QoE-aware video cooperative caching and transmission mechanism based on TWDM-PON and C-RAN

The quality of user experience suffers from performance deterioration dramatically due to the explosively growing data traffic.To improve the poor performance of cell-edge users and heavy-load cell users,which caused by dense network and load imbalance respectively,an QoE-aware video cooperative caching and transmission mechanism in cloud radio access network was proposed.Cooperative gain-aware virtual passive optical network was established to provide cooperative caching and transmission for video streaming by adopting collaborative approach in optical domain and wireless domain.Furthermore,user experience for video streaming,bandwidth provisioning and caching strategy were jointly optimized to improve QoE,which utilized the methods of dynamic caching in optical domain and buffer level-aware bandwidth configuration in wireless domain.The results show that the proposed mechanism enhances the quality of user experience and effectively improves the cache hit rate.     

Headlight Prefetching and Dynamic Chaining for Cooperative Media Streaming in Mobile Environments

Media streaming in mobile environments is becoming more and more important with the proliferation of 3G technologies and the popularity of online media services such as news clips, live sports, and hot movies. To avoid service interruptions, proper data management strategies must be taken by all parties. We propose a two-level framework and cooperative techniques for mobile media streaming. Headlight prefetching is for the cooperation of streaming access points to deal with unpredictable client movement and seamless hand-off. For each user, we maintain a virtual fan-shaped prefetching zone along the direction of movement similar to a vehicle headlight. The overlapping area and accumulated virtual illuminance of the headlight zone on a particular cell determine the degree and volume of prefetching on that cell. Dynamic chaining facilitates cooperation among users to maximize cache utilization and streaming benefit. On receiving a request from a client, the streaming access point starts a search for supplying partners before attempting to a remote media server. If a qualified partner is found, the client is chained to the partner and receives subsequent segments without server intervention. The client can itself be a supplying partner for other clients and naturally form a chain of users that are viewing and sharing the same media. Simulation results demonstrate that headlight prefetching and dynamic chaining can significantly decrease streaming disruptions, reduce bandwidth consumption, increase cache utilization and improve service response time.     

基于信息中心5G车联网中社会感知的流媒体缓存与转发策略

5G 通信技术的到来为车载自组网（VANET）提供高质量的视频流服务奠定了基础。然而,现有的VANET 仍然采用以主机通信而非内容分发的 IP 网络来分发视频数据,造成了网络功能与设计目标之间的不匹配,为提供高质量的视频服务带来了巨大挑战。基于上述问题,提出了一种以信息为中心的社会感知流媒体缓存和转发策略（SACF）,其时间复杂度为O(m²)。首先,通过分析用户节点的行为构建社会感知的虚拟社区;然后,提出了一种视频快速转发机制来支持用户就近获取视频内容;最后,提出了一种基于社区的缓存策略来优化视频的缓存分布。仿真实验结果表明,与最新的解决方案相比,该算法的缓存命中率提高了18%,查找时延降低了33%,平均网络开销减少了14.6%。     

内容分发网络下的用户原创视频热度研究

视频的热度是指用户对视频的关注程度.主要对大规模内容分发网络环境下的在线共享网站原创视频的热度进行分析.提出了综合视频点击数、评论数、评分等多元指标对视频热度进行统计刻画,分析各个指标的分布模型以及指标之间的相互关系,并对视频热度随时间的变化趋势进行了详细分析.通过对实际的爬虫数据统计分析,发现热度指标的分布具有典型的无标度特征,随着视频上传时间的增长,热度越来越趋于稳定.上述发现对于视频内容提供商和互联网运营商在服务器部署、内容缓存、容量规划和流量优化等方面具有重要的意义.     

Resource assignment in short video accelerator system

Video accelerator is developed for better user experience in video sharing websites such as YouTube.PPLive video accelerator (PPVA),which has the largest number of users in China,is based on peer-to-pe...     

Maximizing the number of users in an interactive video-on-demand system

Video prefetching is a technique that has been proposed for the transmission of variable-bit-rate (VBR) videos over packet-switched networks. The objective of these protocols is to prefetch future frames at the customers' set-top box (STB) during light load periods. Experimental results have shown that video prefetching is very effective and it achieves much higher network utilization (and potentially larger number of simultaneous connections) than the traditional video smoothing schemes. The previously proposed prefetching algorithms, however, can only be efficiently implemented when there is one centralized server. In a distributed environment there is a large degradation in their performance. In this paper we introduce a new scheme that utilizes smoothing along with prefetching, to overcome the problem of distributed prefetching. We show that our scheme performs almost as well as the centralized prefetching protocol even though it is implemented in a distributed environment. In addition, we introduce a call admission control algorithm for a fully interactive video-on-demand (VoD) system that utilizes this concept of distributed video prefetching. Using the theory of effective bandwidths, we develop an admission control algorithm for new requests, based on the user's viewing behavior and the required quality of service (QoS).     

UAV deployment and caching scheme based on user preference prediction

In order to design an efficient edge caching policy considering spatial heterogeneity and temporal fluctuations of users’ content requests,a proactive caching scheme was proposed with UAV’s deployment location design based on user preference prediction.Firstly,each user’s preference characteristics were predicted based on file similarity and user similarity,and the request time and user location were also predicted when a content request occurs.Thereafter,on the basis of the predicted geographical location,request time and user preference,each UAV’s deployment location and the corresponding content placement were determined by virtue of clustering method based on SOM and AGNES.Simulation results show that the proposed scheme outperforms other three comparison schemes in terms of hit ratio and transmission delay.Furthermore,the results also reveal that content preference is correlated with different user features by different weights.Accordingly,different impact weights should be matched with different user features.     

A prefetching protocol for continuous media streaming in wirelessenvironments

Streaming of continuous media over wireless links is a notoriously difficult problem. This is due to the stringent quality of service (QoS) requirements of continuous media and the unreliability of wireless links. We develop a streaming protocol for the real-time delivery of prerecorded continuous media from (to) a central base station to (from) multiple wireless clients within a wireless cell. Our protocol prefetches parts of the ongoing continuous media streams into prefetch buffers in the clients (base station). Our protocol prefetches according to a join-the-shortest-queue (JSQ) policy. By exploiting rate adaptation techniques of wireless data packet protocols, the JSQ policy dynamically allocates more transmission capacity to streams with small prefetched reserves. Our protocol uses channel probing to handle the location-dependent, time-varying, and bursty errors of wireless links. We evaluate our prefetching protocol through extensive simulations with VBR MPEG and H.263 encoded video traces. Our simulations indicate that for bursty VBR video with an average rate of 64 kb/s and typical wireless communication conditions our prefetching protocol achieves client starvation probabilities on the order of 10^-4 and a bandwidth efficiency of 90% with prefetch buffers of 128 kbytes     

面向移动内容分发网络环境的移动视频预取技术研究进展

随着移动互联网的发展和视频应用的普及,移动内容分发网络(MCDN)应运而生。预取技术是内容分发的关键技术之一,它通过预测用户未来的请求,提前将预测的内容预取至网络边缘,从而减少数据的获取时延、提升用户体验质量(QoE)。为深入阐述移动视频预取技术的发展现状,从用户移动行为感知、内容属性感知、网络资源感知等角度分析梳理了移动视频预取技术的最新研究成果,同时分析了各类预取方案的性能及其主要优缺点,最后指出未来可以进一步研究的方向。     

Distributed servers architecture for networked video services

In an on-demand video system, the video repository generally has limited streaming capacities and may be far from the users. In order to achieve higher user capacity and lower network transmission cost, distributed servers architecture can be used, in which multiple local servers are placed close to user pools and, according to their local demands, dynamically cache the contents streamed from the repository. We study a number of caching schemes as applied in the local servers depending on whether the repository is able to multicast movie contents to the local servers or not, and whether the local servers can exchange their cached contents among themselves or not. Our caching schemes keep a circular buffer of data for the movie requested, and hence movies are partially cached. By adjusting the size of the buffer, such caching is able to achieve better tradeoff between network channels and local storage as compared to the traditional caching in which a movie is treated as an entity. For each caching scheme, we study the tradeoff between the local storage and the network channels, and address how the total cost of the system can be minimized by appropriately sizing the buffer. As compared to a number of traditional operations (request batching and multicasting, true-VOD, etc.), we show that distributed servers architecture is able to achieve much lower system cost to offer on-demand video services     

基于内容分块流行度分级的信息中心网络缓存策略

信息中心网络(ICN:Information-Centric Networking)域内缓存机制的研究大多假定单个内容的流行度相同,而忽视了同一内容的不同分块具有不同流行度的特性.本文提出了一种基于内容分块流行度以及缓存节点位置的分级缓存策略,通过兴趣包和数据包携带标签的方式实现隐式缓存协作.仿真实验证明相比于其他方案,该方案可以充分利用细粒度的内容分块流行度这一特性,提高缓存路由器缓存命中率,减小用户请求内容时延以及网络流量,进而提升用户对实时业务的服务体验.     

Design and implementation of geo-tagged video search framework

User generated video content is experiencing significant growth which is expected to continue and further accelerate. As an example, users are currently uploading 20 h of video per minute to YouTube. Making such video archives effectively searchable is one of the most critical challenges of multimedia management. Current search techniques that utilize signal-level content extraction from video struggle to scale.Here we present a framework based on the complementary idea of acquiring sensor streams automatically in conjunction with video content. Of special interest are geographic properties of mobile videos. The meta-data from sensors can be used to model the coverage area of scenes as spatial objects such that videos can effectively, and on a large scale, be organized, indexed and searched based on their field-of-views. We present an overall framework that is augmented with our design and implementation ideas to illustrate the feasibility of this concept of managing geo-tagged video.     

Dual Cache Architecture for Low Cost and High Performance

We present a high performance cache structure with a hardware prefetching mechanism that enhances exploitation of spatial and temporal locality. Temporal locality is exploited by selectively moving small blocks into the direct‐mapped cache after monitoring their activity in the spatial buffer. Spatial locality is enhanced by intelligently prefetching a neighboring block when a spatial buffer hit occurs. We show that the prefetch operation is highly accurate: over 90% of all prefetches generated are for blocks that are subsequently accessed. Our results show that the system enables the cache size to be reduced by a factor of four to eight relative to a conventional direct‐mapped cache while maintaining similar performance.     

Partial video sequence caching scheme for VOD systems withheterogeneous clients

Video on demand (VOD) is one of the key applications in the information era. A hinge factor to its widespread use is the huge bandwidth required to transmit digitized video to a large group of clients with widely varying requirements. This paper addresses issues of heterogeneous clients by proposing a program caching scheme called the partial video sequence (PVS) caching scheme. The PVS caching scheme decomposes video sequences into a number of parts by using a scalable video compression algorithm. Video parts are selected to be cached in local video servers based on the amount of bandwidth that would be demanded from the distribution network and central video server if it was only kept in the central video server. We also show that the PVS caching scheme is suitable for handling vastly varying client requirements     

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

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 p...     

Cross-Layer Optimized Rate Adaptation and Scheduling for Multiple-User Wireless Video Streaming

We present a cross-layer optimized video rate adaptation and user scheduling scheme for multi-user wireless video streaming aiming for maximum quality of service (QoS) for each user,, maximum system video throughput, and QoS fairness among users. These objectives are jointly optimized using a multi-objective optimization (MOO) framework that aims to serve the user with the least remaining playback time, highest delivered video seconds per transmission slot and maximum video quality. Experiments with the IS-856 (1timesEV-DO) standard numerology and ITU pedestrian A and vehicular B environments show significant improvements over the state-of- the-art wireless schedulers in terms of user QoS, QoS fairness, and the system throughput.     

Hybrid layered video encoding and caching for resource constrained environments

Video playback on a mobile device is a resource-intensive task. Since the battery life of a mobile device decreases with time, it is desirable to have a video representation which adapts dynamically to the available battery life during the playback process. A novel Hybrid Layered Video (HLV) encoding scheme is proposed, which comprises of content-aware, multi-layer encoding of texture and a generative sketch-based representation of the object outlines. Different combinations of the texture- and sketch-based representations are shown to result in distinct video states, each with a characteristic power consumption profile. Further, a smart content-aware caching scheme is proposed which is suitable for low-latency dissemination of HLV over the Internet. The proposed HLV representation, combined with the proposed caching scheme, is shown to be effective for video playback and dissemination on power-constrained mobile devices.     

Cache‐at‐relay: energy‐efficient content placement for next‐generation wireless relays

Uploading and downloading content have recently become one of the major reasons for the growth of Internet traffic volume. With the increasing popularity of social networking tools and their video upload/download applications, as well as the connectivity enhancements in wireless networks, it has become a second nature for mobile users to access on‐demand content on‐the‐go. Urban hot spots, usually implemented via wireless relays, answer the bandwidth need of those users. On the other hand, the same popular contents are usually acquired by a large number of users at different times, and fetching those from the initial content source each and every time makes inefficient use of network resources. In‐network caching provides a solution to this problem by bringing contents closer to the users. Although in‐network caching has been previously studied from latency and transport energy minimization perspectives, energy‐efficient schemes to prolong user equipment lifetime have not been considered. To address this problem, we propose the cache‐at‐relay (CAR) scheme, which utilizes wireless relays for in‐network caching of popular contents with content access and caching energy minimization objectives. CAR consists of three integer linear programming models, namely, select relay, place content, and place relay, which respectively solve content access energy minimization, joint minimization of content access and caching energy, and joint minimization of content access energy and relay deployment cost problems. We have shown that place relay significantly minimizes the content access energy consumption of user equipments, while place content provides a compromise between the content access and the caching energy budgets of the network. Copyright © 2015 John Wiley & Sons, Ltd.     

Continuous-Time Collaborative Prefetching of Continuous Media

The real-time streaming of bursty continuous media, such as variable-bit rate encoded video, to buffered clients over networks can be made more efficient by collaboratively prefetching parts of the ongoing streams into the client buffers. The existing collaborative prefetching schemes have been developed for discrete time models, where scheduling decisions for all ongoing streams are typically made for one frame period at a time. This leads to inefficiencies as the network bandwidth is not utilized for some duration at the end of the frame period when no video frame ldquofitsrdquo into the remaining transmission capacity in the schedule. To overcome this inefficiency, we conduct in this paper an extensive study of collaborative prefetching in a continuous-time model. In the continuous-time model, video frames are transmitted continuously across frame periods, while making sure that frames are only transmitted if they meet their discrete playout deadlines. We specify a generic framework for continuous-time collaborative prefetching and a wide array of priority functions to be used for making scheduling decisions within the framework. We conduct an algorithm-theoretic study of the resulting continuous-time prefetching algorithms and evaluate their fairness and starvation probability performance through simulations. We find that the continuous-time prefetching algorithms give favorable fairness and starvation probability performance.