The UWB Channel in Medical Wireless Body Area Networks (WBANs)

Abstract

UWB is a technology that has several advantages when considered for a Wireless Body Area Network (WBAN). A WBAN is a network with its communications devices in very close proximity to the human body. In medical applications these devices are connected to sensors that can monitor vital signs such as ECG, temperature, and mobility. A WBAN allows for the remote monitoring of a patient’s health minimizing the number of cables needed. The monitoring of vital signals usually require a relatively low data-rate which in the case of UWB translates into very small transmitting power, long battery life, and less potential side effects caused by electromagnetic radiation. All of these features are very desirable for devices that are close to the body and meant to be used for extended periods of time. The human body is a complex structure and human tissues have different electrical properties which affect the propagation of electromagnetic signals. Moreover, as the human body moves, the characteristics of the radio links changes, e.g. the link from the chest to a wrist will change from line-of-sight to non-line-of-sight as a person walks. To be able to design and develop UWB devices that can interface with WBANs it is then necessary to understand well the characteristics of the radio propagation channel at UWB frequencies and in close proximity to the human body. UWB measurements around a human body have been carried out by several researchers (Fort et al., 2006). There is however a lack of measurements, and subsequent analysis, carried out in real medical environment such as hospitals. The studies described in this chapter focus on scenarios most likely to be found in medical applications and as such they do not assume a large amount of antennas in close proximity to the skin. Among the several issues taken into account are the effects of mobility, and the interaction of the UWB signal with medical implants.