Design And Implementation Of A Wireless Multi-hop Polling Network For Data Gathering

In recent years,WSN(Wireless Sensor Network)becomes more and more popular in data gathering applications,especially in wildland environment monitoring of the forest-fire,flood,earthquakes and heritages.However real-time remote data gathering is hard to achieve due to the limited coverage area of WSN node.At present,data RF module based devices are widely used for data gathering.They are low in cost,and can transmit data in a long distance without pre-deployed infrastructure facilities.But the scalability and reliability of these devices are limited because of the lack of contention detection,link quality measurement and self-organization.This thesis constructs a wireless multi-hop network which consists of a Router(Route Node)and several Relayers(Relay nodes)to overcome above disadvantages.Relayer relays the data from WSN to the Router.Router transmits the data from the Relayers to the server of Internet.Router polls Relayers for data gathering by using multi-hop polling paths based on DSR(Dynamic Source Route)which are centrally computed.Each Relayer estimates the link qualities to neighbor node.The protocol of above network follows below:At first,Relayers estimate the link qualities by counting the sequence of packets received from neighbors.Once a Relayer is polled,it transmits the link qualities and sensors' data to the Router.After obtaining the link qualities information of entire network,the Router calculates the link costs and finds the shortest path to each Relayer with Dijkstra algorithm and can start polling.Every node in the network now is contention-free,and achieves the optimal channel utilization.This thesis designs a hardware platform and software implementation for Router and Relayer.In order to make the data delivery more reliable, the Router stores the data in an embedded database,transmits the data with an ARQ(Automatic Repeat-reQuest)socket protocol.Experiments and the field application of the wireless multi-hop polling network prove effectiveness in remote data gathering,and the scalability,reliability,easy deployment and high channel utilities of the system is further analyzed in the thesis.