Key Issues In Topology Control Of Wireless Sensor Networks

Emerging new applications of Wireless Sensor Networks(WSNs) have introducednew features, such as intermittently connectivity, delay tolerance and error-tolerance,which incur new challenges in analysis and development of WSNs. Regarding thetopology control problem, dynamic coverage and energy e?ciency are two criticalfactors that attract both academic and industrial interests. The contributions of thisthesis in this area are listed below.First, theorems are proposed and proved to formulate statistic characters of areacoverage in mobile WSNs, including ?rst hit time, coverage degree distribution, dy-namic and accumulated coverage ratio, et al. Area coverage problem of mobile WSNsis modeled as a Jackson queueing network, and it is proved that the area coverageproblem is equivalent to a queueing problem in terms of statistical problem. By jointsimulations with a variety of mobile models and the real Beijing taxi traces, we showedthat the theoretical results could be used in analyzing large scale mobile WSNs.Second, a Cellular Automata(CA) based energy scheduling mechanism is pro-posed, utilizing delay tolerant features to build intermittently connected graph. Theenergy scheduling is modeled as"game of life", facilitating the study of sensor statetransition from collective dynamic system viewpoint. It is found that the spacial evolu-tion of CA topology can be classi?ed into several patterns, including oscillation, atten-uation and stabilization. Moreover, the tradeo? relations among connectivity, coverageand system lifetime under the stable mode is revealed.Third, a new topology control algorithm for WSNs, namely LICO(LocalInformation-based Cognition and Operation) is proposed. LICO dose not require con-nectivity of network graph, and sensors can made state transition merely according toone hop interactions. Simulations showed that LICO enjoys much longer network life-time, which is about 7 times of that of LEACH under rule S2B03, in sacri?cing thedynamic coverage ratio by 15%, and the network's intermittent loss of connectivity. Finally, the asynchronized version of LICO, namely A-LICO is proposed, whichis based on exponential back-o?. Large scale WSNs'lack of synchronization restraintsthe applications and performance of LICO. A-LICO conquer the problem and enjoyslonger lifetime. Simulation shows A-LICO is ?ne turnable in that the coverage andconnectivity quality decreases as the the average back-o? time rises. Therefore A-LICO is more suitable to general large scale WSNs.The proposed theoretical results, prototype and algorithms can be applied to prac-tical WSN applications.