LDSL发展的第一步READSL

LDSL是ITU的一个研究课题，其目标是延长DSL传输距离。READSL是LDSL课题发展的第一步，它能使基于G．992．1／G．992．3的ADSL传输距离延长至18kft(约5．5km)。文中分析了延长ADSL传输距离的技术难点以及可行的解决方案，最后介绍了频谱分配技术在READSL中的应用。     

铜双绞线模型仿真与其信道容量分析

通过分析ADSL传输线路,对铜制双绞线进行了分析,包括线路特性、噪声特性的仿真.仿真中参考了6种典型的CSA环路作为分析的依据,讨论了近端串音(NEXT)、远端串音(FEXT)以及高斯白噪声对传输线路的影响,并将ADSL线路和HDSL、T1以及ISDN线路近端串音作了比较,最后得到ADSL信道的传送容量与线路长度的关系曲线.     

xDSL设备的测试技术

DSL技术支持的线对数速率③Mbit/s0.4线经上传输距离km线路编码方式相关标准应用情况HDSL①1,2,3对称23～42B1Q或CAPITU-TG.991.1YDN056-1997YDN059-1997主要用于延长传统E1应用的传输距离,如移动基站之间的互连等SHDSL1对称0.192～2.33～10TC-PAMITU-TG.991.2YD/T1185-2002宽带接入应用、ATM应用等ADSL.dmt(带话音分离器的全速率ADSL)1最大下行6,最大上行0.0404DMTITU-TG.992.1G.dmtYD/T1055-2000YD/T1188-2002宽带接入、Internet接入、IP应用、VOD点播、多媒体应用等ADSL.lite(不带话音分离器的子速率AD…     

对ADSL接人方式铜缆可用线对率的分析

指出了为发展ADSL而提高市话音频铜线电缆的传输质量和维护水平的必要性，分析了铜线电缆线对有关指标参数低劣的原因和对传输ADSL的影响，并提出了一些改进的意见。     

全塑市话电缆对ADSL传输的影响及改进措施

本文通过济南本地网内市话电缆的现状,分析全塑市话电缆对ADSL传输的影响,提出相应的改进措施。     

对ADSL接入方式铜缆可用线对率的分析

指出了为发展ADSL而提高市话音频铜线电缆的传输质量和维护水平的必要性,分析了铜线电缆线对有关指标参数低劣的原因和对传输ADSL的影响,并提出了一些改进的意见。     

ADSL2＋技术特点与标准简介

从传统的ADSL到ADSL2 ,有一个中间的协议ADSL2,既G.992.3。ADSL2标准在传统ADSL的基础上,做了很多增强:如提高线路稳定性,增加可达距离,增强的线路检测能力,更强的功率控制等等。本文着重介绍了ADSL2中所没有的ADSL2 的技术特点。     

浅谈广电网双向改造的几种接入方案

1 ADSL方式 非对称数字用户线技术(ADSL,Asymmetric Digital Subscriber Line))方式是一种主要应用于电信网络的传输方式,其物理底层为铜双绞线(见表1),它是继56kb/s M0dem和64～128kb/s以后的一种传输方式.其传输带宽一般为512k,即使采用ADSL2+(G.992.5)标准,在接入距离大于7km时,存在串音的情况下,在0.4mm2的电话线上上行速率只能保证128kbps,下行速率只能保证192kbps.     

用于ADSL2+芯片组的2.2MHz降压或升压变换电源

过去几年来,ADSL标准沿着ADSL、ADSL2、ADSL2 以及"Extended Reach ADSL2"逐步演进,数据传输率增加到24Mb/s,传输距离长达22000英尺.ADSL2标准规定的下行频段上至1.1MHz,而ADSL2 为2.2MHz,使较短电话线上的数据传输率显著提升.图1和图2给出了不同标准所覆盖的带宽、数据速率和距离.当同一线束中传输多条ADSL业务时,ADSL2 也可用于降低串扰.     

中国联通现网测试G.654.E光纤陆地应用性能优越

目前国内外运营商和光纤光缆供应商已开展400G技术研究及测试,主流400G技术均存在无电中继距离受限的问题,而相关实验室测试证明,基于新型光纤技术,可以很好地提升400G传输能力、延长传输距离、降低网络整体建设成本. 为了更好满足400G等超高速传输技术应用,ITU-T自2013年7月开始讨论适用于陆地传输系统应用的G.654光纤(G.654.E),在保持与现有陆地用单模光纤基本性能一致的前提下,增大光纤有效面积,同时降低光纤衰减系数,从而提升400G传输性能.     

The first step of long-reach ADSL: smart DSL technology, READSL

Long-reach DSL (LDSL) is a project in the ITU, with the objective to increase the reach of DSL solutions. Range extended ADSL (READ-SL) is the first step in the LDSL project, driven primarily by requirements for North America. READSL extends the connectivity of G.992.1/G.992.3 based ADSL up to 18 kft, increasing the ADSL reach by more than 3 kft under the severe crosstalk conditions typically experienced in the North American access network. To cope with the multiple physical layer field conditions, READSL uses "smart" DSL technology based on a selectable mask procedure. READSL is spectrally compatible with the basis systems in the North American Spectrum Management Standard T1.417, and requires minimum changes to both the G.992.1/G.992.3 standards and product platforms. This article reviews READSL as a subset of the LDSL project.     

Residential broadband architecture over ADSL and G.Lite (C.992.2):PPP over ATM

The objective of this article is to present the end-to-end broadband service and protocol architecture over DSL that has been adopted for both ADSL and G.Lite (PPP over ATM). G.Lite is a new form of DSL, and its characteristics are discussed. The article then presents a vision for the evolution of an analog modem-based service to G.Lite and ADSL services. The article explains the standardized architecture of PPP over ATM for DSL, and explores how the unique characteristics of G.Lite affect higher-layer protocols (PPP over ATM). Finally, it discusses a vision of how DSL will be deployed together with home networking to provide broadband services to multiple devices in a user-friendly fashion     

The error performance of digital subscriber lines in the presenceof impulse noise

This paper describes the error performance of the ISDN basic access digital subscriber line (DSL), the high bit rate digital subscriber line (HDSL), and the asymmetric digital subscriber line (ADSL) in the presence of impulse noise. Results are found by using data from the 1986 NYNEX impulse noise survey in simulations. It is shown that a simple uncoded ADSL would have an order of magnitude more errored seconds than DSL and HDSL     

ADSL宽带测试技术

介绍国内外数字用户线DSL业务现状、发展趋势、宽带测试需求分忻以及ADSL宽带测试技术，测试项目、组网技术等。     

ADSL网络体系结构

ADSL是DSL的一种非对称版本，是目前一种重要的宽带接入方式，ADSL能够向终端用户提供8Mbit/s的下行传输速率和1Mbit/s的上行传输速率，比传统的28．8kbit/s模拟调制解调器快将近200倍。文中讨论了一组能够支持基于PPP／ATM／ADSL接入网体系结构的核心网体系结构，分析了几种不同组网方式的特征与协议栈模型。     

DSL技术的发展趋势

详细介绍了当前三种主要的DSL技术--ADSL、VDSL、SHDSL的发展过程及趋势,并结合DSL的应用情况分析了DSLAM技术的发展趋势.     

DSL技术及其在宽带设备中的应用

数字用户线(DSL)技术是国内宽带接入的主流技术,DSLAM(DSL接入复用器)是目前广泛使用的局端宽带接入设备。文中从传输速率、传输距离等方面介绍了ADSL(非对称用户线)、SHD-SL(单线对高速数字用户线)、VDSL(甚高速数字用户线)等多种DSL技术特性,讨论了DSLAM与DSL的复合技术,提出基于SHDSL技术的高速对称数据传输方案将成为IP-DSLAM系统的发展方向。还对基于SHDSL技术的IP-DSLAM网络结构、工作原理进行了阐述。     

Near-end crosstalk mitigation in ADSL systems

Near-end crosstalk (NEXT) is one of the major impairments to the current asymmetric digital subscriber line (ADSL) downstream transmission. This paper presents two methods for an ADSL receiver to cancel one (dominant) NEXT signal from other types of services (such as HDSL (high-bit-rate DSL), SDSL (single-pair, symmetric DSL), T1, etc.). The methods exploit the fact that the crosstalk signal has a large excess bandwidth and its spectra in the main lobe and in the excess band are strongly correlated. The principal idea is then to estimate the crosstalk in some frequency bands (e.g., excess band) and cancel it in other frequency bands (e.g., main lobe). The frequency-domain analysis in this paper provides an intuitive explanation of the crosstalk estimation and cancellation, as well as a guidance to select the right frequency bands to observe the crosstalk signal. Moreover, a fast algorithm is proposed for practical implementation. This algorithm avoids matrix inversion and large matrix multiplication in every transmission block. Simulation results show that one of the proposed methods, minimum mean-squares error estimation and cancellation, is very effective to cancel one (dominant) NEXT and the improvement is significant in terms of the data rate and the line reach for the ADSL service. For example, using a real measured NEXT transfer function, the proposed method can increase the ADSL downstream data rate by 200% for some loops. The methods are extended to estimate and cancel two or more crosstalkers. The amount of improvement depends on the crosstalkers' characteristics and it is generally less than that of a single crosstalker case     

金属线缆用户接入网技术

说明了充分利用现有金属线缆用户线的必要性，介绍了数字用户线ＤＳＬ技术的概念，对各种ＤＳＬ技术类型的传输速率、传输距离做了比较，对其中的ＨＤＳＬ和ＡＤＳＬ技术类型的思路、原理等做了详细的说明。     

数字用户线的充分利用

文章介绍公共交换电话网数字用户线(DSL)和非对称数字用户线(ADSL)的基本形式。概括说明在数字用户线上传送话音(VoDSL)的技术特点和传送通路化话音(CVoDSL)的优点及其相关问题。