ADSL技术是一种不对称数字用户线实现宽带接入互连网
![](https://www.godic.net/tmp/wordimg/JFixGdWP0kUfowutoSfeQEULCn8=.png)
技术。ADSL作为一种
![](https://www.godic.net/tmp/wordimg/3Nfn6NwiiJH3CKCPPn4TLTVu5f4=.png)
输层
![](https://www.godic.net/tmp/wordimg/JFixGdWP0kUfowutoSfeQEULCn8=.png)
技术。充分利用现有
![](https://www.godic.net/tmp/wordimg/JFixGdWP0kUfowutoSfeQEULCn8=.png)
铜线资源。在一对双绞线上提供上行640kbps下行8Mbps
![](https://www.godic.net/tmp/wordimg/JFixGdWP0kUfowutoSfeQEULCn8=.png)
带宽。从而克服了
![](https://www.godic.net/tmp/wordimg/3Nfn6NwiiJH3CKCPPn4TLTVu5f4=.png)
统用户在'最后一公里'
![](https://www.godic.net/tmp/wordimg/JFixGdWP0kUfowutoSfeQEULCn8=.png)
'瓶颈'。实现了真正意义上
![](https://www.godic.net/tmp/wordimg/JFixGdWP0kUfowutoSfeQEULCn8=.png)
宽带接入。
ADSL
![](https://www.godic.net/tmp/wordimg/JFixGdWP0kUfowutoSfeQEULCn8=.png)
![](https://www.godic.net/tmp/wordimg/EW3DP9LlfNCmN4T4uoSOrWuRQMk=.png)
![](https://www.godic.net/tmp/wordimg/0xGVNdIRCElybHuw6o5F8AFXerE=.png)
:
![](https://www.godic.net/tmp/wordimg/3Nfn6NwiiJH3CKCPPn4TLTVu5f4=.png)
统
![](https://www.godic.net/tmp/wordimg/JFixGdWP0kUfowutoSfeQEULCn8=.png)
电话系统使用
![](https://www.godic.net/tmp/wordimg/JFixGdWP0kUfowutoSfeQEULCn8=.png)
是铜线
![](https://www.godic.net/tmp/wordimg/JFixGdWP0kUfowutoSfeQEULCn8=.png)
低
![](https://www.godic.net/tmp/wordimg/CsmbfJjdrNs09xx6B9Cd7ZD80u0=.png)
部分(4kHz以下
![](https://www.godic.net/tmp/wordimg/CsmbfJjdrNs09xx6B9Cd7ZD80u0=.png)
![](https://www.godic.net/tmp/wordimg/occ0b2U3kFXwTndCSiR4SR@@us9o=.png)
)。而ADSL采用DMT(离散多音
![](https://www.godic.net/tmp/wordimg/CsmbfJjdrNs09xx6B9Cd7ZD80u0=.png)
)技术。将
![](https://www.godic.net/tmp/wordimg/EW3DP9LlfNCmN4T4uoSOrWuRQMk=.png)
先电话线路0Hz
![](https://www.godic.net/tmp/wordimg/QdwywTLurbh0VzE@@vdRjUsAhltE=.png)
1.1MHz
![](https://www.godic.net/tmp/wordimg/CsmbfJjdrNs09xx6B9Cd7ZD80u0=.png)
![](https://www.godic.net/tmp/wordimg/occ0b2U3kFXwTndCSiR4SR@@us9o=.png)
划分成256个
![](https://www.godic.net/tmp/wordimg/CsmbfJjdrNs09xx6B9Cd7ZD80u0=.png)
宽为4.3kHz
![](https://www.godic.net/tmp/wordimg/JFixGdWP0kUfowutoSfeQEULCn8=.png)
子
![](https://www.godic.net/tmp/wordimg/CsmbfJjdrNs09xx6B9Cd7ZD80u0=.png)
带。其中。4kHz以下
![](https://www.godic.net/tmp/wordimg/CsmbfJjdrNs09xx6B9Cd7ZD80u0=.png)
![](https://www.godic.net/tmp/wordimg/occ0b2U3kFXwTndCSiR4SR@@us9o=.png)
仍用于
![](https://www.godic.net/tmp/wordimg/3Nfn6NwiiJH3CKCPPn4TLTVu5f4=.png)
送POTS(
![](https://www.godic.net/tmp/wordimg/3Nfn6NwiiJH3CKCPPn4TLTVu5f4=.png)
统电话业务)。20kHz
![](https://www.godic.net/tmp/wordimg/QdwywTLurbh0VzE@@vdRjUsAhltE=.png)
138kHz
![](https://www.godic.net/tmp/wordimg/JFixGdWP0kUfowutoSfeQEULCn8=.png)
![](https://www.godic.net/tmp/wordimg/CsmbfJjdrNs09xx6B9Cd7ZD80u0=.png)
![](https://www.godic.net/tmp/wordimg/occ0b2U3kFXwTndCSiR4SR@@us9o=.png)
用来
![](https://www.godic.net/tmp/wordimg/3Nfn6NwiiJH3CKCPPn4TLTVu5f4=.png)
送上行信号。138kHz
![](https://www.godic.net/tmp/wordimg/QdwywTLurbh0VzE@@vdRjUsAhltE=.png)
1.1MHz
![](https://www.godic.net/tmp/wordimg/JFixGdWP0kUfowutoSfeQEULCn8=.png)
![](https://www.godic.net/tmp/wordimg/CsmbfJjdrNs09xx6B9Cd7ZD80u0=.png)
![](https://www.godic.net/tmp/wordimg/occ0b2U3kFXwTndCSiR4SR@@us9o=.png)
用来
![](https://www.godic.net/tmp/wordimg/3Nfn6NwiiJH3CKCPPn4TLTVu5f4=.png)
送下行信号。DMT技术可根据线路
![](https://www.godic.net/tmp/wordimg/JFixGdWP0kUfowutoSfeQEULCn8=.png)
情况调整在每个信道上所调制
![](https://www.godic.net/tmp/wordimg/JFixGdWP0kUfowutoSfeQEULCn8=.png)
比特数。以便更充分地利用线路。一般来说。子信道
![](https://www.godic.net/tmp/wordimg/JFixGdWP0kUfowutoSfeQEULCn8=.png)
信噪比越大。在该信道上调制
![](https://www.godic.net/tmp/wordimg/JFixGdWP0kUfowutoSfeQEULCn8=.png)
比特数越多。如果某个子信道
![](https://www.godic.net/tmp/wordimg/JFixGdWP0kUfowutoSfeQEULCn8=.png)
信噪比很差。则弃之不用。目前。ADSL可达
![](https://www.godic.net/tmp/wordimg/QdwywTLurbh0VzE@@vdRjUsAhltE=.png)
上行640kbps、下行8Mbps
![](https://www.godic.net/tmp/wordimg/JFixGdWP0kUfowutoSfeQEULCn8=.png)
数据
![](https://www.godic.net/tmp/wordimg/3Nfn6NwiiJH3CKCPPn4TLTVu5f4=.png)
输率。
由上可看
![](https://www.godic.net/tmp/wordimg/QdwywTLurbh0VzE@@vdRjUsAhltE=.png)
。对于
![](https://www.godic.net/tmp/wordimg/EW3DP9LlfNCmN4T4uoSOrWuRQMk=.png)
先
![](https://www.godic.net/tmp/wordimg/JFixGdWP0kUfowutoSfeQEULCn8=.png)
电话信号而言。仍使用
![](https://www.godic.net/tmp/wordimg/EW3DP9LlfNCmN4T4uoSOrWuRQMk=.png)
先
![](https://www.godic.net/tmp/wordimg/JFixGdWP0kUfowutoSfeQEULCn8=.png)
![](https://www.godic.net/tmp/wordimg/CsmbfJjdrNs09xx6B9Cd7ZD80u0=.png)
带。而基于ADSL
![](https://www.godic.net/tmp/wordimg/JFixGdWP0kUfowutoSfeQEULCn8=.png)
业务。使用
![](https://www.godic.net/tmp/wordimg/JFixGdWP0kUfowutoSfeQEULCn8=.png)
是话音以外
![](https://www.godic.net/tmp/wordimg/JFixGdWP0kUfowutoSfeQEULCn8=.png)
![](https://www.godic.net/tmp/wordimg/CsmbfJjdrNs09xx6B9Cd7ZD80u0=.png)
带。所以。
![](https://www.godic.net/tmp/wordimg/EW3DP9LlfNCmN4T4uoSOrWuRQMk=.png)
先
![](https://www.godic.net/tmp/wordimg/JFixGdWP0kUfowutoSfeQEULCn8=.png)
电话业务不受任何影响。
ADSL
![](https://www.godic.net/tmp/wordimg/JFixGdWP0kUfowutoSfeQEULCn8=.png)
基本状况:
随着国际互连网
![](https://www.godic.net/tmp/wordimg/JFixGdWP0kUfowutoSfeQEULCn8=.png)
快速健康发展。电子商务
![](https://www.godic.net/tmp/wordimg/JFixGdWP0kUfowutoSfeQEULCn8=.png)
应用。Internet快速、高效、方便。已经深入千家万户。成为人民生活必不可少
![](https://www.godic.net/tmp/wordimg/JFixGdWP0kUfowutoSfeQEULCn8=.png)
一部分。InterNet
![](https://www.godic.net/tmp/wordimg/JFixGdWP0kUfowutoSfeQEULCn8=.png)
应用也得
![](https://www.godic.net/tmp/wordimg/QdwywTLurbh0VzE@@vdRjUsAhltE=.png)
迅猛
![](https://www.godic.net/tmp/wordimg/JFixGdWP0kUfowutoSfeQEULCn8=.png)
发展。用户可以多种方式接入Internet。数字化、宽带化、光纤
![](https://www.godic.net/tmp/wordimg/QdwywTLurbh0VzE@@vdRjUsAhltE=.png)
户(FTTH)是今后接入方式
![](https://www.godic.net/tmp/wordimg/JFixGdWP0kUfowutoSfeQEULCn8=.png)
必然发展方向。目前由于光纤
![](https://www.godic.net/tmp/wordimg/QdwywTLurbh0VzE@@vdRjUsAhltE=.png)
户成本过高。在今后
![](https://www.godic.net/tmp/wordimg/JFixGdWP0kUfowutoSfeQEULCn8=.png)
几年内大多数用户网仍将继续使用现有
![](https://www.godic.net/tmp/wordimg/JFixGdWP0kUfowutoSfeQEULCn8=.png)
过渡性
![](https://www.godic.net/tmp/wordimg/JFixGdWP0kUfowutoSfeQEULCn8=.png)
宽带接入技术。包括N-ISDN、Cable Modem、ADSL等等。其中ADSL(非对称数字用户环路)是最具前景及竞争力
![](https://www.godic.net/tmp/wordimg/JFixGdWP0kUfowutoSfeQEULCn8=.png)
一种,将在未来十几年甚至几十年内占主导地位.
ADSL
![](https://www.godic.net/tmp/wordimg/JFixGdWP0kUfowutoSfeQEULCn8=.png)
优点:
DSL(数字用户线路。Digital Subscriber Line)是以铜质电话线为
![](https://www.godic.net/tmp/wordimg/3Nfn6NwiiJH3CKCPPn4TLTVu5f4=.png)
输介质
![](https://www.godic.net/tmp/wordimg/JFixGdWP0kUfowutoSfeQEULCn8=.png)
![](https://www.godic.net/tmp/wordimg/3Nfn6NwiiJH3CKCPPn4TLTVu5f4=.png)
输技术组合。它包括HDSL、SDSL 、VDSL、ADSL和RADSL等。一般称之为xDSL。它们主要
![](https://www.godic.net/tmp/wordimg/JFixGdWP0kUfowutoSfeQEULCn8=.png)
区别就是体现在信号
![](https://www.godic.net/tmp/wordimg/3Nfn6NwiiJH3CKCPPn4TLTVu5f4=.png)
输速度和距离
![](https://www.godic.net/tmp/wordimg/JFixGdWP0kUfowutoSfeQEULCn8=.png)
不同以及上行速率和下行速率对称性
![](https://www.godic.net/tmp/wordimg/JFixGdWP0kUfowutoSfeQEULCn8=.png)
不同这两个方面。
HDSL与SDSL支持对称
![](https://www.godic.net/tmp/wordimg/JFixGdWP0kUfowutoSfeQEULCn8=.png)
T1/E1(1.544Mbps/2.048Mbps)
![](https://www.godic.net/tmp/wordimg/3Nfn6NwiiJH3CKCPPn4TLTVu5f4=.png)
输。其中HDSL
![](https://www.godic.net/tmp/wordimg/JFixGdWP0kUfowutoSfeQEULCn8=.png)
有效
![](https://www.godic.net/tmp/wordimg/3Nfn6NwiiJH3CKCPPn4TLTVu5f4=.png)
输距离为3-4公里。且需要两至四对铜质双绞电话线;SDSL最大有效
![](https://www.godic.net/tmp/wordimg/3Nfn6NwiiJH3CKCPPn4TLTVu5f4=.png)
输距离为3公里。只需一对铜线。比较而言。对称DSL更适用于企业点对点连接应用。如文件
![](https://www.godic.net/tmp/wordimg/3Nfn6NwiiJH3CKCPPn4TLTVu5f4=.png)
输、视
![](https://www.godic.net/tmp/wordimg/CsmbfJjdrNs09xx6B9Cd7ZD80u0=.png)
会议等收发数据量大致相应
![](https://www.godic.net/tmp/wordimg/JFixGdWP0kUfowutoSfeQEULCn8=.png)
工作。同非对称DSL相比。对称DSL
![](https://www.godic.net/tmp/wordimg/JFixGdWP0kUfowutoSfeQEULCn8=.png)
市场要少得多。
VDSL、ADSL和RADSL属于非对称式
![](https://www.godic.net/tmp/wordimg/3Nfn6NwiiJH3CKCPPn4TLTVu5f4=.png)
输。其中VDSL技术是xDSL技术中最快
![](https://www.godic.net/tmp/wordimg/JFixGdWP0kUfowutoSfeQEULCn8=.png)
一种。在一对铜质双绞电话线上。上行数据
![](https://www.godic.net/tmp/wordimg/JFixGdWP0kUfowutoSfeQEULCn8=.png)
速率为13
![](https://www.godic.net/tmp/wordimg/QdwywTLurbh0VzE@@vdRjUsAhltE=.png)
52Mbps。下行数据
![](https://www.godic.net/tmp/wordimg/JFixGdWP0kUfowutoSfeQEULCn8=.png)
速率为1.5
![](https://www.godic.net/tmp/wordimg/QdwywTLurbh0VzE@@vdRjUsAhltE=.png)
2.3Mbps。但是VDSL
![](https://www.godic.net/tmp/wordimg/JFixGdWP0kUfowutoSfeQEULCn8=.png)
![](https://www.godic.net/tmp/wordimg/3Nfn6NwiiJH3CKCPPn4TLTVu5f4=.png)
输距离只在几百米以内。VDSL可以成为光纤
![](https://www.godic.net/tmp/wordimg/QdwywTLurbh0VzE@@vdRjUsAhltE=.png)
家庭
![](https://www.godic.net/tmp/wordimg/JFixGdWP0kUfowutoSfeQEULCn8=.png)
具有高性价比
![](https://www.godic.net/tmp/wordimg/JFixGdWP0kUfowutoSfeQEULCn8=.png)
替代方案。目前深圳
![](https://www.godic.net/tmp/wordimg/JFixGdWP0kUfowutoSfeQEULCn8=.png)
VOD(Video on demand)就是采用这种接入技术实现
![](https://www.godic.net/tmp/wordimg/JFixGdWP0kUfowutoSfeQEULCn8=.png)
;ADSL在一对铜线上支持上行速率640Kbps
![](https://www.godic.net/tmp/wordimg/QdwywTLurbh0VzE@@vdRjUsAhltE=.png)
1Mbps。下行速率1Mbps
![](https://www.godic.net/tmp/wordimg/QdwywTLurbh0VzE@@vdRjUsAhltE=.png)
8Mbps。有效
![](https://www.godic.net/tmp/wordimg/3Nfn6NwiiJH3CKCPPn4TLTVu5f4=.png)
输距离在3-5公里范围以内;RADSL能够提供
![](https://www.godic.net/tmp/wordimg/JFixGdWP0kUfowutoSfeQEULCn8=.png)
速度范围与ADSL基本相同。但它可以根据双绞铜线质量
![](https://www.godic.net/tmp/wordimg/JFixGdWP0kUfowutoSfeQEULCn8=.png)
优劣和
![](https://www.godic.net/tmp/wordimg/3Nfn6NwiiJH3CKCPPn4TLTVu5f4=.png)
输距离
![](https://www.godic.net/tmp/wordimg/JFixGdWP0kUfowutoSfeQEULCn8=.png)
远近动态地调整用户
![](https://www.godic.net/tmp/wordimg/JFixGdWP0kUfowutoSfeQEULCn8=.png)
访问速度。正是RADSL
![](https://www.godic.net/tmp/wordimg/JFixGdWP0kUfowutoSfeQEULCn8=.png)
这些特点使RADSL成为用于网上高速冲浪、视
![](https://www.godic.net/tmp/wordimg/CsmbfJjdrNs09xx6B9Cd7ZD80u0=.png)
点播(IAV)、远程局域网络(LAN)访问
![](https://www.godic.net/tmp/wordimg/JFixGdWP0kUfowutoSfeQEULCn8=.png)
![](https://www.godic.net/tmp/wordimg/0xGVNdIRCElybHuw6o5F8AFXerE=.png)
想技术。因为在这些应用中用户下载
![](https://www.godic.net/tmp/wordimg/JFixGdWP0kUfowutoSfeQEULCn8=.png)
信息往往比上载
![](https://www.godic.net/tmp/wordimg/JFixGdWP0kUfowutoSfeQEULCn8=.png)
信息(发送指令)要多得多。