Joint Design Of Data Transmission And Clock Synchronization For Wireless Sensor And Actuator Networks

A WSAN usually consists of a group of sensor nodes and actuator nodes. Thereare wireless links between the sensor and actuator nodes. WSANs have a wide rangeof applications in the military, fre-fghting, monitoring and other felds. Sensor nodessenseandreportthestateofthemonitoredobjectwhileactuatornodesgatherdatafromsensors and then do the appropriate data fusion and decision-making. Compared withthe sensor nodes, actuator nodes typically have greater capacity in the data processingand wireless communication.Compared to traditional wireless sensor network (WSN), a WSAN works throughcoordination between the sensors and the actuators and it has stronger monitoring andexecuting capacity. But at the same time, it faces new challenges. First, due to themobility of the actuators, it is difcult for the sensors in the event area to transfer thesensingdatatotheactuatortimely. Itneedstoquicklysearchtheactuatoranddetermineits location. Secondly, it remains a problem how to synchronize the sensors on thedata transfer path from the sensor to the actuator and avoid the huge cost for clocksynchronization of the whole network.In this thesis, for the above two problems, we consider the event report transferprocess when searching the mobile actuator as well as the large number of sensing datatobetransferredaftertheeventreportanddesignthejointalgorithmforthedatatransferpath establishment and clock synchronization. The following works are included:1. Analysis of the structural characteristics of WSAN as well as data transfer mech-anism is done. We analyze clock synchronization problems in WSAN and do classifcation and comparison for existing synchronization protocols in the as-pects of how the information is exchanged, the scale of nodes to be synchronizedand the synchronization overhead.2. We investigate the suddenness of the event data and the timeliness requirementof the event report. A recontamination-avoided, delay-bounded search strategy-XY-expansion is proposed for the recontamination problem when searching themobile actuator. Recontamination will bring about search failure and it occurswhen the actuator moves to the already searched area. By analyzing the feasi-bility and necessity of clock synchronization during the event data transmissionprocess, we propose to jointly solve the search and clock synchronization prob-lems. The proposed sachem can avoid recontamination and use the event reportdata to synchronize the sensors on the path in an on-demand and energy efcientway.3. When the sink issues the relevant operational instructions, a connected domi-nating set (CDS)-based virtual backbone started from the sink is constructed toestablish the data transfer path quickly. And the information exchange while dis-tributing the instructions is used to synchronize the network which will lay thesynchronization foundation for the subsequent series of instructions.In the end, the thesis is summarized and the future works are discussed.