On the QoS Assessment of Video Sessions in Heterogeneous 3G-WLAN Networks with Seamless and Secure Mobility Support

Real-time video data transmission is currently emerging as a popular application among mobile users but it is very sensitive to QoS degradation due to packet losses in wireless networks.In order to achieve service continuity and integrity upon handoffs among heterogeneous networks,provisioning of seamless and secure mobility is required.However,in order to reduce the delay and packet losses during vertical handovers we need to employ supportive protocols like context transfer.In this paper we evaluate the QoS of video transmission over a heterogeneous 3G-WLAN network.The aggregate video data traffic is represented by a dynamic two-dimensional Markov chain model,which has been evaluated against real video data measurement.Upon the vertical handover, appropriate AAA handshaking and enhanced mobility management using context transfer have been considered.Perceived QoS evaluation of video streams was performed based on peak signal-noise ratio(PSNR) measurements,while we analyticallyestimated the number of packet losses during handovers.The results show that both packet loss within the converged network and loss occurrence affecting the perceived video quality is reduced. Moreover,the proposed context transfer scheme minimizes handover delay and the number of lost packet up to 3 times compared to standard AAA handshaking.

Real-time ultra-wideband video streaming in long-reach passive optical networks with wireless radiation in the 10 and 60 GHz bands

Real-time video streaming using ultra-wideband(UWB) technology is experimentally demonstrated along long-reach passive optical networks(LR-PONs) with different wired and wireless reaches. Experimental tests using external and direct modulation with UWB wireless radiation in the 10- and 60-GHz bands are performed. An ultra-bendable fiber is also considered for a last-mile distribution. The video quality at the output of the optical fiber infrastructure of the LR-PON is assessed using the error vector magnitude(EVM), and the link quality indicator(LQI) is used as a figure of merit after wireless radiation. An EVM below –17 dB is achieved for both externally and directly modulated LR-PONs comprising up to 125 km of optical fiber. EVM improvement is observed for longer LR-PONs when directly modulated lasers(DMLs) are used because of the amplitude gain provided by the combined effect of dispersion and DML's chirp. Compared with optical back-to-back operation, the LQI level degrades to the maximum around 20% for LR-PONs ranging between 75 and 125 km of fiber reach and with a wireless coverage of 2 m in the 10-GHz UWB band. The same level of LQI degradation is observed using the 60-GHz UWB band with a LR-PON integrating 101 km of access network, a last-mile distribution using ultra-bendable fiber, and a 5.2-m wireless link.

基于3G无线网络实时传输MPEG-4流媒体的设计与实现

首先介绍了视频监控系统所涉及的一些基础理论(MPEG-4;RTP/RTCP),简述了嵌入式移动视频监控系统的实现方案;然后给出了系统的总体设计框架,着重对基于无线传输的嵌入式移动视频监控系统的传输部分设计进行了详细描述。

基于3G的双模远程视频监控系统设计

设计并实现了一种基于TD-SCDMA和CDMA2000 1X无线网络的双模远程视频监控系统,描述了监控系统设计和实现中的关键技术,包括监控终端的软、硬件结构,以及监控中心的软件设计。实验结果表明,该系统充分利用了TD-SCDMA和CD-MA2000 1X的传输带宽,相比于单模视频传输系统,有效提高了视频传输速率。

基于J2ME平台的手机实时监视系统的设计

随着3G时代的逐步到来,集办公、娱乐、通讯等多功能于一体的智能化手机已成为各移动设备开发商的开发热点。J2ME(Java 2 Mobile Edition)平台被认为是最杰出的手机程序开发平台,J2ME应用程序可运行在不同制造商的不同设备上,真正体现了Sun公司所倡导的"write once,run anywhere"。讨论了在Windows下的J2ME开发环境下的手机(或PDA等手持移动设备)实时监视系统问题,设计并实现了对远程计算机的实时监视。

远程遥控移动机械手的可视化实时控制

采用OTG接口连接摇杆手柄的Android手机和无线视频传输方案,来实现对移动机械手的可视化实时控制。本设计以OMAP4430开发板和Android手机为核心,通过响应摇杆水平、竖直方向的移动事件和手柄按键事件来控制机械手的地表移动及机械手马达操作,同时借助车载USB摄像头拍摄720P视频,经H264编码后用无线网卡发送到Android手机,解码后显示在控制界面上。实验结果表明,可视化远程遥控机械手能够实现全方位移动、捉取地面目标等功能,同时无线视频传输帧率达到28fps,满足实时视频传输要求。

基于无线网桥的鄂北调水工程视频监控系统建设

在当前信息化、智能化快速发展的背景下,部署视频监控系统有利于提高水利工程建设管理水平和工作效率。经现场查勘和技术比对,鄂北调水工程视频监控系统采取的是视频采集、网络传输、数据存储、数据访问的4层架构。结合视频监控系统在鄂北工程的应用场景和实际需求,并考虑经费、部署难度、稳定性等方面因素,充分利用工区已有互联网上行链路资源,提出了基于无线网桥技术的视频监控传输模式。实践表明:鄂北调水工程视频监控系统不仅实现了施工现场的实时在线远程监控,更为工程安全、质量、进度、环保等方面的建设管理提供了信息化技术支撑,极大提高了便捷性、精准性、高效性。

基于负载自适应的Ad Hoc网视频传输队列调度算法

移动终端多媒体业务的发展目前已经成为终端发展的必然趋势。如何在移动终端构成Ad hoc网络时有效地进行视频传输是无线网络研究的热点之一。提出了一种基于负载状况的跨层优化方案,其基本思想是结合应用层视频编码的特点和接入层的网络负载和资源的情况联合进行优化。在特定的资源下通过概率接入的方法对重要性更高的数据包进行更优先的接入。仿真结果显示,在网络处于高负载、多跳传输等场景下,提出的方案视频传输质量PSNR值提升3 dB以上。相对于传统调度算法,系统时延也可以大幅度降低。

基于DirectShow架构的无线视频服务系统设计研究

视频实时网络化已经成为信息传播的重要途径,特别是随着无线技术的不断发展,以无线网络承载的视频业务将进一步推动各类迫切需要通过视频才能尽情表达的内容和服务。但无线网络本身固有的种种约束与人们对视频服务的期望和要求存在距离,通过优化视频数据的传输和控制机制,系统架构设计的层次与方法和图像处理策略,以不依赖于具体某种视频压缩技术为前提,进一步有效的挖掘现有无线网络的潜力,让视频尽早的进入商业服务领域成为可能。