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Distributed upload bandwidth assigning algorithm in P2P vod system

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The Journal of China Universities of Posts and Telecommunications 2011年第6期18卷 78-88页

作者： DENG Guang-qing1,WEI Ting1,CHEN Chang-jia1,ZHU Wei2,WANG Bin2,WU Deng-rong2 1.School of Electronic and Information Engineering,Beijing Jiaotong University,Beijing 100044,China 2.Department of PPLive P2P-CDN R&D,Shanghai 201203,China School of Electronic and Information Engineering Beijing Jiaotong University Beijing 100044 China Department of PPLive P2P-CDN R&D Shanghai 201203 China

In a peer-to-peer(P2P) live streaming system,each peer uses greedy strategy to download chunks as many as possible so as to assure smooth playback and promote the chunk ***,diversity of video playback rate,heterogeneity of peer downlink bandwidth and no prefetching limitation determine that greedy strategy is not the best strategy for P2P video-on-demand(vod) system though this strategy performs well in P2P live *** reasonably assign upload bandwidth among peers,we first present a stochastic model to relate expected downloading speed(EDS) with buffered data amount(BDA,the amount of data has been fetched in buffer,however has not been played yet by the peer),video playback rate and fluency(the probability of no interruption in a viewing process).On the base of this model,we design an equal fluency bandwidth assigning algorithm(EFBAA).In this algorithm,requesting peers compute EDS according to several local parameters(such as BDA,video playback rate and fluency) dynamically and independently and send the EDS to neighbor peers together with buffer *** the neighbor peer proportionally partitions and assigns its upload bandwidth to requesting peers according to their *** simulations demonstrate that EFBAA outperforms greedy strategy in terms of server load and startup latency.

关键词： P2P vod fluency bandwidth quality of service(QoS)

Model of downloading strategy from peers and server for saving server bandwidth in P2P vod system

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The Journal of China Universities of Posts and Telecommunications 2011年第5期18卷 76-86,101页

作者： WEI Ting DENG Guang-qing CHEN Chang-jia ZHU Wei School of Electronic and Information Engineering Beijing Jiaotong University Beijing 100044 China Department ofPPLive P2P-CDN R＆D Shanghai 201203 China

In peer-to-peer （P2P） video on demand （vod） system, once the P2P downloading rate cannot satisfy the need of playback, server is quickly referred to for help in providing enough bandwidth. Thus the switch of downloading from other peers （P2P） and server （HTTP） exists. This paper uses the proportion of P2P downloading amount （PPDA） during the video watching process to measure server load. This article is interested in finding a better strategy or switch rule between P2P and HTTP downloading for saving server bandwidth. The authors suggest and model a kind of switch rule based on local buffer amount, using mathematical theory of Brownian motion. It can effectively alleviate the impact of P2P rate fluctuation, reduce the switch times and improve the PPDA by at least 3%-5% on the basis of the former switch rule, which means substantial cost can be saved. Particularly the PPDA is related with the ratio of playback bit rate to the HTTP downloading rate which means the PPDA can be restricted by controlling the ratio in the real-world system. Though the result comes from constant bit rate （CBR） video supposition, it provides perspective and method for variable bit rate （VBR） application, and valuable insights for the future development of P2P vod system.

关键词： P2P vod downloading server load

Modeling and application of moderate prefetching strategy based on video slicing for P2P vod systems

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The Journal of China Universities of Posts and Telecommunications 2012年第2期19卷 57-66页

作者： DENGGuang-qing WEITing CHENChang-jia ZHUWei WANGBin WUDeng-rong SchoolofElectronicandInformationEngineering BeijingJiaotongUniversityBeijing100044China DepartmentofPPLiveP2P-CDNR＆D Shanghai201203China

In peer-to-peer （P2P） video-on-demand （vod） streaming systems, each peer contributes a fixed amount of hard disk storage （usually 2 GB） to store viewed videos and then uploads them to other requesting peers. However, the daily hits （namely popularity） of different segments of a video is highly diverse, which means that taking the whole video as the basic storage unit may lead to redundancy of unpopular segment replicas and scarcity of popular segment replicas in the P2P storage network. To address this issue, we propose a video slicing mechanism （VSM） in which the whole video is sliced into small blocks （20 MB, for instance）. Under VSM, peers can moderately remove unpopular blocks from and accordingly add popular ones into their contributed hard disk storage, which increases the usage of peers＇ contributed resource （storage and bandwidth）. To reasonably assign bandwidth among peers with different download capacity, we propose a moderate prefetching strategy （MPS） based on VSM. Under MPS, when the amount of prefetched content reaches the predefined threshold, peers immediately stop prefetching video content and then release occupied bandwidth for others. A stochastic model is established to analyze the performance of the MPS and it is found that perfect playback continuity can be got under MPS. Then the MPS is applied to PPLive vod system （one of the largest P2P vod systems in China） and measurement results demonstrate that low server load and perfect user satisfaction can be achieved. Also, the server bandwidth contribution of PPLive vod system under MPS （namely 5%） is much lower than that of UUSee vod system （namely 30%）.

关键词： bandwidth P2P vod slicing prefetch

EAF+LF+vod/VHD冶炼超级双相不锈钢工艺实践

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中国冶金 2022年第6期32卷 163-167页

作者：谭庆丰陈德利闫占东贾红帅韩志远王玉辉抚顺特殊钢股份有限公司技术中心辽宁抚顺113001 抚顺特殊钢股份有限公司第二炼钢厂辽宁抚顺113001

介绍了抚钢超级双相不锈钢冶炼工艺流程,进行了vod炉真空吹氧去碳、包底吹氮、二次造渣及喂线处理生产实践。研究表明,通过设定合理的吹氧、吹氮工艺,实现了低碳含量、准确氮含量的控制。通过在还原过程中调整合适的炉渣碱度,对钢液进... 详细信息

介绍了抚钢超级双相不锈钢冶炼工艺流程,进行了vod炉真空吹氧去碳、包底吹氮、二次造渣及喂线处理生产实践。研究表明,通过设定合理的吹氧、吹氮工艺,实现了低碳含量、准确氮含量的控制。通过在还原过程中调整合适的炉渣碱度,对钢液进行喂线处理,强化脱硫脱氧,从而改性夹杂物形貌,以确保钢液精准的化学成分及良好的纯净度控制,为热加工创造有利条件。

关键词：超级双相不锈钢 vod 冶炼工艺脱氧还原夹杂物

A Scheduling Policy of Short Video Clips for vod Systems Based on Optical Jukeboxes

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The Journal of China Universities of Posts and Telecommunications 2003年第3期10卷 35-40页

作者： LIQing-guo SUNJing-ao CAIAn-ni InstituteofStandardandPlan TheStateAdministrationofRadioFilmandTVBeijing100866P.R.China BeijingUniversityofPostsandTelecommunications Beijing100876P.R.China

A great number of video clips can be stored in the optical jukebox in vodSystems. In this paper a scheduling scheme, called Combined MQL/FCFS (CMF), of short video clips inthe jukebox is proposed. Simulation shows that the proposed scheme balances the efficiency andfairness, and reduces the defection probability and increases the throughput significantly comparedwith MQL and FCFS schemes.

关键词： vod scheduling tertiary storage

Blocking Probability Based Hierarchical Storage Design in vod Systems

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The Journal of China Universities of Posts and Telecommunications 2003年第1期10卷 44-48页

作者： LI Qing-guo, SUN Song-lin, CAI An-ni, SUN Jing-ao (Beijing University of Posts and Telecommunications, Beijing 100876, P.R. China) Beijing University of Posts and Telecommunications 北京 100876

In this paper, we discuss the relationship between the blocking probabilityand the configuration of storage hierarchy in a Video on Demand ( vod) server using the queueingmodel we propose. With this model, the optimal... 详细信息

关键词： vod hierarchical storage blocking probability

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基于测量的p2p vod系统的模型研究

铁道学报 2011年第2期33卷 60-66页

作者：郑毅陈长嘉李纯喜北京交通大学电子信息工程学院北京100044

peer-to-peer方式的vod系统中,用户的观看行为、网络中资源块(chunk)的分布、下载速度和pre-fetch机制之间相互影响,相互制约。以往的研究通常专注于某个方面,而没有考虑各因素间的相互关系。本文通过对实际数据进行分析,建立模型描述p2... 详细信息

peer-to-peer方式的vod系统中,用户的观看行为、网络中资源块(chunk)的分布、下载速度和pre-fetch机制之间相互影响,相互制约。以往的研究通常专注于某个方面,而没有考虑各因素间的相互关系。本文通过对实际数据进行分析,建立模型描述p2p vod系统中上述各因素间的关系,并基于该模型提出一种新的pre-fetch机制,能在保证用户流畅观看的前提下,尽可能提高下载速度。该模型提供一种更为精确的了解客户端行为的方法,为其他各类p2p应用中研究用户行为、设计下载机制、优化系统提供参考。

关键词： peer-to-peer vod pre-fetch 模型观看行为

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vod系统的最优代理缓存方案

东北大学学报（自然科学版） 2004年第4期25卷 341-344页

作者：胡玉琦臧怀泉高远东北大学秦皇岛分校河北秦皇岛066004 燕山大学电气工程学院河北秦皇岛066004

针对基于代理的分布式vod系统,提出一种使网络带宽消耗最小的最优代理缓存方案,开发了一种全局试探寻优法,使各种流行度节目得到最优的缓存配置;通过把缓存方案与典型的节目调度策略相结合,定量地分析了缓存配置方案和代理缓存空间大小... 详细信息

针对基于代理的分布式vod系统,提出一种使网络带宽消耗最小的最优代理缓存方案,开发了一种全局试探寻优法,使各种流行度节目得到最优的缓存配置;通过把缓存方案与典型的节目调度策略相结合,定量地分析了缓存配置方案和代理缓存空间大小对系统传输开销的影响,证实了方案的有效性,为服务器设计提供了一种实用的在线节目配置方案·

关键词： vod 代理缓存网络带宽传输开销点播强度

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vod视频服务器上用户请求的优先获准策略

西安电子科技大学学报 2003年第6期30卷 806-809页

作者：周宁姜昱明西安电子科技大学计算机学院陕西西安710071

介绍了vod服务器上获准用户请求的几种基本策略,并在此基础上提出了效果更优的混合策略.该策略以视频的长度和位率为参数,增加了请求的获准率,同时降低了获准延迟.对请求排队的普通模型进行了数学分析,给出了采用不同策略时的计算机仿... 详细信息

介绍了vod服务器上获准用户请求的几种基本策略,并在此基础上提出了效果更优的混合策略.该策略以视频的长度和位率为参数,增加了请求的获准率,同时降低了获准延迟.对请求排队的普通模型进行了数学分析,给出了采用不同策略时的计算机仿真结果,显示了混合策略的优越性.

关键词： vod 视频服务器用户请求优先获准策略获准延迟