit-error rate, e.g., the binary orthogonal schemes with non-coherent detection used in many low-power applications.

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