ITU G.992.5 Annex L
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| DSL technologies | |
|---|---|
| Technology | ITU-standard |
| ADSL | ANSI T1.413 Issue 2 ITU G.992.1 (G.DMT) ITU G.992.2 (G.Lite) |
| ADSL2 | ITU G.992.3/4 ITU G.992.3 Annex J ITU G.992.3 Annex L |
| ADSL2+ | ITU G.992.5 ITU G.992.5 Annex L ITU G.992.5 Annex M |
| HDSL | ITU G.991.1 |
| HDSL2 | |
| IDSL | |
| MSDSL | |
| PDSL | |
| RADSL | |
| SDSL | |
| SHDSL | ITU G.991.2 |
| UDSL | |
| VDSL | ITU G.993.1 |
| VDSL2 | ITU G.993.2 |
This is an ITU (International Telecommunication Union) standard, also referred to as RE ADSL2+. This extends the capability of basic ADSL by doubling the number of downstream bits. The data rates can be as high as 24 Mbit/s downstream and 1 Mbit/s upstream depending on the distance from the DSLAM to the customer's home.
The main difference between this specification and ITU G.992.5 (ADSL2+) is the maximum distance that can be used. This increase in distance is made possible by using more power on the lower frequencies, enabling the link to work at a distance of 7 kilometers, or 23,000 ft.
Although the standard development is completed and verified by the ITU, some scrupulous owners of local loop networks don't allow this standard to be used because the high power can create audible cross-talk. In contrast, this standard is implemented nationwide by the ILEC France Telecom. There is no Annex L variant available for ISDN lines, which makes it unavailable in Germany, where exclusively ADSL-over-ISDN variants are implemented by all LECs even on POTS lines.
[edit] See also
The main difference between G.992.3 and G.992.5 is that the latter uses up to 2.2 MHz in the frequency band. The AnnexL mode is designed to improve the reach, by first not sending power upve 552 kHz (because on long loops there is no possible bit loading on the carrier above this point due to the high attenuation of the line and from the other side by increasing the power in the lower frequency band to improve the bit loading where the line attenuation is not that dominant. In G.992.5, the annexL is intentionally left black, because it makes no sense, it is only applicable for G.992.3
