Joint video adaptation and erasure code for video broadcast in wireless networks

Advances in wireless access technologies such as WiMax and LTE have accelerated the development of wireless video applications.Though existing erasure codes are designed for wireless data broadcasting,their potential can only be realized for wireless video broadcasting if the distortions associated with video packets and their complex decoding dependency are taken into consideration.In this paper,we propose the greedy video erasure code(GVEC)to minimize average video distortion by accounting for the temporal scalable decoding dependency among video frames e.g.I,P and B frames in MPEG.GVEC is a greedy algorithm and sufers from high computational complexity.For practical implementation,we have designed the joint video adaptation and erasure code(JVEC)with lower complexity,which can generate erasure codes on the fly to guarantee the decoding of important video frames.Simulation results show that the performance of JVEC is very close to that of GVEC,and is superior to that of existing erasure codes.Our results also show the existence of a performance tradeof between video distortion and video packet throughput.     

矿用IP广播对讲系统回声消除技术研究

分析了矿用IP广播对讲系统的回声产生路径,指出其回声具有来源复杂、路径延迟时间长、路径延迟抖动大的特点;提出在广播主机采用软件算法消除回声,在广播终端采用结构设计和硬件电路设计相结合的方法消除回声的方案。实际应用表明,该回声消除方案有效地提高了矿用IP广播对讲系统的通信质量,系统全双工扩音对讲通话效果良好。     

基于热释电红外传感器的人防警报器防盗系统设计

目前我们所使用的防空警报器经常由于监管不严发生盗窃事故或被不法分子恶意操作发生警报器误响世故,严重扰乱了人民的正常工作、学习和生活,造成了十分严重的后果和影响。为此对现有的人防警报器设计了一个自动防盗、防破坏报警系统,该系统由菲涅尔透镜、热释电红外传感器、单片机、语音警示电路组成,响应速度快,抗干扰能力强,灵敏度高。当有人距离警报器低于1 m时,就会发出语音警示,同时向管理平台回传信息,达到了安全防护的目的。     

基于语义搜索的实名呼叫系统设计

网络和通信技术的飞速发展,使传统的通信方式已经不能满足人们的需求。通信的人性化和智能化成为各个通信厂商追求的目标,但却始终无法摆脱号码这一枷锁。本文针对只能通过号码呼叫带来的通信不便问题,提出利用语义搜索这一未来互联网搜索技术实现实名呼叫的设计方案,并将语音搜索的思想融入其中,使通信变得更简单,实现通信的以人为本。     

企业网实现视频在线播放技术的探讨

随着计算机技术、多媒体技术、通信技术等高新技术的发展以及Intemet的广泛应用,视频在线播放已经成为最主要的信息传播手段。详细讲解了利用ASP、MicrosoftAccess2003、Flash、FrontPage2003等软件工具制作“在线视频服务系统”的过程,并简要介绍了流媒体技术和Intemet及Web技术的发展,对比企业网内各种信息传播的优缺点,并探讨视频在线播放技术在企业网内的前景。     

Bandwidth Efficient All-to-All Broadcast on Switched Clusters

Clusters of workstations employ flexible topologies: regular, irregular, and hierarchical topologies have been used in such systems. The flexibility poses challenges for developing efficient collective communication algorithms since the network topology can potentially have a strong impact on the communication performance. In this paper, we consider the all-to-all broadcast operation on clusters with cut-through and store-and-forward switches. We show that near-optimal all-to-all broadcast on a cluster with any topology can be achieved by only using the links in a spanning tree of the topology when the message size is sufficiently large. The result implies that increasing network connectivity beyond the minimum tree connectivity does not improve the performance of the all-to-all broadcast operation when the most efficient topology specific algorithm is used. All-to-all broadcast algorithms that achieve near-optimal performance are developed for clusters with cut-through and clusters with store-and-forward switches. We evaluate the algorithms through experiments and simulations. The empirical results confirm our theoretical finding.     

P2P流媒体直播系统服务鲁棒性保障机制

给出在P2P直播系统中Peer节点动态变化的情况下保障服务鲁棒性的技术,描述从邻居节点中选择父节点的最优选择方法,研究强节点对区域内全局信息的掌握机制。针对Peer节点动态加入离开对流媒体直播的影响,设计一套加快动态恢复和反应时间的方法。通过原型系统实验及与PeerCast系统比较证明了主要设计机制的有效性和先进性。     

基于实时传输协议的教学直播系统的分析与设计

随着网络传输技术、图像编码技术的成熟,以流媒体技术为基础的RTP协议的视频实时传输有着快速的发展。文章介绍了用于流媒体传输的RTP/RTCP协议格式,给出了一个基于RTP协议的教学直播系统的框架和设计。     

一种基于需求的实时数据广播模型

数据广播是提高移动计算系统可伸缩性的一项重要技术,该文提出了一种实时数据广播模型。该模型采用数据需求驱动机制,不仅充分考虑用户对数据的时效要求,还利用数据广播技术分发数据,有效地利用通信带宽,满足最多用户的数据需求。     

CNG系列话音网关在油田卫星系统中的应用研究

介绍了使用CNG系列话音网关,通过中国石化Ku频段卫星实现油田边远小队话音通信联网。对原有设计方案的编号与计费方式提出了修改建议,阐述了CNG800和CNG300的主要功能、及电话交换机的联网方案,并详细分析了话音网关的参数配置方法。为通过卫星IP网络实现话音通信提供了又一应用实例。