| Wireless sensor network (WSN) is a self-organizing network system which accomplishes a specific function by a large number of sensor nodes via wireless communication. Due to the application particularity and energy constraint of sensor nodes, the primary goal of WSN design is to reduce energy consumption, and the energy efficiency technologies of MAC protocols is an important part in energy efficiency design. IEEE 802.15.4 is the wireless communication standard for low-rate wireless personal area networks, and is also considered as the industry standard for wireless sensor networks.First of all, the MAC protocol of IEEE 802.15.4 based WSN is discussed in this thesis, which includes the superframe structure, the frame structure of MAC layer, the data transmission model, the media access control method and the energy consumption model in WSN. Secondly, a simulation platform for WSN is developed by NS2 based on IEEE 802.15.4 and the network performance is discussed. Finally, an energy-efficient TDMA protocol (EB-TDMA) for burst traffic application in WSN is proposed. The algorithm only allows the nodes in burst state to form the cluster, so the length of the frame changes with the network load dynamically. This dynamic optimization reduces the packet latency and improves the channel utility. At the same time, the protocol lets the nodes in idle state quit the cluster and sleep, which saves energy effectively and prolongs the network lifetime. Simulation results show that EB-TDMA has a better performance in terms of packet latency and energy consumption for burst traffic application with high-density deployment and high traffic load. |
