Research On Discrete-Time Parallel Two-level And Asymmetric Gated Service Polling System

Since the first polling model appeared in the late1950s, when the papers of Mack et al. concerning a patrolling repairman model for the British cotton industry were published, few models have received much attention. The ubiquity of polling systems can be observed in many applications, e.g., computer-communication, production, transportation, maintenance systems, traffic and transportation systems and so on. A huge part of the queueing literature is devoted to polling models both in applications and in the mathematical analysis.Polling systems find a wealth of applications in the area of wireless communication systems media access control, where resources (e.g., bandwidth) are shared among different users without traffic collision. With the enhancing of users demand on network quality, performance and QoS assurance are becoming crucial in protocol design, especially in MAC layer. Correspondingly, polling models for protocol mathimatics analysis are demanded to provide priority differentiation and delay guaranteed.The polling model variants with respect to the arrival process, the service process, the switch-over times, the server routing, the various service disciplines and the queueing disciplines. From the priority differentiation term, we present a two-level polling system with exhaustive and parallel1-limited service, the high priority-level queue acquires more service opportunities by a special design in service routing and service policy, and parallel dispatching of service and switch over time attribute a better delay performance than exist two-level models. Considering the scenario of network node has different characteristics, we study a more universal model, asnymmetric gated service polling system, in which the arrivial rate, service time and switch over time of each queue could be different.The main aim of analyzing polling model is to set up mathematical functions of controlling mechanism and study performance measures like the queue lengths, the waiting times, and the cycle times. In most of literatures, performance characteristics are acquired by numerical inversion of the LSTs and PGFs or iterative analysis, seldom in executive closed form expressions. In this thesis, embedded Markov chain theory with the probability generating function methodology is used to build the mathematical model of the present models. The accurate closed from expression of the mean queue length and mean waiting time for the former model and approximate expression of mean waiting time for the latter are acquired. The calculate results are identical with computer simulation results.At last, aiming at the unbalance traffic load problem and delay sensitive applications, we propose a new WSN MAC protocol called parallel two-level polling control based MAC (PTLP-MAC). The proposed two-level polling model is employed. Besides computer simulations, a testing platform with GAINZ node is set to organize a WSN controlled by the PTLP-MAC, which is performed well in service differentiation.