Research WLAN Infrastructure In Priority Polling Control Policy Model

The wireless local area network (WLAN) is a local area wireless media(Medium) that is used to communicate with the wireless network. It is the product of the combination of wireless communication networks and computer networks, which uses radio frequency technology to replace the fiber wired local area network, and has all the features of the traditional wired LAN. Basic Service Set (Basic Service Set, BSS) is the basic WLAN module, providing with two basic structures:distribution-peer topology (Ad Hoc Network) and infrastructure the centralized (Infrastructure) topology. Distributed peer-to-peer topology (Ad hoc Network) is no central control, while centralized infrastructure mode is a centralized control center, and it is constituted by a wireless station and an access point (AP).With WLAN’s flexibility, mobility, scalability, and economic characteristics, it has become an effective means of broadband access. With the extensive application of WLAN, a higher demand on network performance is proposed, and the MAC protocol is the key to determine the performance of the network. Therefore, the research of the WLAN Access control protocol has important significance. The two main functions of the medium access control sublayer (MAC) in WLAN is the distributed coordination function (DCF) and the Point Coordination Function (PCF). The DCF can only provide non-guaranteed best-effort service mode. Point Coordination Function (PCF) provides access mechanism without competition, and uses a point coordinator control terminal equipments to effectively prevent the collision of the information in the process of sending data and get a better guarantee for QoS of multimedia data. Therefore, MAC protocol PCF research has been a hot area of research communication.The first chapter describes the characteristics of the WLAN and the problems needed to resolve, and introduces the WLAN topology and MAC network work, focus on analysis of the PCF non-competitive way, thus put forward the problem to study and its significance in this paper.The second chapter firstly introduces the concept history and development of the polling of research, and secondly, introduces the present status and significance of the polling system, finally, introduces the polling system with two most commonly used services strategy, and compares their performance to illustrate their advantages and disadvantages.The third chapter proposes two-level-polling system and Gated service on the basis of the two basic polling system in the previous two chapters. The model uses mathematical methods such as Markov chain and probability generating function analysis and study to obtain the mathematical expressions of average polling period, system throughput, average queue length and other system performance parameters. A large number of theoretical calculation and simulation results prove the theory is correct, and draw some conclusions of the model and lay the foundation for the applied research of the next chapter.On the basis of the previous chapter, the fourth chapter combines the model of the system proposed and the WLAN infrastructure network, uses theoretical calculation and experimental simulation test and verify the performance of the system and compare it with the traditional infrastructure-based network PCF polling mechanism to verify superiority of the proposed model.Chapter5makes summary and instructions of the main results in paper, at the same time analysises some problems needed to solve in the subject, and prospects the future research work.