ADSL
Players in High Speed Access
ADSL promises
ADSL and VDSL
數位用戶迴路 xDSL
xDSL- 基本架構
ADSL
VDSL
SHDSL
xDSL 發展情形
ADSL Block Diagram
ADSL for Data Services
Advantage of ADSL
A Network Strategy
Use of ADSL
Conclusion
| Players in High Speed Access |
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FTTH(Fiber to the Home)
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HFC(Hybrid Fiber Coax)
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Telcos
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Cable companies
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Direct Sateliite
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ADSL/VDSL
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Asymmetric Digital Subscriber Loop
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| ADSL promises |
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a cost effective way to provide Internet Access Right now
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a cheap migration path to FTTC+vDSL and provides VOD services later
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| ADSL and VDSL |
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ADSL
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Asymmetric Digital Subscriber Loop
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High speed transmission over POTS
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l.5 to 6 Mb/s downstream(18,000 to 12,000 ft)
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64 to 640 kb/s upstream
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DMT modulation adapted by ANSI T1.413
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Field Trials
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GTE(with Microsoft), AT&T,Bell Atlantic, ...
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VDSL
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l2 to 15 Mb/s downstream(4,400 to 1,000 ft)
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1.5 to 6 Mb/s upstream
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| 數位用戶迴路 xDSL |
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利用現有的雙絞銅線可以讓使用者與電信業者達成高速傳輸的技術
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利用比語音更高的頻帶來傳送資料以達到更高傳輸速率
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可同時允許資料和語音的傳輸
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提供對稱與非對稱式的傳輸
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xDSL 的技術包含 : HDSL、 HDSL2、SDSL、SHDSL、MDSL、R-ADSL、 ADSL、IDSL、VDSL等
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| xDSL- 基本架構 |
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用戶端DSL數據機與交換機房DSL接取多工器 (DSLAM)連接圖
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| ADSL |
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ADSL (Asymmetric Digital Subscriber Line)
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Internet資料傳輸量上下不對稱，正好符合ADSL的傳輸特性
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目前標準已經統一採用離散多重音調 (DMT) 調變
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訊號經過訊號分離器後，語音走PSTN，而較高頻的數據資料則送到數據網路
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| VDSL |
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VDSL (Very High data rate Digital Subscriber Line)
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xDSL技術中速度最快，但傳輸距離也最短
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在一對銅質雙絞線上，以非對稱方式，成為FTTH的替代方案
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| SHDSL |
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SHDSL (Single-pair High Speed Digital Subscriber Line)
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新一代的單銅絞線對稱式DSL技術
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由於G.shdsl標準的確立及成熟，逐漸成為目前對稱式DSL市場的主流
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ITU在2001年2月中通過了一項關於SHDSL的全球標準建議案- G.994.1，
SHDSL的標準就更臻於完整
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| xDSL 發展情形 |
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發揮電話雙絞線最大傳輸量的VDSL
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能提供多種對稱性傳輸速率的國際互通標準-G.shdsl
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語音在DSL傳輸上的應用 (voice over xDSL)
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| ADSL Block Diagram |
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| ADSL for Data Services |
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Internet/Data access is asymmetric
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TCP/IP has 14:1 asymmetry for data transfer
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More reliable and secure than HFC
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| Advantage of ADSL |
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The world is already connected by copper lines, no more new
deployment of wires
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Backward compatible with old systems such as ISDN, telephone,
etc.
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The bandwidth is just about right for Internet/WWW access
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A quick solution for high speed access
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| A Network Strategy |
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Construct lnternet and Interactive Service with
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1.5M to 6M Downstream,
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64 - 640 Kbps Upstream
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Deploy ADSL from Central Office and Remote Nodes
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Deploy VDSL from Remote nodes
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End Game
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25/52 Mbps to all, reintegration broadcast services
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End game is 25 years away
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| Use of ADSL |
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| Conclusion |
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Internet acess over ADSL appears technically feasible
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Consumer packet access could transform both the existing
Internet and POTS services
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Real-time services over consumer packet access could be the
"killer application" for the emerging national information highway
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More efforts are needed to deploy ADSL
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Network-level economics
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Implications for OAM&P
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Technology development to migrate ADSL to ATM
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New internet services & POTS integration
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Deployment assistance and system integration
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