## 1 Introduction  
Mobile (m)Health systems [1] are a fast growing research field that encompasses the use of mobile telecommunication and multimedia technologies within increasingly mobile and wireless health care systems. This field has emerged as a sub-field of eHealth and it is pushing the limits of how to acquire, transport, store, process, and secure both raw and processed medical data to deliver meaningful results. In particular, it offers the possibility of remotely monitoring patients and allowing them to participate in health care systems, a feature which may not have been possible in the past. Two of the main goals of this types of system are to improve the quality of care and reduce cost. The proposed framework addresses issues in both developed and developing nations where mobile communications technologies are becoming widely accessible. A Wireless Body Area Network (WBAN) is a constituent part of mHealth systems and consists of multiple nodes located at different locations on the human body. A WBAN is a wireless network consisting of independent sensor nodes that are attached to the body surface, implanted in the body or around the body, to provide part of the infrastructure in pervasive ubiquitous systems. These devices can be combined with common devices such as personal digital assistants (PDAs), smart phones, and headsets to further provide a platform for applications such as unobtrusive healthcare, sports performance monitoring, ambient intelligence, entertainment, vital signs monitoring, as well as many other potential uses that utilise the physiological signals. The location of a sensor mainly depends on the function of the sensor attached to the node. As a consequence, depending on the physiological parameters being monitored, one can have different sensors and different network topologies. Each individual sensor, or group of nearby sensors, is connected to the main mHealth bridge node wirelessly. The bridge node is often a more powerful device equipped with a larger battery than the sensor nodes. The wireless connectivity is important for multiple reasons, such as to reduce cost of care, to ease the sensor application and improve patient comfort, and, finally, to enable remote (e.g., at home) patient monitoring. Some examples of sensors include electroencephalogram (EEG), electrocardiogram (ECG), oxygen saturation (SpO2), accelerometer, global positioning system (GPS), temperature, microphones, mechanomyography (MMG), electromyography (EMG), blood pressure, _etc_. Figure 1 shows the typical architecture of a WBAN sensor network and its possible integration with larger scale networks. The wearable wireless enabled sensors attached to the body take in the physiological readings, and together form the WBAN. These sensors can be implantable or on body, and can be of various types, such as temperature, accelerometer, ECG, EEG, _etc_. The WBAN has one network coordinator or Master Node. This can be a dedicated device or any PDA or a smartphone. It acts as a gateway between the WBAN and the larger scale network. The master node relays the BAN information to a monitoring station that can provide further services through a Local Area Network or the Internet. If the master node is WiFi or GSM enabled, it can directly transfer data trough the Internet. This interface is already well developed and standardised; however, redundancy is required at this level for critical applications, as this is a single point of failure in the network. The main research effort in the WBAN concept was to reduce the power consumption of a sensor node, while still keeping or enhancing its functionality. Low power consumption is paramount for these devices, since due to their application, the sensors have to be small to be wearable and unobtrusive. The miniaturisation leads to a requirement for reduced battery size, and thus the overall power budget gets reduced.