支持IPTV业务的可控组播设计

根据大规模接入汇聚路由器(ACR)的总体结构,提出了一种支持IPTV业务的可控组播设计方案,从而满足IPTV业务的运营管理需求.     

基于大规模接入汇聚路由器的IPTV系统

介绍网络电视（IPTV）和组播技术的概念，及实现IPTV业务必须的关键技术，给出了在大规模接入汇聚路由器上实现IPTV业务的一种系统结构。     

一种可承载IPTV的大规模接入汇聚路由器

提出了一种大规模接入汇聚路由器,使用光以太网点对点接入技术,把用户直接接入核心网络,可完整地承载IPTV业务.     

基于组播技术的IPTV承载网部署探讨

本文在三网融合和IPTV发展的背景下,首先阐述了IPTV业务概念、IPTV业务对承载网的需求,分析了承载网与IPTV业务结构、单播和组播方式部署IPTV业务的差异,然后通过承载网三层和二层组播部署、组播RP和SR配置、组播控制三个方面的具体探讨,给出了在IPTV承载网上进行组播部署的要点方案。     

依赖源汇聚点的组播协议

域间组播一直是大范围内部署组播时需要考虑的主要因素。依赖源汇聚点组播是一种基于Chord查找协议的简单有效的域间组播方案，方案中接收者的指定路由器（DR）使用Chord协议获得源RP地址，并加入源RP树。依赖源汇聚点的组播方案是一种域同ASM解决方案；能提供很好的容错性和可扩展性；支持主机移动组播，但不会造成三角路由问题。     

IPTV业务组播复制点下移技术研究与实践

随着光宽普及和视频产业链的成熟,IPTV业务已经成为电信运营商的战略性基础业务.为缓解视频流量压力,实施组播复制点下移势在必行.分析组播复制点下移相关协议、技术原理,分析现网部署面临的难点和对策,给出甘肃电信组播复制点下移方案,展示组播下移所取得的效果.     

EPON组播业务工程故障排查

随着Internet的快速发展和三网融合的具体实施,网络传输和处理能力大幅提高使得宽带用户快速增长,以IPTV为代表的视频业务也将得到迅速发展.笔者在某通信公司PON项目组给予的良好科研环境和大力支持下,对PON系统的相关技术和组播技术及其应用进行了深入地研究,并以IPTV视频业务为例,提出了在PON系统上组播技术的工程故障排查步骤.     

IP DSLAM支持IPTV业务的解决方案

IPTV是当前IP网络研究的热点问题.在IPDSLAM上实现IPTV业务必将使原来聚集单一上网业务的DSLAM设备在体系架构、设备功能和设备性能上产生根本性的变化.分析了IP DSLAM支持IPTV组播业务的技术特点,并从IPTV组播控制点的选择、IPTV组播用户认证和接入控制、IPTV业务的运营与管理等方面探讨了IPDSLAM实现对IPTV业务的控制和管理.     

一种分布式ACR中PPPoE快速转发的实现

阐述了大规模接入汇聚路由器(ACR)面向三网融合应用多接入方式的重要意义。在三网融合的大背景下,分析了ACR在网络中所起的作用。基于分布式系统主控与转发分离的思想,分析了PPPoE的原理及流程,并在ACR上实现PPPoE。测试结果表明,基于分布式系统实现的PPPoE能满足大规模接入应用场景,使ACR支持高速宽带接入技术,实现上千台整机并发。     

组播技术在FTTH EPON系统中的应用

随着三网融合和城市光网战略的推进、IPTV业务规模的增长,以及城域网带宽资源的日益紧张,组播技术将会发挥更加重要的作用。近年来,随着互联网的迅速发展,很多高带宽的视频应用逐步走进了人们的生活,如IPTV、视频会议、网络音视频广播、VoD、股市行情发布、远程教     

Quantitative analysis of a hybrid replication with forwarding strategy for efficient and uniform location management in mobile wireless networks

A location management scheme in wireless networks must effectively handle both user location update and search operations. Replication and forwarding are two well-known techniques to reduce user search and update costs, respectively, with replication being most effective when the call to mobility ratio (CMR) of the user is high, while forwarding is most effective when the CMR value is low. Thus, based on the user's CMR, the system can adopt a CMR threshold-based scheme such that if the user's CMR is lower than a threshold, then the system applies the forwarding scheme; otherwise, it applies the replication scheme. Applying different location management schemes based on per-user CMR values introduces undesirable high complexity in managing and maintaining location- related information stored in the system as different system support mechanisms must be applied to different users. In this paper, we quantitatively analyze a hybrid replication with forwarding scheme that can be uniformly applied to all users. The most striking feature of the hybrid scheme is that it can determine and apply the optimal number of replicas and forwarding chain length on a per-user basis to minimize the communication cost due to location management operations while still being able to use the same data structure and algorithm to execute location management operations in a uniform way for all users. We develop a stochastic Petri net model to help gather this information and show how the information obtained statically can be used efficiently by the system at runtime to determine the optimal number of replicas and forwarding chain length when given a use user's profile. We show that the proposed hybrid scheme outperforms both pure replication and forwarding schemes, as well as the CMR threshold-based scheme under all CMR values.     

一种支持树形访问结构的属性基可净化签名方案

在电子医疗档案系统中,用户会频繁更新自己的健康数据.若直接使用现有签名方案保证这些数据的可认证性,在泄露用户身份隐私的同时,也需要大量的计算开销.为了解决上述问题,我们利用属性集合来模糊用户的身份信息,并引入可授权第三方-净化者,提出了一个属性基的可净化签名方案.安全性分析证明,本方案保护了用户的匿名性,同时在标准模型下针对给定策略选择消息攻击具有不可伪造性.通过方案对比分析表明,本方案在有效降低用户签名计算开销的同时,还支持树形访问结构,能在大规模属性集下提供灵活的细粒度访问控制.     

一种基于VCG拍卖的分布式网络资源分配机制

 网络带宽资源分配的不合理是开放性网络环境中的一个突出问题.为抑制用户自私性行为,提出基于VCG(Vickrey-Clarke-Groves)机制的网络资源竞拍分配机制.该机制具有占优策略激励兼容特性,且仅需单维竞价信息.同时给出了指导用户进行策略选取的离散随机式学习算法,进一步分析了该算法的收敛性.仿真结果表明,本文所提出的分配机制通过有效的支付惩罚,使自私用户主动选择真实带宽需求策略,抑制说谎动机;离散随机式学习算法能够正确地引导用户选择出占优策略,合理分配带宽资源.     

IDRMS: an improved dynamic replication management scheme for cloud storage

Cloud storage is getting more and more popular as a new trend of data management. Data replication has been widely used as a means of increasing the data availability in large-scale cloud storage systems where failures are normal. However, most data replication schemes do not fully consider cost and latency issues when users need large amounts of remote replicas. We present animproved dynamic replication management scheme (IDRMS). By adding a prediction model, the optimal allocation of replicas among the cloud storage nodes is determined that the total communication cost and network delay are minimal. When the local data block is frequently requested, the data replicas can be moved to a closer or cheaper node for cost reduction and increased efficiency. Moreover, we replace the B+ tree with the B*tree to speed up the search speed and reduce workload with the lowest blocking probability. We define the value of popularity to adjust the placement of replicas dynamically. We divide the data nodes in the network into hot nodes and cool nodes. By changing to visit cool nodes instead of hot nodes, we can balance the workload in the network. Finally, we implement IDRMS in Matlab simulation platform and simulation results demonstrate that IDRMS outperforms other replication management schemes in terms of communication cost and load balancing for large-scale cloud storage.     

DS-CDMA系统中结合多用户检测的功率控制研究

功率控制和多用户检测是CDMA移动通信中克服远近效应,抑制多址干扰(MAI)的两项关键技术。该文提出了一种在DS-CDMA系统中综合考虑功率控制和多用户检测的方案。该方案能更加有效地消除干扰信号,同时在满足信干比(SIR)要求时,所有用户发射总功率最小,收敛速度最快。     

云化IP城域网中vBRAS池化部署研究

云网融合/云网一体已成为IP承载网的主要发展方向。作为最贴近用户的承载网，IP城域网拥有丰富的业务特性，是网络云化转型的重要试验田。面向多元接入、流量流向变化等网络承载需求，IP城域网从传统南北向树状架构向城域Spine-Leaf架构转型，以适应固移融合、多云接入等新型业务场景。基于云化IP城域网演进，对v BRAS池化部署方案及关键技术进行详细剖析，为v BRAS规模商用部署和技术演进提供技术参考。     

基于IPv6的大规模接入汇聚路由器的设想和实现

针对下一代互联网面临的新业务拓展和安全性服务问题,本文综述了对未来网络的可运营、可管理和可控制的综合要求,提出了基于IPv6的大规模接入汇聚路由器(converging router access,ACR)的新概念,并分析了ACR工程实现的若干关键问题.ACR的提出不仅打破了大容量高性能路由器仅在核心骨干网络中使用的传统观念,开辟了大容量高性能路由器新的应用环境,而且为在下一代互联网中开展大规模、高速稳定和安全可靠的宽窄带新业务提供了创新的技术途径.     

Mitigating Pilot Contamination for Channel Estimation in Multi-cell Massive MIMO Systems

Massive multiple-input multiple-output (MIMO) is a crucial technology platform for the fifth-generation of cellular systems (5G). However, massive MIMO systems are affected by pilot contamination, which influences the data rate of the system. This contamination is caused by the non-orthogonality of the pilot sequences transmitted by users in a cell similar to the neighboring cells. The current study proposes a channel-estimation scheme that employs comprehensive knowledge of large-scale gained by applying an orthogonal pilot reuse sequence to eliminate pilot contamination in edge users with reduced channel quality based on the approximation of large-scale fading, and the performance of this scheme is evaluated using the maximum ratio transmission and zero-forcing precoding techniques. Largely interfering users in neighboring cells are established based on an estimation of large-scale fading, and these users are included in the joint channel processing. The channel quality of users is enhanced by allocating orthogonal pilot reuse sequences to the center user and the edge users based on their levels of pilot contamination estimated from the large-scale fading to mitigate this problem when the number of antenna elements M is infinite. The findings of the simulation indicate that improved channel approximation and reduced performance loss could lead to a high data rate.

     

Roam: A Scalable Replication System for Mobility

Nomadic users require replication to store copies of critical data on their mobile machines while disconnected or poorly connected. Existing replication services do not provide all classes of mobile users with the capabilities they require, which include: the ability for direct synchronization between any two replicas, support for large numbers of replicas, and detailed control over what files reside on their local (mobile) replica. Mobile users must adapt their behavior to match the level of service provided by today's replication systems, thereby hindering mobility and costing additional time, money, and systems management. Roam is a replication system designed to satisfy the requirements of the mobile user. Roam is based on the Ward Model, a replication architecture for mobile environments. Using the Ward Model and new distributed algorithms, Roam provides a scalable replication solution for the mobile user. We describe the motivation, design, and implementation of Roam and report its performance.     

基于深度强化学习的无人机辅助移动边缘计算系统能耗优化

近年来,部署搭载有移动边缘计算(MEC)服务器的无人机(UAVs)为地面用户提供计算资源已成为一种新兴的技术。针对无人机辅助多用户移动边缘计算系统,该文构建了以最小化用户平均能耗为目标的模型,联合优化无人机的飞行轨迹和用户计算策略的调度。通过深度强化学习(DRL)求解能耗优化问题,提出基于柔性参与者-评论者(SAC)的优化算法。该算法应用最大熵的思想来探索最优策略并使用高效迭代更新获得最优策略,通过保留所有高回报值的策略,增强算法的探索能力,提高训练过程的收敛速度。仿真结果表明与已有算法相比,所提算法能有效降低用户的平均能耗,并具有很好的稳定性和收敛性。