宽带卫星网络中基于跨层设计的带宽分配研究

传统的带宽分配策略按照分层结构进行设计,集中在链路层解决问题,没有考虑动态变化的信道状态和所承载的数据流的QoS性能。基于跨层设计的思想,针对支持话音业务和Internet数据业务的卫星网络提出了一种基于跨层设计的带宽分配算法。该策略将应用层的业务特性和数据链路层的带宽分配策略以及物理层的信道状态进行跨层优化。主控站通过建立代价函数的方法将所有相关参数综合考虑,利用动态规划算法得到了最佳的带宽分配方案。数值结果表明：跨层设计方式可以适应变化的信道状态,并且同传统带宽分配算法比较,提高了Internet数据的有效吞吐量并且保持了话音业务的QoS要求。     

Bandwidth allocation in UWB WPANs with ECMA-368 MAC

The new ECMA-368 MAC for UWB WPANs consists of two channel access methods: the distributed reservation protocol (DRP) and prioritized contention access (PCA). The exact method of medium access slot (MAS) allocation in DRP is not specified in the standard. The contribution of this paper is twofold. First, the paper describes a distributed resource allocation method in which a number of interference–avoidance rules are used to reserve slots for devices. Devices maintain sending and receiving tables to track activities in the neighbourhood. The proposed method is a simple, effective solution to the DRP MAS allocation problem, avoiding reservation conflicts and interference from hidden terminals. Secondly, for VBR MPEG-4 video traffic, we propose a bandwidth requirement calculation method based on traffic prediction. In the proposed scheme bandwidth is allocated based on accurate traffic predictions, therefore matching network resources to the traffic demand. Application QoS is maintained while network utilization is kept high. Furthermore, the simple, adaptive linear predictor does not incur much computation overhead. Simulation results have demonstrated the accuracy of the proposed prediction algorithm and effectiveness of the bandwidth allocation method.     

Dynamic resource management considering the real behavior ofaggregate traffic

This paper explains why the theory of effective bandwidth is in general not applicable to characterize realistic traffic sources. Moreover, we show that a static allocation of network resources (bandwidth and/or buffer space) based on large deviation theory can be highly inefficient when the real statistical behavior of traffic is taken into account. As an alternative, we propose a dynamic resource management scheme based on prediction techniques. As a specific example, we apply this scheme to a Differentiated Service (DiffServ) Internet environment, in which the goal, besides policing the incoming traffic, is to optimize the use of network resources, thus minimizing the probability of occurrence of violations of contract guarantees. The performance of the proposed scheme is evaluated via simulations and our results show the superior performance of the new algorithm in terms of buffer overflows, output link utilization, and jitter, as compared to currently used policing and shaping mechanisms     

Methodologies for bandwidth allocation,transmission scheduling,and congestion avoidance in broadband ATM networks

The call types supported in high-speed packet networks vary widely in their bandwidth requirements and tolerance to message delay and loss. In this paper, we classify various traffic sources which are likely to be integrated in broadband ATM networks, and suggest schemes for bandwidth allocation and transmission scheduling to meet the quality and performance objectives. We propose ATM cell-multiplexing using a Dynamic Time-Slice (DTS) scheme which guarantees a required bandwidth for each traffic class and/or virtual circuit (VC), and is dynamic in that it allows the different traffic classes or VCs to share the bandwidth with a soft boundary. Any bandwidth momentarily unused by a class or a VC is made available to the other traffic present in the multiplexer. The scheme guarantees a desired bandwidth to connections which require a fixed wide bandwidth. Thus, it facilitates setting up circuit-like connections in a network using the ATM protocol for transport. The DTS scheme is an efficient way of combining constant bit-rate (CBR) services with variable bit-rate (VBR) stastically multiplexed services. We also described methodologies to schedule delivery of delay-tolerant data traffic within the framework of the DTS scheme. Important issues such as buffer allocations, guarantee of service quality, and ease of implementation are also discussed.     

VBR MPEG视频源流量的智能集成预测模型

由于VBR视频流量的预测能力是直接关系缓冲区设计、动态带宽分配及拥塞控制等提高网络服务质量的关键因素,因此,以多媒体主要应用形式VBRMPEG视频源为研究对象,提出了一种基于模糊神经网络的视频流量智能预测模型。通过设计模糊预测器减少输出比特流的预测误差,采用神经网络减少多步预测的计算量。仿真试验表明,与标准AR模型预测结果相比,该模型显著提高了预测的准确度和可靠性,且易于推广使用。     

Dynamic bandwidth allocation for Internet telephony

Internet telephony is promising for long-distance calls because of its low service charge and value-added functions. To provide Internet telephony to the general public, a service provider can operate a telephone gateway in each servicing city to bridge the local telephone network and the Internet, so that users can use telephones or fax machines to access this gateway for services. In this paper, we propose a dynamic bandwidth allocation scheme for two purposes: (1) each telephone gateway can fully utilize the available bandwidth to serve more telephone and fax sessions and (2) it can respond to the changing environments. We exploit three properties for dynamic bandwidth allocation. First, in a telephone session, each user usually alternates between speaking and listening. When a user is not speaking, she does not send any voice stream and hence the bandwidth can be dynamically released from this session for the other sessions. Second, voice traffic is elastic because it can be further compressed at the cost of a lower quality. Third, fax traffic is flexible because it can be temporarily delayed. We exploit these three properties to allocate bandwidth to telephone and fax sessions dynamically. When a telephone gateway adopts dynamic bandwidth allocation, it can serve more telephone and fax sessions while providing acceptably good quality-of-service (QoS), and it can give more stable QoS when the available bandwidth varies.     

Fairness performance of dynamic weights in the ATM ABR service

Traditional schemes fail to achieve fair distribution of bandwidth among available bit rate connections. In this paper, a new scheme called Active Fairness is proposed which substantially improves fairness in bandwidth allocation. Contrary to one set of weights used in traditional schemes, Active Fairness maintains two sets of weights at each link. The first set is the same as that used in traditional schemes, which represents the relative bandwidth allocation desired out of the available bandwidth at the link. If these weights are used directly in bandwidth allocation, the actual proportion of the bandwidth utilized by an individual connection can deviate substantially due to factors such as the number of links traversed by the connection, its round-trip propagation delay, etc. In order to take into account these factors, another set of weights (dynamic in nature) is derived at each link, which is used in bandwidth allocation. Active Fairness achieves significant fairness improvement which is demonstrated through simulations involving bursty background traffic, network bottlenecks, dynamic VC mixes and different fairness definitions.     

Management,control, and design of integrated networks with real-time dynamic routing

Integrated real-time dynamic routing (IRR) networks provide dynamic routing features for multiple classes-of-service on an integrated transport network. In this paper it is shown that IRR networks allow reduced network management costs since with real-time dynamic routing a number of network operations are simplified or eliminated. These simplifications include eliminating the storage of voluminous routing tables in the network switches, eliminating the calculation of routing tables in network design, simplifying the routing administration operations which require downloading new routing information to the network, and eliminating the automatic rerouting function in on-line traffic management. A new bandwidth allocation technique is described here which is based on the optimal solution of a network bandwidth allocation model for IRR networks. The model achieves significant improvement in both the average network blocking and node pair blocking distribution when the network is in a congested state such as under peak-day loads. In a paper to appear in the next Journal issue we further describe a new algorithm for the transport design of IRR networks which achieves near-optimal capacity engineering. These optimization techniques attain significant capital cost reductions and network performance improvements by properly modeling the more efficient operation of IRR networks.     

A traffic-class burst-polling based delta DBA scheme for QoS in distributed EPONs

Ethernet passive optical network (EPON) preserves the merits of traditional Ethernet network while reducing complexities and improving quality of service (QoS). In this paper, a traffic-class burst-polling based delta dynamic bandwidth allocation (TCBP-DDBA) scheme is presented to provide better QoS to expedited forwarding packet and maximize channel utilization service to assure forwarding and best effort packets. The network resources are efficiently utilized and adaptively allocated to the three traffic classes by guaranteeing the requested QoS. Simulation results using OPNET show that the TCBP-DDBA scheme performs well in comparison to the conventional allocation scheme for a set of given parameters such as: packet delay, queue size, packet delay variation and channel utilization. This work considers system-wide DBA development in contrast to unit-based approach. It is concluded that the algorithm can be used for many types of EPON-based practical distributed networks.     

Interlayer Jitter Index for the Transmission of Layered Video Stream over the Internet

A novel scheme of dynamic bandwidth allocation and buffer dimensioning based on the video playback tunnel and the jitter_index tunnel is proposed to guarantee the synchronization between the basic layer video stream and the enhancement layer video streams in the transmission of layered video streams over the Internet. The performance of the proposed scheme is evaluated using a set of real-life video traces with the focus on the effects of bandwidth, traffic burstiness and network traffic loading on the statistics of jitter_index between the basic layer and enhancement layers. The numerical results show that the proposed dynamic bandwidth allocation and buffer dimensioning scheme is able to significantly reduce the effect of interlayer jitters in the transmission of multiple layer-coded video streams over the Internet.     

Above packet level admission control and bandwidth allocation for IEEE 802.16 wireless MAN

IEEE 802.16 wireless Metropolitan Area Network (MAN) is expected to revolutionize the broadband wireless access technology. Efficient resource management is essential in providing scalability in such large IEEE 802.16-based wireless network and Quality of Service (QoS) for multimedia applications (VoIP, MPEG, FTP, WWW) is usually achieved by appropriate classification of scheduling services and grant/request mechanism. In this paper, we firstly discuss the QoS issue in IEEE 802.16 wireless MANs and propose a dynamic admission control scheme for scheduling services defined in the 802.16 specification. The proposed scheme provides the highest priority for Unsolicited Grant Service (UGS) connections and maximizes the bandwidth utilization by employing bandwidth borrowing and degradation. We develop an approximate analytical model to evaluate the system performance by assuming that the traffic processes of all scheduling services are Poisson processes. In fact, the self-similarity of non-voice traffic makes its traffic process far from Poisson process and should be modeled by Poisson Pareto Burst Process (PPBP). Therefore, in the later part of the paper, we analyze upper bound blocking probabilities of all scheduling services above the packet level using PPBP model for fractal traffic and Gaussian model for aggregated traffic in large wireless network as well as using the Chernoff bound method. Based on the analytical results, we give another admission control and bandwidth allocation mechanism above the packet level so as to minimize the blocking probability of each type of service in IEEE 802.16 wireless MAN. Analytical and simulation results are obtained and compared to demonstrate the effectiveness of proposed schemes and validate our analytical models.     

Performance evaluation of bandwidth allocation methods in a geostationary satellite channel in the presence of internet traffic

Resource allocation represents an important issue for the next generation TCP/IP Quality of Service-based satellite networks. Many schemes, proposed in the recent literature, consider Internet traffic as the superposition of traffic sources without distinguishing between User Datagram Protocol (UDP) and Transmission Control Protocol (TCP) flows, even if UDP and TCP imply very different traffic characteristics. The basic idea of this work is that a resource allocation algorithm which is conscious of the difference may be more efficient because it can make use of the different behaviour of TCP and UDP in the presence of network congestion. Actually TCP reduces the source flow rate and, as a consequence, also the bandwidth occupancy when there is network congestion. The use of this feature within the bandwidth allocation scheme allows reducing the bandwidth waste due to over provisioning and using the residual bandwidth for other sources. The advantage is particularly clear over satellite channels where fading often affects the communication: having some residual bandwidth available for stations which have experienced fading can improve the satellite network performance.This paper presents a detailed performance evaluation of a bandwidth allocation scheme, called E-CAP-ABASC and studied for the satellite environment. The bandwidth is assigned to the earth stations that compose the network by a master station on the basis of a cost function whose main part is represented by a closed-form of the packet loss probabilities for the TCP and UDP traffic. The use of two different packet loss probability models for TCP and UDP allows exploiting the different features of the two traffic types, so improving the overall performance either in terms of packet loss or, on the other hand, in terms of the traffic admitted.The performance evaluation is carried out by varying the link degradation due to fading, the traffic load, and the flow balance between UDP and TCP. The results show a good performance of E-CAP-ABASC, compared with two other schemes. Advantages and drawbacks are discussed.     

A new approach to dynamic bandwidth allocation in Quality of Service networks: Performance and bounds

Efficient dynamic resource provisioning algorithms are necessary to the development and automation of Quality of Service (QoS) networks. The main goal of these algorithms is to offer services that satisfy the QoS requirements of individual users while guaranteeing at the same time an efficient utilization of network resources.In this paper we introduce a new service model that provides per-flow bandwidth guarantees, where users subscribe for a guaranteed rate; moreover, the network periodically individuates unused bandwidth and proposes short-term contracts where extra-bandwidth is allocated and guaranteed exclusively to users who can exploit it to transmit at a rate higher than their subscribed rate.To implement this service model we propose a dynamic provisioning architecture for intra-domain Quality of Service networks. We develop a set of dynamic on-line bandwidth allocation algorithms that take explicitly into account traffic statistics and users’ utility functions to increase users’ benefit and network revenue.Further, we propose a mathematical formulation of the extra-bandwidth allocation problem that maximizes network revenue. The solution of this model allows to obtain an upper bound on the performance achievable by any on-line bandwidth allocation algorithm.We demonstrate through simulation in realistic network scenarios that the proposed dynamic allocation algorithms are superior to static provisioning in providing resource allocation both in terms of total accepted load and network revenue, and they approach, in several network scenarios, the ideal performance provided by the mathematical model.     

Distribution-based bandwidth access scheme in slotted all-optical packet-switched networks

The common approach in an ingress switch to access a slotted all-optical packet-switched network is the TTA (timer-based/threshold-based bandwidth access) bandwidth access scheme in which packet differentiation is provided by a time-out mechanism. In contrast, we propose in this paper the DA (distribution-based bandwidth access) to access the slotted all-optical packet-switched network within a DiffServ domain. Each torrent (the traffic between each pair of ingress and egress switches) is given a bandwidth measured in slots within a frame at an ingress switch. The slots from each torrent are evenly distributed throughout the frame and among the output wavelengths/fibers of the ingress switch. Comparing to the most commonly used technique TTA, we demonstrate that our DA approach can achieve the following: (1) provide each traffic torrent a fairer access to the network bandwidth; (2) reduce the probability of the slot drop rate at the optical network; (3) reduce the excessive bandwidth allocation by the bursty torrents; (4) balance the traffic load much better on wavelength channels; and (5) guarantee a stable edge switch operation to service traffic in which the traffic generation rate to the optical network is lower than the traffic service rate.     

Optimization for adaptive bandwidth reservation in wireless multimedia networks

In future wireless multimedia networks, user mobility management for seamless connection regarding realtime multimedia applications is one of the most important problems. In this paper we propose an opportunity-cost concept-based approach for adaptive bandwidth reservation with admission control for handover calls utilizing network traffic information. Excessive reservation guarantees low blocking probability of handover calls at the cost of high blocking probability of new calls. According to our survey, however, it may degrade bandwidth utilization while no prioritization for handover admissions degrades quality of service (QoS) for ongoing calls. We consider both QoS assurance and bandwidth utilization in order to optimize the amount of bandwidth to reserve for handover admissions. We believe that our scheme could be utilized as a guideline for cost-effective radio resource allocation in mobile multimedia networks.     

一种支持宽带无线多媒体网络QoS的动态呼叫接纳策略

在无线网络中,小区微型化的趋势使得呼叫切换发生的频率越来越高,迫切需要一种有效的呼叫接纳控制策略,对有限的无线带宽资源进行分配,以保证切换时的QoS,同时使带宽利用率最高。传统的预留带宽策略(GC,guard channel scheme)由于其固有的静态特征而不能适应流量模式的变化。最近,人们发现采用动态的随机控制策略能适应流量模式的变化,而且能使精度和稳定性大大提高。但将这种策略应用于多业务环境依然十分困难,挑战来自于多类呼叫的QoS要求、流量模式、切换率的多样性和宽带条件下的实时可计算性。在文[3]中,我们建立了一个随机控制模型,可以在宽带条件下实时地进行多业务接纳控制,但由于没有考虑复杂的边界条件,控制精度受到影响。本文,我们在考虑边界条件的情况下,求解该随机问题,并采用一种有效的数值方法,使计算复杂度大大降低,保证了计算的实时性。最后得到的多业务动态接纳控制策略具有较高的控制精度和良好的可计算性。仿真结果显示该策略能稳定地满足多业务QoS对呼叫中断概率的严格限制,同时又能保证信道的高利用率。     

DiffServ网络中基于流量负载的动态带宽分配

在DiffServ网络中,流量以聚集类的形式存在,聚集类中的流量负载是随时间不断地发生动态变化的.当不同聚集类中的流量负载与调度算法(如WFQ)为其分配的资源(如带宽)不成比例时,即使两个聚集类的优先级相同,它们中的数据包也会得到不公平的待遇.为此,DiffServ网络中面向公平的动态带宽分配引起了广泛的研究.本文中为了实现公平的带宽分配,提出了一种基于流量负载的动态带宽分配的方法,其中在动态计算各个聚集类应分得的新带宽时主要考虑了当前分得的带宽和聚集类的队列长度增量这两个因素.仿真实验结果说明了该方法的有效性.     

Connection admission control of ATM network using integrated MLP and fuzzy controllers

This paper presents a new approach to the problem of call admission control (CAC) of variable bit rate (VBR) traffic in an asynchronous transfer mode (ATM) network. Our approach employs an integrated neural network and fuzzy controller to implement the CAC controller. This scheme capitalizes on the learning ability of a neural network and the robustness of a fuzzy controller. Experiments show that this scheme is able to achieve high throughput and low cell loss while achieving fairness among different classes of VBR traffic. For comparison, we have also implemented four other CAC schemes: (1) peak bandwidth method, (2) equivalent bandwidth method, (3) average bandwidth method and (4) neural network quality of service (QoS) predictor. Results of these experiments are presented in this paper.     

Dynamic slot assignment protocol for QoS support on TDMA-based mobile networks

An efficient bandwidth allocation scheme in wireless networks should not only guarantee successful data transmission without collisions but also enhance the channel spatial reuse to maximize the system throughput. The design of high-performance wireless Local Area Network (LAN) technologies making use of TDMA/FDD MAC (Time Division Multiple Access/Frequency Division Duplex - Medium Access Control) is a very active area of research and development. Several protocols have been proposed in the literature as TDMA-based bandwidth allocation schemes. However, they do not have a convenient generic parameters or suitable frame repartition for dynamic adjustment. In this work, we undertake the design and performance evaluation of a QoS (Quality of Service)-aware scheme built on top of the underlying signaling and bandwidth allocation mechanisms provided by most wireless LANs standards. The main contribution of this study is the new guarantee-based dynamic adjustment algorithm used in MAC level to provide the required QoS for all traffic types in wireless medium especially Wireless ATM (Asynchronous Transfer Mode). Performance evaluation of this approach consists of improving the bandwidth utilization, supporting different QoS requirements and reducing call reject probability and packet latency.     

一种基于流量预测的资源动态管理算法

分析了基于有效带宽理论(effectivebandwidththeory)的静态资源分配方案的弊端。在此基础上,提出了一种基于流量预测的资源动态管理算法,并且把资源动态管理算法具体应用到QoS的区分服务(DifferentiatedService)体系中,算法在区分服务网络的边缘路由器上实现。最后,在ns 2的仿真环境下对两种算法进行了比较,试验结果证明无论在丢包率还是链路利用率上,资源动态管理算法都比静态资源分配方案有明显的优势。