Shunfu Jin

Performance Analysis for a System of Connection Oriented Internet Service with a Release Delay

In this paper, we propose the use of a discrete-time connection oriented Internet service system with a release delay for broadband, high-speed, high-capacity and high-reliability Internet requirements. The release delay called close-delay is set before the release process of a connection. An upper limit length T called timer length is set as a system parameter for the close-delay period. We build a batch arrival Geom*/G/1 queue model with a setup/close-delay/close-down strategy to characterize the system operation. By using a discrete-time imbedded Markov chain approach, we derive the stationary distribution of the system, and present the formula for Probability Generation Functions of the queue length, waiting time, busy period and busy cycle. Correspondingly, we describe the performance measures for the packet response time, setup ratio, and utility of connection. We also develop a cost model to determine the optimal timer length and its expected optimal cost. Based on numerical results, we discuss the influence of the timer length for the close-delay period on the system performance and investigate the minimum timer length and the minimum cost for different offered loads and different burst degrees, and show that the choice of the timer length is significant in improving the system performance.

Modeling and performance evaluation for the sleep mode in the IEEE 802.16e wireless networks

IEEE 802.16e is the latest broadband wireless access standard designed to support mobility. In mobile networks, how to control energy consumption is one of the most important issues for the battery-powered mobile stations. The standard proposes an energy saving mechanism named ¿sleep mode¿ for conserving the power of the mobile stations. According to the operating mechanism of the sleep mode for downlink traffic in the type I power saving class, a discrete-time Geom/G/1 queueing model with a close-down time and multiple vacations is built in this paper. By employing an embedded Markov chain method, the average queue length and the average sojourn time of the system model are derived. Correspondingly, we get the performance measures of the energy saving rate and the average packet delay time for the sleep mode in the IEEE 802.16e. Finally, numerical results are given to demonstrate the dependency relationships between the system performance measures and the system parameters. Furthermore, a cost model is developed to determine the optimum length of the close-down time.

Performance Analysis and Optimization of an Adaptive Admission Control Scheme in Cognitive Radio Networks

In cognitive radio networks, if all the secondary user (SU) packets join the system without any restrictions, the average latency of the SU packets will be greater, especially when the traffic load of the system is higher. For this, we propose an adaptive admission control scheme with a system access probability for the SU packets in this paper. We suppose the system access probability is inversely proportional to the total number of packets in the system and introduce an Adaptive Factor to adjust the system access probability. Accordingly, we build a discrete-time preemptive queueing model with adjustable joining rate. In order to obtain the steady-state distribution of the queueing model exactly, we construct a two-dimensional Markov chain. Moreover, we derive the formulas for the blocking rate, the throughput, and the average latency of the SU packets. Afterwards, we provide numerical results to investigate the influence of the Adaptive Factor on different performance measures. We also give the individually optimal strategy and the socially optimal strategy from the standpoints of the SU packets. Finally, we provide a pricing mechanism to coordinate the two optimal strategies.

A novel spectrum access strategy with ¿-Retry policy in cognitive radio networks: A queueing-based analysis

In cognitive radio networks, the packet transmissions of the secondary users (SUs) can be interrupted randomly by the primary users (PUs). That is to say, the PU packets have preemptive priority over the SU packets. In order to enhance the quality of service (QoS) for the SUs, we propose a spectrum access strategy with an α-Retry policy. A buffer is deployed for the SU packets. An interrupted SU packet will return to the buffer with probability a for later retrial, or leave the system with probability (1 - α). For mathematical analysis, we build a preemptive priority queue and model the spectrum access strategy with an α-Retry policy as a two-dimensional discrete-time Markov chain (DTMC). We give the transition probability matrix of the Markov chain and obtain the steady-state distribution. Accordingly, we derive the formulas for the blocked rate, the forced dropping rate, the throughput and the average delay of the SU packets. With numerical results, we show the influence of the retrial probability for the strategy proposed in this paper on different performance measures. Finally, based on the tradeoff between different performance measures, we construct a cost function and optimize the retrial probabilities with respect to different system parameters by employing an iterative algorithm.

Performance evaluation of self-similar traffic in multimedia wireless communication networks with power saving class type III in IEEE 802.16e

In this paper, we present a theoretical analysis to numerically evaluate the system performance of multimedia wireless communication networks with power saving class type III in IEEE 802.16e for self-similar traffic. Our model is based on system operations using a batch arrival, and we suppose the batch size to be a random variable following a Pareto(c, α) distribution in order to capture the self-similar property. By using a discrete-time embedded Markov chain, we derive the probability generating functions of the number of data frames and batches for when the busy period begins and for when the system is in a busy cycle. Using the first and higher moments of the probability generating functions, we give the averages and the standard deviation for the system performance in the diffusion approximation for the operation process of the system. In numerical results, we show the performance measures such as the energy saving ratio, plus the average and the standard deviation for the handover ratio with different system parameters as examples.

An Adjustable Channel Bonding Strategy in Centralized Cognitive Radio Networks and its Performance Optimization

Abstract One form of spectrum enhancement technologies for cognitive radio networks is a channel bonding strategy, with which a network user can utilize multiple idle channels as one bonding channel. In this paper, we propose an adjustable channel bonding strategy for centralized cognitive radio networks. The main idea is that the number of channels to be aggregated is set according to the number of packets remaining in the system dynamically. Based on the working principle of the proposed adjustable channel bonding strategy, we present a discrete-time priority queueing model with an adjustable transmission rate for this network system. By constructing a two-dimensional Markov chain, we give the transition probability matrix of the Markov chain and obtain the steady-state distribution of the system model. Accordingly, we derive the formulas for the blocking rate, the normalized throughput, the average latency of the Secondary Users (SUs) and the closed channel ratio. Moreover, we provide numerical experiments to investigate the influence of the buffer capacity of the SUs on different performance measures. Finally, with regard to the joining of an SU packet as a trial, we give the Nash equilibrium strategy and socially optimal strategy for the SUs, and propose a reasonable admission fee in order to oblige the SU packets to adopt the socially optimal strategy.

Performance analysis for power saving class type III of IEEE 802.16 in WiMAX

In this paper, we present an effective method to analyze the performance of the networks using the power saving class type III based on the IEEE 802.16e standard in WiMAX with self-similar traffic. We characterize the self-similar traffic in multimedia wireless communication networks as a batch arrival and suppose that the batch size is a random variable following a Pareto(c, α) distribution. By using the discrete-time embedded Markov chain, we analyze the probability generating functions of the numbers of data frames and batches when the busy period begins, the queueing length, the waiting time and the busy cycle for the networks using the power saving class type III. Moreover, we give the formulas for the system performance in terms of the energy saving ratio, the handover ratio, the system utility and the response time of data frames. We also construct a cost function to determine the optimal sleep window lengths to make the cost of the system whole into the minimum. Numerical results are given with analysis and simulation to show the performance measures and optimal results with different degrees of self-similarity and different sleep window lengths.

Performance evaluation for the power saving class type III with a sleep-delay in IEEE 802.16e

Considering the memoryless property of user initiated packet arrivals in wireless broadband metropolitan networks, we present a sleep-delay scheme for the conventional power saving class type III in the IEEE 802.16e. In this paper, a discrete-time multiple vacation queueing model with vacation-delay is built to capture the working principle for the power saving class type III with a sleep-delay. Using the method of the boundary state variable theory to analyze the system model, we derive performance measures such as the queue length, the waiting time and the busy cycle in the steady state. Correspondingly, the formula for some performance measures in terms of the handover ratio, the average response time, the power saving ratio and the system utility for the power saving scheme with sleep-delay are also presented. Numerical results are given to demonstrate the dependency relationships among the performance measures and the time length of the sleep-delay timer, and to validate the effect of the sleep-delay mechanism presented in this paper.

Performance Analysis and Evaluation for Connection-Oriented Networks Based on Discrete Time Vacation Queueing Model

Abstract In this paper, we establish a discrete time Geom/G/1 queue with setup/close-delay/close-down based on operating mechanism of Switch Virtual Channel Connection (SVCC) in connection-oriented networks. The formulas of SVCC performance measures of setup ratio, idle ratio, transmission efficiency and average response time are derived. Combining the formulas with system simulation, we confirm the dependency relationships between these performance measures and the close delay timer’s setting, which have potential applications in system optimal design and network control.

Performance Analysis of Digital Wireless Networks with ARQ Schemes

In this paper, we present a method to analyze the performance of high-reliability Internet systems in wireless environments with Automatic Repeat ReQuest (ARQ) schemes. Considering the setting up procedure of a data link in wireless networks, we build a Geom/G/1 queue model with a setup strategy to characterize the system operation, and analyze the probability distribution of the system to obtain the performance measures. Numerical results are given to evaluate the performance of different ARQ schemes in terms of the response time and the utility, and to show influence of the delay of the setup procedure and the round-trip-time on the system performance.