A New MAC Approach in Wireless Body Sensor Networks for Health Care

Abstract

Although the challenges faced by wireless body sensor networks (BSNs) in healthcare environments are in a certain way similar to those already existing in current wireless sensor networks (WSNs), there are intrinsic differences, which require special attention (Yang, 2006). For instance, human body monitoring may be achieved by attaching sensors to the body’s surface as well as implanting them into tissues for a more accurate clinical practice. One of the major concerns is thereby that of extremely energy efficiency, which is the key to extend the lifetime of battery-powered body sensors, reduce maintenance costs and avoid invasive procedures to replace battery in the case of implantable devices. That is, BSNs in healthcare systems operate under conflicting requirements. These are the maintenance of the desired reliability and message latency of data transmissions, while simultaneously maximizing battery lifetime of individual body sensors. In doing so, the characteristics of the entire system, including physical (PHY), MAC and application (APP) layers have to be considered. In fact, the MAC layer is the one responsible for coordinating channel accesses, by avoiding collisions and scheduling data transmissions, to maximize throughput efficiency (and reliability) at an acceptable packet delay and minimal energy consumption. Now, the design of future MAC protocols for BSNs must tackle stringent quality of service (QoS) requirements, apart from the desired low power consumption. Hence, the right MAC approach is able to handle cross-layer PHY-MAC-APP features. In order to consider all the aforementioned healthcare requirements, this chapter first concentrates on the analysis and evaluation of the energy consumption in a MAC level. Thereafter, novel cross-layer fuzzy-logic techniques are proposed to enhance QoS resource management in the here portrayed MAC approach for BSNs. Simulation results are achieved to validate the overall system performance, and its scalability, by increasing the number of wireless on-body sensors in the BSN (see Fig. 1). In this context, among all IEEE 802 standards available today, the IEEE 802.15.4 (802.15.4, 2003) is regarded as the technology of choice for most BSN research studies (Yang, 2006); (Zhen et al., 2007); (Kumar et al., 2008). However, the 802.15.4 MAC is not actually intended to support any set of applications with stringent QoS, and, even though it consumes very low power, the figures do not reach the levels required in BSNs (Zhen et al., 2007); (Kumar 6