Absolute QoS differentiation in optical burst-switched networks

A number of schemes have been proposed for providing quality-of-service (QoS) differentiation in optical burst-switched (OBS) networks. Most existing schemes are based on a relative QoS model in which the service requirements for a given class of traffic are defined relative to the service requirements of another class of traffic. In this paper, we propose an absolute QoS model in OBS networks which ensures that the loss probability of the guaranteed traffic does not exceed a certain value. We describe two mechanisms for providing loss guarantees at OBS core nodes: an early dropping mechanism, which probabilistically drops the nonguaranteed traffic, and a wavelength grouping mechanism, which provisions necessary wavelengths for the guaranteed traffic. It is shown that integrating these two mechanisms outperforms the stand-alone schemes in providing loss guarantees, as well as reducing the loss experienced by the nonguaranteed traffic. We also discuss admission control and resource provisioning for OBS networks, and propose a path clustering technique to further improve the network-wide loss performance. We develop analytical loss models for the proposed schemes and verify the results by simulation.     

Call admission control schemes under generalized processor sharing scheduling

Provision of Quality‐of‐Service (QoS) guarantees is an important and challenging issue in the design of integrated‐services packet networks. Call admission control is an integral part of the challenge and is closely related to other aspects of networks such as service models, scheduling disciplines, traffic characterization and QoS specification. In this paper we provide a theoretical framework within which call admission control schemes with multiple statistical QoS guarantees can be constructed for the Generalized Processor Sharing (GPS) scheduling discipline. Using this framework, we present several admission control schemes for both session‐based and class‐based service models. The theoretical framework is based on recent results in the statistical analysis of the GPS scheduling discipline and the theory of effective bandwidths. Both optimal schemes and suboptimal schemes requiring less computational effort are studied under these service models. The QoS metric considered is loss probability. This revised version was published online in June 2006 with corrections to the Cover Date.     

Throughput and QoS optimization for EDCA-based IEEE 802.11 WLANs

The enhanced distributed channel access (EDCA) mechanism has been adopted by both the IEEE 802.11e standard and the Multiband OFDM Alliance (MBOA) for quality of service (QoS) provisioning in high speed wireless LANs and UWB-based wireless PANs. Based on an analytical model of EDCA, this paper presents an optimal solution to providing maximum system throughput while maintaining the service differentiation among traffic classes. Contention window sizes are adapted to achieve throughput optimization according to the throughput ratio and number of active stations of each traffic class. To overcome the difficulty of accurate estimation of the number of competing stations we propose to use the method of subrange partitioning. An admission control scheme is also discussed. Simulation results demonstrate the effectiveness of the proposed MAC optimization framework.     

Proportional delay differentiation provision by bandwidth adaptation of class‐based queue scheduling

Supporting quality of service (QoS) over the Internet is a very important issue and many mechanisms have already been devised or are under way towards achieving this goal. One of the most important approaches is the so‐called Differentiated Services (DiffServ) architecture, which provides a scalable mechanism for QoS support in a TCP/IP network. The main concept underlying DiffServ is the aggregation of traffic flows at an ingress (or egress) point of a network and the marking of the IP packets of each traffic flow according to several classification criteria. Diffserv is classified under two taxonomies: the absolute and the relative. In absolute DiffServ architecture, an admission control scheme is utilized to provide QoS as absolute bounds of specific QoS parameters. The relative DiffServ model offers also QoS guarantees per class but in reference to the guarantees given to the other classes defined. In this paper, relative proportional delay differentiation is achieved based on class‐based queueing (CBQ) scheduler. Specifically, the service rates allocated to the classes of a CBQ scheduler are frequently adjusted in order to obtain relative delay spacing among them. The model presented can also be exploited in order to meet absolute delay constraints in conjunction with relative delay differentiation provision. Simulation experiments verify that our model can attain relative as well as absolute delay differentiation provided that the preconditions posed are satisfied. Copyright © 2004 John Wiley & Sons, Ltd.     

A LP-RR principle-based admission control for a mobile network

In mobile networks, the traffic fluctuation is unpredictable due to mobility and varying resource requirement of multimedia applications. Hence, it is essential to maintain traffic within the network capacity to provide service guarantees to running applications. This paper proposes an admission control (AC) scheme in a mobile cellular environment supporting hand-off and new application traffic. In the case of multimedia applications, each applications has its own distinct range of acceptable quality of service (QoS) requirements. The network provides the service by maintaining the application specified QoS range. We propose a linear programming resource reduction (LP-RR) principle for admission control by maintaining QoS guarantees to existing applications and to increase the percentage of admission to hand-off and new applications. Artificial neural networks are used to solve the linear programming problem, which facilitates in real time admission control decision in the practical systems. We present an analytical model and results for the proposed AC scheme with resource reduction principle and a simulation study of the AC for performance evaluation. The simulation results demonstrate that the proposed AC scheme performs well in terms of increasing the number of admitted applications and maintains higher percentage of resource utilization. The suggested principle also shown that it is appropriate for the fair resource allocation with improved resource utilization.     

Fuzzy control of multi‐rate traffic in multimedia cell‐based networks

In this paper, an intelligent scheme for controlling the QoS in multimedia, multi‐rate networks is presented. The scheme implements a dynamic control mechanism, based on buffers with vaguely defined thresholds represented with fuzzy sets. This approach guarantees the QoS of real‐time traffic and delivers non‐realtime traffic at acceptable performance levels. The fuzzy mechanism, based on the principles of fuzzy control, dynamically responds to the alternating traffic patterns at the access node using a set of fuzzy control rules. The fuzzy control rules are carefully formulated to reduce the starvation of non‐realtime traffic which is usually assigned a low priority. We also show in this paper how the proposed schemes offer an improved performance over other access control mechanisms such as moving boundaries and other static priority strategies. This revised version was published online in June 2006 with corrections to the Cover Date.     

WLAN中基于效用的呼叫接纳控制策略

 为了在802.11的网络中提供服务质量(QoS)支持,IEEE 802.11 Task Group E提出了EDCF协议.然而EDCF只能提供业务区分服务,并不能提供服务质量(QoS)保证.为了能在重负载下提供QoS保证,在WLAN中加入呼叫接纳控制(CAC)机制是非常必要的.本文首先提出了一个新的3维Markov模型对非饱和状态下EDCF的吞吐量和平均接入时延进行了分析.并在此基础上,提出了一种基于效用函数的CAC策略,它可以使网络的总收益达到最大.最后通过大量仿真验证了所提出的CAC策略的有效性.     

Providing statistical QoS guarantee for voice over IP in the IEEE 802.11 wireless LANs

Recent years have seen greatly increasing interests in voice over IP in wireless LANs, in which the IEEE 802.11 distributed coordination function protocol or enhanced DCF protocol is used. However, since both DCF and EDCF are contention-based medium access control protocols, it is difficult for them to support the strict QoS requirement for VoIP. Therefore, in this article we propose a novel call admission control scheme that runs at the MAC layer to support VoIP services. The call admission control mechanism regulates voice traffic to efficiently coordinate medium contention among voice sources. The rate control mechanism regulates non-voice traffic to control its impact on the performance of voice traffic. Extensive simulations demonstrate that the proposed schemes can well support statistical QoS guarantees for voice traffic and maintain stable high throughput for non-voice traffic at the same time.     

A traffic control system for IEEE 802.11 networks based on available bandwidth estimation

To support Quality of service (QoS)‐sensitive applications like real‐time video streaming in IEEE 802.11 networks, a MAC layer extension for QoS, IEEE 802.11e, has been recently ratified as a standard. This MAC layer solution, however, addresses only the issue of prioritized access to the wireless medium and leaves such issues as QoS guarantee and admission control to the traffic control systems at the higher layers. This paper presents an IP‐layer traffic control system for IEEE 802.11 networks based on available bandwidth estimation. We build an analytical model for estimating the available bandwidth by extending an existing throughput computation model, and implement a traffic control system that provides QoS guarantees and admission control by utilizing the estimated available bandwidth information. We have conducted extensive performance evaluation of the proposed scheme via both simulations and measurements in the real test‐bed. The experiment results show that our estimation model and traffic control system work accurately and effectively in various network load conditions without IEEE 802.11e. The presence of IEEE 802.11e will allow even more efficient QoS provision, as the proposed scheme and the MAC layer QoS support will complement each other. Copyright © 2006 John Wiley & Sons, Ltd.     

End-to-End Adaptive QoS Provisioning over GPRS Wireless Mobile Network

The General Packet Radio Service (GPRS) offers performance guaranteed packet data services to mobile users over wireless frequency-division duplex links with time division multiple access, and core packet data networks. This paper presents a dynamic adaptive guaranteed Quality-of-Service (QoS) provisioning scheme over GPRS wireless mobile links by proposing a guaranteed QoS media access control (GQ-MAC) protocol and an accompanying adaptive prioritized-handoff call admission control (AP-CAC) protocol to maintain GPRS QoS guarantees under the effect of mobile handoffs. The GQ-MAC protocol supports bounded channel access delay for delay-sensitive traffic, bounded packet loss probability for loss-sensitive traffic, and dynamic adaptive resource allocation for bursty traffic with peak bandwidth allocation adapted to the current queue length. The AP-CAC protocol provides dynamic adaptive prioritized admission by differentiating handoff requests with higher admission priorities over new calls via a dynamic multiple guard channels scheme, which dynamically adapts the capacity reserved for dealing with handoff requests based on the current traffic conditions in the neighboring radio cells. Integrated services (IntServ) QoS provisioning over the IP/ATM-based GPRS core network is realized over a multi-protocol label switching (MPLS) architecture, and mobility is supported over the core network via a novel mobile label-switching tree (MLST) architecture. End-to-end QoS provisioning over the GPRS wireless mobile network is realized by mapping between the IntServ and GPRS QoS requirements, and by extending the AP-CAC protocol from the wireless medium to the core network to provide a unified end-to-end admission control with dynamic adaptive admission priorities.     

A framework for guaranteeing statistical QoS

Continuous-media traffic (i.e., audio and video) can tolerate some loss but have rigid delay constraints. A natural QoS requirement for a continuous-media connection is a prescribed limit on the fraction of traffic that exceeds an end-to-end delay constraint. We propose and analyze a framework that provides such a statistical QoS guarantee to traffic in a packet-switched network. Providing statistical guarantees in a network is a notoriously difficult problem because traffic flows lose their original statistical characterizations at the outputs of queues. Our scheme uses bufferless statistical multiplexing combined with cascaded leaky buckets for smoothing and traffic contracting. This scheme along with a novel method for bounding the loss probability gives a tractable framework for providing end-to-end statistical QoS. Using MPEG video traces, we present numerical results that compare the connection-carrying capacity of our scheme with that of guaranteed service schemes (i.e., no loss) using GPS and RCS. Our numerical work indicates that our scheme can support significantly more connections without introducing significant traffic loss     

Call admission control for voice/data integrated cellular networks: performance analysis and comparative study

In this paper, we propose a new call admission control scheme called dual threshold bandwidth reservation, or DTBR scheme. The main novelty is that it builds upon a complete sharing approach, in which the channels in each cell are shared among the different traffic types and multiple thresholds are used to meet the specific quality-of-service (QoS) requirements. We present a detailed comparative study based on mathematical and simulation models, and quantitatively demonstrate that the DTBR is capable of providing the QoS guarantee for each type of traffic, while at the same time leading to much better channel efficiency. We further show that the DTBR scheme with elastic data service can offer both service guarantee and service differentiation for voice and data services, and enhance the bandwidth utilization.     

A scalable QoS routing model for diffserv over MPLS networks

In this paper, we present a new Quality of Service (QoS) routing model for Differentiated Services (Diffserv) over Multiprotocol Label Switching (MPLS) networks. We use a pre-established multi-path model in which several MPLS label switching paths (LSPs) are established between each ingress-egress router pair in advance. Ingress routers perform per-request admission control and bulk-type resource reservation based on the resource availability on the associated LSPs. We use a utilization-based dynamic load balancing scheme to increase resource utilization across LSPs. The proposed model increases signaling and state scalability in the network core. It also provides hard QoS guarantees and minimizes admission control time. The experimental results verify the achievements of our model under various network topologies and traffic conditions.     

Providing deterministic packet delays and packet losses in multimedia wireless networks

‘Anytime, anywhere’ communication, information access and processing are much cherished in modern societies because of their ability to bring flexibility, freedom and increased efficiency to individuals and organizations. Wireless communications, by providing ubiquitous and tetherless network connectivity to mobile users, are therefore bound to play a major role in the advancement of our society. Although initial proposals and implementations of wireless communications are generally focused on near‐term voice and electronic messaging applications, it is recognized that future wireless communications will have to evolve towards supporting a wider range of applications, including voice, video, data, images and connections to wired networks. This implies that future wireless networks must provide quality‐of‐service (QoS) guarantees to various multimedia applications in a wireless environment. Typical traffic in multimedia applications can be classified as either Constant‐Bit‐Rate (CBR) traffic or Variable‐Bit‐Rate (VBR) traffic. In particular, scheduling the transmission of VBR multimedia traffic streams in a wireless environment is very challenging and is still an open problem. In general, there are two ways to guarantee the QoS of VBR multimedia streams, either deterministically or statistically. In particular, most connection admission control (CAC) algorithms and medium access control (MAC) protocols that have been proposed for multimedia wireless networks only provide statistical, or soft, QoS guarantees. In this paper, we consider deterministic QoS guarantees in multimedia wireless networks. We propose a method for constructing a packet‐dropping mechanism that is based on a mathematical framework that determines how many packets can be dropped while the required QoS can still be preserved. This is achieved by employing: (1) An accurate traffic characterization of the VBR multimedia traffic streams; (2) A traffic regulator that can provide bounded packet loss and (3) A traffic scheduler that can provide bounded packet delay. The combination of traffic characterization, regulation and scheduling can provide bounded loss and delay deterministically. This is a distinction from traditional deterministic QoS schemes in which a 0% packet loss are always assumed with deterministically bounding the delay. We performed a set of performance evaluation experiments. The results will demonstrate that our proposed QoS guarantee schemes can significantly support more connections than a system, which does not allow any loss, at the same required QoS. Moreover, from our evaluation experiments, we found that the proposed algorithms are able to out‐perform scheduling algorithms adopted in state‐of‐the‐art wireless MAC protocols, for example Mobile Access Scheme Based on Contention and Reservation for ATM (MASCARA) when the worst‐case traffic is being considered. Copyright © 2002 John Wiley & Sons, Ltd.     

Hub‐polling‐based IEEE 802.11 PCF with integrated QoS differentiation

IEEE 802.11 is one of the most influential wireless LAN (WLAN) standards. Point coordination function (PCF) is its medium access control (MAC) protocol with real‐time traffic (rt‐traffic) quality‐of‐service (QoS) guarantees. In PCF, it is very likely that non‐real‐time traffic (nrt‐traffic) will use the contention free period (CFP) that should be dedicated to traffic having higher priority such as rt‐traffic. Therefore, a modified PCF protocol called MPCF, which is based on hub polling and an integrated QoS differentiation, is presented in this paper. With the integrated QoS differentiation, MPCF can prioritize bandwidth requests according to service classes and QoS requirements. With hub polling, MPCF can reduce the bandwidth for control frames and improve the network throughput. A simple and accurate analytical model is derived and presented in this paper to calculate the system throughput of MPCF. Simulation results show that MPCF protocol is much better than PCF in terms of system capacity and rt‐traffic QoS guarantees. Copyright © 2008 John Wiley & Sons, Ltd.     

QoS-driven adaptive congestion control for voice over IP in multiservice wireless cellular networks

This work establishes a QoS-driven adaptive congestion control framework that provides QoS guarantees to VoIP service flows in mixed traffic scenarios for wireless cellular networks. The framework is composed of three radio resource management algorithms: admission control, packet scheduling, and load control. The proposed framework is scalable to several services and can be applied in any current or future packet-switched wireless system. By means of dynamic system-level simulations carried out in a specific case study where VoIP and Web service flows compete for shared access in an HSDPA wireless network, the proposed framework is able to increase the overall system capacity twofold depending on the traffic mix, while keeping the system operating optimally in its target QoS profile.     

Adaptive Call Admission Control for QoS/Revenue Optimization in CDMA Cellular Networks

In this paper, we show how online management of both quality of service (QoS) and provider revenue can be performed in CDMA cellular networks by adaptive control of system parameters to changing traffic conditions. The key contribution is the introduction of a novel call admission control and bandwidth degradation scheme for real-time traffic as well as the development of a Markov model for the admission controller. This Markov model incorporates important features of 3G cellular networks, such as CDMA intra- and inter-cell interference, different call priorities and soft handover. From the results of the Markov model the threshold for maximal call degradation is periodically adjusted according to the currently measured traffic in the radio access network. As a consequence, QoS and revenue measures can be optimized with respect to a predefined goal. To illustrate the effectiveness of the proposed QoS/revenue management approach, we present quantitative results for the Markov model and a comprehensive simulation study considering a half-day window of a daily usage pattern.     

On providing blocking probability and throughput guarantees in a multi‐service environment

As the Internet evolves from a packet network supporting a single best effort service class towards an integrated infrastructure supporting several service classes—some with QoS guarantees—there is a growing interest in the introduction of admission control and in devising bandwidth sharing strategies, which meet the diverse needs of QoS‐assured and elastic services. In this paper we show that the extension of the classical multi‐rate loss model is possible in a way that makes it useful in the performance analysis of a future admission control based Internet that supports traffic with peak rate guarantee as well as elastic traffic. After introducing the model, it is applied for the analysis of a single link, where it sheds light on the trade‐off between blocking probability and throughput. For the investigation of this trade‐off, we introduce the throughput‐threshold constraint, which bounds the probability that the throughput of a traffic flow drops below a predefined threshold. Finally, we use the model to determine the optimal parameter set of the popular partial overlap link allocation policy: we propose a computationally efficient algorithm that provides blocking probability‐ and throughput guarantees. We conclude that the model and the numerical results provide important insights in traffic engineering in the Internet. Copyright © 2002 John Wiley & Sons, Ltd.     

IPhone系统中的QoS控制系统的设计与实现

本文提出一种用于解决IPhone系统语音质量问题的端到端的服务质量控制方案.该QoS控制系统依据端到端的准入控制结果,为时间敏感的语音数据流建立/维护流状态并保留网络资源,在数据传输阶段使用虚拟时间片公平轮转算法保证流的统计特性.本文首先描述了QoS控制系统的组成结构,然后给出网络资源分配的准入控制算法和流量控制算法,最后依据实验数据讨论该系统对语音质量的控制效果.     

多业务蜂窝CDMA系统中的呼叫接纳控制策略

基于码分多址(CDMA)技术的第三代(3G)移动通信系统将支持多种业务传输,有效的呼叫接纳控制策略将使系统在满足各类业务不同QoS要求的同时,能够为更多的用户提供服务,该文首先分析了多业务蜂窝CDMA系统的剩余容量与QoS约束间的关系,接着提出了适用于任意多类业务环境、基于信号干扰比(SIR)测量的两种呼叫接纳控制策略,局部策略与全局策略,并通过大量计算机仿真研究了两种策略在业务均匀分布和非均匀分布环境下的性能,仿真结果表明,在两种业务分布情况下,全局策略的性能部优于局部策略。