Link-Budgets with Body Implanted Nodes: Can we Obtain Simple Analytical Approximate Models That are Useful?

Wireless Communication with a body implanted device (e.g., medical sensor) represents a challenge, for three reasons: First, the antenna used for the link has to be highly miniaturized. Second, biological tissues have high losses, and thus will attenuate any wireless signal. Finally, as the implant is placed in a living host, levels of powers that may be used for a wireless link are heavily limited by regulations, in order to protect the host from exposure to electromagnetic fields. Thus, such wireless links should be designed in a way achieving the best possible efficiency in order to be viable. To this aim, good propagation models for electromagnetic fields through biological tissues are a good help in the design process. They should be precise enough to enable a good link budget at the planning stage of a project, and simple enough to enable an easy use. One of the major difficulties in establishing such models is that in the case of wireless communication with a device located in a lossy medium, it is not always possible to decouple the channel (i.e., the propagation in the medium) from the antenna characteristics, as the near field generated by the antenna can couple to the lossy medium.