Adaptive bandwidth framework for provisioning connection-level QoS for next-generation wireless cellular networks

The next generation of wireless cellular networks is expected to support real-time multimedia services with different classes of traffic and diverse bandwidth requirements. Bandwidth is a scarce resource in wireless networking that needs to be carefully allocated amid competing connections with different quality of service (QoS) requirements. In this paper, an adaptive framework for supporting multiple classes of multimedia services with different QoS requirements in wireless cellular networks is proposed. The framework combines the following components: (1) a threshold-based bandwidth allocation policy that gives priority to handoff calls over new calls and prioritizes among different classes of handoff calls by assigning a threshold to each class; (2) an efficient threshold-type call admission control (CAC) algorithm; and (3) a bandwidth adaptation algorithm (BAA) that dynamically adjusts the bandwidth of ongoing multimedia calls to minimize the number of calls receiving lower bandwidth than they had requested. Numerical results show that the proposed adaptive multimedia framework outperforms existing non-adaptive schemes in terms of the handoff call dropping probability and effective utilization.     

基于3G物联网的高压输电线路多状态信息监测系统

开发了一种基于3G物联网技术的综合数字化图像监控及运行状态参数监控等多种监测方法于一体的输电线路多状态信息监测系统,系统将图像信号、传感器采集的设备状态信号进行数字化,通过3G无线通信网络实时传输至多种移动接入终端,从而实现高压输电线路多状态信息监测。系统设计分为数据采集终端层、3G传输层、专家分析控制系统层3层结构,其中3G传输层采用自适应带宽的3G无线数据传输技术,充分利用中国电信、中国联通、中国移动3G网络,通过软件自动切换3种网络中信号较好的1个网络,根据多条链路的带宽,自动分配音视频数据以及设备运行状态数据的带宽,大大增加了网络通信带宽,提高了视频、音频的传输质量,保证了输电线路监测系统的稳定性、可靠性、实时性。     

基于RTP与DirectShow的网络视频监控系统

为了解决远程视频监控系统数据量大、实时性要求高的特点,本文提出了一种基于网络实时传输的视频监控系统,并且描述了该系统的技术原理与设计方案.本文介绍了系统中几个主要模块的工作方式以及关键技术,并详细阐述了利用Http协议实现流媒体播放的控制方法,利用RTP协议实现数据传输的策略,以及应用DirectShow技术进行应用程序开发的实现流程,最终完成了基于MPEG4压缩格式视频流的传输与播放控制.该解决方案具有良好的可重用性和可扩展性.     

基于无线网络的实时视频传输技术

随着移动通信业务的发展,人们对多媒体信息服务的需求也在逐年增加。数字化视频服务作为多媒体信息的核心,正日益成为人们研究的热点。文章基于无线网络实时视频传输的特点以及有线网络环境下的实时视频传输技术,分析了无线网络实时视频传输技术的参考模型和实现方案。     

CMT‐CQA: Cross‐layer QoS‐aware adaptive concurrent multipath data transfer in heterogeneous networks

Stream control transport protocol (SCTP)‐based concurrent multipath transfer (CMT) can help multi‐homed devices to increase their throughput by making use of parallel transmissions over multiple paths and bandwidth aggregation. However, if CMT cannot identify wireless error, it cannot really achieve the desired performance. Furthermore, if CMT only utilizes all available paths for data delivery, it will undoubtedly degrade application‐level performance since the asymmetric paths may involve large quality differences. This paper proposes a novel cross‐layer quality‐of‐service (QoS)‐aware adaptive CMT (CMT‐CQA) with the following aims: (i) to provide an adaptive ‘CMT‐to‐partial CMT’ adjustment strategy for efficient bandwidth aggregation by jointly considering transport layer QoS, MAC layer QoS, and path history information; (ii) to address an enhanced congestion window (cwnd) fast recovery mechanism to reduce bursty transmission in multi‐homed wireless network environments where fail‐over occurs frequently; and (iii) to introduce a proper multimedia transmission behavior to improve users' quality of experience (QoE) for multimedia streaming service. Simulation results show that CMT‐CQA outperforms the existing CMT solutions in terms of performance and QoS. © 2014 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

基于AOS与ATM协议互联的空——地组网技术

载人太空站、无人空间平台、深空探测器等空间任务系统的一个共同特征是需要在整个空间链路,即空一地、地一空之间传输多种类型、不同速率的数据.空间任务系统由空间无线网和地面网两部分组成.根据空间数据系统咨询委员会(consultative committee for space data systems,CCSDS)制定的高级在轨系统(advanced orbiting systems,AOS)协议和异步传输模式(asynchronous transfer mode,ATM)协议的特点,提出了一种基于AOS与ATM协议互联的空-地组网方法.仿真结果表明:该方法实现了异构网络(地面网与空间无线网)的互联,视频、语音等流媒体传输性能可满足用户对服务质量(quality of service,QoS)控制的要求.     

电力系统监控视频传输速率自适应控制设计

为解决电力系统视频监控工程领域的实际技术问题,提出一种电力系统监控实时视频传输速率的自适应控制方案。系统可以根据网络传输时间、传输延迟和数据包丢失率等参数对网络拥塞状况进行监测,并按照传输速率自适应控制的一定算法动态地调整视频发送端的输出速率,具有一定的鲁棒性,从而改善视频输出质量。经实验测试,该系统在减小视频数据包丢失率、提高网络带宽利用率和避免网络拥塞等方面,具有良好的对比效果。     

基于HTTP的流媒体自适应码率切换算法

基于HTTP的动态流媒体自适应(DASH)系统已经广泛地应用于互联网上的视频传输.针对客户端缓冲区受限和网络环境不稳定的情况,提出了一种新的基于缓冲区的码率控制算法.该算法将缓冲区分成不同等级,并采用滑动窗技术对视频的下载时间进行平滑处理,使缓存尽最大可能地维持在均衡区内.该算法在向上切换码率时采用保守策略,而在向下切换时则利用逻辑斯谛方程来决定码率切换的幅度.此外,该算法采用快速启动策略,能使系统开始时下载码率迅速匹配网络带宽.实验结果表明,算法能在复杂的网络环境中,充分利用带宽和缓冲区,降低码率的切换次数.     

MPLS体系、性能及应用

就MPLS的产生背景，MPLS标签，MPLS流量工程，MPLS VPN应用等展开叙述，MPLS的问世可以保证如语音传送，视频服务，多媒体信息服务传输等应用业务按各应用的特性正确予以传送。MPLS网络中数据的传输告标签引导，标签是固定长度的，无结构的值，采用MPLS流量工程可以避免引起网络阻塞，为用户提供更好的服务。在Cisco IOS网络中，MPLS虚拟专用网提供了发展和管理第3层VPN骨干服务的能力。     

Handoff resource prediction in multimedia wireless networks

This paper presents a local-based approach for predicting handoff resources in multimedia wireless networks, where the underlying prediction mechanism is the recursive least-squares (RLS) algorithm. Performance of the proposed handoff resource prediction scheme is evaluated for a multimedia wireless network characterized by various handoff traffic conditions, different bandwidth requirements, and general call and channel holding time distributions. The accuracy of handoff resource prediction is measured in terms of a mean-square-error metric. Results from performance evaluation show that the proposed RLS-based scheme has better resource prediction accuracy than Wiener-filter and autoregressive (AR) processes. It is shown that the proposed RLS-based handoff resource prediction scheme achieves capacity gains of up to 60% and 23% compared to the Wiener- and AR-based schemes, respectively.     

QoS on LEO satellites

This paper discusses the role played by wireless network infrastructure in mobile commerce applications. The user's perception of service quality depends on the available resources and capabilities of the network. The new generation of low earth orbit (LEO) mobile satellite networks, deployed at altitudes ranging from 500 km to 2000 km, are well suited to handle multimedia traffic and to offer end-users equipped with hand-held devices at low cost-per minute access to network services. A wide range of multimedia services and applications are expected to provide users with QoS based asynchronous transfer mode (ATM) technology. LEO satellite networks provide significant wide area coverage, unique broadcast capability, ability to meet different QoS requirements, the ability to communicate with hand-held devices and low cost access. The main resources in the LEO networks are satellite radio bandwidth and the buffer capacity of the onboard ATM switch. The most important ATM resource management function is connection and call admission control. The real objective of this article is to introduce the general framework of resource reservation in multimedia LEO satellite networks which offers a unified approach to handle all the important aspects of resource reservation and radio-resource management functions required by E-commerce and mobile commerce applications.     

一种有效的802.16 BWA系统MAC层QoS框架

IEEE 802.16系列标准定义了WiMAX的无线空中接口,尽管标准详细的定义了MAC层信号机制,但并没有一套完整的资源管理调度机制,而资源管理和调度是影响QoS性能的重要部分.本文首先简要介绍了IEEE 802.16协议,分析了其QoS机制的主要内容,包括带宽的请求分配机制,准人和调度机制等.然后提出了一套有效的QoS框架,主要包括准入控制策略和上行调度策略.为了让不同业务的QoS得到保证,文章重点探讨了多优先级公平队列算法(MPFQ),通过这套机制,可以为不同级别的业务提供不同等级的Qos服务.     

多模式无线视频码流的传输与控制

采用快速传送协议/用户数据报协议/IP方式实现了多模式无线网络（WLAN、GPRS、CDMA）的码流传输,并完成无线通信下的RTCP双向控制信息链路.针对无线IP网络的传输特性,选取了适当的QoS参数反馈控制传输质量.实验测试表明,多模式无线通信系统下的码流传输在接收端取得了较好的视频传输质量.     

基于加权公平性的Ad Hoc网络带宽分配

本文基于已有的带宽管理机制,采用加权公平对竞争的流进行带宽分配.通过该方案,不仅实现了对流的准入控制,以保证每条流的最低信道时间需求,同时,也能动态地调节流所分配的信道时间.另外,该方案也适用于多跳的情况.本文在相同的控制机制下,对最大最小公平性与加权公平这两种分配方案达到的吞吐量和公平系数进行了比较,通过实例说明,在考虑到用户基本需求的同时,提高了网络的吞吐量,实现了效益与公平性的均衡.     

无线多媒体传感器和操作器网络（WMSANs）在智能电网中的应用

高度自动化和灵活性的通信与操作系统是智能电网的重要组成部分。结合多媒体无线传感器和操作器网络（Wireless Multimedia Sensor and Actor Networks,WMSANs）的主要技术特点,探讨了WMSANs在分布式发电厂、输电线、变电站、工业建筑、商业建筑和家庭用户的潜在应用,WM-SANs在目前尚需解决连接质量、延迟、视频流、决策和控制算法等关键技术问题。     

Objective and subjective evaluation of QOAS video streaming over broadband networks

This article presents objective and subjective testing results that assess the performance of the Quality-Oriented Adaptation Scheme (QOAS) when used for high quality multimedia streaming over local broadband IP networks. Results of objective tests using a QOAS simulation model show very efficient adaptation in terms of end-user perceived quality, loss rate, and bandwidth utilization, compared to existing adaptive streaming schemes such as LDA+, and TFRCP. Subjective tests confirm these results by showing high end-user perceived quality of the QOAS under various network conditions.     

Resource management in LEO satellite networks

To provide truly global coverage needed by increased Personal Communication Services (PCS), a new generation of mobile satellite networks has been proposed. These low Earth orbit (LEO) mobile satellite networks handle multimedia traffic and can be used for non-real-time as well as real-time service to remote areas. Due to the many handoffs, resource management and connection admission control are important tasks for fair bandwidth sharing and QoS guarantees. Because the total link capacity has to be divided among several carriers and given the limited buffer capacity of the ATM switch, resource management is vital. It ensures the ability of the network to provide users with their negotiated QoS while protecting the network and the end-systems from congestion. We introduced a simple connection admission control (CAC) priority policy based on the delay and cell loss requirements for the investigated types of traffic. We took into account the handoff status of the satellite beams involved. Thus, we propose an onboard buffer architecture with separated buffers for new calls and intra-satellite handoff calls. The priority scheme applied is as follows: highest priority is given to CBR, followed by rt-VBR, nrtVBR and ABR.     

Fairness based channel borrowing strategy in multimedia LEO satellite communications

A novel bandwidth allocation strategy along with a connection admission control technique was proposed to improve the utilization of network resources. It provides the network with better quality-of-service (QoS) guarantees, such as new call blocking probability (CBP) and handoff call dropping probability (CDP) in multimedia low earth orbit (LEO) satellite networks. Simulation results show that, compared with other bandwidth allocation schemes, the proposed scheme offers very low call dropping probability for real-time connections while, at the same time, keeping resource utilization high. Finally we discussed the fairness for the borrowed nonreal-time connections under three different channel borrowing methods. Translated from Journal on Communications, 2006, 27(8): 10–17 [译自: 通信学报]     

An adaptive resource reservation strategy for handoff in wireless CDMA cellular networks

A threshold-based adaptive resource reservation scheme for soft handoff calls in wireless code division multiple access (CDMA) cellular networks is proposed. The scheme gives handoff calls a higher admission priority than new calls, and is designed to adaptively adjust the reservation-request time threshold according to the varying traffic load. The individual reservation requests form a common reservation pool, and handoff calls are served on a first-come, first-served basis. With the proposed scheme, a minimum grade of service (GoS) in terms of new call blocking and handoff call dropping probabilities can be achieved. Simulation results are given to demonstrate the improvement in the GoS performance in comparison with other schemes.