Researches On Continuous-Time Priority Polling System Under The Exhaustive And Limited Service Policy

Polling provides noncompetition access control for the distribution of the service resources in the system. The completion of its control process is brief and dependable, which will effectively avoid the conflicts caused by customers'competition for service resources and will maintain a higher utility for resources sharing especially in high-loaded situation. Over the past few decades, abundant findings have been produced by scholars at home and abroad in the studies of the polling theories. The findings of polling system have been widely applied in industry control, communications network, production management, traffic and transportation, and economic activities. The polling system model are often used in the analysis of practical issues during which the function and service quality of the system will accordingly be tested via quantificational method. Therefore, it is of great practical significance to promote the researches on polling system.Polling system model is a typical multi-queue multi-server queuing system. The server, following the queuing order, cyclically visits at each queue. The control process covers the arrival service after the customers enter into the queue, the server's inquiry transformation in the queues, and the server's service for each queue. The services are divided into three categories of gated, exhaustive, and limited service policies. In this sense, polling system is a complex one formed by three n-dimensional stochastic processes. It is thus difficult to make an accurate analysis on the system's one-order characteristics like the mean queue length and the mean inquiry cycle, and on the two-order characteristics like the mean waiting time.The key points and special difficulties in the researches on polling system are thus found in the establishment of a corresponding mathematical model by means of probability, queuing, stochastic process and based on the control mechanism of the practical system so as to give accurate analysis on the key performance parameter formulas such as the mean queue length, the mean cyclic time, throughput, and the mean waiting time of customers, and the evaluation on the system's functions via quantificational methods. Moreover, the difficulties are on the rise in that higher demands of the system are expected for practical use and the structure of the system is getting more and more complex.Polling queuing system is divided into the system of continuous time and the system of discrete time. The former is a queuing model which have long been established and widely applied. The researcher of this study has made a thorough and comprehensive analysis on the above-mentioned three polling systems of basic service policies. Over the past 20 years, communication network has enjoyed accelerated development along with the advancement of microelectronic technology and communications theories. Still, the service resources of the system are limited. MAC layer protocol, determining the right of resources use, becomes the important guarantee to the enhancement of the entire network function. MAC mechanism, the key to the QoS supported by the system, enables the wide use of shared resources while it also influences the performances of the above layers. Therefore, the design of a high-efficiency MAC layer protocol remains a valuable research program. With the increased requirements for network service and multimedia performance, it is urgent to break away from the single polling policy service control policies and to develop new and varied control policies for inquiry service order and mixed service on the basis of cyclic access so that the system service performances will be greatly enhanced and optimized. Currently, the research concentration in polling lies with the establishment of real-time, robust and high-quality QoS for multi-priority services.This dissertation is the research work aiming at the analysis of the two-class priority station polling system under the policies of exhaustive and limited services at the continuous time and the improved system. It also makes a systematic study on the MAC protocol policies in communications and computer fields that have been connected with media. All the research work owes greatly to the supports by the Program of Natural Science Foundation of China (NSFC) (No.61072079,"The Evolution of Polling System and the Study of Applied Control Protocol"), by the NSFC Program (No.60362001, entitled "Theories and Approaches of Dynamic Priority Control in Communication Network"), by the Program of "Network Communication and Wireless Communication Technology Lab" under the Cooperation between the Central Government and the Local Government in support of the peculiar advantageous disciplines of the local institutions of higher learning, and by the Science-Engineering Program of Yunnan University (No.2007Q021C, entitled "The Research on Multi-Queuing Multi-Servers Polling System Control Policy"). This research has produced some creative findings which are seen as follows:1. This research shows that the traditional single system structure can hardly meet the higher requirements of differentiating priority service after a comprehensive analysis is made on the typical features of three fundamental queuing systems based on an overview of the control mechanisms and queuing system modeling of the gated, exhaustive and limited services polling systems, and on the mathematical resolving process, simulated experiment and system function of the key performance indexes. It proposes the idea of the two-class priority station polling system under the exhaustive and limited services control policies, and improved system on the basis of the enhancement and optimization of inquiry order, service policy and service order. The practice has optimized the system performance and has ensured that the high-priority customers in communications network enjoy more qualified service.2. Further, this research, based on queuing theory and the mathematical analyses via Markov chain, multidimensional probability generating function, and Laplace -Stieltjes transformation, has produced a comparatively perfect mathematical model for the polling system and its expanded system, has deduced probability generating function of the system status variable, and has made accurate mathematical resolving and simulated experiment on the mean queue length, the mean inquiry cyclic time, and the mean waiting time of customers at the key and the common stations. The findings from the comparative analysis of the theoretical computing and simulated experiment verify the correspondence of theoretical analyses with simulated experiments. The new polling system modeling has enabled the differentiation of the controls of different priorities so as to satisfy the practical demand for priority services, and has optimized the system performance. It has the evident features of fairness, flexibility and pertinence.3. Meanwhile, this research has proposed a polling system of exhaustive and limited services based on probability flow control. In the system model, information packets of each station, following M/G/1 regulations, arrive in batch by means of multiple vacations and in accordance with geometry probability p. Likewise, the approaches of Markov chain and multiple-probability generating function are applied in the analysis of the model at the continuous time. Moreover, mathematical analysis and computer simulation are conducted, under the circumstances of similar system operation and primary parameters, to expound the arrival rate of information packets, service time, system switching time, and the change of geometry probability p. It turns out that the result of theoretical numerical analysis identifies well with that of computer simulation, which justifies the validity of the theoretical analysis of system model. The result of system operation analysis proves that the system model, in addition to the advantages of the exhaustive and limited services of priority polling stations, has further practical values in applied researches in that it has performed the functions of traffic flow control (0< p< 1), dormancy (p= 0) and awakening (p= 1) via geometry probability p.4. This research aims at the scheduling policies of Web server cluster, and NoC (Network on Chip), and WSNs with the MAC protocol. Detailed analyses are made on the above-mentioned network systems concerning their features and service demands. Based on the priority-based polling schedule Algorithm, scientific optimization is conducted respectively on the load balance scheme policy of the Web Server Cluster System on the basis of Internet application, the SoC Arbitration policy of MPSoC, and the clustering scheme control policy of the WSNs. Corresponding theoretical models are established and mathematical resolving and simulated experiment are conducted on the key parameters of system performance. As a result, it has been testified that the new scheduling strategy works well in providing good service of differentiating priorities according to different demands in WAN, NoC and Wireless Communications Network. Moreover, it optimizes the performance of network system and reduces the expense on system operation. The findings of this research will be of great help in the enhancement of the system performance.Finally, besides a summary of this research, further suggestions are given so as to promote the researches of the similar kind.