Senin, 14 September 2009
ADSL standards
| Standard name | Common name | Downstream rate | Upstream rate | Approved in |
|---|---|---|---|---|
| ANSI T1.413-1998 Issue 2 | ADSL | 8 Mbit/s | 1.0 Mbit/s | 1998 |
| ITU G.992.1 | ADSL (G.DMT) | 12 Mbit/s | 1.3 Mbit/s | 1999-07 |
| ITU G.992.1 Annex A | ADSL over POTS | 12 Mbit/s | 1.3 Mbit/s | |
| ITU G.992.1 Annex B | ADSL over ISDN | 12 Mbit/s | 1.8 Mbit/s | |
| ITU G.992.2 | ADSL Lite (G.Lite) | 1.5 Mbit/s | 0.5 Mbit/s | 1999-07 |
| ITU G.992.3 | ADSL2 | 12 Mbit/s | 1.0 Mbit/s | 2002-07 |
| ITU G.992.3 Annex J | ADSL2 | 12 Mbit/s | 3.5 Mbit/s | |
| ITU G.992.3 Annex L | RE-ADSL2 | 5 Mbit/s | 0.8 Mbit/s | |
| ITU G.992.4 | splitterless ADSL2 | 1.5 Mbit/s | 0.5 Mbit/s | 2002-07 |
| ITU G.992.5 | ADSL2+ | 24 Mbit/s | 1.0 Mbit/s | 2003-05 |
| ITU G.992.5 Annex M | ADSL2+M | 24 Mbit/s | 3.5 Mbit/s | |
Annexes J and M shift the upstream/downstream frequency split up to 276 kHz (from 138 kHz used in the commonly deployed annex A) in order to boost upstream rates. Additionally, the "all-digital-loop" variants of ADSL2 and ADSL2+ (annexes I and J) support an extra 256 kbit/s of upstream if the bandwidth normally used for POTS voice calls is allocated for ADSL usage.
ADSL1 access utilizes the 1.1 MHz band, and ADSL2+ utilizes the 2.2 MHz band.
The downstream and upstream rates displayed are theoretical maxima. Note also that because digital subscriber line access multiplexers and ADSL modems may have been implemented based on differing or incomplete standards some manufacturers may advertise different speeds. For example, Ericsson has several devices that support non-standard upstream speeds of up to 2 Mbit/s in ADSL2 and ADSL2+.
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