Body Area Networks: Radio channel modelling and propagation characteristics

Many current and future wireless devices are wearable and use the human body as a carrier. This has made the body an important part of the transmission channel of these wireless devices. Inclusion of the body as a transmission channel will see future wireless networks rely heavily on Body Area Networks (BAN). BAN will be used not only in medical applications but also in personal area network applications. In order to build BAN devices, it is imperative to model the channel accurately. Channel measurements are important, however, a closer look on the body channel can only be attained through Electromagnetic (EM) propagation modelling. This paper presents an analytical EM channel model for BAN. Specifically, the dyadic Green´s function for a cylindrical human body model is used to propose a simple channel model. Four possible cases are considered, where the transmitter and receiver are either inside or outside the body. An exact analytical expression is derived for the case where both the transmitter and receiver are outside the body. This case is then used to show how the received signal power varies around the body, with the receiver at a constant radial distance from the cylindrical axis of the body.