## 2 Healthcare Projects Using Wireless Medical Sensor Networks  
The advancement of WMSNs in healthcare applications have made patient monitoring more feasible. Recently, several wireless healthcare researches and projects have been proposed, which aim to provide continuous patient monitoring, in-ambulatory, in-hospital, in-clinic, and open environment monitoring (e.g., athlete health monitoring). This section describes few of the popular research projects about healthcare systems using medical sensor networks. CodeBlue [7; 44] is a popular healthcare research project based on a medical sensor network developed at the Harvard Sensor Network Lab. In this architecture, several medical sensors (e.g., pulse oximeter, EMG, EKG, and SpO2 sensor board onto the Mica2 motes [45]) are placed on the patient's body. These medical sensors sense the patient body data and transmit it wirelessly to the end-user devices (PDAs, laptops, and personal computers) for further analysis. The basic idea of CodeBlue is straightforward, a doctor or medical professional issues a query for patient health data using their personal digital assistant (PDA), which is based on a _publish_ and _subscribe_ architecture. The medical sensors _publish_ their relevant data to a specific channel and end-user _subscribes_ the channel by using their hand-held devices (e.g., PDA and laptop). A TinyADMR routing component is used that is based on an adaptive demand-driven multicast routing (ADMR) protocol. TinyADMR facilitates node mobility, multicast routing and minimal path losses. Further, the CodeBlue architecture facilitates RF-based localization (_i.e._, called MoteTrack [46]), which is accurate enough to locate a patient's or medical professional's position. More importantly, CodeBlue's authors acknowledge the need of security in medical applications, but until now security is still pending or they intentionally left the security aspects for future work, although, in [44] the authors suggested that elliptic curve cryptography (ECC) [47] is a good candidate for the key generation, and TinySec [48] is good forsymmetric encryption in CodeBlue project. Further, [PERSON] _et al._[49] have sketched-out some security threat and attacks on the CodeBlue project such as denial-of-service attacks, snooping attacks, modification attacks, routing loop attack, grey-hole attack, Sybil attack and masquerading attacks. They address suitable countermeasures for CodeBlue security; for details reader may refer to [49]. CodeBlue is anticipated for deployment in pre-hospital and in-hospital emergency care, stroke patient rehabilitation and disaster response. We assumed that the authors have left security work for future. A heterogeneous network architecture named Alarm-Net was designed at the University of Virginia [13]. The research is specifically designed for patient health monitoring in the assisted-living and home environment. Alarm-net consists of body sensor networks and environmental sensor networks. Three network tiers are applied to the proposed assisted-living and home environment, as shown in Figure 4. In the first tier a resident wears body sensor devices such as ECG, accelerometer, SpO2 (_i.e._, a MicaZ boards [50]) which sense individual physiological data; and in the second tier environmental sensors such as temperature, dust, motion, light (_i.e._, MicaZ boards) are deployed in the living space to sense the environmental conditions. In the third tier an internet protocol (IP)-based network is used which is comprised of Stargate gateways called AlarmGate. The idea of Alarm-net is very simple, body sensors broadcast individual physiological data using single-hop to the nearest stationary sensor (_i.e._, second tier). Thereafter, the stationary emplaced sensor nodes forward the body data using multi-hop communication (_i.e._, shortest-path-first routing protocol) to the AlramGate. The AlarmGate is a gateway between the wireless sensor and IP networks, and is also connected to a back-end server.