Dynamic Probabilistic Caching Algorithm with Content Priorities for Content‐Centric Networks

This paper presents a caching algorithm that offers better reconstructed data quality to the requesters than a probabilistic caching scheme while maintaining comparable network performance. It decides whether an incoming data packet must be cached based on the dynamic caching probability, which is adjusted according to the priorities of content carried by the data packet, the uncertainty of content popularities, and the records of cache events in the router. The adaptation of caching probability depends on the priorities of content, the multiplication factor adaptation, and the addition factor adaptation. The multiplication factor adaptation is computed from an instantaneous cache‐hit ratio, whereas the addition factor adaptation relies on a multiplication factor, popularities of requested contents, a cache‐hit ratio, and a cache‐miss ratio. We evaluate the performance of the caching algorithm by comparing it with previous caching schemes in network simulation. The simulation results indicate that our proposed caching algorithm surpasses previous schemes in terms of data quality and is comparable in terms of network performance.     

Dynamic Resource Allocation and Scheduling for Cloud‐Based Virtual Content Delivery Networks

This paper proposes a novel framework for virtual content delivery networks (CDNs) based on cloud computing. The proposed framework aims to provide multimedia content delivery services customized for content providers by sharing virtual machines (VMs) in the Infrastructure‐as‐a‐Service cloud, while fulfilling the service level agreement. Furthermore, it supports elastic virtual CDN services, which enables the capabilities of VMs to be scaled to encompass the dynamically changing resource demand of the aggregated virtual CDN services. For this, we provide the system architecture and relevant operations for the virtual CDNs and evaluate the performance based on a simulation.     

移动流媒体内容传输网络模拟器的设计和实现

通过扩展和修改内容传输网络模拟器CDNsim,设计和实现了更能适应移动流媒体内容传输网络需求的网络模拟器:MSM-CDN模拟器,以缓解MSM-CDN研究中缺少实验环境的限制.MSM-CDN模拟器在CDNsim中新增了入口服务器、管理服务器和无线用户小区等节点,使用了一种能有效减少CPU开销和节省内存空间的路由实现方式以及支持多文件请求的SMIL文件处理算法.实验结果表明,MSM-CDN模拟器能较好地用于MSM-CDN的缓存服务器路由策略、缓存策略和缓存服务器配置的仿真研究.     

基于节点介数和替换率的内容中心网络网内缓存策略

网内缓存技术是内容中心网络(CCN)的关键技术之一,CCN采用传统的ALWAYS缓存策略,会造成较大冗余。改进的Betw方案仅考虑了节点介数,容易造成高介数节点缓存更替频繁,内容可用性下降。为了解决这个问题,该文提出一种综合使用网络节点介数和节点缓存内容更替速率作为缓存决策度量的新型网内缓存策略BetwRep,通过权衡节点位置重要性和缓存内容时效性实现回传内容的最佳放置。最后,基于ndnSIM平台进行的网络仿真表明,该文提出的BetwRep缓存策略取得了比Betw方案和ALWAYS方案更低的源端请求负载和更少的平均跳数。     

移动边缘计算中基于内容流行度的深度强化学习缓存机制

随着5G商用的推进,涌现出大量依赖高速率、低时延的新应用,混合现实(Mixed Reality,MR)就是其中之一.考虑到从中心云传输服务内容到MR设备会带来很大时延和能耗问题,引入移动边缘计算(Mobile Edge Compu?ting,MEC)技术,通过在MEC服务器上缓存用户的预渲染环境帧,以减少延迟和能耗.针...     

内容分发网络研究

内容分发网络是一种以降低互联网访问时延为目的,在网络边缘或核心交换区域部署内容代理服务,通过全局负载调度机制进行内容分发的新型覆盖网络体系.随着多媒体网络流及实时交互技术的兴起,现今内容分发网络已成为互联网的核心应用之一.本文介绍了内容分发网络的演变过程与体系结构,深入剖析了内容分发网络的核心功能组件与工作机制,对当前主流内容分发网络进行分类,并讨论了内容分发网络性能度量,最后探讨了内容分发网络的未来挑战与进一步研究方向.     

雾无线接入网中基于内容流行度和信息新鲜度的缓存更新策略

将边缘缓存技术引入雾无线接入网,可以有效减少内容传输的冗余。然而,现有缓存策略很少考虑已缓存内容的动态特性。该文提出一种基于内容流行度和信息新鲜度的缓存更新算法,该算法充分考虑用户的移动性以及内容流行度的时空动态性,并引入信息年龄(AoI)实现内容的动态更新。首先,所提出算法根据用户的历史位置信息,使用双向长短期记忆网络(Bi-LSTM)预测下一时间段用户位置;其次,根据预测得到的用户位置,结合用户的偏好模型得到各位置区的内容流行度,进而在雾接入点进行内容缓存。然后,针对已缓存内容的信息年龄要求,结合内容流行度分布,通过动态设置缓存更新窗口以实现高时效、低时延的内容缓存。仿真结果表明,所提算法可以有效地提高内容缓存命中率,在保障信息的时效性的同时最大限度地减小缓存内容的平均服务时延。     

基于信息分发管理的内容分发网络模型

介绍了信息分发管理的概念和顶层视图.在此基础上,利用信息分发管理体系构建了一种新的内容分发网络模型,并进一步阐述了该领域未来需要突破的重点研究方面.     

基于内容分发网络的视频通信系统研究

随着宽带技术和业务的发展以及人们对视频通信需求的增长,视频通信业务和技术得到了大规模的发展。首先比较了目前各种实现方案的特点和不足;然后基于内容分发网络技术及系统,提出了一种低成本、高扩展性、高质量视频通信的系统方案,详细叙述了该方案的结构、流程及特点;最后给出了验证系统的初步结果。     

雾网络中基于统计分布的内容缓存与交付方案

作为5G中的一种重要模型,雾无线接入网络(Fog Radio Access Network, F-RAN)通过设备到设备通信和无线中继等技术获得了显著的性能增益,而边缘设备中合适的缓存则可以让内容缓存用户(Caching Users, CUs)向内容请求用户(Requesting Users, RUs)直接发送缓存内容,有效减小前传链路的负担和下载延迟。考虑一个F-RAN模型下用户发出请求并获得交付的场景,将每个CU的内容请求队列建模为独立的M/D/1模型,分析导出CUs缓存命中率和平均下载延迟关于内容缓存与交付方案的表达式,证明CUs缓存命中率与内容统计分布之间的联系有助于实现前者的近似最优解。针对在一段时间内的期望视角下建立的优化问题,提出了基于统计分布的算法并注意了执行时的交付控制。仿真结果表明,相较于现有缓存策略,优化内容整体统计分布的方案能够最大化CUs缓存命中率,同时减小平均下载延迟。     

CCN中基于业务类型的多样化内容分发机制

针对内容中心网络(Content Centric Networking,CCN)如何提供差异化的业务需求服务的问题,采用区分服务的思想,从内容传输和缓存决策的角度出发,提出了一种基于业务类型的多样化内容分发机制.该机制依据不同的业务请求特征,分别设计了持久推送、并行预测和逐包请求的数据分发模式,对应提出了透明转发、边缘概率缓存和渐进式推进的沿途存储策略,实现了内容传递对于业务类型的感知和匹配.仿真结果表明,该机制减小了内容请求时延,提高了缓存命中率,以少量额外的控制开销提升了CCN网络整体的内容分发性能.     

内容分发网络的研究

随着宽带网络和宽带流媒体应用的兴起,内容分发网络（CDN）作为一种提高网络传输内容,特别是流媒体内容传输的服务质量、节省骨干网络带宽的技术,在国内外得到越来越广泛的应用。CDN是一个建立在不同区域的节点服务器组成的虚拟网络,CDN可以实现把互联网上的内容高效、稳定地发送到离网民最近的地方。这里总结介绍CDN出现的原因,CDN的技术基础及其分层模型,流媒体CDN的性能指标。     

Self‐Adaptive All‐In‐One Delivery Chip for Rapid Skin Nerves Regeneration by Endogenous Mesenchymal Stem Cells

Skin wound therapy aims not only to restore skin protection but also to recover excitation functions through nerve regeneration. During the restoration of skin nerves, the recruitment of endogenous stem cells and promotion of neuronal regeneration on site work stepwise are foundations of in situ regeneration. However, current therapeutic systems usually execute each process separately, leading to limited regeneration and recovery of excitation functions. Herein, a novel self‐adaptive all‐in‐one delivery chip (G:P:Al‐Chip) is constructed that combines therapeutic protein release, gene delivery, and electrical conduction in a single microfluidic chip by 3D coaxial printing. G:P:Al‐Chip consists of an outer conductive hydrogel shell anchored with chemokine and an inner microchannel filled with enzyme‐initiated vector/plasmid DNAs microcomplexes. G:P:Al‐Chip delivers chemokine, functional plasmid DNAs, and promotes electrical conduction with a self‐adaptive program that significantly enhances the recruitment of endogenous mesenchymal stem cells and promotes neuronal regeneration. G:P:Al‐Chip is shown to enhance nerve regeneration with excitation functions within 23 days. G:P:Al‐Chip organizes recruitment and neuronal regeneration cues along with bioelectrical signal in one degradable chip for accelerated skin nerve regeneration.     

内容中心网络中基于内容迁移的协作缓存机制

内容中心网络(CCN)是为了适应未来网络通信模式的转变,提供对可扩展和高效内容获取的原生支持而提出一种新型的网络体系架构,内容缓存机制是其研究的关键问题之一。现有机制在缓存节点的选择时往往过于集中,缓存负载分布严重不均,大大降低了网络资源利用率以及系统的缓存性能。该文提出一种基于缓存迁移的协作缓存机制,首先在缓存节点选择时考虑节点的中心性保证内容尽可能缓存在位置更重要的节点。同时,在缓存压力过大时,通过可用缓存空间大小、缓存替换率以及网络连接的稳定性等信息选择合适的邻居节点进行缓存内容的转移,充分利用邻居资源实现负载分担。仿真结果表明该机制能有效地改善缓存负载在节点上分布的均衡性,提高缓存命中率和缓存资源利用率并降低平均接入代价。     

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.     

D2D协作边缘缓存系统中基于传输时延的缓存策略

为了满足5G系统低时延高可靠的需求,针对单缓存终端直传(D2D)协作边缘缓存系统,提出了一种基于传输时延的缓存策略.运用随机几何理论,将请求用户和空闲用户的动态分布建模为相互独立的齐次泊松点过程,综合考虑内容流行度、用户位置信息、设备传输功率以及干扰,推导出用户的平均传输时延与缓存概率分布的关系式.以平均传输时延为目标...     

CAKA: a novel cache‐aware K‐anycast routing scheme for publish/subscribe‐based information‐centric network

In the past few years, many publish/subscribe‐based information‐centric network (PS‐ICN) architectures have been proposed and investigated to efficiently deliver information from content publishers to subscribers. However, most existing studies on PS‐ICN have not considered how to utilize in‐network caches, which is a common but important feature in ICN. To address this issue, in this paper, we propose a novel cache‐aware K‐anycast routing scheme, namely, CAKA, that can significantly improve the performance of content delivery. Specifically, we choose PURSUIT, which is one of the most important PS‐ICN architectures, and leverage its bidirectional communication procedure to do the following: (1) enable multiple publishers to send probing messages to the same subscriber; and (2) allow the subscriber to retrieve content objects using K‐anycast routing and network coding. In this study, we extend the PURSUIT protocol to support cache‐aware K‐anycast routing and design the algorithms to choose multiple partially disjointed paths for probing, and to select paths for content retrieval. To evaluate the performance of the proposed scheme, we develop not only a simulation testbed, but also a prototype running in a realistic network environment. Our studies show that the proposed scheme can significantly reduce the average hops to retrieve content objects, with very small overheads. Copyright © 2015 John Wiley & Sons, Ltd.     

DTMSN中基于效用和网络编码的数据传输

基于SF数据传输策略和网络编码,提出了一种新的数据传输策略,即SF-NC。SF-NC的基本思想是把消息编码后转发给更有可能与数据汇聚节点通信的传感器节点。SF-NC有Spray和Focus这2个阶段组成,前者完成对冗余数据消息的分发,后者根据不同时刻各传感器节点效用值的大小进行编码数据消息的传输。仿真实验结果表明,SF-NC在提高网络的传输性能上比DTMSN中现有的几种数据传输策略要优越。     

基于参数化强化学习的车联网内容缓存和功率分配联合优化

车联网场景下的业务内容具有海量和高度动态的特性,使得传统缓存机制无法较好地感知内容动态变化,且巨量接入设备与边缘缓存设备的有限资源之间的矛盾会引起系统时延性能差的问题。针对上述问题,该文提出一种基于强化学习的联合内容缓存和功率分配算法。首先,考虑联合优化内容缓存和功率分配,建立最小化系统整体时延的优化模型。其次,将该优化问题建模为马尔可夫决策过程(MDP),并进一步将内容缓存和内容提供者的选择映射为离散动作集,并将功率分配映射为与离散动作相对应的连续参数。最后,借助参数化深度Q-Networks (P-DQN)算法求解这个具有离散-连续混合动作空间的问题。仿真结果表明,相较对比算法,该文所提算法能提高本地缓存命中率并降低系统传输时延。     

Virtual‐coordinate‐based delivery‐guaranteed routing protocol in three‐dimensional wireless sensor networks

Because of the wide range of applications, many geographic routing protocols have been proposed in three‐dimensional (3D) wireless sensor networks. However, all the methods require assistance from a global positioning system (GPS), which is not always available. In this paper, we propose a method of constructing an axis‐based virtual coordinate assignment in 3D wireless sensor networks (ABVCap_3D) that requires no GPS assistance. We also propose a routing protocol based on ABVCap_3D, which guarantees packet delivery in 3D networks. Using simulations, we evaluate the performance of ABVCap_3D routing and other well‐known routing protocols, such as greedy‐random‐greedy routing, greedy‐hull‐greedy routing, and the routing based on axis‐based virtual coordinate assignment in 2D wireless sensor networks (ABVCap routing). Simulations show that ABVCap_3D routing requires significantly relative lower cost for guaranteeing packet delivery in comparison with ABVCap routing. Simulations also demonstrate that ABVCap_3D routing ensures a moderate ratio for routing path length to the shortest (ideal) path length. Copyright © 2012 John Wiley & Sons, Ltd.