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1.
Cognitive Radio (CR) system based on Orthogonal Frequency Division Multiple Access (OFDMA), such as Wireless Regional Area
Networks (WRAN) and Worldwide Interoperability for Microwave Access (WiMAX), often attempt to improve performance via dynamic
radio resource management, which is characterized as concurrent processing of different traffic and nondeterministic system
capacity. It is essential to design and evaluate such complex system using proper modeling and analysis tools. In the previous
work, most of the communication systems were modeled as Markov Chain (MC) and Stochastic Petri Nets (SPN), which have the
explicit limitation in evaluating adaptive OFDMA CR system with wide area traffic. In this paper, we develop an executable
top-down hierarchical Colored Petri Net (CPN) model for adaptive OFDMA CR system, and analyze its performance using CPN tools.
The results demonstrate that the CPN can model different radio resource management algorithms in CR Systems, and the CPN tools
require less computational effort than Markov model using Matlab, with its flexibility and adaptability to the traffics which
arrival interval and processing time are not exponentially distributed. 相似文献
2.
1 Attack Modeling A typical attack contains the following elements: 1) Objects attacked. These objects belong to the victims or can be regarded as public resource, such as networking bandwidth. 2) Attacker. These objects contain the hacker’s information, attacking tools and other states of attacker. 3) Attack processes. The stages of an attack and attack processes are used to depict the attacking action. 4) Control actions. These actions can be classified into response actions and defensiv… 相似文献
4.
Zhang Dandan Fang Xuming Zhu Longjie 《电子科学学刊(英文版)》2007,24(1):39-45
As the radio spectrum is a very scarce resource, the Call Admission Control (CAC) is one of the most important parts in radio resource management. The Code Division Multiple Access (CDMA) based next generation wireless communications systems will support the transmission of multimedia traffic, such as voice, video and data, thus the CAC, which can support the multimedia traffic and guarantee the Quality of Service (QoS) of different traffic, has gained broad attention. In this paper, a novel multimedia traffic modeling method and a corresponding dynamic QoS based CAC are proposed. The analysis and simulation results show that the proposed CAC scheme can guarantee the QoS to different traffic demand, and improve the system performance significantly. 相似文献
5.
Dynamic spectrum access (DSA) based on interruptible spectrum leasing allows secondary users (SUs) to lease a licensed, but idle, spectrum that is owned by primary users (PUs) on condition that the PUs preempt the access to the leased spectrum. This paper considers a DSA scenario where the SUs opportunistically use the primary spectrum in addition to their own band and the PUs use their own band regardless of the opportunistic access. This operating scenario can contribute to leverage the spectrum utilization by exploiting underutilized spectrum resources, but involves a problem that the SUs may be forced to interrupt on-going services in response to the PUs?? reclamation of the leased spectrum. In this paper, we address the optimal call admission control (CAC) problem in order to coordinate the DSA based on interruptible spectrum leasing by considering the tradeoff between the additional spectrum use and the penalty on the service interruption. To this end, we adopt the profit of the secondary wireless service provider as a cost function of the CAC policy in a market mechanism manner. The optimization problem is modeled as a profit maximization problem, and a linear programming (LP) formulation of the semi-Markov decision process approach is provided. Through the simulation results, we analyze the LP solution of the optimal CAC for the leasing based DSA and demonstrate that the proposed CAC policy judiciously uses the access opportunities of the SUs considering the service interruption. 相似文献
6.
The subject of Call Admission Control (CAC) for wireless networks has been studied extensively in the literature. Another subject on which many researchers have focused their attention is that of video traffic modeling. However, user mobility, combined with the rapidly growing number of "greedy" multimedia applications, in terms of bandwidth and Quality of Service (QoS) requirements, form a challenging and yet unresolved problem for third and fourth-generation wireless networks. In recent work, we have built a Discrete Autoregressive (DAR (1)) model to capture the behavior of multiplexed H.263 videoconference movies from variable bit rate (VBR) coders. Based on this model, we propose in this work a new efficient CAC scheme for wireless cellular networks, which differs from the existing proposals in the literature in that it uses precomputed traffic scenarios combined with online simulation for its decision making. Our scheme is shown, via an extensive simulation study comparison and a conceptual comparison with well-known existing approaches, to clearly excel in terms of QoS provisioning to users receiving videoconference videoconference and Web traffic. To the best of our knowledge, this is the first work in the relevant literature where such an approach has been proposed. 相似文献
7.
The authors discuss the broad issue of bandwidth allocation and call admission control (CAC) in high-speed networks, focusing on asynchronous transfer mode technology. It is maintained that despite the considerable amount of high-quality work carried out in this area, the debate surrounding these issues is not yet resolved. The complexity of dealing with a wide variety of as yet unknown user traffic types, as well as the evolving architecture of networks, means that currently proposed solutions are only an intermediate step of the design process. The authors discuss the nature of user traffic and illustrate how it can impact the debate on the quality of service, concentrating on some “equivalent bandwidth” type CAC strategies. Also discussed is a method which uses diffusion approximations. Finally, the authors discuss the novel issue of evaluating the overload created by the CAC procedure itself on network nodes. The article is complemented by several numerical and simulation results which illustrate the discussion 相似文献
8.
Many networks, such as Non-Geostationary Orbit Satellite (NGOS) networks and networks providing multi-priority service using advance reservations, have capacities which vary over time for some or all types of calls carried on these networks. For connection-oriented networks, Call Admission Control (CAC) policies which only use current capacity information may lead to excessive and intolerable dropping of admitted calls whenever the network capacity decreases. Thus, novel CAC policies are required for these networks. Three such CAC policies are discussed, two for calls with exponentially distributed call holding times and one for calls whose holding time distributions have Increasing Failure Rate (IFR) functions. The Admission Limit Curve (ALC) is discussed and shown to be a constraint limiting the conditions under which any causal CAC policy may admit calls and still meet call dropping guarantees on an individual call basis. We demonstrate how these CAC policies and ALC represent progressive steps in developing optimal CAC policies for calls with exponentially distributed call holding times, and extend this process to the more general case of calls with IFR call holding times. 相似文献
9.
In order to achieve the Quality of Service (QoS) provisioning and efficient resource utilization in cellular network and Wireless Local Area Network (WLAN) integration, an Integrated Service-Based Call Admission Control (ISB-CAC) scheme is proposed in this paper. The integrated network is modeled by using multi-dimensional Markov chains. The numerical analysis is presented to evaluate the important performance measures such as the blocking probability of originating calls, the dropping probability, and the average transfer time, etc. The steady-state probabilities of the multi-dimensional Markov chains are obtained by using an iterative approach, and the CAC parameters are optimally designed. The analytical model is validated by the computer simulation. It is shown that compared with the conventional WLAN-First Call Admission Control (WF-CAC) scheme, the proposed ISB-CAC scheme not only provides better QoS for mobile users but also utilizes the bandwidth resources more efficiently. 相似文献
10.
Spectral efficiency of WCDMA based spread spectrum 3G/4G air interface technology is highly influenced by the common channel interference, hence the applied Call Admission Control method has great importance because it determines the number of active users admitted to the network. In this paper we present a dynamic air interface CAC algorithm which provides efficient usage of radio resources and allows real-time adaptation to the always changing network parameters. Required CAC parameters are derived for generalized multiplicative fading and generalized memory-less traffic sources. In order to validate its capabilities our proposed CAC method was investigated with ON/OFF traffic sources and lognormal fading channels. 相似文献