Optimized P2P streaming for wireless distributed networks

The future Internet will support pervasive applications and communications models that require end-nodes cooperation, such as fog computing and machine-to-machine communications. Among the many applications, also video streaming can be provided with a cooperative and peer-to-peer approach. Cooperative distribution requires building a distribution overlay on top of the physical topology (the underlay). This work proposes an optimized, cross-layer approach to build this overlay minimizing the impact on the underlay. We design an optimal strategy, which is proven to be NP-complete, and thus not solvable with a distributed, lightweight protocol. The optimal strategy is relaxed exploiting the knowledge on the betweenness centrality of the nodes in the underlay topology, obtaining two easily implementable solutions applicable to any link-state protocol for distributed wireless mesh networks. The additional introduction of heuristic improvements further optimizes the performance in real network scenarios. Extensive simulation results support the theoretical findings using three different network topologies. They show that the relaxed implementations are reasonably close to the optimal solution, and provide vast gains compared to the traditional overlay topologies that peer-to-peer applications build.     

无线Mesh网络中的P2P流媒体性能评估

通过搭建基于无线Mesh网络的P2P流媒体点播测试平台,对影响无线Mesh网络中P2P流媒体性能的流媒体编解码方式、编码速率、数据转发路径的选择和跳数四个因素进行了测试。实验结果表明,采用H.264编解码标准更适合无线Mesh网络中流媒体的传输;编码速率必须不大于网络连接速率才能获得高视频质量;P2P技术可以抵抗10%的丢包对视频质量的影响,比采用非P2P技术在视频的前1 000帧视频质量平均高出3 dB;由于P2P技术带来的流间干扰的影响使得1 000帧以后视频质量下降了6 dB,严重影响了流媒体性能;无线Mesh网络的传输能力随着跳数的增加而减弱,但是流媒体质量并未随着跳数的增加而降低。     

Stochastic modelling of peer-assisted VoD streaming in managed networks

Video on Demand is the leading service in Internet Protocol Television environments both in popularity and in quantity of generated traffic. Peer-assisted streaming in combination with an optimal distribution of the video contents on the peers has emerged as one of the most accepted solutions by the operators, especially in the privately managed networks, which helps to alleviate the streaming servers. However, an important question in these environments is how the system parameters and the various distributions of the video contents on the peers would impact the overall system performance. In order to give answers to these questions, we propose a precise and flexible stochastic model that takes into consideration parameters like uplink and storage capacity of the peers, number of peers, size of the video content library, size of contents and content distribution scheme to estimate the benefits of the peer-assisted streaming. We use this model as a tool that helps to find the optimal values of these parameters for best performance, as well as the limits of the system for a given configuration.     

C/S、P2P自适应的流媒体区域传输研究

针对流媒体传输中服务器资源和网络带宽资源的瓶颈问题,提出了局域网络中C/S、P2P自适应的流媒体区域传输模式,分析了系统实现的关键技术。测试表明自适应模式可以有效改善流媒体传输的Qos。     

P2P流媒体网络的关键节点识别算法

P2P流媒体网络中普遍存在一些关键节点,关键节点对网络的安全和通信性能起着重要作用,识别网络中的关键节点尤为重要,而传统方法对于大规模网络的关键节点识别时间开销很大,无法保证实时性。提出P2P流媒体网络中的关键节点识别算法,结合混合模式的网络结构特点,采用分区域的计算模型解决网络规模过大造成的巨大时间开销问题,根据节点的贡献度和传播能力差异定量化描述节点的重要性程度。仿真结果表明,所提算法可以快速获得节点重要性排序,有效识别P2P流媒体网络中的关键节点。     

An efficient scheduling algorithm for scalable video streaming over P2P networks

During recent years, the Internet has witnessed rapid advancement in peer-to-peer (P2P) media streaming. In these applications, an important issue has been the block scheduling problem, which deals with how each node requests the media data blocks from its neighbors. In most streaming systems, peers are likely to have heterogeneous upload/download bandwidths, leading to the fact that different peers probably perceive different streaming quality. Layered (or scalable) streaming in P2P networks has recently been proposed to address the heterogeneity of the network environment. In this paper, we propose a novel block scheduling scheme that is aimed to address the P2P layered video streaming. We define a soft priority function for each block to be requested by a node in accordance with the block’s significance for video playback. The priority function is unique in that it strikes good balance between different factors, which makes the priority of a block well represent the relative importance of the block over a wide variation of block size between different layers. The block scheduling problem is then transformed to an optimization problem that maximizes the priority sum of the delivered video blocks. We develop both centralized and distributed scheduling algorithms for the problem. Simulation of two popular scalability types has been conducted to evaluate the performance of the algorithms. The simulation results show that the proposed algorithm is effective in terms of bandwidth utilization and video quality.     

P2P流媒体播放系统中插播广告的实现技术

为了满足P2P流媒体播放系统中插播广告需求,结合P2P网络的特点,提出了消耗系统内存少的无缝插播广告技术.该技术采用基于资源相关性的流媒体主动预取算法获取广告资源,应用动态共享内存池技术来存储和播放广告.该插播广告技术的应用拓展了广告发布的领域,提高了广告的影响力,增加了广告商的客户量,使P2P流媒体运营商具有更强的竞争力.     

Service quality in P2P streaming systems

Relying on end users to contribute bandwidth to the system peer-to-peer (P2P) overlays provide a cheap and scalable way to distribute live video content in the Internet. However, being inherently dynamic due to peers joining and leaving the system at arbitrary time and running over the best-effort Internet, successful commercial usage of these systems may suffer from unstable media quality provided to end users. In this survey, we consider problems related to providing quality of media delivery in P2P streaming systems. We show that in spite of numerous systems available today no one incorporates mechanisms capable to maintain a certain level of quality of delivered media. We identify reasons behind that and discuss possible solutions to this problem.     

P2P流媒体数据调度研究综述

P2P流媒体通过利用网络上普通主机节点的资源来提供流媒体数据服务,是一种扩展性好、性价比高的流媒体服务体系。数据调度是P2P流媒体研究中的核心问题,流媒体中严格的服务质量要求、Peer节点状态的不稳定性以及其带宽资源的有限性是其面临的主要挑战。介绍了近几年来该领域基于单播树、多组播树和随机拓扑三类典型的数据调度策略的原理特点和Peer节点搜索定位技术的研究进展,指出了未来的几种研究方向。     

PatchPeer: A scalable video-on-demand streaming system in hybrid wireless mobile peer-to-peer networks

Video-on-demand service in wireless networks is one important step to achieving the goal of providing video services anywhere anytime. Typically, carrier mobile networks are used to deliver videos wirelessly. Since every video stream comes from the base station, regardless of what bandwidth sharing techniques are being utilized, the media stream system is still limited by the network capacity of the base station. The key to overcome the scalability issue is to exploit resources available at mobile clients in a peer-to-peer setting. We observe that it is common to have a carrier mobile network and a mobile peer-to-peer network co-exist in a wireless environment. A feature of such hybrid environment is that the former offers high availability assurance, while the latter presents an opportunistic use of resources available at mobile clients. Our proposed video-on-demand technique, PatchPeer, leverages this network characteristic to allow the video-on-demand system scale beyond the bandwidth capacity of the server. Mobile clients in PatchPeer are no longer passive receivers, but also active senders of video streams to other mobile clients. Our extensive performance study shows that PatchPeer can accept more clients than the current state-of-the-art technique, while maintaining the same Quality-of-Service to clients.

Channel allocation in multi-channel wireless mesh networks

In this article, we survey the latest progress in multi-channel wireless mesh networks, focusing on wireless interference models and channel allocation algorithms with the goal of maximizing the network performance. We present the studies of different interference models and illustrate how they could affect the design of channel assignment. We also summarize channel allocation algorithms with different strategies in both omni-directional and directional antenna networks. We conclude that both static and dynamic channel allocation strategies have advantages and disadvantages, and the design of channel allocation algorithms strongly depends on the interference model and the assumption of network traffic.     

基于P2P的流媒体技术

现有的流媒体系统一般是基于客户／服务器模式和IP组播技术,这限制了用户数量且IP组播需先得到ISP支持,故其发展受到很大限制。而在P2P网络中,每个接收数据的用户同时向外转发数据,这就充分利用了以往忽视的客户机资源。首先指出了P2P流媒体应用中所面临的挑战,并着重从应用层多播树、网络异构性、激励机制等方面阐述了P2P流媒体的研究现状,分析讨论了存在的问题,最后指出进一步的研究方向。     

P2P在线视频研究综述*

P2P技术凭借其开放性、可扩展性和高性价比等优点成为了目前解决在线视频问题的有效手段之一。 虽然P2P技术在文件共享和IP语音等方面的应用已经基本趋于成熟,但其在在线视频领域的应用尚处于起步 阶段,还面临着许多需要解决的问题。对P2P在线视频进行了全面而深入的分析,首先介绍了网络广播分类及 体系结构设计,整理和总结了已有的关于P2P在线视频系统的测量研究结果,最后对于P2P在线视频信任和污 染攻击等安全问题进行了概述。     

基于P2P的流媒体直播系统研究与设计

传统的流媒体系统建立在客户-服务器模式的基础上,系统伸缩性差,服务器常成为系统的瓶颈.根据当前流媒体播放系统存在的问题,设计了基于对等网络模式的流媒体直播系统,其中每个节点既是服务的消费者同时又是提供者,克服了当前流媒体系统的服务器瓶颈问题。     

基于P2P的无线mesh网移动性管理研究

无线Mesh网是一种新型的无线组网技术,现有的无线移动管理协议还不能在这一网络结构上直接适用.在典型无线mesh网络分层结构模型上,对现有的几种无线网络移动管理协议进行了比较,并且针对无线mesh网的结构特点提出了一种大型无线mesh网络下的移动性管理方案,采用了基于P2P的分层结构实现网络移动定位信息的自动注册、自动管理和快速查询,同时网络具有较好的负载均衡和抗毁性能.仿真结果表明,与传统的分层移动管理协议相比,该方案可以得到更优化的移动路由.     

基于P2P的流媒体教学系统结构研究

随着计算机网络技术和数字技术的迅速发展,网络教育已经进入了数字化、智能化、个性化的发展阶段。本文致力于研究网络学习系统中的基于P2P流媒体技术的视频教学资源系统平台的构架,为学习者提供一个＂以学习者为中心＂的网络化学习环境。     

结构化P2P网络拓扑匹配技术综述 *

结构化P2P网络中由DHT（分布式哈希表）来决定网络中资源的映射位置,这种方式在系统的可扩展 性和资源的定位速度上都有了很大的提高。但是,在利用DHT构建覆盖网络时,并没有过多地考虑底层物理拓 扑结构,因而产生了逻辑拓扑与物理拓扑的失配问题,造成了很多不必要的路由,降低了资源定位的效率。针对 这种情况进行了大量的文献调研,对结构化P2P网络拓扑匹配现有的算法进行了介绍,分析了各种算法的优缺 点,并在现有算法的基础上进一步展开研究。     

基于应用层签名的P2P流媒体流量识别*

通过对P2P流量识别技术现状的研究,提出了基于应用层签名的P2P流媒体流量识别方法。分析和提取了五种主流P2P流媒体平台的应用层签名特征,并通过实验验证了基于应用层签名的P2P流媒体流量识别方法的有效性。     

基于PeerCast的P2P流媒体多点播放缓存管理设计

随着网络流媒体的广泛应用,P2P流媒体技术作为C/S结构的有力补充越来越引起人们的重视。而现有P2P单点播放系统并没有充分发挥出P2P网络的优势。在研究开源P2P流媒体软件PeerCast的基础上,提出了P2P流媒体多点播放的设计方案,针对如何在多源环境下进行准确有效的缓冲区管理给出了算法实现,并实验证明其稳定性和高效性。     

基于网络编码的P2P应用系统研究进展

将网络编码引入P2P应用系统是当前的研究热点之一。着重介绍基于网络编码的P2P应用系统在国内外的主要研究进展,包括基于网络编码的P2P文件下载系统、基于网络编码的P2P流媒体直播系统和基于网络编码的P2P流媒体点播系统三个方面,并对该方向的研究趋势进行展望。