一种分级WFQ的宽带无线接入系统QoS架构

文章介绍了加权公平排队(WFQ)分组调度算法和IEEE 802 16的QoS架构.在此基础上,文章结合分级WFQ分组调度算法和IEEE 802 16协议中所提供的控制机制提出了一种适合于BWA系统的QoS架构.该架构充分利用IEEE 802.16提供的控制机制,结合分级WFQ公平队列调度算法,在主动授予业务(UGS)、实时轮询业务(rtS)、非实时轮询业务(nrtPS)和尽力传输业务(BE)之间公平分配带宽,并保证各种业务的QoS特性,完成了在IEEE 802 16协议中留给用户自己定义的调度策略.     

Deterministic Time-Varying Packet Fair Queueing for Integrated Services Networks

In integrated services networks, the provision of Quality of Service (QoS) guarantees depends critically upon the scheduling algorithm employed at the network layer. In this work we review fundamental results on scheduling, and we focus on Packet Fair Queueing (PFQ) algorithms, which have been proposed for QoS wireline-wireless networking. The basic notion in PFQ is that the bandwidth allocated to a session is proportional to a positive weight _i . Because of the fixed weight assignment, the inherent in PFQ delay-bandwidth coupling imposes limitations on the range of QoS that can be supported. We develop PFQ with deterministic time-varying weight assignments, and we propose a low-overhead algorithm capable of supporting arbitrary piecewise linear service curves which achieve delay-bandwidth decoupling. Unlike existing service-curve based algorithms, our time-varying PFQ scheme does not exhibit the punishment phenomenon, and allows sessions to exploit the extra bandwidth in under-loaded networks.     

Efficient Packet Scheduling Using Channel Adaptive Fair Queueing in Distributed Mobile Computing Systems

In a distributed mobile computing system, an efficient packet scheduling policy is a crucial component to achieve a high utilization of the precious bandwidth resources while satisfying users' QoS (quality of service) demands. An important class of scheduling techniques, namely, the wireless fair queueing algorithms, have been extensively studied recently. However, a major drawback in existing approaches is that the channel model is overly simplified – a two-state channel (good or bad) is assumed. While it is relatively easy to analyze the system using such a simple model, the algorithms so designed are of a limited applicability in a practical environment, in which the level of burst errors is time-varying and can be exploited by using channel adaptive coding and modulation techniques. In this paper, we first argue that the existing algorithms cannot cater for a more realistic channel model and the traditional notion of fairness is not suitable. We then propose a new notion of fairness, which bounds the actual throughput normalized by channel capacity of any two data connections. Using the new fairness definition, we propose a new fair queueing algorithm called CAFQ (Channel Adaptive Fair Queueing), which, as indicated in our numerical studies, outperforms other algorithms in terms of overall system throughput and fairness among error prone connections.     

A Packet Scheduling Approach to QoS Support in Multihop Wireless Networks

Providing packet-level quality of service (QoS) is critical to support both rate-sensitive and delay-sensitive applications in bandwidth-constrained, shared-channel, multihop wireless networks. Packet scheduling has been a very popular paradigm to ensure minimum throughput and bounded delay access for packet flows. This work describes a packet scheduling approach to QoS provisioning in multihop wireless networks. Besides minimum throughput and delay bounds for each flow, our scheduling disciplines seek to achieve fair and maximum allocation of the shared wireless channel bandwidth. However, these two criteria can potentially be in conflict in a generic-topology multihop wireless network where a single logical channel is shared among multiple contending flows and spatial reuse of the channel bandwidth is possible. In this paper, we propose a new scheduling model that addresses this conflict. The main results of this paper are the following: (a) a two-tier service model that provides a minimum fair allocation of the channel bandwidth for each packet flow and additionally maximizes spatial reuse of bandwidth, (b) an ideal centralized packet scheduling algorithm that realizes the above service model, and (c) a practical distributed backoff-based channel contention mechanism that approximates the ideal service within the framework of the CSMA/CA protocol.     

A Distributed Fair Queueing (DFQ) Architecture for Wireless ATM Local Access Networks

The application of Asynchronous Transfer Mode (ATM) to a Wireless Local Area Network (WLAN) environment is an undertaking that poses many problems not encountered in either wireline ATM or data-only WLAN. Wireline ATM networks do not have to transmit over multiple-access, unreliable transmission media while data-only WLANs do not have to satisfy heterogeneous Quality of Service (QoS) contracts for multimedia services. To address this issue, we propose in this paper a DFQ-based WLAN architecture, designed as a centrally controlled network where a complex base station polls simpler mobile terminals for channel access.DFQ is an implementation of Fair Queueing (FQ) algorithm to schedule the access to the transmission channel among the mobile terminals. The implementation of DFQ introduces new design challenges, mainly in the packet scheduler. A DFQ scheduler is designed to allow fast and efficient processing of scheduling data. The DFQ algorithm is introduced and simulated for delay-sensitive connections, and the hardware implementation of the packet scheduler is discussed.The Centre for Wireless Communications is a national R&D Centre funded by the Singapore National Science and Technology Board     

An Improved Round Robin Packet Scheduler for Wireless Networks

Scheduling algorithms are important components for providing quality-of-service (QoS) guarantees in wireless networks. The design of such algorithms need to take into account bursty errors and location-dependent channel capacity that are characteristics of wireless networks. In this paper, a new scheduling algorithm for packet cellular networks, wireless deficit round robin (WDRR), is proposed. WDRR is a round robin scheduler that has low implementation complexity and offers a low delay bound, tight fairness index, and good isolation property. In error-prone channels, the algorithm provides short-term fairness among sessions that perceive a clean channel, long-term fairness among all sessions, ability to meet specified throughput objectives for all sessions, and graceful service degradation among sessions that received excess service. Both analysis and simulation are used to verify the WDRR properties.     

Channel-Aware Earliest Deadline Due Fair Scheduling for Wireless Multimedia Networks

Providing delay guarantees to time-sensitive traffic in wireless multimedia networks is a challenging issue. This is due to the time-varying link capacities and the variety of real-time applications expected to be handled by such networks. We propose and evaluate the performance of a channel-aware scheduling discipline and a set of policies that are capable of providing such delay guarantees in TDM-based wireless networks. First, we introduce the Channel-Dependent Earliest-Due-Date (CD-EDD) discipline. In this discipline, the expiration time of the head of line packets of users' queues is taken into consideration in conjunction with the current channel states of users in the scheduling decision. This scheme attempts to guarantee the targeted delay bounds in addition to exploiting multiuser diversity to make best utilization of the variable capacity of the channel. We also propose the violation-fair policy that can be integrated with the CD-EDD discipline and two other well-known scheduling disciplines [1, 2]. In this policy, we attempt to ensure that the number of packets dropped due to deadline violation is fairly distributed among the users. The proposed schemes can provide statistical guarantees on delays, achieve high throughput, and exhibit good fairness performance with respect to throughput and deadline violations. We provide extensive simulation results to study the performance the proposed schemes and compare them with two of the best known scheduling disciplines [1, 2] in the literature. Khaled M. F. Elsayed (S90-M95-SM02) received his B.Sc. (honors) in electrical engineering and M.Sc. in engineering mathematics from Cairo University in 1987 and 1990 respectively. He received his Ph.D. in computer science and computer engineering from North Carolina State University in 1995. He is now an Associate Professor in Cairo University, Egypt and is an independent telecommunications consultant. Between 1995 and 1997, he was a member of scientific staff with Nortel Wireless Systems Engineering in Richardson, TX.Dr. Elsayed was the editor for the Internet technology series of the IEEE Communications Magazine from 1998 until 2002. He has served on technical program committees for several IEEE, IFIP, and ITC conferences. He was the technical co-chair for IFIP MWCN 2003 conference in Singapore. He also served as an expert evaluator for the European Commission FP5 and FP6 programmes. His research interest is in the area of performance evaluation of communication networks including IP, wireless and optical networks. Ahmed Khattab received his B.Sc. (honors) and MS.C in Electronics and Communications Engineering from Cairo University in 2002 and 2004 respectively. Since August 2005, he is pursuing his PhD degree at Rice University, Texas. His research interests are in wireless networking and radio resource management.     

QoS maintenance for fair queueing algorithms in wireless mobile networks

In order to extend fair queueing algorithms to wireless networks, we propose a channel error and handoff compensation scheme. A compensation is performed by a compensation server and a priority swapping mechanism. The proposed compensation scheme provides a short‐term fairness guarantee for an error‐free session, long‐term fairness guarantee for an erroneous session, fast handoff and traffic‐specific quality of service control. Copyright 2002 John Wiley & Sons, Ltd.     

Wireless Convergence Architecture: A Case Study Using GSM and Wireless LAN

The evolution of wireless networks has motivated the expansion of the static business environment to a mobile and wireless one. However, current and forthcoming wireless technologies are characterized by different attributes, regarding coverage area, offered bandwidth and delay. The transparent conjunction of various wireless technologies into a single mobile terminal can further boost the wireless explosion. This paper presents the Wireless Convergence Architecture (WCA) that incorporates different wireless interfaces under the same mobile terminal. Depending on the location and the availability of the underlying wireless network, automatic and seamless switching is performed to the most appropriate wireless network interface. Special care is taken to maintain continuous connectivity at the transport layer (TCP). WCA introduces software components both at the terminal and network side. A specific implementation is presented, based on two complementary wireless technologies – in terms of coverage area – an IEEE 802.11-compliant in the short local and a GSM in the wide area. To demonstrate the operational correctness of the architecture, experiments were performed using standard and proprietary networking applications.     

Lightweight Deployment-Aware Scheduling for Wireless Sensor Networks

Wireless sensor networks consist of a large number of tiny sensors that have only limited energy supply. One of the major challenges in constructing such networks is to maintain long network lifetime as well as sufficient sensing areas. To achieve this goal, a broadly-used method is to turn off redundant sensors. In this paper, the problem of estimating redundant sensing areas among neighbouring wireless sensors is analysed. We present simple methods to estimate the degree of redundancy without the knowledge of location or directional information. We also provide tight upper and lower bounds on the probability of complete redundancy and on the average partial redundancy. With random sensor deployment, our analysis shows that partial redundancy is more realistic for real applications, as complete redundancy is expensive, requiring up to 11 neighbouring sensors to provide a 90 percent chance of complete redundancy. Based on the analysis, we propose a scalable Lightweight Deployment-Aware Scheduling (LDAS) algorithm, which turns off redundant sensors without using accurate location information. Simulation study demonstrates that the LDAS algorithm can reduce network energy consumption and provide desired QoS requirement effectively. This research was partially supported by Natural Sciences and Engineering Research Council of Canada. Kui Wu received his Ph.D. in Computing Science from the University of Alberta, Canada, in 2002. He joined the Department of Computer Science at the University of Victoria, Canada in the same year and is currently an Assistant Professor there. His research interests include mobile and wireless networks, network performance evaluation, and network security. Yong Gao received his Master's degree and Ph.D. degree in computer science from University of Alberta, Canada, in 2000 and 2005 respectively. He is currently with the Irving K. Barber School of Arts and Sciences, UBC Okanagan, Canada. His research interests include search algorithms and AI, communication networks, and computational biology. Yang Xiao worked at Micro Linear as an MAC (Medium Access Control) architect involving the IEEE 802.11 standard enhancement work before he joined Department of Computer Science at The University of Memphis in 2002. Dr. Xiao is an IEEE Senior member. He was a voting member of IEEE 802.11 Working Group from 2001 to 2004. He currently serves as Editor-in-Chief for International Journal of Security and Networks (IJSN) and for International Journal of Sensor Networks (IJSNet). He serves as an associate editor or on editorial boards for the following refereed journals: (Wiley) International Journal of Communication Systems, (Wiley) Wireless Communications and Mobile Computing (WCMC), EURASIP Journal on Wireless Communications and Networking, and International Journal of Wireless and Mobile Computing. He serves as five lead/sole guest editor for five journal special issues. He serves as a referee/reviewer for many funding agencies, as well as a panelist for NSF. His research interests are Security/ Reliable Communications, Medium Access Control, Mobility/Location/Paging Managements, Cache Access and Replacement Policies, Quality of Service, Energy Efficiency, and Routing in wireless networks and mobile computing.     

Extended Performance Evaluation of PRADOS: A Scheduling Algorithm for Traffic Integration in a Wireless ATM Network

The MAC protocol, known as MASCARA (Mobile Access Scheme based on Contention And Reservation for ATM), is an infrastructure-based, adaptive TDMA scheme, which combines reservation- and contention-based access methods to provide multiple access efficiency and Quality-of-Service (QoS) guarantees to wireless ATM terminal connections that share a common radio channel. Radio channel sharing is performed by the PRADOS (Prioritized Regulated Allocation Delay Oriented Scheduling) algorithm. In this paper we assess the capability of PRADOS to guarantee to voice and data traffic types the QoS they need. The analysis leads to the conclusion that PRADOS cannot avoid the interference between the various types of traffic. A criterion to alleviate this drawback is also outlined at the end of the paper.     

基于跨层设计的无线网络QoS技术

随着多媒体业务的不断发展,如何保证无线网络上的QoS成为一个很重要的问题.基于传统的分层设计方法很难适应快速变化的无线通信环境.主要研究无线网络QoS的跨层设计技术,分析了无线网络的特点及其QoS需求,在此基础上阐述跨层设计的思想和方法,讨论了QoS跨层设计目前存在的问题,对QoS跨层设计技术进行了展望.     

Modeling and Simulation of Mixed Queueing and Loss Systems

In this paper, we investigate a multi-rate network in which wide-band calls are allowed to wait if insufficient resources are available at the time of the call arrival. On the link level, an analytical model is presented and simulations have been carried out on the network level. The results indicate that allowing a few wide-band calls to queue can give a significant improvement in performance in terms of network revenue , as well as a means to level out the blocking probabilities of the different traffic classes. This improvement becomes significant when the service discipline of the waiting calls (of different bandwidth requirements) is adaptive in the sense that longer queues get served first. This observation motivates the investigation of the impact of various buffer space assignment and queueing disciplines on network revenue and call blocking probabilities. The study of such mixed delay and queueing networks is motivated by its possible applications to traffic problems in future Broadband Integrated Services Digital Networks as well as in multi-rate cellular radio networks.     

针对安全关键无线网络的实时可调度分析方法

像机载应用这样的安全关键(safety-critical)系统通常具有非常高的可靠性和实时性需求,而无线连接通常被认为是易错的.因此,在考虑设计或者分析一个安全关键的无线网络时,需要新的QoS参数来衡量系统的实时性.一个合适的参数是在给定信道条件下消息的丢包率,即消息不能在时限之前可靠传输的概率.一种应用于实时系统的概...     

Scheduling Algorithms for Packet-Oriented MAC Protocols in Wireless Multimedia Systems

Future generation wireless multimediacommunications will require efficient Medium AccessControl (MAC) protocols able to guarantee suitable Qualityof Service (QoS) levels for different traffic classes whileachieving a high utilization of radio resources. This paperproposes a new scheduling technique to be adopted at the MAClevel in wireless access systems, named Dynamic Scheduling-Time DivisionDuplexing (DS-TDD), that efficiently managesvideo, voice, Web and background traffics. A theoretical approachis proposed in this paper to evaluate the DS-TDD performance withvoice and Web traffics. Simulation results have permitted tohighlight the following promising characteristics of the DS-TDDscheme: (i) a high capacity of real-time traffics isattained with a QoS insensitive to Web and background trafficloads; (ii) a high throughput can be guaranteed whilepreserving the QoS levels of the different traffic classes;(iii) heavier downlink traffic loads do not modify the QoSof uplink traffics. Finally, extensive comparisons with differentscheduling schemes proposed in the literature have permitted tohighlight the better performanceof DS-TDD.     

Performance of Queueing Model of one UMTS Cell with R Virtual Zones by the Maximum Entropy Solution

UMTS stands for Universal Mobile Telecommunications System, which is one of the third generation (i.e., 3G) cellular systems, will come into full commercial phase by year 2005 and the first UMTS services are launched commercially in 2001. Therefore, the research of UMTS is an important and urgent task. In this paper, the performance of UMTS systems is studied through a queueing model which consists of one UMTS with many virtual zones to evaluate the system uplink traffic performance. The two performance measures: blocking probability and system utilization are obtained by the Maximum Entropy Principle, i.e., ME solutions for S _RXR (GGeo/GGeo/1)/N queue. S _RXR (GGeo/GGeo/1)/N system means that arrival time and service time are both GGeo (Generalized Geometric) distributed, each output port has a single server and the maximum capacity is N. After the theoretical analysis, the numerical results are found for the idiographic example, 8×8 (GGeo/GGeo/1)/512 queueing model. Additionally, the performance of this queueing model is discussed with the effect of the parameters Ca ² (squared coefficient of variation of the interarrival time), Cs ² (squared coefficient of variation of the service time) and the arrival rate, λ. Aymen I. Zreikat has obtained his B.Sc. in Computer Science from Yarmouk University, Jordan in 1990 and MSc in Computational Engineering (honour degree) from University of Erlangen, Germany in 2000. In January, 2001, he has joint the Performance Modelling and Engineering Research Group in the Computing Department of Bradford University, UK. His area of research is in the Performance Evaluation and Resource Management of 3G Wireless Mobile Networks. He has a set of international Journal and Conference papers in this field and he was responsible for reviewing a set of papers in this area of research. Furthermore, he is a member of some international organizations; i.e., MOSEL, etc. He has obtained his Ph.D. from Bradford University, UK in 2003. In January, 2004, he has appointed as an Assistant Professor at the Information Technology Department, Mutah University, Jordan where he is currently teaching some courses in performance modelling of Wirelsss Networks, programming languages, advanced simulation techniques and some other important courses.     

无线传感器网络体系结构研究

对无线传感器网络的体系结构进行了深入研究,从无线传感器网络的物理体系结构、软件体系结构、通信体系结构三个层面进行了分析,分析结果对于无线传感器网络的设计具有参考价值。     

Energy-Efficient Routing for Connection-Oriented Traffic in Wireless Ad-Hoc Networks

We address the problem of routing connection-oriented traffic in wireless ad-hoc networks with energy efficiency. We outline the trade-offs that arise by the flexibility of wireless nodes to transmit at different power levels and define a framework for formulating the problem of session routing from the perspective of energy expenditure. A set of heuristics are developed for determining end-to-end unicast paths with sufficient bandwidth and transceiver resources, in which nodes use local information in order to select their transmission power and bandwidth allocation. We propose a set of metrics that associate each link transmission with a cost and consider both the cases of plentiful and limited bandwidth resources, the latter jointly with a set of channel allocation algorithms. Performance is measured through call blocking probability and average energy consumption and our detailed simulation model is used to evaluate the algorithms for a variety of networks.     

Performance Evaluation of Routing Protocols for Ad Hoc Wireless Networks

A mobile ad hoc network is a collection of autonomous mobile nodes that communicate with each other over wireless links. Such networks are expected to play an increasingly important role in future civilian and military settings, being useful for providing communication support where no fixed infrastructure exists or the deployment of a fixed infrastructure is not economically profitable and movement of communicating parties is possible. However, since there is no stationary infrastructure such as base stations, mobile hosts need to operate as routers in order to maintain the information about the network connectivity. Therefore, a number of routing protocols have been proposed for ad hoc wireless networks. In this paper, we study and compare the performance of the following routing protocols AODV, PAODV (preemptive AODV), CBRP, DSR, and DSDV. A variety of workload and scenarios, as characterized by mobility, load and size of the ad hoc network were simulated. Our results indicate that despite its improvement in reducing route request packets, CBRP has a higher overhead than DSR because of its periodic hello messages while AODV's end-to-end packet delay is the shortest when compared to DSR and CBRP. PAODV has shown little improvements over AODV.