Research On Low Delay Routing Protocols In Low-duty-cycle Sensor Networks With Unreliable Links

Low-duty-cycle wireless sensor networks(LDC-WSN)can be deployed in harsh environments that humans are difficult to access to perform long-term monitoring and target tracking tasks.LDC-WSN has broad application prospects.In LDC-WSN,nodes will enter sleeping state for most of their time,and only wake up for a small duration of time to work.In the process of data transmission,sending nodes need some time,called sleep delay,to wait for the receiving nodes to wake up.In general,sleep delay is several times or more than a hundred times larger than the delay of data transmission.Therefore,traditional all-node-active routing protocols cannot be applied in LDC-WSN directly.On the other hand,many existing routing protocols for LDC-WSN do not consider unreliable links.Therefore,these routing protocols are difficult to achieve good performance in real applications.As a result,designing low-delay routing protocols in LDC-WSN with unreliable links is a challenging issue.In this paper,we research the above problem and research the following issues:(1)Designing an Energy-aware dynamic routing algorithm in LDC-WSN.Existing LDC-WSN routing protocols are focused on the reduction of end to end delay,but they did not fully consider the balancing of energy consumption of nodes in the networks.Therefore,some nodes would consume their energy quickly and die soon.To solve this problem,we consider link quality and node's energy levels,and then propose a novel routing algorithm called EADR(Energy-aware Dynamic Routing).In EADR,each node maintains a forward set,which contains a set of neighbor nodes with high quality links.During data transmission,a sending node would send its data to the neighbors with larger decision-making factors,which are dynamically determined according to work/sleep schedules and energy levels of the neighbors.Simulation results show that EADR can reduce the end to end delay,achieve higher successful rate of data transmission,and extend the network lifetime.(2)Designing a data collection protocol based on constructive interference in asynchronous LDC-WSN.In event-driven sensor applications,nodes will send data to the Sink when an event is detected.Existing data collection protocols always require that every node has to maintain a neighbor table at regular intervals,which results in large control overheads.Due to the existence of sleep delay and unreliable communication,the requirement is difficult to be satisfied in LDC-WSN with unreliable links.To solve this problem,we propose a data collection protocol based on constructive interference in asynchronous LDC-WSN,called ADCCI(Asynchronous Duty Cycle and Constructive Interference).In ADCCI,all the nodes in the network need not to store and maintain neighbor tables.In the process of data collection,a source node will first establish multiple transmission paths from it to the Sink.Then,all the nodes on the paths will send data to the Sink quickly and reliably by using concurrent transmission based on the constructive interference.Simulation results show that ADCCI can effetely reduce the end to end delay and improve data receiving rate with lesser control overheads in data collection.