ADSL Modulation Scheme Attributes
I could not find any reliable comprehensive source and don’t want to read all the specs…. Therefore I compiled a short summary of commonly used DSL modulation schemes and their key attributes.
Different max. speed is given on different sources. I will complete this table step by step as I find reliable figures.
| Specification | Spectrum | Remark | Up | Dn | Line Length |
| ITU G.922.1 Annex A (G.dmt) | 25-138/138-1100 | over-POTS | 640kb | 6Mb | |
| ITU G.922.1 Annex B (G.dmt) | 138-276/276-1100 | over-ISDN | |||
| ITU G.992.3 (ADSL2)Annex A | over-POTS | ||||
| ITU G.992.3 (ADSL2)Annex B | over-ISDN | ||||
| ITU G.992.3 (ADSL2)Annex L (“reach extended”) | over-POTS | 1Mb | 12Mb | ||
| ITU G.992.3 (ADSL2) Annex M | over-POTS | 3.5Mb | |||
| ITU G.992.3 (ADSL2) Annex J | ?-276/276-? | NO POTS | 3.5Mb | 12Mb | |
| ITU G.992.5 (ADSL2+) Annex A | 25-138/138-2200 | over-POTS | |||
| ITU G.992.5 (ADSL2+) Annex B | 138-276/276-2200 | over-ISDN | |||
| ITU G.992.5 (ADSL2+) Annex L | over-POTS | 1Mb | 24MB | ||
| ITU G.992.5 (ADSL2+) Annex M | 25-276/276-3300 | over-POTS | 3.5Mb | 24Mb | |
| ITU G.992.5 (ADSL2+) Annex J | NO POTS | 3.5Mb |
Annex A: ADSL-over-POTS
Annex B: ADSL-over-ISDN 138-276 kHz up / 275-1104 dn
Annex M: More BW for uplink, over POTS, 3.5 MB up
Annex L: extended reach, over-POTS
Annex J: NO POTS (but ISDN???), 3.5Mb up
http://en.wikipedia.org/wiki/Asymmetric_Digital_Subscriber_Line
Example: ADSL line in Bangkok, ISP Telephone Organisation of Thailand (TOT)
Subscribed package: “Best Fit”, 8Mbps dn / 1Mbps up
| Selected mode | remark | dn att | dn SNR | dn speed | up att | up SNR | up speed |
| G.dmt Annex A | 28.5 | 13.5 | 8064 | 15.0 | 12.0 | 800 | |
| G.dmt Annex M | invalid ->2+ | ||||||
| ADSL2 Annex A | 24.0 | 12.0 | 9151 | 14.7 | 16.5 | 737 | |
| ADSL2 Annex M | 25.0 | 12.0 | 8045 | 13.5 | 18.8 | 1278 | |
| ADSL2+ Ann. A | 28.0 | 23.3 | 10240 | 14.7 | 13.0 | 729 | |
| ADSL2+ Ann. I | no sync. | ||||||
| ADSL2+ Ann. A/L | =A | ||||||
| ADSL2+ Ann. M | 30.0 | 22.7 | 10240 | 19.7 | 13.5 | 1278 | |
| ADSL2+ Ann. A/I/J/L/M | =M |
Modem default was A/L, which led to “A”. In this mode the possible uplink speed could not be fully utilized. Annex M assigns more spectrum to the uplink, almost doubling the speed. There is still enough BW for the uplink to allow the maximum uplink speed of 10Mbps.
This ADSL line connect earlier with 8192 / 1023 kbps (Annex M mode). Recently the downlink limit seems to be lifted up to 10 Mbps, while the uplink might be unlimited (?) and only the line quality is the limit.
Annex J could improve the uplink even more, but is not specifically selectable. Also the phone line would be unusable for POTS.
