面向SDN网络虚拟化平台的控制器放置算法

随着网络技术发展,以网络虚拟化为手段解决TCP/IP网络体系结构僵化问题已成为未来网络领域发展的主流方向之一.SDN(software defined networking,软件定义网络)作为一种新兴的网络体系结构,为网络虚拟化提供了有效的解决方案.首先总结了当前具有代表性的SDN网络虚拟化平台,并对比了SDN与传统网络环境中部署虚拟网的区别,然后针对SDN网络虚拟化平台中的虚拟网络映射问题,提出一种时延敏感的虚拟化控制器放置算法,最后通过实验验证了该算法在提高网络资源的利用效率的同时,保证了控制器与底层交换机的通信时延在可接受范围之内.     

基于电信边缘云的流量调度研究

电信运营商传统的电信机房面临着大量的运营和运维成本开销,网络功能虚拟化(NFV)与软件定义网络(SDN)也在迅猛发展.本文提出了基于网络功能虚拟化(NFV)与软件定义网络(SDN)的电信边缘云化数据中心流量优化调度机制.电信边缘云有效减少了资本性支出和运营及运维成本,并使得新业务的部署及推广发布具有较高的灵活性和伸缩性,有效增强了业务创新能力.     

网络功能虚拟化弹性和可扩展性研究

在NFV(网络功能虚拟化)过程中,将PNF(物理网络功能)转换为VNF(虚拟化网络功能)会面临诸多挑战。VNF(虚拟化网络功能)支持网络服务的按需部署和弹性增长,助力提升NFV的弹性和可扩展性。文章介绍主机VNF(虚拟化网络功能)和中间盒VNF两种类型,探讨多路径和分布式VNF设计思路,列举与VNF弹性设计相关的v PE(虚拟提供商边缘)实例,阐述NFV和SDN(软件定义网络)之间的关系。     

SDN试验床网络虚拟化切片机制综述

未来网络体系架构和关键技术的研究需要灵活开放的测试验证环境,基于传统分布式的网络架构难以达到动态虚拟化、有效管控和新协议灵活部署的需求。随着软件定义网络（SDN）技术的出现和发展,上述问题找到了有效的解决途径,因此,基于SDN构建网络试验床成为了近年来该领域的主流研究方向之一。其中,基于SDN的网络虚拟化切片技术更是试验床中的核心支撑技术,可以根据不同试验的需求切分物理网络资源,从而提供并行、独立的网络环境。将重点研究基于SDN的试验床中使用的网络虚拟化切片机制,从“流量识别和切片网络标识”、“虚拟节点抽象”和“虚拟链路抽象”这3个关键技术出发,对当前基于SDN试验床中的典型网络虚拟化切片机制进行介绍与分析,并总结了该领域未来可行的研究方向。     

基于SDN的网络虚拟化仿真研究

软件定义网络的集中控制和可编程能力解决了传统网络虚拟化技术的弊端。为了进一步研究网络虚拟化技术,采用Mininet、OpenVirteX和Floodlight等软件,提出一种基于SDN的网络虚拟化仿真平台实现方案。总结了SDN网络和网络虚拟化特性,介绍了基于SDN的网络虚拟化仿真平台的系统架构,验证了其功能和隔离特性。提出的仿真平台为基于SDN技术的网络虚拟化创新提供了良好的平台支撑。     

基于SDN和Overlay的云计算数据中心网络

云计算环境下,为适应计算虚拟化和存储虚拟化对网络的需求,以VXLAN为代表的Overlay、SDN等实现技术和发展思路相继被提出。围绕云计算数据中心存在的问题,提出基于SDN控制的Overlay数据中心网络方案,使得网络的控制更加灵活,更加方便快速的部署网络设备,便于网络的扩展。     

IMS核心网网络功能虚拟化方案研究

网络功能虚拟化将传统网络设备的软件功能和硬件功能解耦合,从而降低网络的投资和运营成本,提高新业务的部署效率。SDN为网络功能虚拟化的承载网提供了解决方案,确保网络功能虚拟化的实现。主要对IMS核心网网络功能虚拟化方案进行了论述,并基于SDN架构提出了IMS核心网虚拟化环境下的承载网组网方案。     

一种面向多样化网络业务融合的SDN网络架构

提出一种支持多样化网络业务融合的软件定义网络(SDN)基础架构——SDNIMS.SDNIMS在数据平面上提供了高灵活度的可编程性,支持以软件定义方式实现不同业务异质化的融合数据转发;利用网络虚拟化,为不同的业务网络提供独立且相互隔离管理控制平面;支持多种业务在统一的SDN网络基础设施中的部署.     

SDN/NFV的发展与挑战

网络云化的趋势已经越来越明显,SDN(软件定义网络)/NFV(网络功能虚拟化)作为其中的关键技术,受到通信业界的广泛关注和重视,标准化组织对其进行了深入研究,在产业链多个环节也得到实践应用。SDN和NFV在快速发展、不断推进的同时,也面临着一些相应的挑战和问题,如安全性、互操作性和性能等,针对这些问题,提出了针对性的应对和解决方案。     

软件定义网络安全优势和挑战研究

为了满足数据流量迅猛增加所带来的持续变化的网络需求,服务提供商需要将其基础设施转变为软件支持的架构。这依赖于两种支撑技术:SDN (软件定义网络)和NFV(网络功能虚拟化)。这些技术不仅可以使网络更具动态性,而且还可以使网络更加安全。文章给出采用非传统访问面临挑战的边界网络模型,介绍SDN和NFV部署带来的安全优势:设计增强、性能改善和实时功能,比较3种类型安全优势的特点,分析SDN和NFV面临的新安全挑战。     

Efficient MAC protocol design and performance analysis for dense WLANs

In this paper, we analytically study the dense basic service set network transmission problems in very high throughput (VHT, namely IEEE 802.11ac) wireless local area networks (WLANs) due to nervous bandwidth resources. Our contributions are threefold as follows. Firstly, we derive the closed-form expressions of throughput gains for primary channel establishment from multi-band selection using the optimal skipping rule, which balances the throughput gain from finding a good quality band with the overhead of measuring multiple bands. Secondly, in order to satisfy the quality of service of overlapping BSS users, we design a space interference avoidance mechanism, which can improve the system throughput for the whole dense WLANs. Thirdly, in order to further improve the transmission performance of dense BSS networks, we propose an unequal bandwidth transmission mechanism based on the VHT WLANs, which can not only clear the redundant network allocation vector duration timely but also use the limited bandwidth efficiently. The proposed protocols and mechanisms exploit both time and frequency diversity sufficiently, and are shown to result in typical throughput gains compared with the traditional IEEE 802.11 MAC protocol.     

Dynamic handover algorithm with interference cancellation in 5G networks for emergency communication

The integration of 5G networks with cognitive radio (CR) technology enables the software‐defined networking (SDN) infrastructure to support emergency applications. In future, CR can be integrated with 5G and many wireless networks like Wi‐Fi, WSN, and MANET for efficient spectrum utilization with higher data rate and lower latency. This CR technology allows unlicensed users to access the licensed spectrum, whenever it is free. In this paper, an efficient SDN architecture with cognitive ability for emergency network is proposed in which the SDN controller prolong communication between disaster victims and first responders and so the first responders can arrive at the spot directly and rescue the victims. The SDN controller has cognitive ability so that the victims can utilize the vacant licensed band to communicate with the first responders, thereby improving the spectrum utilization of the network. Another two main challenges during emergency are the occurrence of interference and link failure. The proposed dynamic handover algorithm with interference cancellation (DHAIC) cancels the interference between the nodes inside the network and performs dynamic handoff, whenever link failure occurs between the cluster head (CH) and the controller. An optimum throughput and minimal delay is achieved to ensure the network performance.     

Performance optimization of smartphones in dual-band high-efficiency and very high throughput mobile networks

Wireless Networks - By focusing on dense areas, 802.11ax high-efficiency wireless (HEW) standard offers some improvements over 802.11ac very high throughput (VHT). The HEW improvements are mainly...     

超密集异构无线网络中基于位置预测的切换算法

在密集异构蜂窝网络和无线局域网络构成的超密集异构无线网络中, 变速移动的车辆终端会面临更加频繁的切换,导致用户服务质量(QoS)变差。该文针对上述问题,首先,利用高斯马尔可夫移动模型,预测车辆下一时刻的位置,筛选出满足终端服务质量的候选网络集,与当前的候选网络集做交运算,其次,当前接入网络不在交集中,则使用变步长的萤火虫算法寻找最佳网络;再次,对因预测误差导致的切换失效,则把终端用户迁移到宏蜂窝,以保证通信的持续性。仿真结果表明,在超密集异构无线网络中,使用该文所提算法能够减少乒乓切换等频繁切换现象,同时,提升了用户的服务质量和网络吞吐量。     

宽带无线网络的新选择——Wi-Fi分流

以iPhone为代表的智能手机及笔记本电脑,带来了爆发性的数据流量,用Wi-Fi分流部分用户数据已渐成潮流。文章认为通过引入智能天线技术可以增强信号覆盖能力,改良AP/AC能够减少切换时间,引入PMIP从而提供IP移动,使用相对透明Wi-Fi网络有利于提供新业务。文章提出一种无缝覆盖、无缝切换、满足中速移动的Wi-Fi热区,大大分流了用户的Internet及其他数据,而2G/3G/LTE网络则通过业务区分,继续承载语音及其他高附加值业务。     

基于认知自选择决策树的垂直切换方法研究

在异构无线网络环境下高速移动的终端用户需要随时随地接入网络,然而,在垂直切换过程中,由于终端用户对网络选择的偏好不同以及切换之后网络连接时间和状态难以得到保障,无法满足用户的切换需求。因此,提出了一种支持终端用户高速移动的基于认知自选择决策树的垂直切换方法。该方法首先根据网络属性和终端运动趋势建立相应的切换概率分布,然后根据用户偏好选择相应的决策树进行决策,最后通过对切换后终端的业务类型和运动状态进行反馈分析,提出了反馈认知决策方法。仿真结果表明,所提的方法不仅能够保证高速移动终端在异构无线网络下的切换质量,而且减少了不必要的切换,保证了网络的及时更新。     

TD-LTE切换问题分析与解决

随着TD-LTE无线网络的初具规模,网络优化成为网络建设的重点。切换性能的优化是网络优化中的重要工作之一,TD-LTE采用的是硬切换技术,为了保证通话不中断,有必要对系统可能存在的切换问题进行研究,从而使切换性能达到最佳。     

Performance Analysis of an Improved Common Radio Resource Management Algorithm Based on Load Balance and Service Characteristics

In order to provide users with satisfactory quality of service and reduce service cost as much as possible, a key issue is how to manage radio resources reasonably and effectively in heterogeneous wireless networks (HWNs). Based on load balance and service characteristics, a common radio resource management (CRRM) algorithm for HWNs consisting of CDMA2000 and IEEE802.11 is proposed. The proposed algorithm selects appropriate access and handoff networks for new and handoff calls respectively, according to users’ mobility characteristic, location information, service type and network load. The performance of the proposed algorithm is analyzed based on a three-dimensional Markov chain model. Based on the HWNs model and handoff rate analysis, the model’s parameters are determined. In order to resolve the steady-state distribution of the three-dimensional Markov model, successive over-relaxation iteration method is adopted to work out steady state equations. According to the steady state probabilities of the Markov model, the closed formulas of HWNs performance metrics are given to evaluate the proposed CRRM algorithm, e.g. call blocking probability, handoff blocking probability, throughput, and service cost. For the purpose of illustrating advantages of the proposed algorithm, two other CRRM algorithms are employed for comparison. The simulation results show that the proposed algorithm can effectively reduce call blocking probability, and improve HWNs throughput.     

无线异构网络中带有动态权值的新型垂直切换算法

In order to enhance the quality of vertical handoff in an overlay wireless network, multiple attributes are taken into account when optimizing the vertical handoff decision including user-based and network-based QoS factors. In this paper, we develop a novel vertical handoff algorithm in an integrated 3G cellular and Wireless LAN networks. The proposed algorithm can adjust the weight of each QoS attribute dynamically as the networks change, trace the network condition and choose the optimal access point at transient regions. Simulation results show that this algorithm is able to provide accurate handoff decision, resulting in small unnecessary handoff numbers, good performance of throughput and handoff delay in heterogeneous environments.