Wireless Sensor Network Communication Protocols Based On Opportunistic Mechanism

With the development of sensor technology, micro electro-mechanical system and modern wireless communication networks, wireless sensor network has developed greatly. Wireless sensor network consists of lots of sensor nodes in the monitored area which form a multi hop network through wireless communication. It is used to sense, collect and deal with the information about the objects in the area. Wireless sensor network is of high value for research and application due to its agileness and flexibility.Whether WSN can work efficiently or not depends on the design of communication protocols. In the past, because sensor node has limited energy, most of the protocols are designed for saving energy and prolonging the network lifetime. But Wireless sensor network is usually deployed in different scenarios and has different performance requirements. Besides energy consumption, network throughput, fairness and end-to-end delay are also important metrics, especially for time-varying and location dependent channel conditions. The different channel condition and unbalance of energy consumption facilitate us to design communication protocols which can exploit the diversity between nodes.According to the time-varying characteristic of channel condition in wireless sensor network, this thesis proposes a MAC protocol and a routing protocol both based on opportunistic mechanism. For MAC layer, we propose OF-MAC protocol which is a modification of SMAC protocol. OF-MAC computes the back off time according to the current channel condition of sensor nodes. The better the link quality, the shorter the back off time. This enables the nodes with better link quality to access the channel with higher priority. We also consider the fairness among nodes to prevent some node from starvation. For routing layer, due to the similarity of the ant algorithm and the WSN, we design a routing protocol which introduces opportunistic metric into the ant colony routing. Opportunistic metric represents the condition of sensor nodes including energy condition, channel condition and the distance from the sink node. Sensor node choose next forwarding node dynamically according to the probability depending on the current condition of neighboring nodes and accumulated information about the routes. Simulation results show that the opportunistic MAC protocol and routing protocol proposed in this thesis could improve the network throughput greatly without losing energy performance.