Research And Implementation Of Mac Protocols In Wireless Sensor Networks

Wireless Sensor network (WSN) is a research hotspot in present information technology field. It is used to cooperatively sense, collect and process the information of monitored objectives, which is ultimately transmitted to the aimed receivers. The main function of MAC protocol is reasonably and efficiently sharing the limited wireless channel resources and avoiding collision, which is a key technology in WSN. This article centers on the research of WSN MAC protocol and places special emphasis on design and implementation of the MAC protocol which should meet design requirements. The main tasks are as follows:1,Combined with applied requirements, the technology scheme of the MAC protocol is formulated and a WSN MAC protocol, which can support reliable unicast, general broadcast and reliable broadcast services(RB-MAC), is designed. The performance of RB-MAC is simulated by using NS2 in Linux, and simulation results indicate that the protocol considerately improves network performance indicators such as packet delivery ratio and reliability, and meets design requirements.2,Based on RB-MAC, an adaptive way of guaranteeing broadcast reliability is introduced. Simulation results show that average broadcast efficiency of the adaptive way is the best among those having been studied. A pilot study on the dynamic adjustment algorithm of the sending probability in RB-MAC is also made and its performance is analyzed by means of a two-dimensional Markov chain. Analytical results indicate that this algorithm has a relatively better performance compared with p-persistent CSMA.3,The article gives a detailed description of the implementation procedure of MAC protocol RB-MAC in the embedded real-time operating systemμC/OS-II. According to the software design requirements of theμC/OS-II, the RB-MAC software architecture is divided into three modules and three tasks. Function testing is carried out on the module level to verify the performance of the three modules. The test results show that the MAC protocol software has a reasonable decomposition of the modules and tasks and all these modules function correctly.4,The application layer software is designed and implemented in the embedded real-time operating systemμC/OS-II. After the functional test of the MAC protocol and routing protocol, joint functional test of the upper layer protocols including MAC protocol, routing protocol and application protocol is also carried out in order to verify their performances. The test results demonstrate that the modules of the upper layer protocols operate properly and can be capable of performing their normal functions.Finally, the conclusion is given in the last part of the article, which contains the shortcomings, the improvements needed, and the prospect for the future work.