UMTS-to-IP QoS mapping for voice and video telephony services

Quality of service mapping between UMTS services and IP transport is crucial for maintaining a suitable end-to-end delay for emerging UMTS multimedia telephony. However, due to incompatibilities in QoS classifications within these two technologies, straightforward mapping is impossible and current proposals within the 3GPP could lead to unpredictable and undesirable behavior for certain services. In this article we focus on two very important UMTS services, voice and video telephony, and establish the QoS issues that exist for these services. We then propose a refined QoS mapping that differentiates between the transmission of voice and video-telephony and a weighted fair queuing scheduler to schedule the transmissions. Through a simulation study, we show the effect on the queuing delays of both traffic types when their WFQ weights vary and then derive an optimal weight that provides the best overall delays for multimedia telephony services.     

为何IP电信网是大势所趋?

随着企业日益面临降低成本和提高效率的挑战,语音和数据融合的网络正在受到其青睐,然而伴随其中的安全、投资回收以及收益问题始终令人关注,此外,国外在IP-VPN发展上的经验教训也值得尚处于落后状态的我国借鉴。本期的IP融合专题将对上述问题综合阐述。     

Integrated video and voice transmission using packet reservation multiple access

This paper proposes a new protocol for the integration of voice and video transmission over the packet reservation multiple access (PRMA) system that is a modification of reservation‐ALOHA protocol. We focus on low bit‐rate video applications like video conferencing and visual telephony for wireless communications. The ITU–T H.263 standard provides a solution to the need for low bit‐rate video compression under 64 kbytes/s. The proposed protocol assumes that each voice terminal follows a traffic pattern of talk spurts and silent gaps with fixed permission probability (p=0.3), and each video terminal has the higher permission probability (p=1) to access the available slot based on ITU–T H.263 standard. Again, we present a ‘pseudo‐reservation’ scheme to release slots reserved by video terminals according to the contents of each video transmission buffer, and the active voice terminals can temporarily access the additional slots to improve the performance without sacrificing the video capacity of the system. The packet dropping probability of the active voice terminals and bandwidth utilization of the system are superior to the original PRMA, as indicated in simulation results. Copyright © 2001 John Wiley & Sons, Ltd.     

话音无阻塞的可视电话系统设计与实现

为实现话音无阻塞、视频图像清晰流畅和低延迟的高品质可视通话,提出了一种使用PSTN单独传送话音,使用IP网络单独传送通话者视频并在终端同步还原的可视电话系统及其实现方法,系统由终端和支撑服务器群构成。设计用PSTN的话音拨号信号或来电振铃信号作为视频呼叫的触发信号,终端通过捕获电话号码封装为SIP的Invite消息并发起视频呼叫,与对端建立P2P连接并使用UDP报文传送RTP视频流来实现视频通话。系统测试表明通话话音始终无阻塞;在带宽为256kbit／s、IP网络无拥塞的条件下,实现了视频CIF分辨率,帧频30fps,视频延迟小于60ms;用户使用习惯如电话号码和拨号方式无需任何改变。其综合性能优于现有的PSTN可视电话和IP可视电话。     

Supporting voice and video applications over IEEE 802.11n WLANs

In this paper, an analytical model is developed for the performance study of an IEEE 802.11n wireless local area network (WLAN) supporting voice and video services, considering the new features of the medium access control (MAC) protocol proposed in IEEE 802.11n, i.e., frame aggregation and bidirectional transmission. We show that these enhanced MAC mechanisms can effectively improve the network capacity by not only reducing the protocol overheads, but also smoothing the AP-bottleneck effect in an infrastructure-based WLAN. Voice and video capacity under various MAC mechanisms are compared as well.

将永远改变我们购物方式的RFID

新的技术和应用总是层出不穷.有些技术已经消失在历史的长河中;有些在一些特殊行业内扎了根;其他的则已经流行而且进入寻常百姓家.笔者并不想就此阐述些什么,只是用它来引出一个新的话题.     

A low-rate multi-level voice/video transceiver for personal communications

A personal communication system (PCS) transceiver is proposed and investigated. A 4.8 kbit/s transformed binary pulse excited (TBPE) linear predictive speech codec, embedded source sensitivity-matched binary Bose-Chaudhuri-Hocquenghem (BCH) block error correction codecs, non-coherent differentially coded 16-level quadrature amplitude modulation (16-QAM) modem and packet reservation multiple access (PRMA) are deployed. The 2.15 kBd transceiver requires a signal-to-noise ratio (SNR) and signal-to-interference ratio (SIR) in excess of about 24 dB over Rayleigh-fading channels in order to support 10–11 nearly un-impaired voice conversations within a bandwidth of 30 kHz. Additionally, by reserving two PRMA time slots for video telephony, an 8.52 kbps videophone user can also be supported.The constructive criticism of the anonymous Reviewers is gratefully acknowledged.     

PCA-based approach for video scene change detection on compressed video

An automatic, real-time detection approach to video scene change detection is presented. Owing to the high correlation of two consecutive video frames, it is proposed that only the eigenvector corresponding to the largest eigenvalue is retained in the principal component analysis (PCA) for video data. A one-dimensional PCA feature of video data is then generated from the PCA. It shows superior performance compared to the histogram feature and the pixel feature. The detection algorithm based on this PCA feature is then designed to detect both abrupt and gradual transitions. The proposed approach is tested on the TREC video test repository to validate its performance     

Why do employees resist change?

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基于DPI技术的语音视频流量监控系统设计与实现

采用软硬件相结合的方法,将硬件识别语音视频网络常见的协议,软件识别网络复杂的网络协议,并结合端口、统计等多种识别技术的识别方案,提出语音视频流量监控架构的监控系统;详细对系统的架构和相关模块的设计进行分析,并通过实际试验环境对系统性能进行验证,结果表明该系统的语音视频流量监控客户端识别率都大于91%,没有误报,表明系统的识别性能可以满足用户需求。     

一种改进的视频切变检测方法

在分析视频切变类型、常用切变检测算法及问题的基础上，提出了一种改进的累积平均差值视频渐变检测算法，降低了阈值选取难度，取得了较好的实验效果。     

10 emerging technologies that will change your world

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The growth of international VSAT: Satellite-based solutions for data,voice and video

Emerging countries are installing digital satellite transmission systems that eliminate the cost and geographic problems of traditional telecommunication systems and give them the switching and connectivity capabilities of more advanced countries.     

Everything over IP — an overview of the strategic change in voice and data networks

This paper investigates the changes that are required in networking technology for ‘everything over IP’ to become a reality. Initially the changes that are taking place in the telecommunications industry are reviewed. This review ranges from a discussion about the companies installing massive global IP networks to the emergence of novel routeing technologies, e.g. multi-protocol label switching (MPLS) and terabit router technologies. The role of existing telecommunications operators is then discussed, along with the reasons why they are developing interworking and intelligence layers based on distributed computing principles to support all their networks — mobile, fixed, broadband and IP.     

Scene change detection algorithms for content-based video indexingand retrieval

There is an urgent need to extract key information from video automatically for the purposes of indexing, fast retrieval, and scene analysis. To support this vision, reliable scene change detection algorithms must be developed. Several algorithms have been proposed for both sudden and gradual scene change detection in uncompressed and compressed video. In this paper some common algorithms that have been proposed for scene change detection are reviewed. A novel algorithm for sudden scene change detection for MPEG-2 compressed video is then presented. This uses the number of interpolated macroblocks in B-frames to identify the sudden scene changes. A gradual scene change detection algorithm based on statistical features is also presented     

基于FPGA的视频图像变化检测系统设计

介绍了一种以FPGA为核心的,在静止摄像机条件下,对运动目标引起背景图像变化进行检测和报警的系统.系统采用FPGA为系统主控芯片,是一种基于嵌入式设备的实用系统,在性能上更加稳定,同时由于可编程逻辑的大容量、灵活性,可以大大提高系统的运行速度,可以实现SOPC,利用NIOSⅡ这一可定制的,精简指令处理器,可以加快系统开发.