无线多媒体传感器网络实时MAC协议

实时性是无线多媒体传感器网络的重要考虑因素之一,而MAC协议能否高效地使用无线信道对保障无线多媒体传感器网络的实时性起着决定性作用。针对无线多媒体传感器网络的业务数据特点,提出了一种基于时隙预留的多信道实时MAC协议。该协议在响应流媒体查询之前,事先建立一条从源节点到汇聚节点的时隙预留流路径,从而最小化数据包在每一次转发时的信道接入时延。仿真结果表明,该协议明显减小了流媒体数据的端到端时延与时延抖动,并且具有较好的能量有效性。     

一种可支持多种多媒体业务的基于IMS的IPTV架构

IP多媒体子系统用于实现端到端的IP多媒体通信,具有接入无关性、对各种接入技术广适性的特点,因此,下一代网络采用IP多媒体子系统作为核心架构.提出一个基于IP多媒体子系统的IP电视架构,在IP多媒体子系统核心模块的基础上,以一组互相独立的基于会话初始化协议的功能模块构成应用服务器,并设计了能够支持和提供不同IM S业务的客户端与内容提供商端,使该IPTV框架可以在下一代网络上支持基于IP多媒体子系统的包括IPTV业务在内的多种多媒体业务.     

流控制传输协议传输流媒体性能研究

SCTP协议（Stream Control Transmission Protocol）是一种面向报文的、可靠的传输层协议。它基于不可靠的、无连接的分组IP网络,具有多宿（multi-homing）和多流（multi-streaming）等特性。通过仿真的方法分析,证实SCTP在支持实时多媒体网络应用时的许多性能参数明显优于传统的TCP和UDP,包括数据包投递率、带宽开销、端到端延迟、延迟抖动等。在此基础上,探讨一个适合在流媒体应用中,能够有效提高流媒体传输质量的策略。     

基于SIP、RTP／RTCP和RTSP协议的视频监控系统

从流媒体协议入手,描述会话发起协议SIP（Session Initiation Protocol）、实时传输协议RTP（Real time Transport Protocol）、实时传输控制协议RTCP（RTP Control Protocol）和实时流传输协议RTSP（Real Time Streaming Protocol）的原理以及它们在IP单播或多播网络上的通信过程。在此基础上,进一步分析RTP/RTCP和RTSP协议的关系,并对基于RTP/RTCP和RTSP协议的流媒体服务器进行设计。流媒体服务器是视频监控系统的核心部分,采用C/S结构,服务器和客户端之间的多媒体数据之间的传递都在这一部分完成。在基于RTP/RTCP和RTSP协议的流媒体服务器的基础上,使用SIP协议让用户和服务器建立会话连接,并在流媒体服务器上进行多媒体数据的传递,从而设计出基于SIP、RTP/RTCP和RTSP协议的视频监控系统。     

一种具有双重QoS保证的VOD流媒体系统结构

文中提出了一种基于IP网络具有双重QoS保证的VOD流媒体系统结构.此结构使用RSVP协议对流媒体预留资源,资源预留采用基于节的资源管理方法;服务器端通过RTP协议传输实时多媒体数据流,RTCP协议监视传输服务质量进行动态QoS控制,因此对基于IP网络的VOD系统的流媒体传输QoS提供了双重保证.其客户端使用SDP协议取得流媒体文件描述信息和组播地址,通过RTSP协议与流媒体文件服务器交互,建立和控制多媒体会话.     

网络流媒体服务器的机制与实现研究

网络流媒体服务器是指在IP网络上提供实时视频(音频)流服务的网络服务器，对服务器的机制与实现进行了深入研究，在RTP／RTCP协议和RTSP协议基础上，提出了“生产者线程-消费者线程”的架构，用面向对象的方法和事件驱动的机制实现服务器异步工作方式，充分利用系统资源，提高了服务器的并发性和实时性。基于反馈报文的流服务器流量自调节，解决了网络拥塞时实时数据传输的问题。     

基于Android的HLS播放器的实现和优化

HTTP Living Streaming(缩写HLS)是由苹果公司提出的基于HTTP的流媒体网络传输协议。在网络视频直播服务中,基于HLS协议构建的流媒体传输服务能更好的适应现有的网络,为用户提供接近实时的播放体验。本文介绍了Android平台上VLC开源播放器的HLS流解析部分实现,然后针对3G网络环境对播放器进行优化和改进。最后采用凤凰中文频道(支持HLS协议)作为测试源,结果表明改进后的播放器在3G网络环境播放体验大幅提升。     

一种基于移动网络流媒体的Qos指标测量方法

用户对网络业务的性能要求不断提高,服务质量(QOS)成为衡量系统可靠传输关键业务的重要指标.本文在分析移动流媒体Qos测量原理基础上,提出了一种基于端到端流媒体QoS测量方法,特别对移动流媒体端到端层次质量管理体系和流媒体质量评估指标进行了探讨和建议.经实践证明,该方法具有较广泛的应用前景和市场.     

基于RTP协议流媒体识别算法的设计及实现分析

与其他网络协议相比,实时传输协议（BTP协议）识别在管理网络流媒体及其应对风险方面具有一定的优越性。但BTP协议流媒体的识别有一定难度。从网络流识别技术入手．详细分析BTP协议特征,并提出基于BTP协议流媒体识别算法的设计和实现。     

基于RTP/RTCP的拥塞控制算法的研究

流媒体的传输使用RTP/RTCP协议实现端到端的网络传输服务,基于AIMD的拥塞控制算法容易导致媒体流发生抖动.本文对AIMD算法进行改进,提出了平稳增长因子算法以提高媒体流的平稳性.     

A robust method for soft IP handover

Multimedia streaming over wireless networks - often called mobile multimedia streaming lets users access music, movie, and news services at any time, regardless of location. Given that multimedia streaming is a key goal of third-generation and future wireless networks, vendors will soon deploy streaming clients in advanced mobile terminals. Current mobile terminals, however, fail to adequately support mobile multimedia communication because wireless networks have high packet-loss rates. To eliminate packet loss during handover, we use a packet path diversity scheme and an end-to-end bicasting mechanism that enables soft IP handover. To offset wireless errors, we use a forward error correction (FEC) scheme and embed it in the bicasting mechanism. Our bicasting method encodes the data stream and then splits it, providing more effective diversity than general bicasting, which sends the same data down both paths.' To support our method, we propose the mobile multimedia streaming protocol (MMSP), a new transport-layer protocol that supports multihoming and bicasting in combination with FEC.     

Toward the mobile Internet

The promise of ubiquitous computing is a future in which highly specialized, embedded computing devices operate seamlessly within the everyday environment and are transparent to users. Realizing this vision will require next-generation networks to support mobile multimedia devices with capabilities well beyond those of today's handsets. These networks will exploit wideband radio access technologies and IP-based protocols to provide IP transparency-all network elements support IP; mobility management for a globally networked environment; unique addressing for every user; personalization of information; positioning to enable location-dependent services; and end-to-end security. Such functionality requires more than providing wireless Internet access and e-mail.     

基于IMS的E2E QOS控制机制

3GPP提出的IMS用于提供各种实时多媒体业务,未来的实时多媒体服务将以视频、音频以及视频、音频的混合为主,对于实时性和延迟的要求很高,需要E2E的QOS的支持。文章分析了现有的IMS的QOS机制的实现以及存在的不足,提出了一种新的基于策略的E2EQOS机制。新的机制主要实现了IMS中的各个层次间的相互协作、SIP协议的扩展和PDF功能的改进,实现了对多媒体业务实时性的提高并且缩短了延迟。     

Wireless MediaNets: application-driven next-generation wireless IP networks

Thanks to the explosive creation of multimedia contents, the pervasive adoption of multimedia coding standards and the ubiquitous access of multimedia services, multimedia networking is everywhere in our daily lives. Unfortunately, the existing best effort IP network infrastructure, originally designed with little real-time QoS requirement, has started to suffer from performance degradation on emerging multimedia networking applications. This inadequacy problem is further deepened by the prevalence of last/first-mile wireless networking, such as Wi-Fi, mobile WiMAX, and many wireless sensors and ad-hoc networks. This can be evidenced by more and more fragmentation of application-driven IP-based networks, such as for power grid distribution, networked security surveillance, intelligent transportation communication, and many other sensor networks. To overcome the QoS challenges, the next generation wireless IP networks have to be architected in a top-down manner, i.e., application-driven layered protocol design. More specifically, based on the application media data, compression schemes are applied, the subsequent Network, MAC- and PHY-layered protocols need to be accordingly or jointly enhanced to reach the optimal performance. This is the fundamental concept behind the design of Wireless MediaNets. In this survey paper, I will address the QoS challenges specifically encountered in video over heterogeneous wireless broadband networks and address several application-driven Wireless MediaNet solutions based on effective cross-layer integration of APP and MAC/PHY layers. More specifically, the congestion control for achieving airtime fairness of video streaming to maximize the link adaptation performance of Wi-Fi, the minimum latency event-driven data exchange for distributed wireless ad-hoc sensor networks, and the opportunistic multicast of scalable video live streaming over mobile WiMAX.     

移动终端气象流媒体服务的研究与设计

移动3G/4G网络的逐步成熟促进了移动终端多媒体技术的发展以及相关产品的推广。专业实时的气象流媒体服务迎来了新的机遇和挑战,为此设计了一种移动终端气象流媒体服务的解决方案。本方案扩充了FFMPEG 技术对信息编码和文件格式的支持,完善了气象流媒体 Web 服务功能,更快捷地提供了多样化的气象预报形式。同时,也为移动终端气象产品应用拓展了新思路。     

一种基于IMS的BitTorrent文件分布系统架构

随着移动通信网络的迅速发展,在移动网络中提供P2P服务,特别是BitTorrent(BT)文件共享系统的需求日益突出。该文从BT协议的特点及3G网络的实际情况出发,分析扩展eDunkey体系、移动代理服务器等方式的不足,提出一种基于IMS的BT文件分布系统架构,研究了系统的工作机制和各组成部分的功能,解决了网络结构复杂、成本高、不易推广等问题。     

A scalable multimedia QoS architecture for ad hoc networks

Communication demands have grown from separate data and voice to integrated multimedia, paving the way to converging fixed, mobile and IP networks. Supporting Multimedia is a challenging task for wireless ad hoc network designers. Multimedia forms high data rate traffic with stringent Quality of Service (QoS) requirements. Wireless ad hoc networks are characterized by frequent topology changes, unreliable wireless channel, network congestion and resource contention. Providing scalable QoS is the most important challenge for multimedia delivery over ad hoc networks. We introduce here a provisioning and routing architecture for ad hoc networks which scales well while provisioning QoS. The proposed architecture is analysed using a mix of HTTP, voice and video streaming applications over 54 Mbps 802.11 g-based ad hoc networks. The architecture is simulated and compared to well-known routing protocols using the OPNET Modeller. The results show that our architecture scales well with increase in the network size, and outperforms well-known routing protocols.     

Active network supports for mobile IP

The basic mobile IP protocol is difficult to implement on the traditional IP network and not flexible and efficient under certain conditions.For example,firewalls or boundary routers may drop packets sent by mobile nodes for security reasons.Traditional networking devices such as routers cannot dynamically load and unload extended services to achieve different qualities of services.In this paper,a new scheme of using the active network to support the mobile IP is presented.The Softnet,a prototype of active networks based on mobile agents,is introduced.The active network is characterized by the programmability of its intermediate nodes and therefore presents dynaic and flexible behaviors.Special services can be dynamically deployed onto the active nodes in the Softnet.This property is definitely required in implementing the mobile IP protocols.The SOftnet.This property is definitely required in implementing the mobile IP protocols.The Softnet.This property is definitely required in implementing the mobile IP protocols.The Softnet supports not only the basic mobile IP protocol but also other extended mobile IP protocols.Virtual networks for mobile IP services are dynamically formed by mobile agents in the Softnet to provide different qualities of services.     

INSIGNIA: An IP-Based Quality of Service Framework for Mobile ad Hoc Networks

We present the design, implementation, and evaluation of INSIGNIA, an IP-based quality of service framework that supports adaptive services in mobile ad hoc networks. The framework is based on an in-band signaling and soft-state resource management approach that is well suited to supporting mobility and end-to-end quality of service in highly dynamic environments where the network topology, node connectivity, and end-to-end quality of service are time varying. Architecturally INSIGNIA is designed to support fast reservation, restoration, and end-to-end adaptation based on the inherent flexibility and robustness and scalability found in IP networks. We evaluate the framework, paying particular attention to the performance of the in-band signaling system, which helps counter time-varying network dynamics in support of the delivery of adaptive services. Our results show the benefit of our framework under diverse mobility, traffic, and channel conditions.     

Interworking of heterogeneous access networks and QoS provisioning via IP multimedia core networks

Moving towards packet networks, where IP will have a prominent role, constitutes nowadays a widely accepted perception of future communications, the first instance of which has begun to materialise with the IP multimedia core network subsystem (IMS). By specification, IMS is the first implementation towards reaching converged communications which allows users to communicate with video, audio and multimedia content, via any fixed, mobile and wireless access network type, with controllable QoS. To enable IMS communications across heterogeneous networks, incorporating UMTS, WLAN and fixed IP access points, 3GPP and ETSI’s TISPAN currently work on schemes for controlling bandwidth allocation at the service level by employing logical interfaces that carry SIP messages. This article analyzes how interconnection between such heterogeneous networks may be performed on real platforms. In this effort, special attention is paid to the way the various interconnection possibilities can affect end-to-end QoS provisioning.