关于下一代网络VoIP业务的QoS体系结构研究

如何保证VoIP的QoS是VoIP网络向NGN目标演进必须解决的问题。本分析了目前VoIP网络中存在的问题，针对VoIP的QoS需求，阐述了下一代网络支持VoIP QoS保证的技术和机制，并且提出了一种基于SIP的下一代网络VoIP QoS体系结构。     

关于下一代网络VoIP业务的QoS体系结构研究

如何保证VOIP的QoS是VoIP网络向NGN日标演进必须解决的问题。本文分析了目前VoIP 网络中存在的问题,针对VoIP的Qos需求,阐述了下一代网络支持VoIP Qos保证的技术和机制,并且 提出了一种基于SIP的下一代网络VoIP Qos体系结构。     

Softswitch实现VoIP的研究

软交换是网络演进和下一代分组网络的核心设备之一,随着网络融合技术的不断发展,软交换受到了越来越多的关注。本文介绍了软交换的体系结构和其在实现VoIP中的应用,并重点讨论了软交换实现VoIP和现有H.323方案的不同。     

基于QoS的WiMAX与TD-SCDMA网络融合研究

分析了WiMAX的QoS策略和基于IMS的TD-SCDMA系统QoS机制，给出了二者详细的QoS业务类型和要求，提出了在下一代网络IMS框架下采用VoIP技术的TD—SCDMA和WiMAX网络融合架构，并给出QoS融合时不同QoS业务类型的映射方案．     

基于集成服务模型的QoS保证机制

为了实现VoIP端到端的QoS,本文首先介绍了两种已有的体系结构存在的不足,并在此基础上给出了一种基于集成服务模型的架构,研究了它的QoS保证机制.然后,构造了一种映射函数和网络配置,以服务流的吞吐量、路由器中的队列长度和分组的丢包率作为衡量参数,通过具体的仿真评估了VoIP服务在此模型中所能获得的QoS.     

端到端服务质量(QoS)体系建设探讨

本文简要介绍了服务质量QoS相关概念.以即将到来的下一代网络(NGN)和2G/3G融合网络为例,分别从两者的内涵和体系结构出发,阐述了其中QoS框架模型和新业务体系建设.     

Softswitch实现VoIP的研究

软交换是网络演进和下一代分组网络的核心设备之一，随着网络融合技术的不断发展，软交换受到了越来越多的关注。本文介绍了软交换的体系结构和其在实现VoIP中的应用，并重点讨论了软交换实现VoIP和现有H．323方案的不同。     

漫谈VoIP技术发展趋势——H.325:第三代多媒体系统

目前在Internet或IP网络上应用的VoIP技术主要是基于H．323或者SIP开发的。随着技术和需求的发展，VoIP要求能够同时提供话音、数据和视频等多种业务，向下一代网络NGN演进。为了更好地满足NGN的需求，弥补现有系统的不足，ITU提出了下一代多媒体系统H．325协议的概念，它的重点在于实现控制单元和服务单元的分离，更好地支持多种媒体编码协议的互通，提高系统的QoS以及安全性。H．325有望成为下一代VoIP技术的支撑协议。     

基于EV—DO的VoIPQoS研究

为了对基于EV-DO的VoIP QoS有一个定性的了解,文章首先给出了基于EV-DO的QoS架构,提供了EV-DO为VoIP定制的QoS参数,而后在此基础上阐述了在EV-DO网络中实现VoIP端到端的QoS保证的技术方式,对今后顺利实现VoIP应用有着很好的指导意义.     

下一代网络QoS问题研究

分析了下一代网络的QoS要求和关键技术,论述了下一代网络端到端的QoS控制策略,并基于ITU-T建议,对下一代网络QoS控制策略的部署进行了讨论.     

在MPLS网络中如何保证VoIP的QoS

在以IP为基础的网络中,IP网络上传送语音(VoIP)成为新一代语音系统的代表,但其业务质量因由IP网络承载而受到限制.多协议标签交换(MPLS)是当前被普遍看好的高速骨干网络技术,通过MPLS,第三层的路由可以得到第二层技术的很好补充,以保证端到端的服务质量(QoS).将MPLS的QoS特性与区分服务(DiffServ)相结合,可实现更优化的网络业务QoS.     

VoIP语音时延的分析和研究

文章介绍了VoIP(IP网络上传送语音)语音质量的测试方法,分析了影响VoIP语音质量的主要因素:延迟、抖动、丢包率和时延.利用E模型定量地分析了语音质量与端到端时延的关系,通过建立数学模型,指出了VoIP 系统中主要的时延分量,并研究了这些时延分量产生的机理和影响它们的参数.在设计实际的VoIP系统时,可以通过优化影响时延分量的主要参数,改善VoIP系统的时延.     

RPR技术及其QoS分析

弹性分组环(RPR)是目前在城域网中进行数据传输的一种新的传输技术。网络的服务质量(QoS)是下一代IP光因特网中一个很重要的问题。RPR作为一种新的光传输技术,必须支持QoS。基于此,主要介绍了RPR网络特点,并回顾和总结了已有的RPR网络QoS方案。最后,提出了MPLSoverRPR的QoS方案。     

A call admission control framework for voice over WLANs

In this article a call admission control framework is presented for voice over wireless local area networks (WLANs). The framework, called WLAN voice manager, manages admission control for voice over IP (VoIP) calls with WLANs as the access networks. WLAN voice manager interacts with WLAN medium access control (MAC) layer protocols, soft-switches (VoIP call agents), routers, and other network devices to perform end-to-end (ETE) quality of service (QoS) provisioning and control for VoIP calls originated from WLANs. By implementing the proposed WLAN voice manager in the WLAN access network, a two-level ETE VoIP QoS control mechanism can be achieved: level 1 QoS for voice traffic over WLAN medium access and level 2 QoS for ETE VoIP services in the networks with WLANs as the local access. The implementation challenges of this framework are discussed for both level 1 and level 2. Possible solutions to the implementation issues are proposed and other remaining open issues are also addressed.     

Performance evaluation of packet aggregation scheme for VoIP service in wireless multi-hop network

In a wireless multi-hop network environment, energy consumption of mobile nodes is an important factor for the performance evaluation of network life-time. In Voice over IP (VoIP) service, the redundant data size of a VoIP packet such as TCP/IP headers is much larger than the voice data size of a VoIP packet. Such an inefficient structure of VoIP packet causes heavy energy waste in mobile nodes. In order to alleviate the effect of VoIP packet transmission on energy consumption, a packet aggregation algorithm that transmits one large VoIP packet by combining multiple small VoIP packets has been studied. However, when excessively many VoIP packets are combined, it may cause deterioration of the QoS of VoIP service, especially for end-to-end delay. In this paper, we analyze the effect of the packet aggregation algorithm on both VoIP service quality and the energy consumption of mobile nodes in a wireless multi-hop environment. We build the cost function that describes the degree of trade-off between the QoS of VoIP services and the energy consumption of a mobile node. By using this cost function, we get the optimum number of VoIP packets to be combined in the packet aggregation scheme under various wireless channel conditions. We expect this study to contribute to providing guidance on balancing the QoS of VoIP service and energy consumption of a mobile node when the packet aggregation algorithm is applied to VoIP service in a wireless multi-hop networks.     

下一代家庭网关

介绍了下一代家庭网关的概念和与之相关的家庭网络技术与接入网技术,讨论了下一代家庭网关功能特征,如:QoS、多媒体网关、多媒体网关控制器、NAT、DHCP、放火墙等,重点讨论了家庭网络支持VoIP的功能。     

Supporting multimedia applications through network redesign

Recent evolutions in high‐performance computing and high speed broadband Internet access have paved a way to enterprise‐wide multimedia applications, which require stern QoS from the underlying networks. In this paper, we have explored threefold studies on existing enterprise network, whereby we proposed an analytical approach to evaluate the performance of the existing network; we have examined the feasibility of existing enterprise networks to accommodate voice over Internet protocol (VoIP) services with acceptable QoS, and we have redesigned the enterprise network to accommodate VoIP services to comply with the user defined QoS. The network performance is evaluated by number of VoIP calls sustained by the network, bandwidth utilization, loss rate and latency through Network Simulation (NS‐2) tool. We have derived a cost model to show the cost‐effectiveness of VoIP services over telephonic network. For a medium‐size enterprise network of 200 clients and 9 servers, our simulation results show that the redesign improves the network performance by increasing the number of VoIP calls by 57% and decreasing bandwidth utilization and packet loss rate by 20% and 7%, respectively. Moreover, the proposed network redesign demonstrates that the network can be scalable and it can handle up to 4% increased voice calls in the future maintaining QoS standards. Copyright © 2012 John Wiley & Sons, Ltd.