Research On MAC Protocol Based On Expected Beacon In Wireless Sensor Networks

Wireless sensor network which is mainly used in monitoring of the target area, is made up of a large number of low-cost micro sensor nodes in the target area, forming a multi-hops and self-organized network by wireless communication way.Media Access Control(MAC) protocol determines how to choose the wireless channel,and distributes the wireless communication resources to the node. With a significant impact on the overall performance of the network directly, MAC protocol is an important content in the research of wireless sensor network. In wireless sensor network the first issue of the MAC protocols is saving energy, therefore, we usually use the duty cycle working mode with low-energy consumption. Nodes in duty cycle mode have two states:active and sleep. In the PW-MAC receiver broadcasts its active by sending beacon frames,which greatly reduces the duty cycle ratio of the nodes.This article firstly makes a detail analysis of the PW-MAC protocol's operation principle which based on expected beacon frame model,then designs and implements PW-MAC protocol based on MLA architecture in the Tiny OS operation system. This article put forward the improvement of PW-MAC protocol: BDPW-MAC aims at solving the problem that PW-MAC has high energy consumption.By using the channel reservation mechanism in bulk transactions, BDPW-MAC protocol effectively avoid the problems as packet collision, energy consumption caused by idle listening during competing, network latency due to retreat. After comparing the simulation results between BDPW-MAC and PW-MAC protocol through the TOSSIM, it is proved that BDPW-MAC protocol reduces energy consumption of the network, decreases data gathering completion time and increases delivery rate.Considering that network topology and the wireless link quality changes with environment,which could lead to the decrease in the quality of the communication,neighbor discovery and link estimator play an important role in the aspect of ensuring the stability of the communication link. Using the beacon frame broadcast by the BDPW-MAC protocol as the control message,we design and implement the neighbor discovery and link estimator using hardware and software combination which are suit for BDPW-MAC protocol by monitoring the beacon frame with a variable period,and make the BDPW-MAC into a protocol which works as MAC, neighbor discovery and link estimator.Finally in the TOSSIM simulation experiment, it is proved that BDPW-MNL shows better performance in energy consumption, data gathering completion time and packet delivery ratio,compared with PW-MAC.