Study On The Beacon Of IEEE802.15.4 MAC

Generally, node energy is limited and can’t be added in wireless sensor network. So energy conservation is the priority for designing the protocol of wireless sensor network. As the underlying MAC layer directly communicate with the physical layer, the MAC protocol has a direct influence on the quality of the network, the network performance and the network life cycle. In IEEE802.15.4 protocol, MAC layer can solve the channel access, establish and break connection, process and maintain the protective time slot and so on. But it hasn’t the optimization for low duty cycle operation and the perfect process for beacon collision. These aspects of not optimization and not perfection are the key of MAC layer in a waste of energy. So this paper is going to handle the two aspects.Firstly, a dynamic adaptive duty cycle algorithm is proposed for optimizing the IEEE802.15.4 fixed duty. In the ABC algorithem, all terminal nodes put the rest number of frame into the queue and send data frames. Then the coordinator receives data frames and saves the information of queue into a matrix. Through the analysis of matrix, there is a conclusion that whether we need to modify the duty cycle and whether nodes are inhibited. Finally, according to the analysis of conclusions, the values of duty cycle and contention window are modified.Secondly, it is analyzed that the problem of beacon collision includes direct collision and indirect collision. For the two collision situations, it is proposed that NLC-BOP algorithm based on BOP uses neighbor list to solve problem. The coordinator establishes 1 hop and 2 hop neighbor list at MAC layer, at the same time as the coordinator allocates the beacon transmitting order. Finally, the size of the BOPL can be estimated and we make assumption and processing for the coordinator of death and isolation.In this paper, two algorithms use the network simulation tool NS2 for simulation comparison of the protocol. The results indicate that new algorithm compared with the original algorithm greatly reduce energy consumption, packet loss rate. In the case of guaranteeing delay, it improves the goodput.