【作者】 秦开涌；

【导师】 胡业发；

【作者基本信息】 武汉理工大学 ， 通信与信息系统， 2006， 硕士

【摘要】 下一代网络(Next Generation Network,简称NGN)是电信网络变革的必然方向。随着NGN试验与商用网络规模的不断扩大,对NGN所提供综合业务的服务质量(Quality of Service,简称QoS)需求将会越来越突出。NGN采用IP技术承载多业务(Everything over IP),但传统IP网络只提供“尽力而为”的服务,这使其在大业务量的音频、视频等实时多媒体传输的要求下常常显得力不从心,甚至基本的语音QoS也达不到传统公共交换电话网(Public Switch Telecom Network,简称PSTN)所提供的质量等级。在这样的背景下,NGN的QoS研究具有重要的理论价值和实用意义,并且已经成为业界的研究热点之一。 本文以媒体网关(Meida Gateway,简称MG)支持的语音功能入手,对NGN架构下如何保障和提高媒体网关的语音服务质量展开研究。论文首先从整体上简单介绍了NGN的发展现状,给出了NGN的基本概念,介绍了NGN的四层网络体系结构:接入层、传输层、控制层和业务层,分析NGN的基本特征、特点以及发展优势;之后,分析了几种NGN中常用的QoS模型:IntServ、DiffServ、MPLS、CAC和VPN等,并从接入层、传输层、控制层三个方面,详细讨论并比较了现有NGN的QoS保障机制的特点;接着,从MG的作用入手,介绍了MG需要支持的语音质量保障功能,在分析H.248和Q.931协议的基础上,阐述了媒体网关控制器(Meida Gateway Controller,简称MGC)控制MG实现基本呼叫和媒体协商的过程,通过扩展H.248协议,提出了一种基于媒体协商策略的QoS保障机制,并利用MGC的接续控制、资源管理等功能,给出了语音编码、RTP属性、语音增强等语音QoS的动态协商过程及NGN中的流量控制实现机制;紧接着,结合NGN网络的特点,在不增加硬件资源和影响业务的基础上,提出了一种NGN中的QoS主动测试方法,该方法扩展了H.248协议,完全仿真实际的语音呼叫,真实地反映了NGN中的网络状况和语言质量。本文最后对NGN中语音质量的研究现状和发展趋势进行了总结和展望。更多还原

【Abstract】 The next generation network (NGN) is the inevitable direction in which the telecommunication network will transform. And with the incessant expansion of the NGN experiment and the commercial network, Quality of Service (QoS) of the comprehensive service provided by NGN will be more and more prominent. NGN uses the IP technology to take on multiple tasks (Everything over IP), while the traditional IP network only provides sole service, therefore it frequently appears as unable to fulfill the requirement of the real-time data transmission in large-scale business multimedia such as audio, video and so on, and even the basic voice QoS that NGN provides is worse than traditional Public Switch Telephone Network (PSTN). In this case, the QoS research of NGN would be of great theoretical and the practical significance, and it has already become one of hot research issues in this field.This dissertation, based on the media gateway (MG) of the voice quality function, studied how to guarantee and enhance the voice QoS of the media gateway in the NGN framework. The dissertation first simply introduced the current development of NGN comprehensively, defined the basic concept of the NGN, and described the four levels of NGN framework: the access layer, the transmission layer, the control layer and the service layer, and it also analyzed the fundamental characteristics and the privilege of NGN development. Afterwards, it analyzed several kinds of commonly used QoS models: IntServ, DiffServ, MPLS, CAC and VPN and so on, and detailedly discussed about the QoS guarantee mechanism of NGN from several aspects in terms of the access layer, the transmission layer, and the control layer. Then, rooted upon the role MG played, it introduced the function MG needed to provide to guarantee voice quality, and on the basis of analyzing H.248 and Q.931 protocol, explained how media gateway controller (MGC) realized basic calling flow and media capacity match by controlling the MG, proposed a kind of QoS guarantee mechanism grounded on the media match policy by expanding H.248 protocol, and utilized the call controlling and resource management of MGC, to provide dynamic negotiation process of voice QoS capacity, including voice encoding, RTP attribute, voice enhancing attribute and so on, and realized mechanism of traffic control in NGN. And then, according to the feature of NGN, based on not increasing the hardware resources and not influencing the original function, the dissertation proposed an initiative testing method of QoS in NGN, which expanded H.248 protocol, and simulated real calling flow totally and reflected real network state and voice QoS in NGN. Finally, this dissertation put forward a summary to the current research and advanced the prospect to the development trend of voice quality in NGN.更多还原