ADSL2 vs ADSL2+

Hi just a quickish question why is it that when you select ADSL2 in the router it syncs slower than ADSL2+ from what i understand there just the same except ADSL2 has a 12meg max limit and 2+ is 24.

But if i change it i lose speed on ADSL2 as you can see from stats below there's a considerable drop i also included G.dmt for reference in different speeds BTW i know my SNR is high ive posted on talktalk forum for them to lower it but they haven't dont it yet.

Also odly enough the first day of the connection it was Rate(Kbps) 9121/871 now its Rate(Kbps) 8165/872 both on ADSL2 with the same SNR.

ADSL2+

Mode
Routing
ADSL Mode ADSL2+
ADSL Type Annex A
Status Up

Downstream Upstream
Rate(Kbps) 8165 872

SNR Margin(dB) 10.6 11.9
Attenuation(dB) 21.4 40.0
Output Power(dBm) 0 12

Super Frames 10348357 10348358
RS Correctable Errors 61767 65505
RS Uncorrectable Errors 0 0

HEC Errors 0 0
Total Cells 553 51061
Data Cells 8238616 580889
Bit Errors 0 0

ADSL2

Mode
Routing
ADSL Mode ADSL2
ADSL Type Annex A
Status Up

Downstream Upstream
Rate(Kbps) 6965 872

SNR Margin(dB) 12.1 11.9
Attenuation(dB) 21.4 37.0
Output Power(dBm) 0 0

Super Frames 229 230
RS Correctable Errors 0 0
RS Uncorrectable Errors 0 0

HEC Errors 0 0
Total Cells 49 100
Data Cells 8238616 580889
Bit Errors 0 0

G.dmt

Mode
Routing
ADSL Mode G.dmt
ADSL Type Annex A
Status Up

Downstream Upstream
Rate(Kbps) 6464 736

SNR Margin(dB) 13.0 13.0
Attenuation(dB) 21.5 40.0
Output Power(dBm) 19 12

Super Frames 3025 3025
RS Correctable Errors 0 0
RS Uncorrectable Errors 0 0

HEC Errors 0 0
Total Cells 1139 1463
Data Cells 1 1
Bit Errors 0 0

Ash

Interesting!

Not only that but notice your attn. is 3 dB lower on ADSL2 & G.DMT, as it should be (note your router reverses the UP/Down Attns.).

I would say that all the diffs in your Down Syncs are mostly attributable to changes in NMs.

What you should be aiming at on a Target NM of 6dB is:

• ADSL2+: 9 Meg on 40 dB attn.
• ADSL2: 10.5 Meg on 37 dB attn.
• G.DMT: 7 Meg on 37 dB attn.

In reply to a post by XRaySpeX:

Interesting!

Not only that but notice your attn. is 3 dB lower on ADSL2 & G.DMT, as it should be (note your router reverses the UP/Down Attns.).

I would say that all the diffs in your Down Syncs are mostly attributable to changes in NMs.

What you should be aiming at on a Target NM of 6dB is:

• ADSL2+: 9 Meg on 40 dB attn.
• ADSL2: 10.5 Meg on 37 dB attn.
• G.DMT: 7 Meg on 37 dB attn.

yea i noticed the router been backwards on atten lol my other line sat next to it with sky is 37 atten on ADSL2+ i get 11meg on that 1, some reason the TT one is higher lol must be slightly longer. Most of me neighbours get 30-32 atten on ADLS2+ my luck to have longer lines haha.

im switching to FTTC in dec thats the reason i got talktalk fitted so i supose its not a hige prob its just puzzled me why it slows down thats all lol

Ash

Edited by acpsd775 (Sun 20-Nov-11 20:05:04)

From memory ADSL2+ has double the frequency band available (compared to g.dmt & ADSL2) which allows for the potentially higher line rates. G.DMT and ADSL have the same frequency band but the later uses more advanced coding to achieve a max downstream of 12Mbit/s

Edited by deleted (Sun 20-Nov-11 21:20:40)

In reply to a post by Ribble:

From memory ADSL2+ has double the frequency band available which allows for the potentially higher line rates

yea i think thats right actually ive goto say i miss DMT tools lol good app to push the line to the max,
The pants thing about the talktalk router is its got a compatible chipset to use DMT tools but the firmware blocks it so it connects but wont display ant stat or allow SNR tweaking so its a bit of a kick in the teeth lol.

Ash

Disagree

The 3dB difference is because the ADSL2 and ADSL attenuation is measured on an up to 1.1MHz, with ADSL2+ the range is up to 2.2MHz, so twice as much attenuation hence the 3dB change.

Now as the same maths is used to populate the ADSL2+ frequency range, you should still have the same bits per bin as you had when using ADSL2.

Short answer, ADSL2 is not likely to run 1.5Meg faster based on a graph attenuation lookup.

Routers where the ADSL2+ runs slower than the ADSL2 version can be down to errors in the ADSL2+ frequency range wasting ADSL2 capacity, and differences in the router code.

In reply to a post by MrSaffron:

Disagree

Not with me you don't!

You do agree that there is 3dB difference between ADSL2+ and ADSL2 attenuation, which is all I stated in this thread w/out attempting to give any reasons behind it.

You have performed a complete volte-face since we last argued on this topic when you denied there was a drop in attenuation, in a most childish manner

Edited by XRaySpeX (Sun 20-Nov-11 23:31:33)

Hi acpsd,

Can you confirm if your thread in the TT Members Forum has yet been picked up?

Regards

Mark
TalkTalk Online Community Department

i'm guessing MrSaffron meant within each frequency band the attenuation would be the same, but when taken as a whole, adsl2+ attenuation figures show as higher as they include higher frequency bands in the average. IIRC, higher frequencies are attenuated more.

Like a boy racer opening his window, the bass doesnt change but suddenly you hear the treble. Now there's an analogy! I wonder if it is right