Non-Uniform Traffic Issues in DCA Wireless Multimedia Networks

Wireless networks that utilize dynamic channel allocation (DCA) are known to perform better than those with fixed channel allocation, in terms of the call level QoS measures such as the handoff dropping probability. On account of this, the DCA networks are usually designed without the call admission control (CAC). However, given the decrease of cell sizes, together with ever increasing mobile phone and terminal population, dynamic channel allocation policies (such as channel borrowing) may not be sufficient to cope with the hot-spot area size and its traffic intensity. This paper analyses the performance of the DCA networks, both with and without the call admission control, under the hot-spot traffic regime. In such cases, the pure DCA approach fails to ensure sufficiently low level of QoS in both the hot-spot area and the surrounding cells. We propose a CAC policy that can stabilize the QoS under non-uniform traffic, whilst being easy to integrate in the distributed DCA policies.     

Provisioning Methods for Bit-Rate-Differentiated Services in Hybrid Optical Networks

This paper addresses the problem of routing and wavelength assignment of bit-rate-differentiated optical services in a hybrid network. Hybrid optical networks are composed of resources, such as fiber links and photonic/electronic switches, that vary in their capabilities and transmission qualities. These networks are also responsible for the realization of optical services with varying quality-of-service (QoS) guarantees. In such networks, it is required to have a cost-effective assignment of the optical and electronic resources to these services in order to maximize the revenue of the network operator. This paper deals with optical services that are defined according to their tolerance to transmission impairments. We first divide the provisioning problem into two phases: (1) routing and (2) wavelength assignment and regeneration reservation. In the routing phase, a set of k-routes are generated to select from in the second phase, where each route optimizes a specific aspect of the problem (e.g., number of hops, maximum accumulated noise, etc.). The second phase, using the information about the resources along each route, attempts at finding the best wavelength allocation on that route such that the signal quality meets the service-level agreement (SLA). The second phase also uses the minimum number of regenerator ports on intermediate nodes for the purpose of wavelength translation and signal clean-up. Comparisons of the above scheme with a probing-based method, reveal substantial enhancements to the blocking performance with a maximum running time increase of 60%. In addition, the use of multiple routes provides higher reduction in the blocking probability over single-routing schemes. Moreover, the proposed, non-pessimistic, provisioning approach has a major impact on reducing the regeneration budget of the network.     

Queue Analysis and Multiplexing of Heavy-tailed Traffic in Wireless Packet Data Networks

Recent research based on traffic measurements shows that Internet traffic flows have a fractal nature (i.e., self-similarity property), which causes an underestimation of network engineering parameters when using the conventional Poisson model. Preliminary field measurements demonstrate that packet data traffic in wireless communications also exhibits self-similarity. In this paper, we investigate the queuing behavior of self-similar traffic flows for data applications in a packet-switching single-server wireless network. The traffic is generated by an on–off source with heavy-tailed on periods and exponentially distributed off periods. We extend previous analysis of a relation among the asymptotic distribution of loss probability, traffic specifications, and transmission rate for a wireline system to a wireless system, taking into account wireless propagation channel characteristics. We also investigate the multiplexing of heavy-tailed traffic flows with a finite buffer for the downlink transmission of a wireless network. Computer simulation results demonstrate that assumptions made in the theoretical analysis are reasonable and the derived relationships are accurate.     

Reducing Encoder Bit-Rate Variation in MPEG Video

A shortcoming of current video transmission using the MPEG standard is that its encoder produces a variable bit rate (VBR). Due to this, the encoder output has to be buffered and released over the network at a constant rate. This buffering of the encoder output introduces an additional delay between the encoding and decoding phases of the video transmission. To remedy this problem, we present a strategy to distribute the load produced by the encoder as evenly as possible, i.e., try to have a constant bit rate (CBR). This is done by treating the slices in each frame separately while compressing them and then mixing the different kinds of slices that are sent over the network. The resulting load variation is much more uniform, reducing the buffering delay and making future bandwidth requirement estimates more accurate.This material is based upon work supported in part by the National Science Foundation under Award No. IRI-9526004, by the Texas Advanced Research Program under Grant No. 3652270, and by a grant from the University of Houston Institute of Space Systems Operations. Rajat Agarwal is now with Lucent Technologies. This paper is an extended version of a shorter paper presented at IEEE ICMCS 1999.Albert Mo Kim Cheng received the B.A. with Highest Honors in Computer Science at age 19, graduating Phi Beta Kappa, the M.S. in Computer Science with a minor in Electrical Engineering at age 21, and the Ph.D. in Computer Science at age 25, all from The University of Texas at Austin, where he held a GTE Foundation Doctoral Fellowship. Dr. Cheng is currently a tenured Associate Professor in the Department of Computer Science at the University of Houston, where he is the founding Director of the Real-Time Systems Laboratory. He has served as a technical consultant for several organizations, including IBM, and was also a visiting faculty in the Departments of Computer Science at Rice University (2000) and at the City University of Hong Kong (1995).He is the author/co-author of over seventy refereed publications in IEEE Transactions on Software Engineering, IEEE Transactions on Knowledge and Data Engineering, Real-Time Systems Symposium, Real-Time and Embedded Technology and Applications Symposium, and other leading conferences. One of his recent work presents a timing analysis of the NASA X-38 Space Station Crew Return Vehicle Avionics, which contains a fault-tolerant distributed system.Dr. Cheng has received numerous awards, including the National Science Foundation Research Initiation Award (now known as the NSF CAREER award). He has been invited to present seminars and tutorials at over 30 conferences, and has given invited seminars/keynotes at over 20 universities and organizations, most recently at ICEIS, Ecole Superieure de l Ouest (ESEO), Angers, France, April 2003. His next invited keynote speech will be at the 1st Intl. Conf. on Informatics in Control, Automation and Robotics (ICINCO), Setubal, Portugal, August 2004.He is an Associate Editor of the IEEE Transactions on Software Engineering (1998-2003), a Guest Co-Editor of two IEEE TSE Special Issues on Software and Performance (Nov. and Dec. 2000), an Associate Editor of the International Journal of Computer and Information Science, the work-in-progress program chair of the 2001 IEEE-CS Real-Time Technology and Applications Symposium, the work-in-progress session chair of the 2003 IEEE-CS Real-Time Systems Symposium, and the invited special panel chair for the software engineering for multimedia session at the 1999 IEEE-CS International Conference on Multimedia Computing Systems (ICMCS). Currently, he is a member of the program committees of RTSS, RTAS, ICEIS, ICECCS, RTAS, LCN, COMPSAC, ICCCN, AIA, DBA, PDCN, SE, and ICINCO. Dr. Cheng is an Honorary Member of the Institute for Systems and Technologies of Information, Control and Communication (INSTICC). He is a Senior Member of the IEEE.Dr. Cheng is the author of several book chapters on E-commerce/Enterprise Information Systems, and an article entitled Embedded OS, in the upcoming Encyclopedia of Computer Science and Engineering (John Wiley & Sons). He is the author of the new senior/graduate-level textbook entitled Real-Time Systems: Scheduling, Analysis, and Verification (John Wiley & Sons). cheng@cs.uh.eduRajat Agarwal received the M.S. in Computer Science from the University of Houston. He is currently a Member of the Technical Staff at Lucent Technologies. His research interest is in real-time multimedia systems.     

QoS Recovery Schemes Based on Differentiated MPLS Services in All-Optical Transport Next Generation Internet

The Internet is evolving from best-effort service toward an integrated or differentiated service framework with quality-of-service (QoS) assurances that are required for new multimedia service applications. Given this increasing demand for high bandwidth Internet with QoS assurances in the coming years, an IP/MPLS-based control plane combined with a wavelength-routed dense wavelength division multiplexing (DWDM) optical network is seen as a very promising approach for the realization of future re-configurable transport networks. Fault and attack survivability issues concerning physical security in a DWDM all-optical transport network (AOTN) require a new approach taking into consideration AOTN physical characteristics. Furthermore, unlike in electronic networks that regenerate signals at every node, attack detection and isolation schemes may not have access to the overhead bits used to transport supervisory information between regenerators or switching sites to perform their functions. This paper presents an analysis of attack and protection problems in an AOTN. Considering this, we propose a framework for QoS guarantees based on the differentiated MPLS service (DMS) model and QoS recovery schemes against QoS degradation caused by devices failures or attack-induced faults in an AOTN. We also suggest how to integrate our attack management model into the NISTs simulator—modeling, evaluation and research of lightwave networks (MERLiN).     

认知无线电具有时延约束的干扰功率分析

为量化认知无线电队列时延与干扰功率之间的关系,提出一种功率分配方案。此方案以最小化主用户接收端平均干扰功率为目标,受限于次用户时延服务质量约束。推导非对称 Nakagami-m 衰落信道平均干扰功率闭合解。仿真结果表明,干扰功率与时延约束之间存在折中。当时延约束较严格时,认知无线电系统通过天线分集可显著降低次用户对主用户的干扰。     

基于SDN分级分域架构的QoS约束路由算法

传统分布式的网络架构制约路由算法的创新,软件定义网络的出现为路由算法的优化提供了新思路。已有研究中,启发式算法广泛应用于服务质量路由,但由于计算复杂度高而无法在大型网络中应用。而其他算法均存在不同程度的问题,要么复杂度较高,要么算法性能较差,如最短路径算法。基于 SDN 分级分域架构,提出了 LC-LD 路由算法,综合时延条件和代价度量约束并在计算复杂度和算法性能之间保持平衡。仿真分析表明,LC-LD路由算法在有较低的计算复杂度的同时还有较高的服务质量路由选路性能。     

OFDMA 协同网络中基于QoS 保证的资源分配算法

针对正交频分多址(OFDMA)协作通信系统,为了解决数据传输速率最大化并提供尽力而为业务与实时业务的服务质量(QoS)保证问题,提出新型资源分配算法.通过以总功率受限为约束条件,定义基于数据速率、时延和丢包率的效用函数,并以在协作传输中以最大化效用函数为目标进行中继选择和子载波分配.通过中继和用户上的子载波和功率分配方案的设计,从而最大化网络数据传输速率并最小化时延与丢包率,为多种业务提供服务质量保证.采用最优化理论与方法求解效用函数,得到了资源分配结果.仿真结果验证了算法收敛,并给出功率分配结果,以及网络吞吐量和时延性能指标情况,验证了算法的有效性.     

A TQM-Based Approach to QoS Management

Total Quality Management (TQM) is one of the most interesting and effective concepts of management. Although, as of today, it has been extensively applied to manufacturing and industrial sectors, TQM principles have not received wide acceptance in the area of Telecommunications Network and Service Management. Application of those principles in Telecommunications can be facilitated by employing pertinent techniques and tools. This paper focuses on aspects of the performance management of Telecommunications Networks and Services. As basic quality control mechanisms, two versions of a Dynamic Scaling Service (DSS) are used to regulate the end-user perceived quality: a Crisp DSS and a Fuzzy Logic DSS. A quality-oriented user behavior model is built and a comparative study between the different quality control schemes is presented. Concluding, the paper delineates the scope of TQM with respect to QoS management in telecommunications.     

QoS-aware dynamic bandwidth allocation algorithm for Gigabit-capable PONS

The Gigabit-capable passive optical network (GPON) technology is being considered as a promising solution for the next-generation broadband access network. Since the network topology of the GPON is point-tomultipoint, a media access control called dynamic bandwidth allocation (DBA) algorithm is an important factor for determining the performance of the GPON. In this paper, we propose a new DBA algorithm to effectively and fairly allocate bandwidths among end users. This DBA algorithm supports differentiated services—a crucial requirement for a converged broadband access network with heterogeneous traffic. In this article we first reviewed the signaling and configuration of the DBA, and then proposed a new DBA scheme that implemented QoS-based priority for this need to maximally satisfy the requirements of all optical network units (ONUs) and provide differentiated services. Analyses and simulation results show that the new algorithm can improve the bandwidth utilization and realize the fairness for both different ONUs and services.