Ultra wideband propagation for future in-body sensor networks

Body area network (BAN) technology can enable the real-time collection and monitoring of physiological signals for personalized healthcare. Implantable biomedical sensors transmitting continuously clinical information to an external unit can facilitate the involvement of the patients in the management of chronic diseases. In addition, ingestible sensors like the wireless capsule endoscope (WCE) have been proven extremely useful as clinical diagnostic tools. It is envisaged that such devices will evolve to also perform in-body therapeutic procedures. Future medical applications may require the interconnection of two or more of these in-body devices to interchange information for better diagnostics or to relay data from deeply implanted sensors. In this context, ultra wideband (UWB) radio links can be used for the communication interfaces of in-body sensors due to their large bandwidth and low power consumption. Nevertheless, little is known about the behavior of the in-body to in-body (IB2IB) radio channel in the UWB spectrum. This paper aims to fill this gap by providing insight into the behavior of the IB2IB channel based on propagation measurements in 3.1-8.5 GHz. Because of the impossibility to conduct in-body measurements with human subjects, we used a phantom that emulated the dielectric characteristics of the human muscle tissue. The path loss as a function of the distance between antennas and the frequency are thoroughly discussed.