A Study Of Key Communication Technologies For Wireless Sensor Networks Based Healthcare System

ABSTRACT:With the rapid development of medical sensor technology, the wireless sensor networks(WSN)based technology has invaded the Medicine and Health Care scopes.At the same time, me new requirements of Health Care applications, Such as achieving universaL, seamless wireless sensing and other long-distance medical care, proyide an important opportunity for finding killer application of wireless sensor network.However, current WSN systems can not support the core requirements of medical monitoring and health care very well.Many aspects of the existing problems urgently call for solutions.In this dissertation, the characteristics of the medical monitoring application are analyzed, the system architecture is re-designed, and several key communication protocols in link layer, network layer and session layer are proposed.A WSN based health care system for senior citizens is also designed and implemented to explore the dailylife of senior citizens.1.The mutual interference effects of 2.4 GHz devices widely deployed at home are examined via both theoretical analysis and real-life experiments.An analytical model is proposed to estimate me packet error rate(PER)of radio frequency(RF)coexistent networks.The model is verified through a series of experiments.An interference avoidance model is also proposed, which is based on multi-channel and single radio selection scheme.Experimental results show this scheme can reach high performance.2.When IEEE 802.15.4 is deployed in body area networks,there will be several key issues, including Beacon Conflict, and Inter-cluster GTS Crosstalk.In this dissertation, an improved MAC protocol, named BS-MAC, is proposed to solve these issues.By adding the command frame in IEEE 802.15.4, BS—MAC reduces the effects of Beacon Conflict, and Inter-cluster GTS Crosstalk.To verify and compare the performance of the BS—MAC, T-MAC,the traditional IEEE 802.15.4 and other protocols, a series of simulation experiment are executed.SimulatiOn results show that BS-MAC Can achieve a certain degree of upgrading in throughput, delay and energy consumption compared with other MAC protocols mentioned above.3.The communication requirements in difierent application scenarios of wireless sensor networks based health care systems are very complex. Several new communication schemes are required to dynamically fulfill these requirements and achieve efficient data transmission.3 novel routing schemes are introduced individually including modified MintRoute (designed for simple data collection scenario), Virtual Hypercube Routing (designed for stationary scenario) and MinVar Data-collection Scheme (designed for group BSN sinks mobility scenario). Simulation results show that these 3 schemes can achieve high routing performance individually.4. A new approach, named H-SIP is proposed to couple SIP with wireless sensor network based health care system by jointing the session initiation process with WSN topology generation process. In this approach, more consideration is given to improve the dynamic-message-update and energy-saving-mechanism of SIP communications. Simulation results show that H-SIP can be used in the dynamic sensor networks, which is suitable for medical care applications.5. A prototype of WSN based health care system for senior citizens is deployed by integrating wireless sensor networks and the technologies of public communication networks to construct a healthcare system for senior citizens at home without interfering their daily activities. Based on this prototype, a novel location and activity detection approach is proposed to detect accidental falls for senior citizens. A series of experimental results show that this system can perform high validity and reliability.