Virtual path control for ATM networks with call level quality ofservice guarantees

The configuration of virtual path (VP) connection services is expected to play an important role in the operation of large-scale asynchronous transfer mode (ATM) networks. A major research challenge is to understand the fundamental tradeoff between the network call throughput and the processing load on the signaling system and to provide an algorithm for VP capacity allocation that achieves an optimal network operating point while guaranteeing quality of service (QoS) at the call level and satisfies a priori bounds on the processing load of the call processors. We present a taxonomy of previous approaches to the problem and identify their strengths and weaknesses. Based on these observations, we provide an algorithm for the VP capacity allocation problem that satisfies nodal constraints on the call processing load and blocking constraints for each source-destination (SD) pair. The algorithm maximizes the network revenue under the above set of constraints and is parameterized by the number of traffic classes in the network, the method of presentation of networking resources, the admission control policy used in every link and VP, and the network routing scheme. Finally, we apply the algorithm to three sample networks and study several of its performance characteristics. In one case, we applied the calculated VP distribution to the Xunet ATM testbed and verified experimentally the predicted performance     

Exploitation of DWDM for optical packet switching with quality ofservice guarantees

This paper addresses the problem of building optical packet switches that are able to effectively cope with variable length packet traffic and quality of service management, therefore able to support IP traffic. The paper aims at showing that the availability of dense wavelength division multiplexing is crucial. By suitably exploiting the wavelength dimension a multistage fiber delay line buffer can be implemented, with fine granularity and long delay with an architecture of limited complexity. This is necessary to fulfill the buffering requirements of variable length packets. Furthermore, the wavelength domain is proved to be more effective than the time domain to manage different levels of quality of service. Algorithms are presented that are peculiarly designed for this environment showing that they can effectively differentiate the packet loss probability between three priority classes     

A programmable MAC framework for utility-based adaptive quality ofservice support

We describe the design and evaluation of a programmable medium access control framework which is based on a hybrid centralized/distributed data link controller. The programmable framework and its associated algorithms are capable of supporting adaptive real-time applications over time-varying and bandwidth limited networks (e.g., wireless networks) in a fair and efficient manner taking into account application-specific adaptation needs. The framework is flexible, extensible and supports the dynamic introduction of new adaptive services on-demand. As part of the service creation process, applications interact with a set of distributed adaptation handlers to program services without the need to upgrade the centralized adaptation controller. This approach is in contrast to existing techniques that offer a fixed set of “hard-wired” services at the data link from which applications select. We present a framework where a centralized adaptation controller responsible for the fair allocation of available bandwidth among adaptive applications is driven by application specific bandwidth utility curves. A set of distributed adaptation handlers execute at edge devices interacting with a central controller allowing applications to program their adaptation needs in terms of utility curves, adaptation time scales and adaptation policy. The central controller offers a set of simple meta-services called “profiles” that distributed handlers use to build sophisticated adaptive real-time services     

Channel assignment with QoS guarantees for a multiclass multicode CDMA system

In a wireless system that supports multimedia services, each traffic requires different quality of service (QoS) at both communication on radio links and connection admission. We initially derive the uplink capacity satisfying the QoS constraint on radio links in a multiclass multicode code-division multiple-access (CDMA) system. Based on the derived capacity, the number of channel elements, which is one of the system resources, is determined. Then, we define the QoS parameters associated with connection processes. To guarantee the defined QoS at the connection level, under given channel elements, we propose a channel-assignment scheme with dynamic priority adjustment (DPA). The proposed scheme gives multipriority to different traffic classes. Real-time classes can preempt non-real-time classes with restricted preemptive priority. Such restriction is regulated by preemption-free code channels and a buffer threshold for non-real-time classes. Among real-time classes, different priorities are assigned to each traffic class by code reservation parameters. These multipriority parameters are dynamically adjusted in order to guarantee different QoS requirements. We analyze the DPA scheme by the matrix-geometric method, and evaluate the performance of each traffic class. The results show that the proposed scheme flexibly guarantees QoS depending on traffic loading condition and achieves high channel utilization.     

Deterministic loss ratio quality of service guarantees for highspeed networks

Current research for the provision of deterministic quality of service guarantees in both IP networks and high speed networks involve only bounded delay guarantees, In this letter, loss ratio is considered. We propose constraints on the service function in order to provide not only deterministic bounded loss ratio under a given buffer capacity but also bounded delay. Network operation can be easily managed by existing service-function-based scheduling algorithms     

MSS4TQM-a management support system for total quality management

The paper describes the research and development of a management support system (MSS) for total quality management (TQM). A prototype system called management support system for total quality management (MSS4TQM) is designed and developed to facilitate management or a quality team in conducting quality barrier assessment and critical factor analysis of TQM for an organization. MSS4TQM is implemented on personal computers under a Microsoft Windows^TM environment. To evaluate the performance of MSS4TQM, selected quality practitioners in manufacturing and service industries in Hong Kong, as well as quality experts from thirteen nations, are invited to participate in testing the system. The evaluation study of the prototype system in the context of a proposed MSS evaluation framework is described. The results of prototype evaluation are satisfactory and support the contention that MSS4TQM performs its functions as expected     

Cross-layer-based modeling for quality of service guarantees in mobile wireless networks

In this article we propose a cross-layer approach to investigate the impact of the physical-layer infrastructure on the data-link-layer QoS performance in mobile wireless networks. At the physical layer, we take the MIMO diversity schemes as well its AMC into account. At the data-link layer, our focus is on how this physical-layer infrastructure influences the real-time multimedia QoS provisioning performance such as delay-bound violation and buffer-overflow probabilities. To achieve this goal, we first model the physical-layer service process as a finite state Markov chain. Based on this FSMC model, we then characterize the QoS performance at the data-link layer using the effective capacity approach, which turns out to be critically important for the statistical QoS guarantees in mobile wireless networks. The numerical and simulation results obtained demonstrate that the proposed cross-layer model can efficiently characterize the interaction between the physical layer infrastructure and upper layer protocols' QoS provisioning performance.     

High quality networking of audio-visual information

An overview of low bit rate coding and the interaction between source coding and channel coding is presented. The interaction of coding with networking in a multiuser environment, including algorithms for robust coding which anticipate imperfect network performance, and techniques of decoding a signal that has traversed an imperfect network are described. The performances of such algorithms are illustrated with examples from speech, audio, and video transmission in the presence of packet losses. The challenges in measuring the quality of service (QOS) in the context of new algorithms for coding and networking and the difficulty of measuring QOS in the networking of multimedia information are discussed     

Sampling receiver to support low power wireless networking

A simple and successful design for a sampling receiver that consumes very little power is presented. Measurements from a prototype receiver that show the potential of this technique are presented.     

Preserving quality of service guarantees in spite of flowaggregation

We investigate how quality of service may be guaranteed to a flow of packets in the presence of flow aggregation. For efficiency, multiple flows, known as the constituent flows, are merged together resulting in a single aggregate flow. After the network node where the aggregation occurs, packet schedulers are aware of the aggregate flow, but are unaware of its constituent flows. In spite of this, we show that quality of service may be guaranteed to the constituent flows, provided the aggregation is performed fairly. When the delay bound of a flow is de-coupled from the flow's reserved rate, flow aggregation preserves the delay bound. When the delay bound of a flow is coupled to the flow's reserved rate, flow aggregation preserves, and in some cases improves, the delay bound     

An uplink CDMA system architecture with diverse QoS guarantees forheterogeneous traffic

The uplink access control problems for cellular code-division multiple-access (CDMA) systems that service heterogeneous traffic with various types of quality-of-service (QoS) and use multicode CDMA to support variable bit rates are addressed. Considering its distinct QoS requirements, class-I real-time traffic (e.g., voice and video) is differentiated from class-II non-real-time traffic (e.g., data). Connection-oriented transmission is achieved by assigning mobile-oriented code channels for class-I traffic, where each corresponding mobile needs to pass an admission test. Class-II traffic is transmitted in a best-effort manner through a transmission-rate request access scheme which utilizes the bandwidth left unused by class-I traffic. Whenever a mobile has class-II messages to transmit, the mobile requests code channels via a base station-oriented transmission-request code channel, then, according to the base station scheduling, the transmission is scheduled and permitted. Addressed are the admission test for class-I connections, transmission power allocation, and how to maximize the aggregate throughput for class-II traffic. The admission region of voice and video connections and the optimum target signal-to-interference ratio of class-II traffic are derived numerically. The performance of class-II traffic transmissions in terms of average delay is also evaluated and discussed     

A bit system that guarantees better accuracy for monopulse antennadetection systems

Accurate integration and calibration of well-designed components can compensate for time-varying errors in a monopulse antenna system. A switchable four-port bit system, using a balanced four-way splitter and four balanced, electronically controlled, fast switches, make it possible to know the signal location measured by the monopulse antenna with very great accuracy in the presence of these errors     

测量机器人联网远程控制系统设计

汽车量的不断增长导致地上交通的拥挤,地下空间的开发与利用迫在眉睫。建造地铁过程中安全问题及其地铁施工周期长、变形速度快等特点,研究测量机器人远程联网系统,综合利用4G网络、GPRS模块进行通信,测量机器人高精度、智能化的特点,开发了测量及数据处理一体化系统。研究同时远程控制多台测量机器人,有效解决单台测量机器人在狭长的地铁中难以完成的监测任务,大大提高了监测效率及其数据精度。     

α-channel: a network framework to support applicationreal-time performance guarantees

A framework to support performance requirements for real-time applications in packet-switched networks is proposed. This framework is based on a network-level abstraction called α-channel. An α channel represents a simplex end-to-end communication channel characterized by a set of application-specific real-time performance values. Applications treat the α-channel as an end-to-end abstraction and specify their required performance characteristics in terms of the maximum end-to-end packet delay, the maximum number of packets that can be sent within that delay, and the on-time reliability. Based on specified parameters, the network verifies that it can guarantee the performance of the channel under any conditions baring hardware failures. The approach the framework uses to verify the feasibility of accepting an α-channel and the characteristics of the run-time environment to guarantee the applications' performance requirements are described. The results of a simulation experiment implementing the basic functionalities of the proposed scheme are also presented     

校园社交平台中标签系统的研究

标签系统作为信息过滤的重要工具,已经广泛运用于生活中。文章提出了一种运用于校园社交平台的标签系统,用来描述自身的兴趣,并基于标签系统进行信息流推荐,为大学生在校园内形成依托于自身兴趣的社交圈,寻找志同道合的朋友提供了可能。     

Extending EDCA with distributed resource reservation for QoS guarantees

In this paper we describe how the contention-based medium access mechanism of 802.11e, EDCA, can be enhanced in order to allow stations to reserve medium access for their real-time applications with QoS requirements. We present our proposed scheme, which is called EDCA with resource reservation (EDCA/RR), and describe how it can be extended in order to be used in wireless multi-hop networks. EDCA/RR operates in a completely distributed manner and manages to provide deterministic, contention-free medium access, making it an attractive scheme for wireless networks.     

浅议数字电视整体转换技术保障体系

结合秦皇岛市农村地区数字电视整体转换过程,介绍了河北广电网络集团秦皇岛燕山有限公司数字电视整体转换技术保障体系的设计与实施,提出了数字电视整体转换后的技术保障体系的发展方向。     

Load balancing routing with bandwidth-delay guarantees

The current generation of network carriers competes intensely to satisfy the diverse wide-area connectivity requirements of customers. At the same time, the carriers inherently wish to maximize the usage efficiency of their network infrastructure. Much of the research in network resource management has been devoted to providing bandwidth guarantees and preventing network congestion. However, the rapid growth in number and diversity of real-time network applications has made it imperative to consider the impact of end-to-end delay of traffic requirements on network resource provisioning. We present an efficient network resource provisioning algorithm, called link criticality based routing (LCBR), which relies on the guiding theme that load balancing leads to higher resource utilization efficiency. LCBR applies a simple but very effective notion of link criticality to achieve networkwide load balance while simultaneously meeting the QoS requirements of bandwidth and end-to-end delay. In addition, LCBR can simultaneously provision both primary and backup routes to support fast recovery from node or link failures. This article reviews the state of the art in network resource provisioning with QoS guarantees, introduces the LCBR algorithm, and identifies future research challenges.     

Ad hoc networking with directional antennas: a complete system solution

Directional antennas offer tremendous potential for improving the performance of ad hoc networks. Harnessing this potential, however, requires new mechanisms at the medium access and network layers for intelligently and adaptively exploiting the antenna system. While recent years have seen a surge of research into such mechanisms, the problem of developing a complete ad hoc networking system, including the unique challenge of real-life prototype development and experimentation has not been addressed. In this paper, we present utilizing directional antennas for ad hoc networking (UDAAN). UDAAN is an interacting suite of modular network- and medium access control (MAC)-layer mechanisms for adaptive control of steered or switched antenna systems in an ad hoc network. UDAAN consists of several new mechanisms-a directional power-controlled MAC, neighbor discovery with beamforming, link characterization for directional antennas, proactive routing and forwarding-all working cohesively to provide the first complete systems solution. We also describe the development of a real-life ad hoc network testbed using UDAAN with switched directional antennas, and we discuss the lessons learned during field trials. High fidelity simulation results, using the same networking code as in the prototype, are also presented both for a specific scenario and using random mobility models. For the range of parameters studied, our results show that UDAAN can produce a very significant improvement in throughput over omnidirectional communications.