OFDMA femtocells: a roadmap on interference avoidance - [topics in radio communications]

OFDMA femtocells have been pointed out by the industry as a good solution not only to overcome the indoor coverage problem but also to deal with the growth of traffic within macrocells. However, the deployment of a new femtocell layer may have an undesired impact on the performance of the macrocell layer. The allocation of spectrum resources and the avoidance of electromagnetic interference are some of the more urgent challenges that operators face before femtocells become widely deployed. In this article a coverage and interference analysis based on a realistic OFDMA macro/femtocell scenario is provided, as well as some guidelines on how the spectrum allocation and interference mitigation problems can be approached in these networks. Special attention is paid to the use of self-configuration and self-optimization techniques for the avoidance of interference.     

漏泄通信系统在地铁中的应用

地铁内信号的覆盖问题始终困扰运营商,目前行之有效的方法是搭建一套漏泄通信系统.此系统首先应用合路平台设备(POI)技术;其次采用漏缆传输方式对地下空间进行信号覆盖;再次通过有线方式将各运营商的信号传送到地铁站内的各自基站,系统信号经POI合路后通过地铁内的漏缆把信号发送出去,从而实现地铁内信号的覆盖.最后将研究成果应用到某运营商地铁线路的网络建设中,为后期地铁无线网络设计提供了思路.     

电力线载波通信EMI滤波电路研究

电力线通信是一个正在发展的崭新学科,但由于电力线传输的无屏蔽性,给电力线通信带来严重的电磁干扰与电磁兼容问题。在深入分析了电力线通信系统产生电磁干扰的主要原因的基础上,对EMI滤波电路进行了设计研究,并通过实验验证了该滤波网络对于抑制电力线载波通信EMI的可行性。     

通信工程中有线传输技术的优化策略

随着科学的发展,有线传输技术也在不断进步。目前,由于该技术具有受干扰较小,可靠性、保密性强等优势,在很多行业领域都已经广泛应用。但是,在实际应用中,有线传输技术还存在一些难以攻克的技术难题。这给有线传输技术的发展带来了严重的影响。因此,首先介绍了通信工程有线传输技术中不同介质的技术优势,然后分析了通信工程中有线传输技术的具体应用及其存在的不足,最后总结了提高有线传输技术水平的有效手段。     

Spread spectrum techniques in wireless communication Part 2: Transmission issues in free space

The second part of Spread Spectrum Techniques in Wireless Communication focuses on wireless transmission issues and implementation of a water quality assessment wireless system. I present concepts of electromagnetic propagation, some important issues in open space electromagnetic transmission particularly when a transmission link is over a conductive surface, and a simplified analysis of common occurrences that impair the transmission's quality or can even block the communication between network nodes. I introduce the primary techniques that are used to mitigate open space propagation problems, giving particular attention to solutions that can be used to mitigate fading effects in spread spectrum communication systems. Then, I present experimental results of a wireless transmission system used in water quality assessment.     

通信工程中有线传输技术的改进分析

通信工程是网络时代不可或缺的组成部分,为信息交互提供链路。针对通信工程中有线传输技术展开了相关讨论,并对有线传输技术的应用进行了分析,以期能够推动我国通信工程中有线传输技术的全面发展。     

4G/5G LNR动态频谱共享技术

为实现多频多制式网络完全融合,加速5G全面部署,面向存量4G频谱,引入LNR动态频谱共享技术,解决新制式快速引入、老制式平滑退网、网络资源按需分配等问题,重点研究LNR动态频谱共享技术的实现原理,对4G/5G增益影响进行分析;总结该特性引入的同频异制式干扰问题,规避同频干扰的方法;在无线网络验证过程中,单站定点用户测试,LNR频谱共享100%生效,NR占用100 M相比60 M速率增益为65.3%;NR连片拉网测试,NR带宽占用100 M相比60 M,覆盖不会收缩,用户感知速率增益为33.53%,评估结果符合预期。     

5G室内深度覆盖规划解决方案研究

由于5G使用频谱资源的频段相对较高，其绕射能力及电磁波穿透能力相对较弱，因此存在室外基站覆盖、室内隔墙传输难度较大的问题。为满足室内深度覆盖需求，需要做好室内深度覆盖规划。文中通过对5G室内深度覆盖基本情况的介绍，分析了覆盖规划原则，并重点探讨了深度覆盖的解决方案，旨在提高5G室内覆盖效果，保证深度覆盖规划方案的质量。     

Local-area networks go wireless

As standards emerge, data rates rise, and laptops seek connectivity, wireless LANs are finding a market niche as extensions to wired networks. Wireless LANs have found homes in buildings where installing wires would expose asbestos or destroy historic architecture. They have also proved valuable to companies that often relocate and want networks they can take with them. Another common use is for connecting wired LANs that are physically separated. The growth has been fueled by the desire to add wireless adjuncts to wired LANs, so that mobile workers can keep in constant contact with corporate networks over short distances. The author discusses the befits of wireless LANs. The radio based wireless LAN is discussed including multipath interference and data bottlenecks. The infrared based wireless LAN is also discussed and an inset discusses standards for wireless LANs     

无线局域网中的载波侦听

钢铁公司的铁水运输时，需要合理调度运栽鱼雷罐的机车。无线局域网能实时传送机车的位置信息，但在恶劣的电磁干扰下如何保持通信的稳健性，使数据无差错、不丢失的传送是设计无线局域网必须考虑的关键问题。本文介绍利用通信模块RFW102和D100设计局域网时提高通信质量的2种方法。     

通信工程中有线传输技术的优化分析

文中对通信工程中的有线传输技术进行了优化分析,探讨了传输技术的现状与问题,并对有线传输技术进行了概述,包括光纤传输和同轴电缆传输等的基本原理和特点。其次,总结了目前有线传输技术在通信工程中存在的问题,如带宽受限、信号衰减、抗干扰能力不足等。然后,针对存在的问题提出了相应的优化方法。最后,设计了通信工程中的有线传输技术优化试验,通过仿真实验和实际测试,对比优化前后的数据传输效率和可靠性。结果表明,优化后的有线传输技术在数据传输速率和抗干扰能力上均有明显提升,且在实际工程应用中具有良好的使用效能。     

开关电源电磁干扰抑制技术

为了抑制开关电源电磁干扰对电源本身、电网及周围环境的影响,设计者从干扰源、传播途径和受扰设备这三要素入手,分别采用有源滤波技术、屏蔽和接地技术、PCB设计技术、扩频调制技术等来抑制电磁干扰,对抑制电路中的传导干扰和辐射干扰起到了明显的效果,达到了改善开关电源电磁兼容性能的目的。也为工程设计人员提供了理论参考。     

民用航空甚高频通信系统互调干扰分析与建模研究

本文分析了民航甚高频通信系统的干扰机制,建立干扰分析模型,对民航西安区管甚高频系统的实际干扰问题进行了分析,介绍了无线电频率管理的基本概念,讨论了电磁频谱的概念、特点,论述了电磁频谱检测分析和评估的重要性,并对国内外无线电频率管理的现状做了介绍,深入分析了互调干扰机理,总结了调频广播对民航甚高频系统干扰的类型和产生机制。最后,分别从频率和功率两个维度建立了互调干扰频率分析模型。为民航甚高频通信系统的规划和管理提出了有益的参考。     

低轨星座系统电磁发射可视化技术研究

针对国内外低轨卫星互联网的高速发展,O3b、OneWeb、starlink、Teleost、LEOsat等低轨互联网系统的逐步完善并覆盖全球,此时不同星座系统卫星覆盖波束相互叠加,带来了频谱态势的复杂化,给其他系统带来了干扰隐患。与此同时,随着各个星座系统的部署运营,地球所处电磁环境将变得复杂多变、电磁干扰情况发生的频次和程度更为严重。为准确量化评估低轨卫星系统的电磁干扰,本文通过研究低轨星座卫星系统的电磁发射模型,结合轨道运动学研究电磁发射覆盖范围的动态分析法,实现低轨星座卫星电磁发射的可视化。     

Visible light communication: Applications,architecture, standardization and research challenges

The Radio Frequency (RF) communication suffers from interference and high latency issues. Along with this, RF communication requires a separate setup for transmission and reception of RF waves. Overcoming the above limitations, Visible Light Communication (VLC) is a preferred communication technique because of its high bandwidth and immunity to interference from electromagnetic sources. The revolution in the field of solid state lighting leads to the replacement of florescent lamps by Light Emitting Diodes (LEDs) which further motivates the usage of VLC. This paper presents a survey of the potential applications, architecture, modulation techniques, standardization and research challenges in VLC.     

National EMC by Design

Fragmentation of spectrum management responsibilities and authority is resulting in less than optimum electromagnetic spectrum utilization in the United States. To begin to implement a solution to this problem, a phased program which would ultimately centralize all administrative, engineering, and record-keeping activities related to spectrum management is proposed. A ?national spectrum manager? is proposed who would have the authority and capability necessary to design spectrum utilization patterns by applying state-of-the-art analysis, information, and monitoring techniques to the electromagnetic compatibility problem. The need for computer simulation and interference prediction capabilities is discussed. The problems involved in keeping existing spectrum users ?happy,? while serving new users under changing use patterns and rules, are discussed. Approaches to the validation of the analytical capability are treated. Possible applications of the resulting capabilities and techniques to international spectrum management are discussed. The ever-present subject of cost is raised, and several possible methods of financing such a system are reviewed. Also touched upon are future problems and applications, such as those relating to space and satellite communications.     

Interference management and performance analysis of UMTS/HSPA+ femtocells - [femtocell wireless communications]

Femtocells are low-power cellular base stations that operate in licensed spectrum. They are typically deployed indoors to improve coverage and provide excellent user experience, including high data rates. Cellular operators benefit from reduced infrastructure and operational expenses for capacity upgrades and coverage improvements. Femtocells also bring unique challenges, such as unplanned deployment, user installation, restricted access, and interoperability with existing handsets and network infrastructure. Although femtocells may cause some interference to other users in the network, with the use of proper interference management techniques, this can be well controlled. We present interference management techniques for both downlink and uplink of femtocells operating based on 3GPP Release 7 standards (also known as HSPA+). Femtocell carrier selection and femtocell DL Tx power self-calibration are proposed as key interference management methods for downlink. For uplink interference management, adaptive attenuation at the femtocell and limiting the Tx power of the femtocell users are proposed. Different interference models and their analysis are presented. In addition, coverage performance and capacity results are presented to quantify the benefits of femtocells. We demonstrate that in addition to coverage enhancements, significant capacity improvements are achieved on both downlink and uplink when femtocells are deployed in 3G UMTS/HSPA+ networks.     

Personal Communications in the UK—Implementation of PCN using DCS 1800

Personal Communication Networks (PCNs) aim to establish a mass market for mobile communications and provide a competitive alternative to the wired PSTN. This paper explains how the DCS 1800 cellular network standard was developed to provide an appropriate technical basis for the implementation of PCN services. Particular attention was given to RF parameters, small cell radio networks, standardized network interfaces, and enhancement of coverage areas by infrastructure sharing between operators.     

现场环境下设备区域电磁干扰检测与识别方法

现场环境下电磁环境复杂,设备区域电磁干扰的有效识别可为射电天文台站频谱分析提供重要依据.文章基于现场电磁干扰测量频谱,提出了一种电子设备区域干扰信号检测与识别方法.首先,针对对着设备区域和隔过设备区域两种测量状态多组频谱数据进行预处理,实现信噪分离,运用二值法检测信号边界,提取频谱中干扰信号.然后,依据一元回归算法和通道占用统计方法对多组测量频谱中干扰信号进行相关性分析,识别设备区域内电磁辐射频谱.所提方法对新疆天文台南山站内多个设备区域电磁辐射频谱检测结果与人工识别结果对比表明,本文方法94%以上的识别结果与人工识别结果相符,验证了现场环境下设备电子区域电磁干扰检测与识别方法的准确性和通用性.     

新一代超密集异构蜂窝无线网络研究

近年来,随着移动互联网的蓬勃发展和智能终端的快速普及,对无缝网络覆盖和高速数据传输要求日趋增强,超密集异构蜂窝无线网络通过减小小区半径,增加低功率节点数量进行超密集组网,提高无线资源利用率和频谱效率,因而引起了国内外研究学者的广泛关注。然而,超密集异构蜂窝无线网络中愈发密集的网络部署也带来了各种严峻的问题,包括超密集异构蜂窝无线网络中的系统干扰问题、无线信息的安全传输问题、以及网络运营的能量供给问题等。为此,本文首先简单介绍了超密集异构蜂窝无线网络架构,接着从干扰管理、物理层安全和能量效率等方面,深入分析了超密集异构蜂窝无线网络中的关键技术和当前挑战,最后,进一步展望了超密集异构蜂窝无线网络的未来发展。