P2P流媒体服务质量关键技术的研究

流媒体应用已成为当今互联网承载的主要业务之一,如何支持大规模用户在线使用流媒体,并保障流媒体的服务质量(QoS)尤为重要。依据P2P技术的特点和流媒体系统的发展,对比分析了典型流媒体系统的流服务策略,总结归纳了系统的优点与不足。以节点选择机制、数据调度机制、缓存机制、容错机制、激励机制为评价指标,重点对当前流媒体系统服务质量研究进行评述。最后对保障大规模可信流媒体服务质量的研究方向进行了展望。     

一种基于响应度的P2P点播流媒体系统激励机制

针对P2P点播流媒体系统中的搭便车问题,提出了一个基于结点响应度的激励机制GBIM(Responsivity Based Incentive Mechanism).该机制根据结点对来自其它结点数据请求的响应度提供不同网络服务质量,从而激励邻居结点彼此协作,更多地贡献带宽资源,使系统效用最大化.仿真实验表明:GBIM机制促进了系统效用的增长,提高了系统的吞吐量,达到了激励节点参与资源共享的目的.     

P2P流媒体关键技术研究

探讨在Peer节点服务能力的异构性、节点的动态性以及流媒体本身的特殊性下,使P2P流媒体系统保证服务质量的关键技术.从拓扑构建、调度策略、缓存机制三个方面总结P2P流媒体系统涉及的节点选择算法、节点定位方法、数据调度算法、缓存的替换和中继算法等关键技术,分析其存在的问题,指出P2P流媒体关键技术的未来研究方向,对P2P流媒体系统的研究和开发具有重要意义.     

一种基于反馈偏好的P2P信任模型

在P2P网络中,现有的信任模型中的反馈评价只是对服务质量简单评价,不能准确反映该节点的其他方面.不同的节点关注的反馈评价不同,信任模型不仅需要对服务可信度进行评价,还要对用户关心的其他问题进行评估.由于实验基于文件共享系统,我们将从文件可信度、带宽、服务过程、性能等方面计算出节点的信任值,在保证节点可信的情况下,根据用户的侧重点不同,其值有较大的不同.仿真实验表明,该模型不仅能够有效的抵御恶意攻击,而且能够满足用户的偏好需求,并且提供的评价更加客观、真实.     

基于平衡多叉树的P2P网络拓扑研究

为了进一步提高P2P网络的服务质量,构建性能更为优良的P2P网络,提出了一种新的基于平衡多叉树P2P网络(MBTN)拓扑构建方案,对相关的调度算法进行了研究,并详细阐述了在该拓扑网络上节点加入和退出算法.最后,从节点平均恢复时间、平均延迟时间两方面对MBTN拓扑结构组播网络上的P2P业务进行仿真试验.实验表明,基于MBTN仿真出的拓扑网络可以有效减少节点恢复时间和延迟时间,较好地降低了控制成本.     

一种P2P文件共享系统的QoS评价模型

在分析了P2P分层体系结构的基础上,结合P2P文件共享系统应用提出了重叠网络层和应用层的QoS评价模型,并进一步形成了整体QoS评价模型.仿真实验分析了节点的加入和退出、节点的能力和上传策略、节点缓存大小和节点缓存策略等因素对QoS的影响.另外,文件的热度也是影响系统QoS的一个重要因素.     

基于市场机制的P2P流媒体网络节点选择算法

针对P2P流媒体网络中的节点选择问题,将移动代理引入P2P网络,建立起用于有效实现P2P网络节点的市场化节点选择模型.基于该模型,进一步提出了一种基于市场机制的自适应节点选择算法MANS:通过模拟市场经济中的价格机制适时调整节点的带宽价格,并动态划分节点角色,依据所建立的评价模型选择最优节点,进行数据服务.最后将该模型与MANS算法运用于直播场景,对仿真结果进行了分析并和静态选择算法进行了比较.     

一种P2P网络信任模型METrust

 Peer-to-Peer(P2P)网络的异构性、匿名性、自治性等特点导致了一些安全问题,比如伪造、诋毁、协同作弊等,影响了服务质量.提出了一种基于推荐的P2P网络信任模型METrust,节点在网络中拥有唯一的推荐可信度,引入了更新幅度和更新力度两个参数来更新推荐可信度.给出了节点推荐可信度的更新算法;节点根据评价标准的相似程度选择推荐,其中节点的评价标准通过AHP(Analytic Hierarchy Process)方法确定.仿真实验表明,METrust信任模型可以识别恶意节点,有效提高P2P网络的服务质量.     

基于P2P点播系统的数据调度优化策略设计

数据调度策略将直接影响P2P流媒体点播系统的媒体信息完整性与节点用户的媒体信息播放流畅度,并决定用户的观影体验。然而传统的数据调度算法只考虑媒体信息的播放流畅性,并未从提高系统的媒体信息完整性方面考虑。本文所介绍的策略综合考虑P2P分布结构特点,通过引用滑动窗口机制保证媒体信息播放流畅性,并根据媒体信息数据块的提供者数量而提出普通窗口机制,提高系统的媒体信息完整性和系统媒体信息播放流畅度。     

P2P VoIP关键技术分析

1.P2P技术的特点 P2P最根本的思想就是网络中的节点（peer）既可以获取其它节点的资源或服务同时又是资源或服务的提供者。一般P2P网络中每一个节点所拥有的权利和义务都是对等的．包括通讯、服务和资源消费。     

Telesurgery QoS improvement over SDN based on a Type‐2 fuzzy system and enhanced cuckoo optimization algorithm

Telemedicine is a new area based on the information and communication technology for collecting, storing, organizing, retrieving and exchanging medical information. One of the most important applications of telemedicine is indeed telesurgery in which an efficient telecommunication infrastructure between the surgery room and remote surgeons need to be established. One of the most important issues to be tackled in telesurgery is to find favorable links for routing as well as providing high Quality of Service (QoS). In this paper, an efficient model based on the hybridization of Type‐2 Fuzzy System (T2FS) and Cuckoo Optimization Algorithm (COA) over the Software Defined Networks (SDN) is proposed in order to achieve optimal and reliable routes for telesurgery application. Using T2FS, the fitness of the links is determined; then, a COA is conducted over the Constraint Shortest Path (CSP) problem to find the best routes. Delay is considered as a CSP problem which is satisfied by trying to find the paths with minimum cost. Due to the NP‐completeness of the CSP problem, an Enhanced COA (so‐called E‐COA) is proposed and utilized as a metaheuristic solver. To the best of our knowledge, this paper is the first SDN‐based communication model that applies both T2FS and E‐COA for assigning proper costs to the network's links, and solves the consequence CSP problem according to the QoS requirement for telesurgery. The model also recognizes and preserves the second‐best routes in order to keep the reliability for such a critical application. In addition to the simulations, the performance evaluation is also conducted on a real experimental scenario. Many comparisons are carried out between the proposed model and other conventional methods, and the evaluation study shows the superiority of the proposed model on all the three QoS‐related metrics, i.e. average end‐to‐end delay, packet loss ratio and PSNR.     

An Ant-based Multipath Routing Algorithm for QoS Aware Mobile Ad-hoc Networks

In the wireless ad-hoc network management, Quality of Service (QoS) is an important issue. Along with the QoS ensuring, another desirable property is the network reliability. In data communications, multi-path routing strategy can cope with the problem of traffic overloads while balancing the network resource consumption. In this paper, we propose a new multipath routing algorithm for QoS-sensitive multimedia services. Based on the ant colony optimization technique, the proposed algorithm can establish effective multi-paths to enhance the network reliability. According to the load balancing strategy, data packets are adaptively distributed through the established paths while maintaining an acceptable level of QoS requirement. The most important feature of the proposed approach is its adaptability to current traffic conditions. Simulation results indicate the superior performance of the proposed algorithm, while other schemes cannot offer such an attractive performance balance.     

下一代网络中基于遗传算法的QoS组播路由算法

向用户提供多媒体业务是下一代网络业务最基本、最重要的要求,QoS组播路由技术是网络多媒体信息传输的核心技术之一。该文给出了支持QoS组播的网络模型,对已有的QoS组播路由算法进行了优化,提出了适用于下一代网络的基于遗传算法的QoS组播路由算法。仿真实验表明,这种算法收敛速度快,可靠性高,能够很好地满足下一代网络QoS组播的需求。     

MULTIPLE ATTRIBUTE NETWORK SELECTION ALGORITHM BASED ON AHP AND SYNERGETIC THEORY FOR HETEROGENEOUS WIRELESS NETWORKS简

It is a hot issue in communication research field to select the best network for Heteroge- neous Wireless Networks （HWNs）, and it is also a difficult problem to reduce the handoff number of vertical handoff. In order to solve this problem, the paper proposes a multiple attribute network se- lection algorithm based on Analytic Hierarchy Process （AHP） and synergetic theory. The algorithm applies synergetics to network selection, considering the candidate network as a compound system composed of multiple attribute subsystems, and combines the subsystem order degree with AHP weight to obtain entropy of the compound system, which is opposite the synergy degree of a network system. The greater the synergy degree, the better the network performance. The algorithm takes not only the coordination of objective attributes but also Quality of Service （QoS） requirements into consideration, ensuring that users select the network with overall good performance. The simulation results show that the proposed algorithm can effectively reduce the QoS according to different services. handoff number and provide uses with satisfactory     

基于双层P2P架构的VoD系统

本文提出的视频点播系统基于双层P2P架构实现,由城域网与驻地网媒体内容分发构成2级数据分发服务平台,用户终端点播并接受视频服务的同时,还能为其他用户提供数据服务,双层P2P架构有效地扩展了系统带宽,增强了服务能力,降低了系统成本,并提供QoS保证.     

一种基于QoS的QoE到SLA映射方法

该文提出一种算法IQoE2QoS(Improved QoE to QoS),采用模糊理论的方法计算QoE到QoS的映射。该算法有3重目标:从大量的经验数据中通过计算互信息量方式总结被统计指标之间的关联程度。在大量经验数据的基础上通过多指标模糊判定理论将用户感知映射到应用层用户QoS参数。考虑了用户的QoE和QoS的双向映射,并且阐述了得到的QoE如何自然映射到SLA(Service Level Agreement)。通过仿真表明,IQoE2QoS算法对用户体验的分类准确度是线性回归算法的2到3倍。     

A NEW SCHEDULING ALGORITHM TO PROVIDE PROPORTIONAL QOS IN OPTICAL BURST SWITCHING NETWORKS

A new scheduling algorithm, which aims to provide proportional and controllable QoS （Quality of Service） in terms of burst loss probability for OBS （Optical Burst Switching） networks, is proposed on the basis of a survey of QoS schemes in current OBS networks. With simulations, performance analysis and comparisons are carried out in detail. The results show that, in the proposed scheme, burst loss probabilities are proportional to the given factors and the control of QoS performance can be achieved with better performance. This scheme will be beneficial to the OBS network management and the tariffpolicy making.     

NOVEL MULTIMEDIA TRAFFIC MODELING BASED CAC SCHEME FOR CDMA COMMUNICATION SYSTEMS

As the radio spectrum is a very scarce resource, the Call Admission Control （CAC） is one of the most important parts in radio resource management. The Code Division Multiple Access （CDMA） based next generation wireless communications systems will support the transmission of multimedia traffic, such as voice, video and data, thus the CAC, which can support the multimedia traffic and guarantee the Quality of Service （QoS） of different traffic, has gained broad attention. In this paper, a novel multimedia traffic modeling method and a corresponding dynamic QoS based CAC are proposed. The analysis and simulation results show that the proposed CAC scheme can guarantee the QoS to different traffic demand, and improve the system performance significantly.     

无线传感器网络链路层组确认机制的研究与实现

实验测量发现WSNs的底层通信链路存在着丢失、非对称等特性;该文针对传统链路层可靠机制运用于无线传感器网络中存在着路径效率低,能量开销大的缺点,提出了一种面向效率的链路层组确认机制,并就路径效率、缓存需求、时间开销等指标进行了理论分析;最后,与传统链路层可靠传输机制在MicaZ平台上分别加以实现.测试结果表明该文提出的组确认机制的路径效率高、缓存需求固定,特别适合于高可靠,低实时要求的一类应用.     

基于用户个性化服务质量的蜂窝车联网与车载自组织网异构车联网资源分配方法

蜂窝车联网(C-V2X)与车载自组织网络(VANET)的异构融合能够有效提高网络容量.然而,不同网络在非授权频段上共存而引起的信道冲突会导致系统吞吐量降低和用户接入时延增大,无法满足车联网用户对服务质量(QoS)的需求.针对该问题,该文提出一种基于用户个性化QoS需求的时频资源分配方法.首先,分别对C-V2X 和 VANET 的吞吐量和时延进行建模分析,刻画用户数据传输时间配置与吞吐量和时延的数学关系;然后,基于上述模型构建吞吐量-时延联合优化函数,根据用户的个性化QoS需求实现异构网络中吞吐量和时延的优化;最后,提出一种基于改进多目标粒子群优化的时延-吞吐量联合优化算法(DT-JOA)进行求解.仿真结果表明,该文所提网络资源分配算法可以有效地保证用户的个性化QoS需求,提升异构网络综合性能.