无线网络负载均衡技术浅析

随着无线局域网扩展服务集中的终端（STA）的移动和无线信道的时变,各个接入点（AP）上的负载会出现差异,需要加强负载均衡,平衡各个AP的差异,以达到最大化的网络资源利用。无线局域网中的负载均衡算法可以采用STA／AP主控负载均衡或接入式／切换式负载均衡技术。     

无线网络负载均衡技术浅析

随着无线局域网扩展服务集中的终端(STA)的移动和无线信道的时变,各个接入点(AP)上的负载会出现差异,需要加强负载均衡,平衡各个AP的差异,以达到最大化的网络资源利用。无线局域网中的负载均衡算法可以采用STA/AP主控负载均衡或接入式/切换式负载均衡技术。     

IEEE 802.11宽带无线局域网负载均衡优化研究*

在基于IEEE 802.11的宽带无线局域网中,随着终端STA的接入、移动和无线信道的时变性,各个接入点（AP）的负载将会产生差异,需要负载均衡优化机制平衡各个AP的差异,以达到网络资源的最大利用率。详细讨论了无线局域网中用到的几种负载均衡机制,分析了各自的优缺点,结合这些特点给出一种新的负载均衡机制。该机制能较准确地统计终端业务信息,降低切换失败风险,快速达到APs之间的负载均衡,优化提高网络整体性能。     

对邻居图重连接算法的改进

基于IEEE802.11的宽带无线局域网,具有低成本、接入快速等优点,得到了飞速发展和广泛应用.但由于终端STA的随机接入、随时移动、无线信道的时变性和AP负载均衡机制的不完善,使得各个接入点AP的负载产生差异,因此需要负载均衡优化机制平衡各个AP,以达到无线网络资源的有效利用.简单介绍邻居图及其相关算法,对邻居图重连接算法进行改进.经仿真分析证明,改进的算法ONG能有效均衡各个AP负载,从而提高AP的QoS(Quality 0f Service),减少时延,增加系统吞吐量.     

无线局域网有效支持智能天线应用的接入时延性能分析

在无线局域网中使用智能天线可以扩展其无线覆盖范围并增加网络容量，由此可以采用一种新型媒体接入控制（MAC）机制，接入点（AP）通过检测用户的空间特征向更远处的用户提供接入．该文针对这种有效支持智能天线应用的无线局域网接入机制，提出一种准确推导的方法，详细分析了接入时延性能，得到最佳协议参数，确定区分AP广播范围内外用户的接入机制以更快速地提供媒体接入，并且通过仿真证明了理论分析的正确性．     

集中无线局域网：简单技术和复杂技术的对比

基于人们对安全、灵活性和无线接入性能的考虑，集中无线局域网正迅速在一些单位网络构架中得到广泛采用。集中无线局域网(WLAN)供应商正为人们提供了一种简单的、具有一定性价比的无线接入点(AP)，这种无线接入点通过采用无线控制器，实现智能、高级安全和集中化的管理。与其说人们寻找这种无线接入点自身，不如说是在寻找无线控制器。     

软件定义无线局域网的切换接入机制

软件定义无线局域网（WLAN）是管理无线网络的一个趋势。针对无线访问接入点（AP）部署密集环境中频繁切换、接入失败等问题,提出了基于惩罚因子的全局关联记忆保留的接入控制的方法。首先,扩展OpenFlow协议;其次,利用扩展数据报文通过AP向控制器报告网络的质量、负载、吞吐量以及利用率等指标;接着,引入变异系数法确定网络指标的系数,然后利用这些指标参数构建AP接入权值;最后,引入全局惩罚因子记录网络中发生频繁来回切换的情况,根据全局记忆保留的惩罚因子修正AP接入权值和发射功率。通过与信号最强接入法和负载均衡接入法的实验对比表明,终端站点（STA）在复杂网络环境中移动时,该方法能有效地降低切换的“乒乓效应”,减少网络的切换次数和切换时延并提高网络切换成功率。与传统信号最强接入法相比,所提方法的切换请求次数减少了21.7%,增强了网络接入性能的稳定性。     

软件定义无线局域网的切换接入机制

软件定义无线局域网（WLAN）是管理无线网络的一个趋势。针对无线访问接入点（AP）部署密集环境中频繁切换、接入失败等问题，提出了基于惩罚因子的全局关联记忆保留的接入控制的方法。首先，扩展OpenFlow协议；其次，利用扩展数据报文通过AP向控制器报告网络的质量、负载、吞吐量以及利用率等指标；接着，引入变异系数法确定网络指标的系数，然后利用这些指标参数构建AP接入权值；最后，引入全局惩罚因子记录网络中发生频繁来回切换的情况，根据全局记忆保留的惩罚因子修正AP接入权值和发射功率。通过与信号最强接入法和负载均衡接入法的实验对比表明，终端站点（STA）在复杂网络环境中移动时，该方法能有效地降低切换的“乒乓效应”，减少网络的切换次数和切换时延并提高网络切换成功率。与传统信号最强接入法相比，所提方法的切换请求次数减少了21.7%，增强了网络接入性能的稳定性。     

基于CAPWAP协议的集中式无线局域网架构

在WLAN日益普及,组网规模不断扩大的趋势下,如何对数量较多的无线接入点（AP）进行管理,监测和控制的问题,对WLAN的管理提出了挑战。本文讨论一种新出现的WLAN架构：集中式WLAN,以及实现这一架构的协议：CAPWAP（无线接入点控制）。CAPWAP协议规定了接入控制器（AC）对无线终端（WTP）的管理,该协议使通过IP协议进行多个无线终端的网络配置成为可能。     

无线局域网中快速切换的负载平衡

在无线局域网的快速切换过程中,当存在多个可选的目标接入,点（access point,AP）时,为了均衡负载,提出一种结合AP剩余带宽、信号强度以及AP当前负载比的目标AP选择方法。在所有可能的邻接AP中,若AP的剩余带宽小于移动终端所需带宽,则对这些AP不予考虑,否则,利用其邻接AP的负载比和终端接收到的AP的信号强度,计算函数,选择函数值最大的AP进行连接。仿真结果表明,该方法在整体性能上优于其它方法,没有出现某个AP负载超载。     

Throughput analysis and bandwidth allocation for IEEE 802.11 WLAN with hidden terminals

Motivated by observations from real world wireless local area network (WLAN) deployments, we develop in this paper a novel analytical model to characterize the saturation throughput of an IEEE 802.11-based access point (AP) and stations under the influence of hidden terminals. Unlike existing models, our model can accommodate different numbers of hidden nodes without increasing the model complexity. Given any number of hidden nodes, only four constraints are needed to describe the interaction between stations and the AP with the consideration of both uplink and downlink traffic. Simulation evaluation shows that our model predicts network performance accurately over a wide range of network sizes and indicates the existence of a throughput starvation problem. To address this problem, based on our model, we formulate a bandwidth allocation problem to optimize the network throughput and fairness under some predefined requirements by systematically tuning the AP and stations contention windows. Simulation results show that the starvation problem is resolved with our approach, and the target throughput is met.     

WiFi接口的IAD内部带宽控制策略

近年来在一些国家新出现了运营商测试大区域内部署无线局域网的情况,而在较大范围内部署WIFI网络上提供语音和数据,使用IAD（综合接入设备）能够给运营带来极大的便利。IAD其内部存在着语音和数据流量的带宽竞争关系,其控制策略在不同应用模式下尤其在加入WiFi接口后有所不同,用以保证语音质量不受到突发数据或者带宽波动较大等情况影响。介绍了带WiFi接口的综合接入设备在Wifi网络中的应用,和在产品研发过程中为解决IAD内部的语音和数据流量竞争和分流控制所采取的一系列策略,在测试环境中实施这些控制策后无论带宽竞争是在通话过程中还是先有数据流量的情况下都能实现给语音流量合理分配带宽。     

On the wireless local area network design problem with performance guarantees

In this paper, we propose a model for the wireless local area network (WLAN) design problem with performance guarantees. This problem consists of selecting the location of the access points (APs) as well as the power and the channel of each AP. The performance guarantees we refer to are coverage and minimum bandwidth guarantees. Since this problem is -hard, we propose a tabu search algorithm to find solutions for real-size instances of the problem. Finally, numerical results are presented. The results show that good solutions can be found with the proposed algorithm in a reasonable amount of time.     

集中式WLAN网络无线资源管理研究

基于对集中式WLAN无线资源管理框架的分析，提出了相关的负载均衡控制算法和准入控制算法。通过和相关算法仿真对比可以看出：所提算法能够使WLAN系统更有效地均衡各个无线接入点的业务流量，最大限度地满足接入服务。     

基于CAPWAP的集中配置管理机制的研究与实现

随着无线通讯技术的发展,无线局域网的出现给Intemet的应用带来了革命性的变化。IEEE802．11技术的发展,导致大规模部署WIAN网络已成为～种必然趋势,分布式管理和集中式管理的WLAN网络结构是当前主要的体系。集中式管理的WLAN网络由于把无线的业务功能集中在AC上,能够更有效更灵活地配置和管理网络,CAPWAP协议是针对集中式管理的WLAN网络中AC与AP之间的通信提出的最新的标准。文中对基于CAPWAP协议的两种配置无线局域网的方法进行了详细地分析,构建拓扑并通过编写测试例对两种配置方法进行了验证。     

基于SDWN的负载感知终端多点关联方案研究

软件定义无线网络（SDWN）是一种控制与转发分离的无线网络架构。该架构可以快速获取全局拓扑并且其可编程性结合资源虚拟化技术可以对网络接入进行动态控制。针对现有WLAN网络接入负载不均衡问题及移动终端与AP硬关联导致的切换速度较慢的问题,基于SDWN架构提出了一种负载感知终端多点关联方案。该方案对SDWN网络架构下的终端接入算法进行改进,采用多点关联技术,即终端在感知AP负载数据后,可关联多个虚拟AP,达到动态分流并提高网络吞吐量的目的。最后在SDWN的开源Odin平台上验证了方案的可行性,实验表明相比无缝切换至另一AP,此方案可改变原有终端与AP接入一一对应的接入关系,根据AP负载动态接入,可有效提升网络吞吐量。     

WLAN based energy efficient smart city design

The rapid growth of new technologies resulted in a new city model, known as the famous “Smart City”. The main aim in this paper is to create a paradigm for building an energy efficient smart city. Wireless local area network (WLAN) controller that will be used by the city will be constructed in such a manner that when there will be no request from any node to the access point (AP), the AP will be send from active mode to sleep mode. In Qualnet7.2, with the help of three types of energy model generic, mica z and mica motes the energy consumption in three modes transmit, receive and sleep mode is analysed, where it is seen that energy consumption in sleep mode is much less than in any other modes. In this paper, we propose an algorithm where it is shown that the energy consumption in sleep mode is less than in any other modes.

     

Joint reactive jammer detection and localization in an enterprise WiFi network

The deployment of wireless networks for Internet connectivity has been rapid during the last decade. Following this trend, enterprises utilize multiple access points (APs) in order to provide wireless connectivity to authorized users within its premises. However, wireless networks are extremely vulnerable to PHY/MAC layer attacks such as jamming. A jammer transmits electromagnetic energy on the medium in order to either block the access to any legitimate transmitter or cause collisions at the receiver (or both). One of the most advanced jamming models is that of reactive jamming. A reactive jammer does not constantly transmit energy on the air, but only jams when a legitimate (target) packet is on the medium, aiming at its collision at the receiver. Previous studies have shown that reactive jamming is one of the most difficult attack models to detect. In this work, we propose a scheme that performs both detection and localization of a reactive jammer in an enterprise WiFi network. In brief, a reactive jammer can virtually increase the interference range of the target AP and thus increase the busy times of nearby APs that use the same frequency. By quantifying this effect we are able to accurately detect the presence of a reactive jammer and perform a coarse grain localization of the jammer. Our simulation results show that our scheme can achieve high true positives and low false positives simultaneously. In addition, our coarse grain localization scheme exhibits error on the order of the AP coverage area.