The Research On Energy-efficient And Low-latency MAC Protocol Of Wireless Sensor Networks

Along with the rapid development of the micro-electro-mechanism system and technologies of wireless communication, micro-sensor and embedded computing, the wireless sensor networks which integrating data acquisition, processing and communication have been being extensively researched on. Protocol of MAC level is one of the key problems in the research of wireless sensor networks. This thesis has mainly researched on energy-efficient and low-latency MAC protocol of wireless sensor networks.Based on the MAC protocol of data gathering tree, this thesis analyzes the contradictory problem of energy consumption and delay in the MAC protocols by using synchronous frame. Then an improved MAC protocol which adopting"asynchronous frame"is proposed. In this protocol, the receiving and sending state of each node is separated. And it assigns the transmitting time of nodes on the path hop by hop, so that data can be transmitted successively on the path. The analysis and the experiment results show that, this protocol solves the contradictory problem of energy consumption and delay, it is energy-efficient and low-latency in the data gathering, Furthermore, it has good throughput. Based on the collision-free merit of TDMA and simplicity of CSMA, this thesis proposes HMAC, a hybrid MAC protocol of TDMA and CSMA. In this MAC protocol, each node picks the minimum number of hops to Sink as it's distance class. Data sending of nodes with different class uses TDMA protocol, while with the same class to use the slotted CSMA competitive protocol. The analysis and experiment results show that, compared with the classical S-MAC, HMAC is also energy-efficient, furthermore, the delay of data forwarding is reduced. Moreover, this thesis proposes an energy-efficient and low-latency MAC protocol for multicast. This protocol reduces energy consumption and average spending time by cutting down the number of control packets. The multicasting node selects the node with the worst connection quality to return ACK, so that the number of ACK is able to be reduced. The theoretical analysis and the experiment results show that, compared with the other multicasting MAC protocols, this protocol has better performance in energy consumption and delay if the connection quality of nodes is good.