Moved ISP - Noise margin 7db?

I have just moved ISP at the moment my interleave is on my router states are as follows:-

wan adsl linedata near

noise margin downstream: 7 db
output power upstream: 12 db
attenuation downstream: 58 db
tone 0- 31: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone 32- 63: 00 00 00 00 00 02 20 02 46 78 89 79 98 46 9a bb
tone 64- 95: 0b bb bb ba bb bb ab bb ab ba aa aa aa aa aa aa
tone 96-127: a9 99 99 99 99 99 99 99 99 99 89 98 88 88 88 88
tone 128-159: 88 88 87 77 77 77 76 66 76 66 66 55 34 55 44 43
tone 160-191: 00 03 34 44 44 30 34 30 23 20 02 33 33 33 33 22
tone 192-223: 02 22 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone 224-255: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone 256-287: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone 288-319: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone 320-351: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone 352-383: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone 384-415: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone 416-447: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone 448-479: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone 480-511: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

P-660HW-T
wan adsl chandata
DSL standard: ADSL_G.dmt
near-end interleaved channel bit rate: 3456 kbps
near-end fast channel bit rate: 0 kbps
far-end interleaved channel bit rate: 448 kbps
far-end fast channel bit rate: 0 kbps
P-660HW-T
wan adsl linedata far

noise margin upstream: 15 db
output power downstream: 18 db
attenuation upstream: 29 db
tone 0- 31: 00 00 00 04 67 77 88 88 88 88 77 77 76 55 42 00
tone 32- 63: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone 64- 95: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone 96-127: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone 128-159: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone 160-191: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone 192-223: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone 224-255: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone 256-287: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone 288-319: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone 320-351: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone 352-383: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone 384-415: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone 416-447: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone 448-479: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone 480-511: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

P-660HW-T

I remember my downstream noise margin was 6db with my other ISP it is now 7db. Has BT changed my noise margin?

If my noise margin was 6db wouldn't I be able to connect slightly faster?

Or is the downstream noise margin something which will go up and down regardless and is independant.

Thank you

Steve

Edited by steve229 (Wed 29-Jul-09 11:08:33)

If my noise margin was 6db wouldn't I be able to connect slightly faster?

Or is the downstream noise margin something which will go up and down regardless and is independant.

The BT IPStream service you are on has steps of 3dB in sync-time (target) margin. 3dB difference in margin at sync-time changes the sync speed by 500-750kbps depending on many other factors. Then there is the IP Profile system to consider where small changes in sync may make no difference at all to actual download speeds. See this table and the explanations above and below it, so a small increase in sync from 3456kbps wouldn't help your speed but would slightly decrease your stability.

In any case re your second question in the quote, the answer is yes.

Actual noise (SNR) varies 24/7 so the Noise Margin (SNRM) that you see varies with it. The purpose of the margin is to decrease the potential speed so that noise can rise, margin therefore fall, by the amount of the margin before connection is lost. Theoretically at fractionally below 0dB margin, but home-type routers are very variable in their performance in this respect.

From your stats it looks like the noise has decreased very slightly since you connected. Great - given that you need over 600kbps more to get a higher profile.

It is also worth knowing that daylight sync's are always higher than night-time - or evenings in the darker times of the year. Noise goes up when the sun goes down - partly literally because the sun helps reduce noise and partly all the electrical/electronic/lighting/heating/radio ham stuff that starts up late in the day.

Edit - interleaving at these speeds makes no difference to sync speed. It is only at 8128kbps that it may reduce it to 7616kbps. Unless you do interactive gaming where you may get killed if your latency is poor leave it on as it reduces re-transmissions due to errors so actually improves throughput. That's what it is for.

Edited by RobertoS (Wed 29-Jul-09 11:27:30)

Great thank you RobertoS,

Can you explain to me where on the states can you see that my line noise has fallen, I would be most gratfull?

Where can you also tell that I am on steps of 3db in margin.

If it is 3db stepped then it cannot go down to 6db only 4db can it, and if it is to increase the next step from 7db is 10db. Am I wrong in saying this I have a feeling I am?

Thank you for your patience

Steve

6db to 7db could actually be as little as 0.02dB going from 6.49 to 6.51. Unless there is greater precision in the figures I would igore differences of 1 or 2 dB

In reply to a post by steve229:

Can you explain to me where on the states can you see that my line noise has fallen, I would be most gratfull?

Where can you also tell that I am on steps of 3db in margin.

If it is 3db stepped then it cannot go down to 6db only 4db can it, and if it is to increase the next step from 7db is 10db. Am I wrong in saying this I have a feeling I am?

The BT BRAS (Basic Rate Adaptive System) system holds your IP Profile and also a "target" noise margin. That is what is set in steps of 3dB, the default figure being 6dB.

The target noise margin is added to the actual noise level at the time you connect and is always set to whatever the BRAS figure is. So say real noise is 40dB and target margin 6dB the speed is set as though the real noise was 46dB.

Whenever you check the margin after that it is just telling you how much the real noise has changed since you sync'ed. It doesn't do anything.

Real noise varies in fractions of a dB. Some routers report margin in steps of 0.5dB but that is just the firmware rounding the number to the nearest half. Others report it in steps of 0.1dB

So if real noise goes up to say 42.3dB the margin left is 3.7dB. If it goes over 46dB you lose connection.

If real noise falls to say 37.2dB the margin would rise to 8.8dB. Simple really once it is explained.

So it looks as though you are on the normal 6dB target margin and real noise has fallen by 1dB since you sync'ed. The real noise figure isn't reported by the majority if not all home-style modem/routers.

Edited by RobertoS (Wed 29-Jul-09 12:06:00)

In reply to a post by MHC:

6db to 7db could actually be as little as 0.02dB going from 6.49 to 6.51. Unless there is greater precision in the figures I would igore differences of 1 or 2 dB

Very true. Does that explain anything relevant to the OP?

Edited by RobertoS (Wed 29-Jul-09 12:07:55)

over 3M at 58 dB isn't bad at all. The SNR margin has a target of 6 dB at training and will wander around after that, if it gets too low it will retrain.

Thank you all for clarifing everything.

I was particulary concerned as this is my first training day with my new ISP, because of this I was concerned BT had manually set my line to 7.

Regards

Steve

In reply to a post by RobertoS:

The BT BRAS (Basic Rate Adaptive System) system ...

Hmmm... where did you see that?!

I ways thought it was Broadband Remote Access Server (or perhaps Service)???

We probably both think we are right .

It's irrelevant as both effectively mean the same, taking your "Service" option.