作者：
willmax
嗯~我看完ITU有關ADSL的規範, 我還不知道ADSL2+等等可以跑到50M/3M呢?
目前ITU針對ADSL規格有制定以下規範, ADSL2+也是去年才制定出來的.
我先提供ADSL, ADSL2以及ADSL2+的ITU規範, 給大家參考一下!
G.992.1 ADSL Basic
ITU G.992.1 and ANSI T1.413 Issue 2
Discrete MultiTone (DMT) line code
256 carriers with 4.3125 kHz spacing
Upstream: 20 to 138 kHz Max 1024 kbps
Downstream: 140 kHz to 1100 kHz Max 8128 kbps
G.992.3 ADSL2 Improvements
Increases maximum rate to 12 Mbps
Extends ADSL reach by 5 to 10%
Enhancements in transmission technology by:
Reduced overhead by programmable overhead bit/frame
Improved coding and Modulation with Trellis-code QAM for long lines with poor SNR.
Receiver determine tone-reordering to avoid non-stationary noise.
Improved Initialization to provide
Receiver selected Pilot Tone to avoid stationary noise and bridge-tape null.
Extended Training period to characterize channels.
Power Cut-Back and Tone Black out to reduce cross-talk and Interference during Initialization.
In-service Rate Adaptation without service interruption.
Diagnostic mode for communication for lines is too poor for ADSL.
Application Modes for STM, ATM and Packets.
Enhanced Power saving modes: L0, L2 and L3
G.992.5 ADSL2+
Doubles downstream bandwidth
Data rates > 25 Mbps
Geared for advanced services like multi-channel video
Can reduce crosstalk within binder group
Incorporates all feature benefits of ADSL2
Interoperable with legacy ADSL and ADSL2
其實ADSL和ADSL2 line code都是DMT (離散多重音)
只是ADSL2在下行速率比ADSL快! 供裝距離比ADSL多5 ~ 10%
至於ADSL2+所增加雙倍的頻寬都是下行速率.
換言之, ADSL, ADSL2, ADSL2+上行速率都是1 Mbps!
我不知道你所提的50M/3M和47M/5M的ADSL是何種技術?
如果你可以提供資料的話, 我願意在此受教!
至於VDSL是依循ITU-T G.993.1, ANSI T1.424以及ETSI TS 101 270的規範.
其傳送速率可分為~
ETSI: 非對稱~23M/4M 對稱:~28M/28M
ANSI: 非對稱~52M/6.4M 對稱:~34M/34M
你所提的VDSL 100M/50M是何種技術呢?
我希望你能提出詳細的資料, 這樣比較有信服力喔!
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