基于图着色的P2P流媒体数据调度算法

为了提高P2P流媒体的传输性能,提出一种基于图着色的数据调度算法。算法规定加入系统的每个节点和数据块都被分配某种颜色,请求节点优先获取相同颜色的数据块。根据数据稀有性、紧急性、新鲜性定义数据块优先级别,同时评估伙伴节点数据提供能力,以选择恰当的数据提供者。该算法能有效平衡节点负载,合理利用系统带宽,使数据分布更均匀,提高了系统传输性能。仿真实验表明,算法在数据填充率、启动延迟、数据到达率等重要指标上都优于传统数据调度算法。     

基于综合因素的P2P流媒体数据调度算法

为了提高P2P流媒体数据传输的效率,提出一种基于综合因素的P2P流媒体数据调度算法,该算法综合考虑数据块的提供者数量和紧急程度定义数据块优先级,并对与提供者之间的网络带宽进行有效估计,根据优先级和带宽调度P2P数据请求的次序和方向。仿真结果表明,该调度算法在节点吞吐量和系统连续性指标以及启动延迟方面比传统的P2P流媒体调度算法有明显提高。     

Fine-Granularity Transmission Distortion Modeling for Video Packet Scheduling Over Mesh Networks

Packet scheduling is a critical component in multi-session video streaming over mesh networks. Different video packets have different levels of contribution to the overall video presentation quality at the receiver side. In this work, we develop a fine-granularity transmission distortion model for the encoder to predict the quality degradation of decoded videos caused by lost video packets. Based on this packet-level transmission distortion model, we propose a content-and-deadline-aware scheduling (CDAS) scheme for multi-session video streaming over multi-hop mesh networks, where content priority, queuing delays, and dynamic network transmission conditions are jointly considered for each video packet. Our extensive experimental results demonstrate that the proposed transmission distortion model and the CDAS scheme significantly improve the performance of multi-session video streaming over mesh networks.     

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网络多视点立体视频传输的数据块调度策略

立体视频数据量大、编码结构复杂,因此视频数据块的重要性和紧急程度对视频的播放质量有更大的影响作用。综合考虑立体视频播放质量和网络传输效率,提出一种联合优先级和随机传输的P2P数据块调度算法。依据数据块的重要性、紧急性和稀有性计算传输优先级别,同时评估邻居节点传输能力,利用多余带宽传输随机数据块。该算法能够提供优越的视频播放质量,并能够使数据块均匀分布,保证系统传输性能。仿真实验通过分析视频PSNR、启动延迟、节点吞吐量和数据到达率等指标,证明了该算法的有效性。     

无线上行视频流的跨层容错传输方法

如何通过资源受限的移动通信终端提升无线上行视频流的抗误性能是亟待解决的重要问题。通过不同通信层次的联合调度,提出了一种跨层容错传输方案。移动通信终端的网络层代理首先利用容错包调度为视频流的延时约束帧集合提供重要性分类,随后该终端的链路层代理利用无线链路单元的优先级调度实现选择性重传。在调度延时与传输带宽限制下,跨层容错传输能够将突发错误转移到延时约束帧集合的低优先级视频数据中,从而在突发易错传输环境中实现了无线链路单元粒度的渐进式传输和平稳退化。     

P2PVoD中基于束层的调度策略研究与设计

由于P2P环境的高度动态性和异构性,以及流媒体服务的高宽带和连续性强的特征,P2P点播系统中数据片断的调度便显得尤为重要。本文针对基于数据驱动的网状P2P点播系统提出了基于束层的调度策略,通过合理地分配紧急数据片断的调度和非紧急数据片断的调度以保证视频连续播放。模拟实验表明,该调度策略能够很好地保证视频的连续播放。     

An efficient playout smoothing mechanism for layered streaming in P2P networks

Layered video streaming in peer-to-peer (P2P) networks has drawn great interest, since it can not only accommodate large numbers of users, but also handle peer heterogeneity. However, there’s still a lack of comprehensive studies on chunk scheduling for the smooth playout of layered streams in P2P networks. In these situations, a playout smoothing mechanism can be used to ensure the uniform delivery of the layered stream. This can be achieved by reducing the quality changes that the stream undergoes when adapting to changing network conditions. This paper complements previous efforts in throughput maximization and delay minimization for P2P streaming by considering the consequences of playout smoothing on the scheduling mechanisms for stream layer acquisition. The two main problems to be considered when designing a playout smoothing mechanism for P2P streaming are the fluctuation in available bandwidth between peers and the unreliability of user-contributed resources—particularly peer churn. Since the consideration of these two factors in the selection and scheduling of stream layers is crucial to maintain smooth stream playout, the main objective of our smoothing mechanism becomes the determination of how many layers to request from which peers, and in which order. In this work, we propose a playout smoothing mechanism for layered P2P streaming. The proposed mechanism relies on a novel scheduling algorithm that enables each peer to select appropriate stream layers, along with appropriate peers to provide them. In addition to playout smoothing, the presented mechanism also makes efficient use of network resources and provides high system throughput. An evaluation of the performance of the mechanism demonstrates that the proposed mechanism provides a significant improvement in the received video quality in terms of lowering the number of layer changes and useless chunks while improving bandwidth utilization.     

WiMAX网络中基于优先级的视频分组调度算法

无线视频传输是网络传输的研究热点,在WiMAX网络中,实时轮询业务(rtPS)的典型应用是实时视频传输,当前使用较多的是先进先出(FIFO)和最早到达期限数据优先(EDF)队列调度算法,其中EDF算法多用于多业务之间的资源分配,而非单个业务流队列的出对调度。在视频优先级以及WiMAX网络为单个视频流分配带宽限定的条件下进行调度算法的研究,以期待在带宽有限的情况下得到更高的视频服务质量。     

基于改进粒子群算法的P2P流媒体数据调度策略

根据P2P流媒体数据调度特点,改进了粒子群优化算法,并提出适用于离散粒子群算法（MDPSOA）的数字串编码方式。调度策略引入资源紧急度以及资源稀缺度来选择调度数据片,然后用改进离散粒子群算法来进行节点寻优,找出最优调度节点集。最后通过实验仿真算法收敛性、数据调度时间、网络利用带宽和节点负载平衡,从而验证调度策略的可行性和有效性。     

Investigating the Scheduling Sensitivity of P2P Video Streaming: An Experimental Study

Peer-to-peer (P2P) technology has recently been employed to deliver large scale video multicast services on the Internet. Considerable efforts have been made by both academia and industry on P2P streaming design. While academia mostly focus on exploring design space to approach the theoretical performance bounds, our recent measurement study on several commercial P2P streaming systems indicates that they are able to deliver good user quality of experience with seemingly simple designs. One intriguing question remains: how elaborate should a good P2P video streaming design be? Towards answering this question, we developed and implemented several representative P2P streaming designs, ranging from theoretically proved optimal designs to straightforward “naive” designs. Through an extensive comparison study on PlanetLab, we unveil several key factors contributing to the successes of simple P2P streaming designs, including system resource index, server capacity and chunk scheduling rule, peer download buffering and peering degree. We also identify regions where naive designs are inadequate and more elaborate designs can improve things considerably. Our study not only brings us better understandings and more insights into the operation of existing systems, it also sheds lights on the design of future systems that can achieve a good balance between the performance and the complexity.      

Cooperative Media Data Streaming with Scalable Video Coding

Live peer-to-peer (P2P) streaming has become a promising approach for broadcasting non-interactive media content from a server to a large number of interested clients. However, it still faces many challenges such as high churn rate of peer clients, uplink bandwidth constraints of participating peers, and heterogeneity of client throuput capacities. This paper presents a new P2P network called LSONet, a collaborative peer-to-peer streaming framework for scalable layer-encoded bit streams. The contributions are the combination of the advantages of both layered conding and mesh-based packet exchange. With layered coding, it overcomes overlay bandwidth limitatioins and heterogeneity of client capacities. With mesh based overlay streaming, it can better handle peer churns, as compared to tree-based solutions. For achieving these targets, this paper employs a gossip-based data-driven scheme for partnership formation, and proposes two algorithms, optimized transmission policy (OTP) and graceful degradation scheme (GDS), for multi-layers allocation. The proposed system is completely self-organizing, and in a fully distributed fashion. Extensive simulations show that LSONet achieves higher quality of service by peer-assisted streaming and layered video coding. Also, through comparison, results show that the system outperforms some previous schemes in resource utilization and is more robust and resilient for nodes departure, which demonstrate that it is well-suited for quality adaptive live streaming applications.     

User density sensitive P2P streaming in wireless mesh networks

Link rate allocation is very important for supporting high video playback rate in Peer-to-Peer video streaming. Although many studies can be found on resource allocation in P2P streaming in wired networks, very few studies have studied the problem in wireless networks, especially in Wireless multi-hop Mesh Networks (WMNs), which is still challenging. To maximize the users’ satisfaction of P2P streaming in WMNs, this paper focuses on link rate allocation problem and proposes a fully distributed algorithm to efficiently utilize the upload and download bandwidth of wireless mesh nodes. We first build an efficient P2P streaming system based on the experimental results from real deployment of our wireless mesh testbed. Then we design an efficient distributed algorithm based on the solution to a linear optimization model, which optimizes towards a user-density-related objective to decide the best streaming rates among peers. Our scheme is resilient to network dynamics that is characteristic in wireless multi-hop peer-to-peer networks. The simulation experiments demonstrate the significant performance enhancement by using the proposed rate allocation algorithm in WMNs.     

无线网状网多源多径组播P2P流媒体分发

由于无线网络相邻链路间信号相互干扰,无线网状网中P2P流媒体分发不能直接利用现有有线网络P2P流媒体分发的调度算法.为提高无线网状网P2P流媒体分发质量,通过引入流媒体传输率失真模型和组播无线信号干扰模型,提出一种跨层多源多径组播调度策略,并采用改进的遗传算法对该策略进行实现.与多源多径单播调度算法相比,由于多源多径组播调度算法利用了无线网络实质采用广播方式传输数据的特点,能有效的减少流媒体数据传输冲突概率.仿真实验表明,多源多径组播调度算法更能有效的提高无线网状网P2P流媒体分发质量.     

基于SVC的P2P流媒体系统研究综述

根据数据传输系统架构的不同,将基于SVC的P2P流媒体系统分为tree型、混合型和mesh型三类;针对这三种类型研究进行深入调研,对现有关键技术进行总结,并指出当前工作的不足及未来的研究方向。其中mesh型系统中的关键技术是介绍的重点。     

SecP2PVoD: a secure peer-to-peer video-on-demand system against pollution attack and untrusted service provider

The Peer-to-Peer video-on-demand (P2P-VoD) streaming has become widespread in recent years. Unlike the traditional client-server model based video-streaming, the P2P-VoD leverages the peer’s capacity of upload bandwidth for the delivery of video contents in a distributed network. The P2P environment is susceptible to various security threats, in which the pollution attack is one of the potentially destructive threats. Moreover, video streaming is prone to other security challenges, such as authenticity, confidentiality, authorization, and integrity. There have been discussed four possible protection to the pollution attack: blacklisting, hash verification, traffic encryption, and chunk signing. In this paper, we present escrow-free identity-based signcryption (EF-IDSC) scheme for secure data transmission scheme in P2P-VoD streaming with an untrusted service provider. The proposed system enables a peer to establish a session key with other peer using the asymmetric key algorithm. The security analysis shows that the proposed P2P-VoS system prevents pollution attacks under well-known random oracle model and achieves privacy, confidentiality, and subscriber authentication simultaneously. The experimental evaluation shows that the proposed scheme has better computation and communication costs as compared to the related schemes.

     

InstantLeap: an architecture for fast neighbor discovery in large-scale P2P VoD streaming

In large-scale peer-to-peer (P2P) video-on-demand (VoD) streaming applications, a fundamental challenge is to quickly locate new supplying peers whenever a VCR command is issued, in order to achieve smooth viewing experiences. For many existing commercial systems which use tracker servers for neighbor discovery, the increasing scale of P2P VoD systems has overloaded the dedicated servers to the point where they cannot accurately identify the suppliers with the desired content and bandwidth. To avoid overloading the servers and achieve instant neighbor discovery over the self-organizing P2P overlay, we design a novel method of organizing peers watching a video. The method features a light-weight indexing architecture to support efficient streaming and fast neighbor discovery at the same time. InstantLeap separates the neighbors at each peer into a streaming neighbor list and a shortcut neighbor list, for streaming and neighbor discovery respectively, which are maintained loosely but effectively based on random neighbor list exchanges. Our analysis shows that InstantLeap achieves an O(1) neighbor discovery efficiency upon any playback “leap” across the media stream in streaming overlays of any size, and low messaging costs for overlay maintenance upon peer join, departure, and VCR operations. We also verify our design with large-scale simulation studies of dynamic P2P VoD systems based on real-world settings.     

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。     

An incentive scheduling mechanism for peer-to-peer video streaming

P2P video streaming networks are found as a scalable solution and an alternative for traditional client–server based video streaming over the Internet. One of the significant issues affecting the success of any P2P streaming network is cooperation between peers. Practical observations have proved the prevalence of free riders in P2P networks that degrade their performance. To solve this problem, using incentive mechanisms, which encourage peers to contribute more in the network, is necessary. In this paper, we designed and proposed a distributed and scalable incentive mechanism for mesh based P2P video streaming networks. In the proposed approach the contribution of the peers is measured and maintained in a distributed fashion. Furthermore, we proposed an incentive sending side scheduler in which peers are served based on their contribution in the network. Our simulation evaluations show the efficiency of the proposed approach in improving the overall perceived video quality by the non-free rider nodes and consequently in the whole network.