IEEE Standard for WBAN: Propagation Channel Characteristics, Performance Analysis and Improvements

Channel loss and maintaining the Quality of Service (QoS) are two of the major challenges in realizing an effective Wireless Body Area Network (WBAN). This thesis studies the body channel characteristics and proposes a methodology to improve energy efficiency for an entire WBAN system to achieve high throughput and low data latency. Three main contributions are made in this thesis. Firstly, we focus on human body channel (HBC). HBC, as a possible PHY layer for IEEE standards 802.15.6, has been found useful in networking on-body sensors. However, the HBC channel dynamics is not well understood and this is particularly the case when transceivers implanted inside a human body are involved. To this end, channel measurements were performed on real subjects under four different scenarios so that factors affecting channel quality could be identified. Secondly, a channel modelling methodology is proposed for body area network that takes into account the body structure and the dielectric properties of human tissues; this represents the first modelling effort to cover both in-body and on-body communications in vivo. The proposed modelling method composes of two phases: sub-model construction and top-level model construction. The constructed model is a function of two variables, frequency and channel length, enabling channel impedance prediction with respect to either frequency or channel length. Meanwhile, experimental results show that good model accuracy, a maximum error of 2.5 dB, can be achieved in frequencies range from 10 kHz to 60 MHz. In this endeavor, a modified HBC development system was used to measure bit error rate (BER) and signal attenuation during transmission. The measurements show a good match against simulation results and the channel model. Thirdly, a power optimization technique is proposed for the WBAN. The latest IEEE standard 802.15.6 defines several access modes and access methods together with new power management schemes and frame structures. To improve the power efficiency of a body area network, the merit of having data compression was investigated. For this purpose, an analytical model was developed to evaluate the power efficiency of a BAN system. Simulation results show that good power efficiency can be achieved by employing data compression. It is evident that higher data rate can also help improve energy efficiency. When the compression factor is larger than 2, better energy efficiency can be guaranteed by introducing a data processing unit in a sensor node as long as its power consumption is limited to 40% of that of the transceiver unit.