| This thesis researches upon networking technologies for Wireless Sensor Network. The network architecture and the medium access control protocol is studied for the network, and a clustering algorithm is designed. OPNET Modeler is used to implement and verify the proposed algorithms and protocols, and the performance of the algorithms and protocols are evaluated.A multiple-layer structure is presented for distributed Wireless Sensor Network. Three layers are defined for the network. The first layer consists of a backend node, which controls and manages the nodes in the lower layers. The second layer consists of cluster heads, which organize and manage cluster members. The third layer consists cluster members. A structured network addressing system is designed, which supports the clustered structure of the network.To prevent co-channel interference among nodes in different clusters, multiple frequencies are adopted, which are assigned for intra-cluster and inter-cluster communications. The frequencies for intra-cluster communications are assigned by cluster heads, while the one for inter-cluster communications are pre-determined.A TDMA-based medium access control protocol is designed. The time is divided into multiple time frames, and multiple time frames make up a time cycle. Each time frame shares the same structure, which are divided into multiple time slots. Each node transmits their data in time slots. Time slots are categorized into three types: control slots, control reverse slots and data slots. The former two types are used to transmit control frames, while the last type is used for data traffic. The relationship between the data speed of the physical layer and the delay of traffic delivery is also analyzed.A MAC algorithm that combines frequency-split clustering and slot assignment is designed. First, cluster heads send invitations to normal nodes. Then, after a normal node receives an invitation, it sends a request to join the cluster. Finally, when the joining request is received, and there’re free resources, the cluster head allocates a dictated slot for the normal node, and confirms the node to join its cluster. In the entire process of the initial organization of the network, each node learns every reverse route.A multiple-tier routing algorithm is designed to allow dynamic network reconstruction. For intra-cluster routing, a link state routing algorithm is adopted. For inter-cluster routing, an on-demand link state routing algorithm is proposed. The algorithm is activated by the backend node, which prevents the network from using long-distance transmission in constant manner.OPNET Modeler is used to simulate and verify the proposed algorithms and protocols. The results show that the proposed algorithms and protocols are able to establish clusters in the network, and allocate time slots dynamically. Multiple-tier routing protocol is supported, and rapid network establishment is realized. The performance of the algorithms and protocols is good. |
