Zhao Dong-feng

Performance analysis of polling systems with limited service

This paper analyzes a queue model of the polling system with limited service (K=1) in discrete time. By the imbedded Markov chain theory and the probability generating function method, the mean values of queue length and message waiting time are explicitly obtained. Also, we give the simulation results. The results obtained by H. Tagai (1985) are revised.

Analysis of Two-Level-Polling System with Mixed Access Policies

The support for real-time services particularly with QoS guarantees is a challenge in design of MAC protocol for Wireless Local Area Networks (WLANs), several kinds of mixed polling mechanism have been enrolled in design of Point Coordination Function(PCF) MAC protocol recently. In this paper, we propose a novel and efficient mixed polling system with two-level-polling scheme, which consists of a hub station and N common stations in a WLAN, and the hub station and N common stations have been provided with exhaustive service and limited-1 service in discrete time respectively. By the embedded Markov chain theory and the probability generating function method, our scheme gives closed form expressions for obtaining the mean queue length and the mean waiting time, and analytical results are verified through extensive simulations. The results of our system can be potentially used as a model for differentiating services to guarantee better QoS and system stability in IEEE 802.11 WLANs, and it has better efficiency and impartiality than that of the traditional polling system with only exhaustive or limited-1 service.

Performance analysis of wireless sensor networks of serial transmission mode with vacation on fire prevention

To discover firing case in time, the technique of wireless sensor networks is applied to fire early system. This paper establishes the early warning system applied to fire prevention model of serial transmission mode with vacation using exhaustive service for wireless sensor networks. We derive the calculating equation of information packet delay for each sensor node in the system by the Markov chain theory and the probability generating function method. Finally, the theoretical analysis results are confirmed through using simulation.

Analysis of a slotted access channel with average cycle method

Random access techniques in the packet broadcasting environment are a very important research topic. A broadcast channel is a radio packet communication channel, and the relative distances between the users and the receiver can vary greatly. Thus, packets from different transmitters arrive at the receiver with substantially different power levels. These phenomena give rise to a capture effect at the receiver. The packet arriving with the highest power level has a good chance of being detected accurately, even when other packets arrive at the same time. This capture effect improves the system throughput and other performance measures. The mean cycle times of the slotted access channel are analyzed by using the average cycle method. Analytic formulae for mean values of a successful period and a colliding period and an idle period are derived. Also, the upper bounds on the throughput of the system with capture effect are provided.

The Analysis of the MAC Protocol of Two-Class Priority Station Polling System under Mixed Services Policy of Exhaustive and Two-Times Gated Services

AODV (Ad Hoc On-Demand Distance Vector) protocol is an on-demand protocol specialized for ad hoc network and it has been used as a mesh routing in 6LoWPAN (IPv6 over IEEE 802.15.4). In order to adapt to the hardware sources especially energy source restrictions of 6LoWPAN, we propose S-AODV (Sink Routing Table over AODV) routing, a new AODV implementation designed to provide benefits in terms of traffic reduction, power consumption and networks lifetime extension, for 6LoWPAN in this paper. In S-AODV, traffic of route discovery in original AODV is reduced by using SRT (Sink Routing Table). By the new mechanism, the delay and energy consumption of the connection between each internal common node and the sink are reduced.

Analysis of Polling System with Multiple Vacations and Using Exhaustive Service

In this paper we consider the polling system with multiple vacations using exhaustive service. By the imbedded Markov chain theory, the generating functions of queue length at the station is obtained. Then computational equations are explicitly determined for the mean queue length and the mean waiting time of information packet. Especially we obtain some corresponding results under some especial cases. The results are verified through extensive simulations.

Packet delay analysis of continuous-time polling system with M-gated services

This paper proposed a novel analytical model of the polling MAC protocol using M-gated services in continuous time. By the imbedded Markov chain theory, the generating functions of queue length at server arrival epoch is obtained. Also, the Laplace-Stieltjes transform (LST) of packet delay distribution function is derived. Then computational equations are explicitl determined for the mean queue length and the mean packet delay. Through analysis of the mechanism of the polling model, its control values of the M-gated service and the related properties have been obtained. Meanwhile, the basic polling systems using gated service and exhaustive service have been improved. The polling MAC control protocol in the application is more effective.

An Improved Scheduling Algorithm for Multimedia Support in Web Cluster Servers

A solution is urgently expected to meet the higher-quality web service requirements of multimedia applications on the limited bandwidth of internet. Based on the ideas of priority-based service and dynamic load adaptation, this paper presents a new scheduling algorithm for multimedia support in web cluster servers , making possible the service of the two-class priority station polling system under the mixed policy of exhaustive and gated services, optimizing the services of the system in time of load change input via adjustment of the times of the access gated services, and strengthening the flexibility and fairness of multimedia transmissions in web service system. The theoretical model of this algorithm is established with Markov chain and probability generating function. Mathematical analysis is made on the mean queue length and the mean inquiry cyclic time of the common queue and the key station. It turns out that the findings from theoretical analysis correspond well with those from simulated experiments.

Approximate Performance Analysis for the Double Servers in the Asynchronous Schedule Mechanism of Polling

With the popularity of network, web is becoming one of the most effective ways in information sharing. However, with the increase of clicking index, a high-function server can hardly meet the increasing demand for service. This thesis provides the schedule strategy in the asynchronous mechanism of multiqueue double servers polling, which is conducted based on theory of polling multi-access and simulation experiments on computer, along with consideration to the load features of Web. It concludes that this strategy enables Web server to take on the features of good extendibility, utility and function.

A Dynamic Scheme Based on Clustering for Wireless Sensor Networks MAC Protocol

Wireless Sensor Networks(WSNs), as one of the most important techniques in the 21st century, receives a universal attention to the research on its key techniques. A solution is urgently expected to meet the higher-quality service requirements of various applications on the limited bandwidth of wireless networks. Based on the ideas of Priority-based polling transmission with high-efficiency, and dynamic self-adaptation to loading, this paper presents a new analysis model of MAC Scheme of wireless sensor networks, which has made possible the Cluster Header capable of differentiating the nodes of different priority levels under mixed services policy and which has improved the flexibility and adaptability of the system via adjustment of the switch-in service in three time of load change input. The theoretical model of this protocol is established with Markov chain and probability generating function. Mathematical analysis is made on the mean queue length and the mean inquiry cyclic time of the common queue and the key node. It turns out that the findings from theoretical analysis correspond well with those from simulated experiments.