Body Area Channel Models
Body Area Networks (BAN's) involve communication from the human body to distances ranging from a few centimetre to 3 metres, to or from devices (nodes) on the body, implanted in the body or off the body (body to body).
Three types of node are defined in the IEEE 802.15.6 Working Group Channel Model :
- implant node or in-body (a node that is placed inside the human body)
- on-body (a node that is placed on the surface of the human skin or at most 2centimetres away)
- off-body (a node that is not in contact with human skin and is between a few centimeters and up to 3 metres away from the body)
The Channel model is an important area of research for Body Area Networks, as the human body is not an ideal medium for radio frequency wave transmission. In fact, it is a heterogeneous lossy dielectric medium with frequency dependent permittivity and conductivity. The distribution and scattering of electromagnetic fields depends on the body’s physiological properties and shape as it consists of materials of different dielectric constants, thickness, and characteristic impedance. Therefore the human body can lead to high losses caused by power absorption, central frequency shift, and radiation pattern destruction, depending on the frequency of operation.
A characterisation of the body channel enables better understanding of the channel's behaviour and indicates the performance that can be expected of a Body Area network. The IEEE802.15.6 Working Group has categorised the channel models into 4 scenarios : implantable to implantable, implantable to on/off-body, on-body to on-body, on-body to off-body. The WiSAR Lab is currently researching the on-body to on-body scenario for On Body to On Body Network Characterisation.
