| The ageing of the population and the increase in the number of patients with chronic diseases are social issues that cannot be ignored at present or even for a long time to come.For the elderly and chronically ill,affordable telemedicine services are urgently needed to ensure their quality of life.Wireless Body Area Network(WBAN)is a special kind of Wireless Sensor Network(WSN),which can monitor the physiological information of human body in real time through wireless biosensors,and has very promising applications in the field of telemedicine services.However,there are still many problems in the deployment and operation of WBAN.Such as energy shortage,radiation hazards,heterogeneous data scheduling and so on.This thesis proposes alternative solutions at the Media Access Control(MAC)layer and network layer of the WBAN respectively,with a view to alleviating the above issues while ensuring the Quality of Service(Qo S)of the WBAN.The main contributions of this thesis are as follows:(1)A new prioritised channel access mechanism and adaptive back-off mechanism are proposed at the MAC layer in order to ensure fast access to the channel for high-priority data and to achieve real-time response to the current node status in the network.Firstly,since the same scheduling method for different heterogeneous data in the WBAN-oriented IEEE802.15.4 MAC layer mechanism may result in higher latency for high-priority data,the channel access mechanism is changed so that nodes delivering high-priority data can access the channel after the first clear channel assessment(CCA),while nodes transmitting lowerpriority data can access the channel after two CCA stages according to the standard protocol and change the initialisation parameters of the backoff mechanism for high priority data so that they have a higher probability of channel access.Secondly,to address the problem that the traditional MAC mechanism cannot be adaptively adjusted when the nodes in the network are low in energy or facing congestion,the node residual energy ratio and the buffer residual space ratio are used as inputs to the fuzzy controller to quantify the state of the nodes carrying common priority data in the network and adjust the initialisation parameters of the backoff mechanism according to the real-time state of the nodes to achieve network life extension and fast congestion relief.Simulation results show that the proposed scheme can effectively extend the lifetime of the network,reduce packet loss,improve throughput and maximise reliable transmission of high priority data.(2)An on-demand energy-efficient multipath routing protocol for WBAN is proposed at the network layer to extend the network lifetime while ensuring user radiation safety and network quality of service.Firstly,the protocol constructs a cost function for assisting routing decisions using four parameters: node residual energy ratio,specific absorption rate(SAR),buffer residual space ratio and node movement metric.This function can be used to adapt existing routing protocols to the network characteristics of WBAN.Secondly,the analytic hierarchy process(AHP)is used to determine the weights of each parameter in the cost function to achieve the objectives of energy saving,radiation safety and stable link construction.Finally,the standard Ad hoc On-Demand Multipath Distance Vector Protocol(AOMDV)is used as the base routing protocol,and the cost function constructed above is used to adapt the routing decision mechanism of the AOMDV protocol.In addition,a new routing maintenance mechanism is added to achieve path redundancy and fast response to node states to ensure network reliability.Simulation results show that the improved routing protocol has better performance in terms of network throughput,average end-to-end delay and network lifetime in both node movement and node stationary scenarios. |
