VDSL2_Profiles
EKI-1751-AE VDSL2 Ethernet扩展器启动手册说明书
EKI-1751-A EVDSL2 Ethernet Extender1 Startup ManualBefore installation, please make sure that you have received the following:▪ 1 x EKI-1751-AE VDSL Ethernet Extender ▪ 1 x Power Adapt e r▪ 1 x DIN-rail Mounting Bracket and Screws ▪ 1 x EKI-1751-AE Startup ManualIf anything is missing or damaged, contact your distributor or sales representative immediately. For more detailed information, please refer to the full manualwhich can be found on the Advantech’s website.General▪ I/O Port: 1 x 10/100Base-T(X) RJ-45 1 x VDSL2 Extender RJ-45 ▪ Power Connecto r: 2.1mm DC Jack▪ DIP Switch :Pin 1: Selectable CO or CPE mode▪LED Indicators: Port LED : Link / Speed / Activity▪ Power Input : 12V DC , 1A, External Power Adapter ▪ Power Consumption: 4.2 Watts▪Dimensions (W x H x D): 72.5 x 23 x 94.5 mm (2.85" x 0.91" x 3.72") ▪ Enclosure: IP30 ▪ OperatingTemperature: 0 ~ 45°C (32 ~ 113°F) ▪ Storage Temperature: -40 ~ 70°C (-40°F ~ 158°F) ▪Operating Humidity: 0 ~ 95% (non-condensing) ▪ Storage Humidity: 0 ~ 95% (non-condensing) ▪ Safety: UL60950 ▪ EMC: CE, FCC ▪Warranty: 5 yearsFor more information on this and other Advantech products, please visit our websites at: /products/For technical support and service: /support/ This startup manual is for EKI-1751-AE1st Edition Mar 2018The EKI-1751-AE is a Long Reach Ethernet Extender to utilize existing copper cabling infrastructure(twisted pair), extending Ethernet to up to 1200 meters over VDSL2. Applications such as IP-based Internet connections, video surveillance and voice services can benefit from the EKI-1751-AE . The devices support VDSL2 Profiles 17a and 30a.EKI-1751-AE is designed to work in pairs, over twisted pair; as an unmanaged product, it is easy to install and each Extender can be set to a Master (CO) or Remote (CPE) via a DIP Switch. Offering one model that can be set to a Master or Remote and operate as a pair reduces the cost of investment and minimizes inventory as well.The Extenders support SNR Margin, VDSL2 Profile 30a(High Bandwidth Mode) or VDSL2 Profile 17a (Long Reach Mode), and Symmetric/Asymmetric data throughput, all DIP Switch-selectable. The selection of symmetrical or asymmetrical for throughput ofupstream/downstream data rates directly influences the distance covered. LEDs include link activity, VDSL status, and Central Office or Customer Premises Equipment designation.The Extenders meet 802.3 Ethernet standards, as well as transparently supporting VLANS, 802.1q.Pin 2: Selectable 30a or 17a (VDSL2 Profile)Pin 3: Selectable Band plan (Symmetric or Asymmetric)Pin 4: electable target SNR margin (6dB or 9dB)System LED : PWROverviewLEDs for LAN12 Vdc in over 2.1mm DC Jack. (External Power Adaptor included)2DIP 1 DIP2 DIP3 DIP4Side VDSL2 Profile Rate Limit SNROFF OT 30a Symmetric 9dBON RT 17a Asymmetric 6dBDIP 1：OT：RT：LAN Extender acts as Customer Premise Equipment (CPE)side.DIP 2：30a：VDSL2 High Speed Mode.17a：VDSL2 Long Reach Mode.DIP 3：Symmetric：Support the band plan G.997 and provide the symmetrictransmission on both downstream and upstream.Asymmetric：Provides highest line rate in short range in asymmetricmode.DIP 4：9dB：Better channel noise protection with SNR up to 9 dB.6dB：Original channel noise protection with 6 dB SNR.2STEP 1：Set the LAN extender to CO mode orCPE mode from the DIP switch at thefront panel. For Point to PointSTEP 2：STEP 3：STEP 4：STEP 5：STEP 6：connecting the power adapter and thenobserve the status of VDSL2 link LED.Setting as CO side Setting as CPE sideStartup Manual 2。
VDSL2技术原理及应用
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２ ． ３ 编码调制技术
中国电信 VDSL2 用户端设备技术要求
中国电信集团公司技术标准
Q/CT 2169-2009
中国电信 VDSL2 用户端设备技术要求
Technical requirements of China Telecom for VDSL2 CPE
（V1.0）
2009-06 发布
2009-06 实施
中国电信集团公司 发布
I
目录
1. 范围 ..........................................................1 2. 规范性引用文件 ................................................1 3. 缩略语 ........................................................2 4. 参考模型 ......................................................3 5. 设备类型 ......................................................3 6. 接口要求 ......................................................4
7.4.1 线路封装方式...........................................................................................................5 7.4.2 Profile自动选择........................................................................................................5 7.4.3 双端线路测试（DELT） .........................................................................................5 7.4.4 上行功率下调（UPBO） ........................................................................................6 7.4.5 US0 启用功能...........................................................................................................6 7.4.6 紧急速率下调（SOS） ...........................................................................................6 7.5 频段划分...........................................................................................................................6 7.6 功率谱密度（PSD） .......................................................................................................7 7.6.1 发送PSD模板 ...........................................................................................................7
VDSL
何为VDSL?VDSL（甚高速数字用户环路）是一种在普通的短距离的电话铜线上最高能以52Mbit／s合速率传输数据的技术，它的速度大大高于ADSL（非对称数字用户环路）和Cable Medem（线缆调制解调器），相当于T3的数据传输速率。
它可以大大提高因特网的接入速度，提供本地不同区域网络之间的快速链接，并可用来开展视频信息服务。
VDSL技术现在还处在研究阶段，本文首先介绍了VDSL的一些基本规范，然后分析和比较了VDSL的几种调制技术和复用技术，最后介绍了VDSL的发展现状。
2VDSL系统的规范虽然VDSL的国际标准还在制定之中，电话公司通过参加美国的ANSI T1.4和欧洲的ETSI TM6标准化小组已确定了VDSL的系统规范，主要包括数据传输速率及下行上行速率比例、辐射抑制、功率话密度等方面。
ANSI和ETSI都要求支持对称和非对称的数据传输。
ETSI把支持非对称和对称数据传输速率的调制解调器分别归为ChasⅠ和ClassⅡ。
ClassⅠ的最高传输速率为24 Mbit／S，规定的下行上行速率比例有6：1、3：1两种；ClasS Ⅱ的最高传输速率为36 Mbit／S。
ANSI定义的非对称传输时最高速率为52 Mbit／S，下行上行速率比例为8：1、4：1；对称传输模式下的数据传输速率最高为52 Mbit／s。
为了防止双绞线上的VDSL信号通过辐射对业余无线电频段产生干扰，ANSI和EISI都规定了在业余无线电频段内VDSL调制解调器的发送功率话密度不得高于-80dBM。
ANSI和ETSI都规定VDSL系统的最大发送功率为11.5 dBm。
3VDSL的噪声环境影响VDSL的噪声主要有串扰、无线电频率干扰和脉冲干扰。
线缆的线束中有很多对双绞线，由于无法实现完全的互相屏蔽，所以它们会相互耦合形成串扰。
在VDSL应用中，串扰有两种形式：NEXT（近端串扰）和FEXT（远端串扰）。
NEXT是本地接收机检测到了一个或多个本地发送机在其他线路上发送的信号；FEXT是本地接收机检测到在其它频带中传输的一个或多个远端发送机发送的信号。
VDSL2 参数配置指导书-20091112-A(DOC)
VDSL2 参数配置指导书华为技术有限公司Huawei Technologies Co., Ltd.版权所有侵权必究All rights reserved修订记录Revision record目录Table of Contents1VDSL2技术概述 (5)2VDSL2线路配置参数详解 (6)2.1 VDSL2 transmission mode－VDSL2工作模式 (9)2.2 VDSL2 速率自适应方式 (9)2.3 噪声容限（SNR） (10)2.4 频谱开槽（Notching to eliminate RFI） (11)2.5 VDSL2 tone blackout参数 (13)2.6 模板模式和频带划分 (14)2.7 U0频段的设置 (17)2.8 上下行最大发送总功率 (17)2.9 上/下行PSD掩码(PSD mask) (18)2.10 上行功率削减（UPBO） (21)2.11 下行功率削减（DPBO） (22)3VDSL2信道配置参数详解 (23)3.1 数据通道模式 (25)3.2 最小脉冲噪声保护(INP) (26)3.3 最大交织时延 (28)3.4 速率参数 (29)3.5 双延时通道介绍 (30)4VDSL2告警配置参数详解 (30)5VDSL2端口性能统计 (32)MA5600 VDSL2参数配置指导关键词Key words：VDSL2摘要Abstract：本文描述内容包括MA5600产品中VDSL2特性参数介绍和配置以及测试方法介绍，用于指导产品本特性的系统测试和对外测试；缩略语清单List of abbreviations：1 VDSL2技术概述随着DSL技术不断的发展以及各种视频、数据、HDTV和互动游戏等多重业务所要求带宽的不断增加，最新的三重业务包括了至少3个电视频道、若干个VoIP连接和足够快的互联网访问，要求的数据速率至少要达到30~40Mbps，目前的xDSL接入技术（如ADSL/ADSL2/ADSL2+）等已难以满足这样的带宽要求。
华为接入VDSL2业务介绍
如此之高的传输速率，VDSL2的工作频率由12MHz提高至30
MHz。
为了满足中、长距离环路的接入要求，VDSL2的发射功率被提高
至20 dBm，回声消除技术也进行了具体规定，使长距离传输应用
Security Level:
华为VDSL2业务介绍Author/ Email: Author's name/Author's email Version: V1.0(20YYMMDD) HUAWEI TECHNOLOGIES CO., LTD.
VDSL2业务概况介绍 VDSL2业务设备介绍
HUAWEI TECHNOLOGIES CO., LTD.
Huawei Confidential
5
华为VDSL2业务介绍---VDSL2参考模型
局端设备
ATM STM IP
上层 网络 接口 局端 收发器
用户端设备
双绞线
分离器 分离器
VTU-R
业务单元
VTU-O
PSTN/ISDN 电话/ISDN终端
华为VDSL2业务介绍---设备介绍
现网使用版本：V800R308C01/V800R306
测试现场MA5616实物图：ADSL2+和VDSL2混插、纯ADSL2+、纯VDSL2（上至下）
HUAWEI TECHNOLOGIES CO., LTD.
Huawei Confidential 13
华为VDSL2业务介绍---设备介绍
5
实现一路交流输入电压转换，输出-48V DC、+12V DC 和+3.3V DC。 H831PAIB 交流带备电电源板 实现一路交流输入电压转换，输出-48V DC、+12V DC 和+3.3V DC，并支持一路蓄电池接入。 HUAWEI TECHNOLOGIES CO., LTD. 12 Huawei Confidential
VDSL2 简介
遵循协议为G993.2
Chamber Function
下面是一个基于POTS（普通老式电话系统）系统架构图 虚线以下的是原有的电话服务 虚线以上的是VDSL2利用原来就有的电话线加入宽带业务
4
Chamber 操作界面介绍
主要技术特点
１.高传输速率 IPTV ,网络互动游戏等对上行接入带宽要求较高,VDSl2规定６波段高 达30MHZ带宽,在300M距离以内,实现100Mbit/s的传输速率. 300~1500M中等距离内,通过采用珊格编码和交织技术,传输速率依 旧比较高
Program Setting Steps
Thanks!
Chamber 操作界面和按键功能介绍
主要技术特点 2 更远的传输距离
受到双绞线的高频衰减的物理特性的限制,传输速率会受到影响. VDSL2通过增强发送发射功率和回波抑制的方法提高传输距离,使传输距 离高达4.5KM左右.
Program Setting Steps
VDSL ቤተ መጻሕፍቲ ባይዱ术特点
3 PSD管理技术 PSD (Power spectral density) VDSL2 频率范围由于覆盖拉中波 ,短波广播 ,以及业余无线电的频率 , 因此将受到这些无线电波信号的干扰,以及传输线之间的串扰. 这些干扰会对VDSL2应用的主要阻碍. VDSL2采用,UPBO(上行功率衰减) 等PSD管理技术,完成功率的管理, 消除减小这些干扰对传输线影响来提高对接入环境的适应能力
VDSL2
1
目录
VDSL2 简介 VDSL2 主要技术特点 ASV1528 简介
Chamber Function
VDSL2:第二代VDSL(超高比特速率数字用户线)
新型双端口高性能VDSL2线路驱动器ISL1539A
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vdsl2
VDSL2VDSL2：第二代VDSL （Second Generation VDSL）超高比特速率数字用户线2（VDSL2）的ITU-T 建议使电信运营商能够通过标准铜缆电话线提供诸如高清晰度电视（HDTV），视频点播（video-on-demand），视频会议（videoconferencing），高速因特网接入等业务以及VoIP 高级语音业务，从而具备和电缆提供商以及卫星提供商竞争的能力。
这项VDSL2 标准使业务的上载速率和下传速率都能达到100Mbps，是现有的ADSL 业务的十倍。
凭借如此高的速度，新VDSL2 标准能够提供所谓的“光纤扩展业务（fibre-extension）”，即为没有和电信公司的网络光纤段直接连接的建筑物提供类似光纤的带宽。
此外最重要的一点，也是与先前vdsl的不同，ITU 制定了VDSL2+互联互通标准，使VDSL2+实现了不同厂家的兼容，不同厂家的兼容，使得用户的设备采购渠道增加，有效的降低了运营商的经营成本，为vdsl2+大规模商业推广提供了条件。
VDSL2主要技术特点第一，更高的传输速率。
IPTV、网络互动游戏等新兴宽带应用，对接入网的上行带宽提出了要求。
VDSL2充分考虑到这些双向高速宽带应用的需求，规定了6波段高达3 0MHz的频带，在300m的短距离内，可以实现双向的100Mbit/s数据传送速率。
在30 0~1 500m中等距离内，通过采用栅格编码技术和交织技术，传输速率也比第一代VDS L高。
第二，更远的传输距离。
受到双绞线高频衰减物理特性的限制，第一代VDSL的传输距离一般小于1.5km。
VDSL2通过增强发射功率（20.5dBm），并配合U0频段和回波抑制的使用，传输距离最远可达4.5km左右。
第三，兼容ADSL2+技术。
VDSL2摒弃了QAM调制方式，采用与ADSL2+同样的D MT作为惟一的调制方式。
同时规定，在12MHz以下，仍然采用4kHz的子载波宽度，在12MHz以上，频段采用可变子载波宽度。
利用VDSL2设备解决远距离视频信号传输方案
利用VDSL2设备解决远距离视频信号传输方案摘要：在监控工程的设计和施工中，常常会遇到视频超过1000 米甚至更远距离的传输和信号传输过程中遇到干扰源的问题。
而这些问题一直困扰着工程商和运营商，有没有一种可以解决这些问题的方案和设备呢，在本文中，笔者将介绍一种新型VDSL2网络传输设备解决上述问题。
VDSL2简介：VDSL2技术是类似ADSL及ADSL2+技术，采用DMT调制，但是频率范围增加到30MHz，可以提供高达100Mbps 的带宽的一种通信技术。
VDSL2采用在一对铜质双绞线上实现信号传输，用户在安装VDSL2设备时也比较简单方便，只要用分离器将VDSL信号和话音信号分开，或者在电话前加装滤波器就能够轻松使用。
VDSL2设备应用：由于模拟视频信号通过同轴电缆在中长距离的传输过程中存在着信号的衰减和失真现象，或者当同轴电缆遇到干扰源时(如交流电线、强电磁场等)都会造成图像模糊不清或条形干扰等现象。
传统解决传输距离过长的方法是在每隔300-500 米左右加置一个信号放大器，这不仅大大增加了线路的建设成本，同时也增加了线路发生故障的几率。
对于遇到干扰源的问题则不好解决。
另一方面，在同方向存在多路视频线路和控制信号线路的布线工程施工中，多股同轴电缆加上控制信号电缆合在一起，给管道穿越和线路布放造成了比较大的困难。
由于同轴电缆自身的特性，当视频信号在同轴电缆内传输时其受到的衰减与传输距离和信号本身的频率有关。
视频信号在同轴电缆内传输时不仅信号整体幅度受到衰减，而且各频率分量衰减量相差很大，特别是色彩部分衰减最大，因此同轴电缆只适合于传输距离300 米以下的视频。
光纤是为了解决远距离的视频信号传输而使用的。
由于光纤整体传输系统价格太高，光纤铺设、连接需要专门设备，并且安装调试困难，故障难找，损坏不易维修等缺陷，对于3000 米以内近距离视频传输而言，光纤并不是一个很好的选择。
寻求一种经济、传输质量高、传输距离远的解决方案十分必要。
Lantiq发布VDSL2芯片组样品
高达５ ０ Ｍ ｉ 的对称数据传输速率。ＶＮ Ｘ ｖ 将 用于支持全 ０ ｂ／ ｔ ｓ ｌＡ ３
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ＶＮ Ｘ Ｖ 芯片组可将单线路 的下行数据速率和上行数据 ＩＡ ３
速率分别提高到１ ０Ｍｂ／ ５ ｉ ｔ ｓ和１ ０Ｍｂｔ ，为高清 网络 电视 、高 ０ ｉ ／ ｓ
速互联 网接入 、多人游 戏 网络 和网络 电话 等服务 提供 支持。 Ｖ Ｎ Ｘ Ｖ 支持基 于芯片和线卡线路 的绑定技术 ，从而提高家 ＩＡ ３
Ｉｔ ｌ ｅ全资子公 司风河 系统公 司日前表示 ，与新型芯 片、系 ｎ 统与 软件 技术厂商 Ｌ Ｉ Ｓ公司 实施 长期战略合 作 ，共 同推 出多核硬
商满足运营ｉ ￣
￣Ｄ Ｌ ｘ Ｓ 部署要求提供 了—个简单的解决方案。
vdsl2
DSL historyADSLWhile high-bit-rate DSL (HDSL) was stillin prototype phase, Stanford University and AT&T Bell Labs developed asymmetrical DSL (ADSL) technology from concept to prototype (1990-1992). Field technology trials began three years later and ANSI is-sued the first standard for ADSL in 1995(T1 413 issue I); the second issue followed in 1998. The first ADSL recommendation from ITU-T (G.992.1), generally denoted ADSL1, was complete in 1999.1This rec-ommendation was based to a large extent on the ANSI standards.ADSL was originally intended for deliv-ering video on demand at a bit rate of 8Mbps downstream and 640kbps upstream. But it was the popularity of the internet that made ADSL a major commercial success. In fact,ADSL is today mainly used as a form of high-speed internet access.An option in the ADSL1 standard pro-vides for a downstream data rate of up to 12Mbps. Moreover, plain old telephony ser-vice (POTS) or integrated services digital network (ISDN) technology can serve as the underlying service (by not using the fre-quencies occupied by their respective ser-vices: 0.3-25kHz for POTS or 1-120kHz for ISDN). A splitter filter can be used to sep-arate the POTS band from the ADSL band.This means ADSL can share the line with ei-ther POTS or ISDN service. Figure 1 shows how the frequency band is divided between POTS/ISDN upstream and downstream data.ADSL2The second-generation ADSL standards (ADSL2 and ADSL2plus) were issued in 2002 and 2003.2 - 3The most important new features of ADSL2 (G.992.3) were•an annex with extended upstream, which made it possible to have an upstream data rate of up to 3Mbps; and•an annex for extending the reach to more than 5km.ADSL2plusThe ADSL2plus standard (G . 9 9 2 . 5 )dou-bled the spectrum for downstream data (ADSL and ADSL2 have a spectrum of 1.1MHz; ADSL2plus has a spectrum of 2.2MHz), giving even greater data rates on short loops (Figure 1). ADSL2plus also de-fined a toolbox for sculpturing the down-stream transmission to meet different spec-ADSL2plus is currently being deployed worldwide as the new mainstream broadband technology for residential and business customers. But at the same time, the industry is gearing up for the next step of the DSL evolu-tion: VDSL2. This second version of the very high-speed digital subscriber line (VDSL) standard from ITU-T promises to deliver 100Mbps symmetrical traffic on short copper loops.The greater bandwidth of VDSL2 gives telecommunications operators the ability to offer advanced services such as multiple streams of interac-tive standard and high-definition TV over IP over the existing copper plant. TV services are fast becoming strategically important to telecom-munications operators who must now compete head-to-head with cable operators launching voice over IP (VoIP) and high-speed internet services.The introduction of VDSL2 will have a major impact on the way access networks are engineered. To make the most of VDSL2, operators will have to move the DSL access multiplexers (DSLAM) out of the central office environment and build a distributed network with smaller nodes that sit typically less than 1500 meters away from end users. This puts more strin-gent requirements on outside plant building practices. In many cases,power and spacing might also be an issue because existing street-side cabinets lack space and often solely contain passive equipment.Although fiber to every home is the ultimate answer, it is not yet an eco-nomically viable solution for overbuilding existing copper networks. This is because fiber takes a long time to deploy and the cost of deployment runs between USD 1,000 and 1,800 per subscriber. However, in Greenfield building scenarios, fiber to the home (FTTH) is frequently seen as the best way forward.trum capability requirements, in particularwhen ADSL2plus is put in a cabinet.Figures 2-3 show the performance, dur-ing different noise conditions, of Ericsson’sEthernet DSL access (EDA) DSLAM forADSL2 and ADSL2plus.VDSLEfforts to standardize VDSL (currently de-noted VDSL1) got underway in 1995. ITU, ETSI and ANSI (T1E1.4) each carried out simultaneous projects. In 1997, a group of operators belonging to the Full-service Access Network organization specified the end-to-end requirements for VDSL. The process later stalled, however, due to discord regarding two competing line-code tech-nologies:•single carrier, which uses quadrature am-plitude modulation (QAM); and•discrete multitone (DMT). Likewise, major efforts to complete theADSL2 and ADSL2plus standards moved work onVDSL standardization to a back seat. As a result, proprietary implementa-tions of VDSL-QAM and VDSL-DMT were developed and deployed in limited volumes in a few markets.In 2003, eleven major DSL suppliers jointly announced their support for DMT line coding, in particular because it facili-tates greater interoperability and is more compatible with existing ADSL installa-tions. This decision was also influenced by IEEE’s efforts to standardize Ethernet over VDSL as an element of the Ethernet in the first mile (EFM) standard defined in IEEE 802.3ah. A clear objective of the EFM stan-dard was to adopt a single line code in co-operation with established DSL standard-ization bodies. This started a “VDSL Olympics” of sorts in which the performance of VDSL-QAM was tested against that of VDSL-DMT in independent labs run by British Telecom in the UK and Telcordia Technologies in the USA. VDSL-DMT out-performed VDSL-QAM and was thus adopt-ed by IEEE and ANSI. ITU-T SG 15/4 by contrast included both QAM and DMT in the VDSL1 standard but stipulated that •all future evolution of VDSL technology would be based on DMT; and•a new standard, VDSL2, should be de-fined.4The scope of the VDSL2 standard is quite broad. Its goals are to increase performance over longer loops (longer than VDSL1), as an evolution from ADSL2plus, and very short loops, as an evolution from VDSL1.VDSL1 occupies spectrum from 138kHz to 12MHz. The VDSL2 spectrum has been expended both upward and downward,using spectrum from 25kHz to 30MHz. Thekey to increasing performance over longloops lies in the use of spectrum from 25kHzto 138kHz. Similarly, the key to increasing performance over short loops lies in the useof spectrum from 12MHz to 30MHz.The DSL industry successfully transi-tioned from ADSL to ADSL2plus, doublingthe spectrum while maintaining or improv-ing line density and cutting costs. The move to VDSL2 from ADSL2, however, decreases line density due to a significant increase in spectrum. A transition from VDSL1 to VDSL2 can take place without a loss in line density.Perhaps the most important aspect of the VDSL2 standard is that it uses Ethernet as multiplexing technology (64/65 encapsula-tion) in the first mile. The elimination of ATM in the first mile means the access ar-chitecture can be simplified into an end-to-end Ethernet access architecture that uses virtual local area networks (VLAN) as the service-delivery mechanism across the entire access network.6Ericsson is a driving force behind the ar-chitectural transition to high-performancebroadband solutions that will propel broad-band from mere high-speed internet access technology to a complete suite of IP-based services, such as IP telephony and IPTV. Ericsson introduced the first IP-based DSL access solutions in 2002 and has since worked to refine the architectures required to support the enhanced scope of service.5VDSL2 technologyUsing input from the ANSI and ETSI stan-dards, the ITU began drafting its VDSL2 standard (G.993.2) in January 2004. Con-sensus for the standard was reached at a meeting in Geneva in May 2005. As with ADSL/2/plus, the underlying modulation in the VDSL2 standard is discrete multitone (DMT). VDSL2 is based on both the VDSL1-DMT and ADSL2/ADSL2plus rec-ommendations. Therefore, it is spectrally compatible with existing services and en-ables multimode operability with ADSL/2/plus.DMT modulationDMT modulation uses the same principle as orthogonal frequency-division multiplex-ing (OFDM).6That is, it divides the useful frequency spectra into parallel channels, where the center of each channel is repre-sented by a modulated (QAM) subcarrier (Figure 4). One difference from OFDM isthat each carrier in DMT can be loaded with a different number of bits, depending on the signal to noise ratio (SNR). In OFDM, the constellation size of each carrier is the same.Because each subcarrier is orthogonal to the other subcarriers, there is no interference be-tween subcarriers. The number of bits can be varied between 1 and 15. The distance between subcarriers is 4.3125kHz. In VDSL2 a distance of 8.6125kHz may also be used. Inverse fast Fourier transform (IFFT) is used to generate the subcarriers.Band plansADSL can be described as a two-band sys-tem where one part of the frequency spec-trum is used for upstream transmission and the second part is used for downstream transmission (Figure 1). VDSL, on the other hand, uses multiple bands for upstream and downstream transmissions to enable a greater degree of flexibility with regards to rate configurations and symmetry between upstream and downstream data.Two band plans were defined (in 2000) to meet operator requirements for symme-try/asymmetry (Figure 5). The first of these,Band Plan 998, better facilitates asymmet-ric services, whereas Band Plan 997 accom-modates symmetric services. VDSL1 sup-ports a bandwidth of up to 12MHz; in VDSL2 this can be extended to 30MHz. To be spectrally compatible with VDSL1,VDSL2 uses the same band plans below 12MHz. VDSL2 can employ up to 4,096subcarriers. Depending on the band plan in use, a subcarrier is designated for either up-stream transmission or downstream trans-mission. As in ADSL, the lower part of the spectra is allocated for POTS and ISDN ser-vice and a splitter filter is used to separate the POTS or ISDN frequencies from the VDSL2 band. An “all digital mode” option also exists, where virtually all the spectra can be used for VDSL2.DuplexingToday’s deployments of ADSL/2/plus use frequency-division duplex (FDD) technolo-gy to separate the upstream band from the downstream band. Given the physical prop-erties, however, it is not possible to create a “brick wall” transmission band. That is,there is always some spectral leakage be-tween the transmission bands. In ADSL, fil-ters or echo cancellers are used to suppress leakage between transmission bands. VDSL,on the other hand, uses a digital duplexingtechnique based on the “zipper” technologyinvented at Telia Research in Luleå.7Withthis technique, adjacent subcarriers carrydata in opposite directions (Figure 6). How-ever, requirements for spectral compatibil-ity with existing DSL technologies necessi-tate that several tones must be grouped intotransmission bands. One can preserve the or-thogonallity between the received signaland the transmitted signal echoed back into the receiver by cyclically extending the transmitted DMT symbols using a cyclic prefix and cyclic suffix and by synchroniz-ing the transmitters at each end to begin transmitting at the same time (a technique called timing advance). Cyclic extension, which eliminates intersymbol interference (ISI) caused by the channel, reduces the data rate by 7.8%. Windowing, a technique for suppressing side lobes, further reduces spec-tral leakage between transmission bands. Windowing is also used in OFDM (Figure 7). Network evolution when introducing VDSL2Going forward, the introduction of VDSL2technology will account for only a small part of the fundamental changes affecting network architecture. Today, the lion’s share of installed access lines is situated in central office environments. Likewise, the average length of existing copper loops is well beyond the “sweet spot” for deriving added value from VDSL2. Many operators have thus already started to consider fiber deeper into the access network – for exam-ple, fiber to the node (FTTN) and fiber to the curb (FTTC) – shortening the length of copper loops to less than 1500 meters. The second major shift is the introduc-tion of Ethernet as packet technology all the way to the end user. ADSL2/plus em-ploys ATM in the first mile but IP/ Ethernet-based DSLAMs deploy Ethernet in the second mile. Many legacy broadband solutions also use STM1/OC-3 on the ag-gregate side.The shift toward Ethernet and FTTN/FTTC, and the introduction of additionalservices, will lead to a change in the serviceselection point in the network (currently the broadband remote access server, BRAS).FTTN architectureThe push for an FTTN architecture forVDSL2 was initiated by operators in North America, where long copper loops and the early introduction of HDTV call for a steep increase in broadband capacity. By situat-ing VDSL2 nodes close to subscribers, op-erators can boost capacity enough to support multiple HDTV streams to a householdwithout having to replace the entire copperinfrastructure with fiber. The capacity de-livered to each home is on a par with that ofa shared fiber architecture, for example, pas-sive optical network (PON) and hybrid fiber copper (HFC) alternatives (Table 1).The FTTN architecture is also highly dis-tributed to accommodate a smaller numberof subscribers per site as DSLAMs are movedcloser to end users. A large number of dis-tributed nodes calls for an automated customer-activation process that enables op-erators to activate a new subscriber without having to physically visit an FTTN location. Many operators eye the FTTN architecture as an attractive tool for effectively compet-ing with cable and fiber-access alternatives. Challenges of outside plant deploymentsMoving the DSLAM out of the central of-fice poses several new technical challenges.The temperature and environmental re-quirements, for example, are much more stringent. Present-day installations primari-ly operate in a central office environment with a typical temperature range of -5°C to +45°C. Outdoor plant deployments, on the other hand, must be able to operate in non-climate-controlled environments where temperatures can range from -40°C to +65°C.8Power is another area that will be af-fected. Most operators currently use -48Vpower solutions. In most outdoor deploy-ments, however, local power will not be an option. Instead, one must consider remote power (over the existing copper). In met-ropolitan areas, DSLAMs can be deployed in basements of multidwelling units with access to local power.Because there are fewer subscribers per site, many vendors will have to revise the architecture behind DSLAM control me-chanisms. At present, numerous DSLAMs are optimized for large sites where a com-mon control blade supports an entire cabi-net (more than 1,000 subscribers). But with a maximum of, say, 200 subscribers per site, this architecture is not cost-effective. Ethernet in the first mileWith VDSL2, Ethernet is the basic packettechnology all the way out to end users. This change affects the way in which networks are built. A direct benefit of the change isreduced overhead. The elimination of per-manent virtual connections (PVC), whichare an inherent part of ATM solutions, opens the door to new architectures. Ethernet-based features, such as VLAN-per-service incombination with authentication usingDHCP Option 82, can greatly reduce thecosts of operating a network. The simplifiednetwork architecture makes it possible to in-troduce packet transfer mode (PTM) tech-nology. This, and increased requirements to deliver new services with the right QoS, will put new requirements on products and the network architecture. Ericsson has previ-ously outlined many of the architectural principles of IP/Ethernet-based access.5 Ericsson’s product offeringEricsson has three years’ solid experience ofbuilding broadband architectures that canhandle advanced, high-quality services with superior performance. Its EDA product line, which was one of the first true IP DSLAMs to be released to the broadband market, is currently in operation in a large number of commercial deployments around the world.From the outset, Ericsson designed the EDA to be a highly scalable and modular DSL solution based extensively on Ethernet technology. This is precisely what is need-ed for a network in which VDSL2 is the main technology. In other words, for Ericsson, the first step toward VDSL2 is not very dra-matic: Ericsson designed its EDA to be a distributed system with software support for launching new services.In 2005, to show operators how the tech-nology behaves and what services it sup-ports, Ericsson deployed EDA with VDSL2 in live networks. Some features of EDA worth highlighting in the context of VDSL2 are scalability, advanced single-ended line test (SELT) and double-ended line test (DELT) capabilities, QoS, and greater ca-pacity. Vital objectives of the early deploy-ments were•to verify VDSL2 performance advantages in real network conditions; and•to enable an early start of VDSL2 inter-operability activities.ScalabilityThe EDA VDSL2 nodes can be configured to different sizes in steps of 12 lines. Oper-ators can thus cost-effectively build out nu-merous small nodes. This proven concept has been in use since 2002 for deploying a large number of 12-, 24-, and 36-line sys-tems (ADSL2plus).Advanced SELT and DELT capabilities Metallic line-test solutions tailored for cen-tral office use are expensive. What is need-ed instead is a software-based line-test solu-tion that makes key line measurements; in particular because outdoor cabinets seldom have space for test heads nor can the cost of providing this space be justified.QoSThe driving force behind VDSL2 is TV ser-vice bundled with voice and data. This will bring an end to the current paradigm of building best-effort DSLAM solutions. To effectively deliver high-quality services, QoS provisions must be built into levels 1 through 3 (L1-3). TV services can easily be delivered using the VLAN-per-service model coupled with features such as Ether-net overload protection and support for dual latency on the physical layer (PHY).Greater capacityEDA uses distributed processing power allthe way out to the line card. When com-bined with high-capacity Gigabit Ethernetuplinks, this feature provides considerablecapacity (packets-per-second throughput).The current rule of thumb for internet ser-vices is an average capacity of 25-50kbps peruser in the aggregation network. Looking ahead, however, it is estimated that capaci-ty must be increased at least 25- to 50-fold. What is more, apart from the challenge of merely increasing capacity, one must add ca-pacity for QoS-enabled traffic. Ethernet is thus the only truly cost-effective option for increasing capacity. Notwithstanding, even more advanced Ethernet designs are re-quired to support the high capacity of QoS-enabled traffic.Competing technologiesSome might argue that fiber to the home(FTTH) technology competes with VDSL2.In most cases, however, the two architec-tures are complementary. The level of FTTxdeployment is dependent on the specificbusiness case and is driven by telecommu-nications operators (as is the case with VDSL2). For operators wanting to migrate to FTTH, the current location of FTTx nodes is a suitable point for splitters or ac-tive fiber access nodes. Today’s main threat to telecommunications operators comes from the cable industry where new data-over-cable service interface specifications (Docsis3) technology promises to deliverhigh-speed solutions that are comparablewith VDSL2.VDSL2 capabilitiesExtended reachWhereas the physical reach of VDSL1 is lim-ited to around 1500m on 0.4mm cable, the reach of VDSL2 can be extended to around2400m. As a first upstream band (denotedUS0) VDSL2 can use the same upstream fre-quencies as ADSL/2/plus. This extends thereach of VDSL2 compared with VDSL1. Theuse of US0 requires training sequences sim-ilar to those of ADSL to train equalizers and echo cancellers. For distances in excess of 2000-2400m, ADSL2 remains the most ap-propriate choice of DSL access.Profiles of different deployment modes The VDSL2 standard is defined using sets of profiles, where each profile targets a spe-cific deployment. Figure 8 depicts the dif-ferent deployment scenarios anticipated for VDSL2. These include•fiber to the exchange (FTTEx): VDSL2 is located at the central office;•fiber to the cabinet (FTTCab): fiber-fedcabinets are located near customerpremises; and•fiber to the building (FTTB): VDSL2 isplaced, for instance, in the basement of a building.Profiles 8a-8b and 12a-12b apply to FTTEx;17a applies to FTTCab; and 30a, to FTTB(Figure 9). Each profile contains support forunderlying baseband services, such as POTSor ISDN.Figure 10 shows the measured perfor-mance of the EDA VDSL2 with profiles 8a,12a and 17a during typical noise conditions. Packet transfer modeIn all likelihood, when introducing VDSL2 the industry will drop ATM in the first mile, replacing it with Ethernet (64/65 encapsu-lation). At present, the most common solu-tion for transporting Ethernet frames over DSL is bridged IP DSLAM, where Ethernet frames are assembled into ATM adaptation layer 5 (AAL5) and encapsulated into ATM cells before they are sent to the DSL physi-cal link (Figure 11). The Segmentation and Reassembly (SAR) block processes the Eth-ernet frames. The ATM cells are transport-ed over a UTOPIA (universal test and oper-ations PHY interface for ATM) L2 electri-cal interface to an application-specific in-terface called the ATM TPS-TC (transportprotocol-specific – transmission conver-gence). TSP-TC is also sometimes denoted ATM-TC, for example, in the context of thexTU-C (xDSL transceiver unit – central of-fice).A drawback of encapsulating Ethernetframes into ATM cells (Ethernet-to-AAL5-to-ATM cells) is that 64-byte Ethernet frames must occupy two ATM cells. This is because the payload size of the 53-byte ATM cell is only 48 bytes. Therefore, one ATM cell carries 48 bytes and the other cell car-ries only 16 bytes. Given the maximum size of an Ethernet frame, 1518 bytes, the ATM overhead is 160 bytes or nearly 10% of the transmission capacity.IEEE 802.3ah has defined a specific Eth-ernet TPS-TC using the 64/65-octet encap-sulation for Ethernet applications without underlying ATM. For VDSL1, ITU-T spec-ified a different generic packet transfer mode (PTM). In the ITU-T specification, TPS-TC is denoted PTM-TC.The VDSL2 standard fully supports PTM based on 64/65-octet encapsulation. The IEEE 802.3ah task force defined PTM to en-capsulate Ethernet frames before they are modulated in the DSL transceiver. The ITU-T SG15/Q4 has defined PTM for VDSL2 as well as for ADSL2/plus and sym-metrical high-bit-rate DSL (SHDSL). Fur-thermore, it has enhanced the 64/65 encap-sulation technique using a preemption method, and added support fornon-Ethernet packets that are shorter than 64 bytes in length. PTM thus makes it possi-ble to eliminate ATM as the layer-2 carrier over the physical layer (Figure 12).Preemption mechanismThe standard 64/65-octet encapsulation technique has been amended with a pre-emption mechanism that allows high-priority frames to interrupt the transmission of low-priority frames until the high-prior-ity frames have been sent. Transmission of the low-priority frames is then resumed. To understand how this works, let us assumethat a 1518-byte packet with internet traf-fic is being processed when a high-priority voice packet arrives. The preemption mech-anism interrupts transmission of the 1518-byte frame, stores its current state, transmitsthe voice packet, and then resumes trans-mitting the packet with internet traffic. Dual latencyFigure 13 shows a reference model of theVDSL2 transceiver. The TPS-TC serves asan adaptation layer between the transportprotocols and the digital subscriber line.Ethernet frames or ATM cells are input intoTPS-TC. Among other things, the TPS-TC layer provides the transport mechanism, en-capsulates frames or cells, and decouplesinput and output rates.The next station is the PMS-TC (physicalmedia-specific – transmission convergence)layer, which provides latency path func-tions. These functions determine the error-protection capability (together with Trellis coding) and latency. Framing also takes place in the PMS-TC.Ordinarily, only one latency path is im-plemented in ADSL2/plus. This is not a lim-itation of the standard, however. Examina-tion of the latency path (Figure 14) shows that an interleaver used together with Reed-Solomon code creates a powerful error-protection mechanism. However, the inter-leaver introduces delay proportional to its depth; that is, if there is only one latency path and interleaving is used, then every ser-vice experiences the same delay. Services such as video, which must be im-mune to short bursts of errors, must have great interleaver depth. As a consequence, they also experience significant delay. Video service is not sensitive to delay, however, provided there is little jitter. Voice and gaming services, on the other hand, do not require extensive error protection but theyare very sensitive to delay.A dual-latency solution provides a second latency path in the PMS-TC. Data that must be protected uses the interleaved path while data that is sensitive to delay can use the path without interleaving or with only a minimum of interleaving. Eventually, the data streams from each of the latency paths are multiplexed into a single bit stream that is conveyed to the physical media-dependent (PMD) layer for modulation. The number of bits taken from each latency path and put into one DMT frame is determined during initialization. The output from the PMD layer is the analog signal delivered to the analog front end. Operators have indi-cated that they want the dual-latency option in VDSL2 in order to provide the QoS re-quired of triple-play services.Power control for improved spectral compatibilityVDSL2 will mostly be used on short loops, pushing DSLAMs further out into the net-work closer to user premises. It is anticipat-ed that FTTCab deployments will increasein all operator networks. However, servicessuch as ADSL/2/2plus, which are operatedfrom a central office environment and whichshare the binder used for VDSL2 in the cab-inet might experience severe degradation ofdownstream data performance due tocrosstalk from VDSL2 systems. Power con-trol can be used to shape the downstreamVDSL2 signal. This minimizes the impactof crosstalk from VDSL2 systems on central office-based ADSL2/plus systems without penalizing the downstream VDSL2 signal. Upstream power backoffWhen different sets of VDSL2 customerpremises equipment (CPE) are located at un-equal distances from the central office or the cabinet, the transmission of users closest to the central office or cabinet disturbs the up-stream transmission of other users (near-far phenomenon, Figure 14).9A simple reme-dy to this problem is to back off the up-stream power of users closest to the centraloffice or cabinet. An algorithm is thus usedto give every user within a given radius ofthe central office or cabinet the same up-stream capacity.Loop diagnostics modeTo facilitate fault diagnosis, VDSL2 has aloop diagnostic mode and DELT similar tothat defined for ADSL2/plus. VDSL2 trans-ceivers can measure line noise, loop attenu-ation, and signal-to-noise ratio (SNR) ateach end of the line. The measurements can be collected even when line conditions aretoo poor to enable a connection. In this case,as part of the loop diagnostic mode, themodem goes through each step of initial-ization but with improved robustness inorder to exchange the test parameters. Impulse noise protectionElectrical appliances and installations atcustomer premises often generate shortbursts of noise of relatively high amplitude.These bursts, called impulse noise, are elec-tromagnetically coupled into the digital subscriber line, degrading performance and in some cases disrupting service. The ADSL2/plus standard introduced a parame-ter (impulse noise protection, INP) that al-lows operators to select the maximum im-pulse length that the system can correct. VDSL2 uses this same parameter. In effect, an INP value of between 2 and 16 can cor-rect errors from noise impulses ranging from 250µs to 3.75ms in length.Interoperability Interoperability between vendors is a pre-requisite of mass-market technology. Inter-operability testing has thus had a vital role in paving the way for today’s commercial success of DSL: nearly 19 million digital subscriber lines were rolled out during the third quarter (Q3) of 2005.10The DSL Forum is the main driving force behind interoperability. The actual inter-operability tests are performed via “plug fests” which are run by several independent test labs around the world. An advocate of open interfaces, Ericsson has been an active participant at these events. For ADSL2plus, the TR-067 (formerly TR-048) specifies in detail how interoperability is to be tested. Extensive interoperability testing has opened the door to separate DSLAM and CPE markets in many countries.VDSL2 interoperabilityThe initial VDSL standard was never fully embraced by the market due to disagree-ments during standardization regarding modulation scheme (DTM or QAM) and packet technology (ATM or Ethernet). Broad industry consensus and interoper-ability testing of VDSL2 is at the top of ven-dor agendas in 2006. A first meeting for chipset vendors took place at the end of Jan-uary at the University of New Hampshire InterOperability Laboratory. Experience from working with ADSL tells us it will take at least 12 months to reach full interoper-ability in the market: for ADSL2plus the process from agreement on the standard to interoperability in the market took nearly 18 months.The first step in the process is to gain layer-1 interoperability between chipset vendors. With that hurdle cleared, system vendors can perform additional tests be-tween CPE and DSLAMs.The DSL Forum is defining the frame-work for the VDSL2 tests in several impor-tant documents that will guide the indus-try forward. The two main documents cur-rently under development are:。
VDSL2
一、VDSL2技术发展及存在的问题继第一代VDSL后，ITU于2006年2月通过了VDSL2（第二代VDSL）的标准G.993.2。
VDSL2通过扩展频谱至30MHz，可在短距离内实现双向对称100Mbit/s的高速数据传送，从而为高速上网、互联网游戏以及视频业务等应用提供充足的带宽，因此具有良好的应用前景。
VDSL2系统拓宽的频带范围和更短的传输距离同时也带来了比ADSL以及ADSL2/2+更为严重的噪声干扰，包括线路间串扰、背景噪声干扰、脉冲噪声干扰和业务无线电干扰，这些都会对VDSL2业务产生影响。
同时，若不对VDSL2系统的频谱及发射功率加以控制，则可能出现发送功率超出实际需要而产生很大的NoiseMargin的情况，这不但无益于系统的稳定性，还可能因为线路间的串扰制约系统性能的进一步提升。
因此需要通过频谱管理技术来优化VDSL2的配置，从而实现VDSL2系统性能和稳定性的大幅度提升。
二、频谱管理技术由于VDSL2采用FDM方式，近端串扰的影响可以通过滤波器大大降低，但是远端串扰与系统中的接收信号始终是处在同一频段的，无法用滤波器滤除。
此时，若各设备都以最大PSD限制来发送信号，就会大大提高线路间的串扰，造成各设备性能的下降，从而大大降低整个线缆的容量。
因此，需要通过协调线缆中不同设备的发送信号频谱，才能使得在线缆层次上达到性能最优。
频谱管理主要分静态频谱管理和动态频谱管理。
1.静态频谱管理为了避免线路间串扰以及外界干扰导致性能和稳定的严重下降，可以在设备初始化训练过程中选择合适的频谱及相应的参数配置，并在后续的通信过程中加以确定，这就是静态频谱管理技术，通常可通过频谱整形（PSDShaping）来实现，如图1所示。
图1中，对于Centraloffice和R T之间的频谱给出了三种不同的做法，其中a将R T发送信号平坦地削减一定的幅度使得串扰的影响降低；由于高频信号衰减速率要快于低频信号，长线的高频部分实际上已经不可用，因此b将R T的频带放在高端，而CO占据低频段，这样由于互相之间的频谱不重叠，串扰信号可以被滤波器消除；c在b的基础上更进一步，根据线路对信号的衰减与频率的1/2次方成正比的特点，CO和R T的频谱有一些重叠，在重叠部分的功率谱密度随频率削减，使得串扰信号相对于接收信号可以忽略。
VDSL2技术原理及应用
VDSL2技术原理及应用VDSL2（Very-high-speed Digital Subscriber Line 2）是一种用于接入互联网的宽带通信技术。
它是DSL（Digital Subscriber Line）技术的一种改进和升级，提供了更高的传输速度和更大的带宽。
VDSL2技术原理和应用非常重要，下面详细介绍。
1.使用高频谱段：VDSL2技术利用了较高的频谱范围，通常介于30kHz到30MHz之间，相比之下，传统的ADSL技术只使用了10kHz到1.1MHz的频谱范围。
通过扩大频谱范围，VDSL2技术能够提供更高的传输速率和更大的带宽。
2.多个载波技术：VDSL2技术采用了多个载波技术，每个载波通常有不同的传输速率。
通过同时传输多个载波，VDSL2技术能够提供更高的总传输速率。
同时，VDSL2技术还采用了碰撞避免算法，以减少不同载波之间的干扰。
3. 提高调制方式：VDSL2技术采用了高级调制方式，如16QAM （Quadrature Amplitude Modulation）和64QAM等。
这些调制方式比传统的QPSK（Quadrature Phase Shift Keying）调制方式提供了更高的传输速率。
4. 使用信道编码技术：VDSL2技术采用了信道编码技术，如前向纠错编码（Forward Error Correction，FEC）和反馈串扰抵消（FeedBack Cancellation，FBC）等。
这些技术能够降低传输中的错误率，提高传输质量。
1.家庭和企业网络接入：VDSL2技术可以提供较高的传输速率，适用于家庭和企业的宽带接入。
家庭用户可以通过VDSL2技术获得更快速的网络连接，支持高清视频、在线游戏和视频会议等应用。
而企业用户可以通过VDSL2技术实现高速、可靠的数据传输，满足各种业务需求。
2.移动基站回传：VDSL2技术可以用于移动通信基站的回传链路。
传统的T1/E1线路在带宽和传输距离上存在限制，而VDSL2技术可以提供更高的传输速率和更长的传输距离，满足移动通信基站对带宽和信号传输的需求。
最大限度地减小噪声对VDSL2网络“始终在线”服务的影响
全球的数字用户线路 （ Ｓ ）数量 ＤＬ
本文讨论 的重 点在 ： ・ Ｄ Ｌ线路性能降低 的常见 原 Ｓ 因： 串扰、 非平稳无线 电干扰、 脉冲噪 声和温度 变化
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不 同于以往 的 ｘ Ｓ ， ＤＳ ２采用 了大 Ｄ ＬＶ Ｌ
・ 把噪 声影 响降至最低确保服务 量 的改进技术 ，能够 更好地 处理不 同 “ 始终在线” 的技 术 运营 商的不同带宽需求 。例如 ， Ｄ Ｌ Ｖ Ｓ２
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广泛 的部署环境 。每一个 Ｐｏｉ ｒｆ ｌ ｅ都有
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个 特 定 的 带 宽 （ ８ ｚ ３ ＭＨ ） 从 ＭＨ 到 ０ ｚ，
Ｓ Ａ 及 比特交换技术也 可以改变数据 化 ，以及增 强抗干扰 性和提 高运营效 有不同的功率和功率谱密度 （Ｓ ）屏 Ｒ） ＰＤ
必须在所有级别上考虑到 ｘ Ｓ Ｄ Ｌ系 蔽限制 。 率， 以适应 随时间变化 的环路条件 ， 但 率 ， 此外 ， 每一个 Ｐｏｉ 还 针对 特 ｒｆ ｌ ｅ Ｓ 这些方案往 往无法 始终保持线路 的完 统 的性价 比优化 。一个经优 化的 Ｄ Ｌ 定的覆盖距 离和数据 率进行优 化。同 Ｖ Ｓ ２还扩展 了 Ｖ Ｓ １的覆盖 ＤＬ 整性及相 关的开销通 道 ，尤其是在 噪 系统再 加上有保证 的服务可靠 性和稳 样地， Ｄ Ｌ
VDSL2技术发展及芯片解决方案分析
VDSL2技术发展及芯片解决方案分析通过传统电话线路(POTS)实现数据传输的技术，从1996年以前的模拟调制解调器(V.32, V.34, 56K)演变成了后来的非对称数字用户线路(ADSL)，真正实现了宽带互联网接入。
ADSL技术最早是ANSI T1.413，历经了ADSL(G.dmt 和G.Lite)、ADSL2 (G.dmt.bis 和G.Lite.bis)、ADSL2+、VDSL，发展到今天的终极版本VDSL2。
DSL技术每次的演进涉及频谱扩展、提高传输速率和距离、增强稳定性和互通性、缩短上线时间、完善自检功能等等。
扩展频谱是利用更宽的频谱使得在同一根电话线上能够传输更高的速率，由于在等长的电话线上高频部分信号更加容易被衰减，为了使得扩展后的频段(高频部分)能够被有效地使用，传输距离–即从局端(CO)到客户端(CPE)的距离就需要缩短，十几年来电信基础设施的发展满足了这种需求。
除了上述已被全球运营商广泛使用的ADSL技术外，还有一些特殊应用的DSL技术，例如HDSL、SDSL、HDSL2和HSDSL。
VDSL2技术VDSL2的ITU正式编号为G.993.2，它是在ADSL2和VDSL标准的基础上发展而来的。
VDSL2进一步扩展了VDSL的频谱，使得在短距离环路上数据传送速率得到更大提高，300米内的双向速率和可达到200M；同时VDSL2延续了ADSL2的长距离环路传输的能力，保持了QoS功能，如双延迟通道、交织与解交织等，满足宽带用户对无干扰视频传输和电信级VoIP服务的质量要求，从而确保“三网合一”业务的大规模开展。
ITU-T G.993.2 VDSL2标准在附录中(Annex A/B/C)定义了四个频率分配计划，以对应于不同地区的需求：Annex A –北美地区；Annex B –欧洲地区(Annex B里面定义了两个频带计划997和998，分别提供上下行对称和非对称带宽)；Annex C –日本。
串音
的特性和影响
的特性和影响
串音简单地说就是由于DSL所使用的双绞线各线对之间是非屏蔽的，线对间的电磁干扰会导致一对双绞线上 的信号对另外一对双绞线上的信号产生影响。通常认为串音存在于同一电缆束中的各线对之间，且一条双绞线会 受到来自多条线对的干扰。
串音按其特性通常分为“近端串音( NEXT)”和“远端串音(FEXT)”。NEXT是干扰线对的发射机与被干扰线 对的接收机位于同一端，此时干扰信号沿着干扰线对出发，耦合到被干扰线对，然后传回到被干扰线对的接收机； FEXT是干扰线对的发射机远离被干扰线对的接收机，此时干扰信号沿着干扰线对传播，耦合到被干扰线对，然后 产生的串音信号沿着被干扰线对传送到其接收机 。
同样地，还可以对各个同步接收用户端发来的信号做联合处理，消除CO近端串音的影响。以上是串音消除技 术的原理，其实现主要分为三个步骤：信道估计、串音消除以及信道跟踪与更新，其中信道跟踪与更新是通过重 复前两个步骤，来适应不断变化的线路情况 。
信道估计算法
信道估计算法
信道估计是指在串音消除过程中，如何获取线对间的串音传递函数矩阵，已有很多相关的研究报告和论文。 信道估计算法可分为频域信道估计和时域信道估计，大多数都是针对频域信道估计的，这又主要集中在两个方面， 一是通过RLCG一次参数线路模型推导，另一种方法就是通过多用户
k
近端 NearEndCross talk
远端FandCrosstalk
远端串音(FEXT)是在同一电缆束内其他双绞线对位于远端工作的发射机，引起对于本双绞线对中相同方向 另一端接收机造成的干扰。这种远端串音经过环路传输而被平滑衰减，因此其造成的影响较小。
近端NearEndCrosstalk
但是和其他DSL技术相比，VDSL2由于使用很宽的频段，受到的线路噪声干扰也更为严重;而且高频信号本身 的衰减很大，对线路噪声非常敏感，因此噪声已经成为制约VDSL2系统传输性能和稳定性的主要因素。
VDSL技术的基础知识与应用
VDSL技术的基础知识与应用随着科技的不断发展，人们对于网络速度的需求越来越高，而传统的ADSL无法满足大众的需求。
这时候，VDSL技术应运而生。
VDSL是Very-high-bit-rateDigital Subscriber Line（非常高速数码用户线）的缩写，它是一种高速的数字用户线技术，可以提供比ADSL更高的网络带宽和更快的下行速度。
今天，我们来了解一下VDSL技术的基础知识和应用。
一、VDSL技术简介1.1 VDSL技术的原理VDSL技术利用数字电路的传输方式，使用户在电话线上传输数据和语音，是DSL（数字用户线）技术的高速版本。
它的上传速度和下载速度都比ADSL快，尤其是下载速度。
VDSL最大的特点是能够提供两个传输频带，一个是高频带（2.2~30MHz），一个是低频带（25kHz~2.2MHz），为用户提供更高频宽和更多的带宽资源，从而让用户享受更快的网速和更好的网络体验。
1.2 VDSL技术的类型目前，VDSL技术包括两种类型：VDSL和VDSL2。
VDSL是标准的VDSL技术，它采用高频带（12MHz~30MHz）进行数据传输，最大传输距离为300米。
在此传输距离内，用户可以享受高达52Mbps的下载速度和16Mbps的上传速度。
VDSL2比标准VDSL技术更高效，它采用更宽的频带进行数据传输（目前为17MHz），最大传输距离为1.2公里。
在前面300米的传输距离内，用户可以享受高达100Mbps的下载速度和40Mbps的上传速度。
在1.2公里内，用户可以达到30Mbps的下载速度和10Mbps的上传速度。
以上是两种VDSL技术的具体参数，实际上，这些参数会受到各种因素的影响，如电缆长度、电缆质量等。
二、VDSL技术的应用2.1VDSL在家庭网络中的应用VDSL技术可以将广域网（WAN）与局域网（LAN）相连，越来越多的家庭和企业采用VDSL技术搭建数字化网络。
在家庭网络中，VDSL可以提供高速的互联网接入，同时支持多媒体传输、视频监控、在线游戏、视频会议等应用。
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vdsl2
proprietary-feat
psd-shape-down regionbm2-psd-down
psd-shape-up regionbm2-psd-up
rx-psd-shape-up etsi-f
v-noise-psd-down ""
min-bitrate-up 128
max-bitrate-down 100000
max-bitrate-up 100000
max-delay-down 4
max-delay-up 4
active
exit
===========================================================
exit
vdsl2
proprietary-feat
psd-shape-down regionbm2-psd-down
psd-shape-up regionbm2-psd-up
rx-psd-shape-up etsi-f
v-noise-psd-down ""
active
exit
spectrum-profile 12 name 8A-B7-6
version 1
dis-ansi-t1413
dis-etsi-dts
dis-g992-1-a
dis-g992-1-b
dis-g992-2-a
dis-g992-3-a
optional-band up
adsl-band allow-adsl
pbo-mode-down
exit
vdsl2
proprietary-feat
psd-shape-down regionbm2-psd-down
psd-shape-up regionbm2-psd-up
proprietary-feat
exit
vdsl
proprietary-feat
vdsl-band-plan band-plan-b4
optional-band up
optional-endfreq 276
adsl-band allow-adsl
====================================
service-profile 1 name CHINATELECOM
version 1
min-bitrate-down 128
min-bitrate-up 128
max-bitrate-down 100000
pbo-mode-down
exit
vdsl2
proprietary-feat
psd-shape-down regionbm2-psd-down
psd-shape-up regionbm2-psd-up
rx-psd-shape-up etsi-f
pbo-mode-down
exit
vdsl2
proprietary-feat
psd-shape-down regionbm2-psd-down
psd-shape-up regionbm2-psd-up
rx-psd-shape-up etsi-f
dis-etsi-ts
g993-2-8a
rf-band-list 00
adsl-adsl2
proprietary-feat
exit
re-adsl
proprietary-feat
exit
adsl2-plus
proprietary-feat
spectrum-profile 11 name 8A-B7-5
version 1
dis-ansi-t1413
dis-etsi-dts
dis-g992-1-a
dis-g992-1-b
dis-g992-2-a
dis-g992-3-a
dis-g992-3-b
dis-ansi-t1413
dis-etsi-dts
dis-g992-1-a
dis-g992-1-b
dis-g992-2-a
dis-g992-3-a
dis-g992-3-b
dis-etsi-ts
g993-2-8b
rf-band-list 00
dis-etsi-dts
dis-g992-1-a
dis-g992-1-b
dis-g992-2-a
dis-g992-3-a
dis-g992-3-b
dis-etsi-ts
g993-2-8b
rf-band-list 00
adsl-adsl2
proprietary-feat
adsl-adsl2
proprietary-feat
exit
re-adsl
proprietary-feat
exit
adsl2-plus
proprietary-feat
exit
vdsl
proprietary-feat
vdsl-band-plan band-plan-b4
v-noise-psd-down ""
dis-etsi-dts
dis-g992-1-a
dis-g992-1-b
dis-g992-2-a
dis-g992-3-a
dis-g992-3-b
dis-etsi-ts
g993-2-8b
rf-band-list 00
adsl-adsl2
proprietary-feat
proprietary-feat
exit
adsl2-plus
proprietary-feat
exit
vdsl
proprietary-feat
optional-band up
adsl-band allow-adsl
pbo-mode-down
exit
vdsl
proprietary-feat
vdsl-band-plan band-plan-b4
optional-band up
adsl-band allow-adsl
pbo-mode-down
exit
vdsl2
proprietary-feat
psd-shape-down regionbm2-psd-down
psd-shape-up regionbm2-psd-up
rx-psd-shape-up etsi-f
v-noise-psd-down ""
v-noise-psd-up ""