## 4 Wireless Body Area Networks (WBANs)  
The expansion of WSNs for medical applications is increasingly turning these technologies into body sensor networks (BSNs). The biosensors can record electrocardiograms, electromyographs, measure body temperature and blood pressure, electro-dermal activity, among other healthcare parameters. For example, accelerometers can be used to sense heartbeat rate, movement or even muscular activity. Thanks to portable devices such as cellular phones and MP3 players that have became popular; people have started to routinely carry these devices around their body. In 2001, [PERSON] [40]studied how such electronic devices operate at or near the human body. He used the term wireless personal area network (PAN) and used it as a communication channel for intra-body communications. Later around 2001, the term PAN has been changed to body area network (BAN) to include the applications and communications using wearable (on/around) and implantable (in) [40]. A sensor network that senses health parameters thus becomes a body sensor network (BSN). A wireless body-area network (WBAN) is a special purpose wireless-sensor network that incorporates different networks and wireless devices to enable remote monitoring in various environments. One of the targeted applications of WBANs is in medical environments where conditions of a large number of patients are constantly being monitored in a real-time environment. Wireless monitoring of physiological signals of a large number of patients is one of the current needs in order to deploy a complete WSN in healthcare systems. The main goal of WBANs is to provide biofeedback data, the ability to continuously monitor health parameters such as body/intra-body temperature, heartbeat rate, arterial blood pressure, in an unobtrusive and efficient way [41]. Human health monitoring [7-10] is emerging as a prominent application of the embedded sensor networks. A number of tiny wireless sensors are strategically placed on/in a patient's body, to create a WBAN [42]. A WBAN can monitor vital signs, providing real-time feedback to allow many patient diagnostics procedures using continuous monitoring of chronic conditions, or progress of recovery from an illness. Recent technological advances in wireless networking promise a new generation of wireless sensor networks suitable for those on-body/in-body networked systems. Figure 2: A typical WSN system for detecting and transmitting signals from a human body: **(a)** current application of healthcare sensor network and **(b)** future application of healthcare sensor network targeted by wireless body area network. Data acquisition across such sensors can be point-to-point or multipoint-to-point, depending on specific applications. While the distributed detection of an athlete's posture [43] would need point-to-point data sharing across various on-body sensors, applications such as monitoring vital signs as shown in Figure 2, will require all body mounted and/or implanted sensors [44,45] to route data multipoint-to-point to a sink node, which in turn can relay the information wirelessly to an out-of-body server. Data transaction may be also real-time or non-real-time. Although the patient monitoring type of applications requires real-time packet routing, monitoring an athlete's physiological data can be collected offline for processing and analysis purposes. A typical wireless body area network is composed of a number of miniature, lightweight, low-power sensing devices, management electronics and wireless transceivers. As an indispensible part of the system, the power supply for these components should be small-sized, lightweight, environmentally-friendly and long lasting as well. Unlike conventional WSNs, WBANs consists of smaller, less nodes and less space covered and fewer opportunities for redundancy, as shown in Figure 3. Scalability can lead to inefficiencies when working with the two to ten nodes typical of a WBAN.