3G-H.324M终端间的快速会话建立方法

为了提高3G-H.324M终端间的会话建立速度,开发了一种高效地移动多媒体传输协议栈.其中,每个信令实体属于一个类,每个类维护两个独立的状态机.不同的信息驱动不同的状态转换,不同信令实体的不同的类可以独立运行.这样一个3G-H.324M终端能够同时处理两个或者更多的信息,使得多个3G-H.324M终端间能够加速会话建立、进行多媒体通信.同时将该会话建立方法与3G-H.324M中推荐的方法进行了比较,结果显示,新方法更加快速和有效.     

3G-324M和H.323域视讯互通研究与设计

3GPP推荐的3G-324M视频电话协议是在3G网络上实现实时视频通话的协议,而H.323是分组网络中的多媒体通信协议,实现H.323终端和3G-324M终端的多媒体互通成为一个必须解决的问题。为此研究并提出了一种基于该两种不同协议标准的多媒体互通网关VIG的可行方案,并对该方案进行了深入探讨。     

移动通讯媒体流仿真器的设计与实现

介绍了IMS(IP多媒体子系统)中所使用的音频和视频编码;针对IMS系统设计实现了一种应用于移动通讯系统的IP媒体流仿真器,此种仿真器实现了IMS系兢中音频的AMR编码和视频的H.263编码,使用RTP协议产生模拟的实时媒体流。它可对IMS系统的媒体承载节点进行测试,配合其他的会话控制协议仿真器,可对IMS系统进行综合测试。给出了此种仿真器的设计原理和实现方法。在实际的应用中,此媒体仿真器作为IMS协议仿真器的重要组成部分得到了良好的应用效果。     

基于TlTMS320DM642平台的H.324可视电话设计及任务调度策略

TI TMS320DM642芯片运算能力达4800MIPs,时钟频率600MHz,具有强大的多媒体数字信号处理能力.本文提出了一种TI TMS320DM642平台上H.324可视电话的设计方案,重点研究了系统各模块设计和调度对H.324可视电话性能的影响,提出了一种有效的TI TMS320DM642平台上H.324可视电话系统的任务调度策略,提高了可视电话通信系统的性能.     

基于TI TMS320DM642平台的H.324可视电话设计及任务调度策略

TITMS320DM642芯片运算能力达4800MIPs,时钟频率600MHz,具有强大的多媒体数字信号处理能力。本文提出了一种TITMS320DM642平台上H.324可视电话的设计方案,重点研究了系统各模块设计和调度对H.324可视电话性能的影响,提出了一种有效的TITMS320DM642平台上H.324可视电话系统的任务调度策略,提高了可视电话通信系统的性能。     

一种新型双EVDO信道视频传输系统的设计与实现

介绍了一种新型的无线视频传输系统的设计方案,提出了一种全新的基于TCP友好速率控制算法(TFRC)的双通道分流传输模型.相比于传统的视频传输系统,该系统在网络应用层上加入了对会话初始化协议(SIP)的支持,使得传输终端能够接入IP多媒体核心网(IMS)传输数据.传输方式上该系统使用两个3G模块(EVDO)并行传输数据,有效地提高了传输带宽,视频数据采用H.264标准进行编码后根据实时传输协议(RTP)封包传输.经测试,该系统能够实现4CIF (704×576)分辨率下的视频传输.     

一网两制 世界首例H.320与H.323多媒体通信网在京展示

10月29日,在威康(VCON)多煤体通信有限公司的演讨会上,展示了世界首例H.320与H.323多媒体通信网和点到多点视频会议系统。 H.320主要定义了ISDN上的视频会议机制,H.324则定义了分级交换局域网上的视频会议。在     

基于H.324协议的可视电话延时测试的一种方法

论文介绍了基于H.324协议框架的可视电话的基本原理。H.324协议是基于PSTN普通电话线路的多媒体可视通信协议。通过深入研究H.324可视电话的特点,提出了一种环路延时测试方法,提高了系统测试效率;最后给出了运行测试结果。     

基于Gossip协议的多机器人系统通讯机制的研究

多机器人系统的移动特性给无线通讯的设计提出挑战。而广泛使用的移动Ad-Hoc网络处理网络拓扑结构不断变化的任务会产生不可预测的计算开销。针对这种不足,该文对广泛应用于分布式信息管理的Gossip协议进行修改,应用于移动多机器人通讯中,并基于该协议提出一种实现机器人规模统计的算法。实验结果表明,该协议在不同规模的机器人系统中,都能有效地完成信息的分发,且不会造成通讯量锐增。     

下一代网络多媒体会话中H.248与SIP之间协议协作的研究

H.248和SIP是下一代电信网络的两个核心协议,通过H.248和SIP之间的协作来完成多媒体会话的建立、调整和删除是在下一代网络中实现多媒体业务需面临的重要问题。文章在深入研究H.248和SIP协议的基础上针对协议协作的应用环境抽象了一个协作模型。依据此模型,对两方多媒体会话和多方多媒体会话中各信令交互阶段H.248和SIP之间的协作进行了详细阐述。对H.248和SIP协议之间协作的研究可以应用到下一代电信网络的工程技术领域。     

The design and simulated performance of a mobile video telephonyapplication for satellite third-generation wireless systems

The design and performance of a low bit-rate video telephony service for mobile third-generation (3G) systems is presented. The ITU-T G.723.1 speech coding and the ITU-T H.263 video coding recommendations are used, as proposed by the ITU-T H.324 low bit-rate multimedia communications recommendation. The target bit-rate for the H.324 service is 64 kb/s. The design is performed in conjunction with that of a wideband-code division multiple access (W-CDMA) radio transmission technology (RTT) system, proposed by the European Space Agency (ESA) for the satellite component of the ITU IMT-2000 standard. Most of the results could also be applied to the 3G terrestrial systems. The use of concatenated channel coding with convolutional inner coding and Reed-Solomon (RS) outer coding is investigated. Service designs based on equal error protection (EEP) and unequal error protection (UEP) schemes for the audio and video sources are compared. The simulation of the proposed video telephony services shows that significantly more graceful video and audio degradation is obtained with the proposed UEP scheme than with a more straightforward EEP method. The UEP scheme reduces significantly the occurrence of highly annoying audio and video artefacts, allowing satellite-based video telephony services that are compatible with the current Internet-based applications     

甚低带宽环境下的多媒体通信传输控制模型

介绍了基于H．324协议框架的可视电话基本原理．H．324协议是基于PSTN普通电话线路的多媒体可视通信协议．通过深入研究H．223数据复用协议和V．80同步传输协议，针对甚低带宽的PSTN线路特点，提出了一种有效的多媒体通信传输控制模型，改进了H．324可视电话的性能．     

Beyond 3G video mobile video telephony: The role of 3G-324M in mobile video services

3G-324M is a 3^rd Generation Partnership Project (3GPP) umbrella standard for wireless video communications, which was created to satisfy the stringent requirements of real-time, low-delay interactive conversational video services. However it is, in practice, employed today in 3G networks to enable also a variety of multimedia services including messaging, streaming video chat and portals. The unification of this variety of services under the same umbrella standard has significance for the design of the supporting architectures and the applications that run such services. In this paper we will discuss the current advantages and limitations of the 3G-324M standard in supporting such services     

Beyond 3G video mobile video telephony: The role of 3G-324M in mobile video services

3G-324M is a 3 ^rd Generation Partnership Project (3GPP) umbrella standard for wireless video communications, which was created to satisfy the stringent requirements of real-time, low-delay interactive conversational video services. However it is, in practice, employed today in 3G networks to enable also a variety of multimedia services including messaging, streaming video chat and portals. The unification of this variety of services under the same umbrella standard has significance for the design of the supporting architectures and the applications that run such services. In this paper we will discuss the current advantages and limitations of the 3G-324M standard in supporting such services     

SIP协议栈研究

由IETF最年轻的工作组之一的SIP工作组发布的SIP相关标准已经成为通信和网络界的研究热点。SIP起初被作为建立互联网会议、电话、多媒体和其他类型的通信会议可选择的协议而提出，另外它还能被用于新型的通信服务，如即时短消息和应用级的跨网络移动通信及跨用户设备的通信。介绍了SIP相关标准、基本结构、功能特点及应用领域，并介绍了当前比较流行的几个开源SIP协议栈。     

SIP协议栈研究

由IETF最年轻的工作组之一的SIP工作组发布的SIP相关标准已经成为通信和网络界的研究热点。SIP起初被作为建立互联网会议、电话、多媒体和其他类型的通信会议可选择的协议而提出,另外它还能被用于新型的通信服务,如即时短消息和应用级的跨网络移动通信及跨用户设备的通信。介绍了SIP相关标准、基本结构、功能特点及应用领域,并介绍了当前比较流行的几个开源SIP协议栈。     

The usefulness of mobile multimedia communications: a case study

To design new technologies, such as mobile multimedia communications, in a proper way, early assessment of their usefulness and requirements is needed. However, early assessment still lacks a sound methodology. This article presents an early assessment method that has been developed in a case study on the usefulness of mobile multimedia communications. After the introduction, the method will be briefly explained. The method consists of the following stages: preliminary investigation, analysis, scenario development, workshop evaluation, and simulation. These stages contain the aspects and consequences of the reference model that has been explained in the introduction of this volume: (1) the involvement of stakeholder groups; (2) the multi-facet approach to the development and evaluation of telematics applications; (3) the important role of theoretical notions in the development process; (4) the importance of a multi-disciplinary team. A case study in the area of emergency medicine will be presented, focusing on the usefulness of mobile multimedia communications. Finally, conclusions will be drawn from the case study.     

Policy support for H.323 call handling

The need for policies to control calls is justified by the changing face of communications. An overview is given of a general architecture and language for policies. It is then shown how these are adapted for control of calls using the H.323 multimedia communications standard. Policy support for H.323 was created by extending an open source gatekeeper. The core policy language has been specialised to deal with call control in general, and for H.323 in particular. Examples are given of policies for H.323, illustrating how traditional features can be made to work more flexibly through use of policies. Examples are also provided of policies specific to H.323, and policies that can take advantage of other information such as the context of a call.