Thread: SNR Margin and Line Attenuation - What do they mean?

There have been many posts regarding SNR and Line Attenuation.

SNR
SNR means Signal to Noise Ratio. Simply put divide the Signal value by Noise Value and you get SNR. You need high SNR for a stable connection. In general, a higher signal to noise ratio will result in less errors.

• 6bB. or below = Bad and will experience no line synchronisation and frequent disconnections
• 7dB-10dB. = Fair but does not leave much room for variances in conditions.
• 11dB-20dB. = Good with little or no disconnection problems
• 20dB-28dB. = Excellent
• 29dB. or above = Outstanding

Note that most modems display value as SNR Margin and not pure SNR.

SNR Margin
You can think of SNR margin as the measure of quality of the service; it defines the ability of the service to work error free during noise bursts.

This is a measure of the difference between your current SNR and the SNR that is required to keep a reliable service at your connection speed. If your SNR is very close to the minimum required SNR, you are more likely to suffer intermittent connection faults, or slowdowns. You need a high margin to ensure that bursts of interference don't cause constant disconnections.

With traditional broadband, the higher the SNR Margin, the better. With MaxDSL the faster speeds are only available as a trade-off with what your line can reliably support. The Target SNR Margin is about 6dB. If your broadband is provided through an LLU (Local Loop Unbundled) network, this target SNR Margin may be as high as 12dB.

Line Attenuation
In gerneral, attenuation is the loss of signal over distance. Unfortunately, dB loss is not just dependent on distance. It also depends on cable type and gauge (which can differ over the length of the cable), the number and location other connection points on the cable.

• 20bB. and below = Outstanding
• 20dB-30dB. = Excellent
• 30dB-40dB. = Very Good
• 40dB-50dB. = Good
• 50dB-60dB. = Poor and may experience connectivity issues
• 60dB. and above = Bad and will experience connectivity issues

Line attenuation also affects your speed.

• 75 dB+: Out of range for broadband
• 60-75 dB: max speed up to 512kbps
• 43-60dB: max speed up to 1Mbps
• 0-42dB: speed up to 2Mbps+

Please comment on this article.

(and if you give me reputation on this, I shall return the favour)

Thanks just4kix it was good to about it...can u also state the difference b/w adsl+ and g.dmt

Originally Posted by just4kix

(and if you give me reputation on this, I shall return the favour)

Lessons from corporates! Given by management guru just4kix!
^^Thanks for d info! I've added to ur reputation, now its ur turn!

Originally Posted by gurusam

Thanks just4kix it was good to about it...can u also state the difference b/w adsl+ and g.dmt

Basically it is the technology difference.

G.DMT is ADSL1 whereas ADSL2+ is, well, ADSL2+.

Refer these articles: G.DMT and ADSL2+

added repo

and thanks for such a nice and informative post

you are rocking just4kix :rockon:

I too added repo for just4kix for this post but the repo power of just4kix has not increased??

Each repo gives a point. I have 36 points so far. I do not know how Rep Power is calculated.

Post something informative and I promise that I will return your favours.

just4kix u r kix smart buddy i think u r the favourite here .................. Cheers buddy..........................

If you get problems regarding those shits then how do we fix it?

Nice article ,by the way.

best regards,
Spectre

J4X you are tempting me to one more Modem / Router crash !!!
I'll surely be up on something Tonight !!!

If there are problems, then you need to get line checked and replaced if necessary.

BSNL provides BB on copper wires and this poses problem of environmental corrosion. Voice is relatively unaffected but data is not.

http://www.indiabroadband.net/bsnl-b...ions-bsnl.html (My interactions with BSNL)

How could I miss this article(and your offer) for so many days... I played with my router settings to increase SNR... but once achieving that, never cared to research about it... Thanx for the compiled information... U r wonderful...

Reps for u...

lol... system is asking me to spread some reps 1st... so its due...

Originally Posted by itsmemad

How could I miss this article(and your offer) for so many days... I played with my router settings to increase SNR... but once achieving that, never cared to research about it... Thanx for the compiled information... U r wonderful...

Reps for u...

lol... system is asking me to spread some reps 1st... so its due...

You are really generous on Reps Mad.... we must admit !! (Rep from my side to you. Like the Way !!)

What exactly you played with your router to increase SNR ?

Originally Posted by lovelyMe

You are really generous on Reps Mad.... we must admit !! (Rep from my side to you. Like the Way !!)

What exactly you played with your router to increase SNR ?

Assuming that your SNR is low, you can do the following to increase your SNR are the following:

a) Identify where the telephone wire runs into your home
b) Trace it all the way back to the junction box
c) Check whether the cable is in good shape - not too much weathered, etc.
d) At the junction box, check the connection. Is it corroded, oxidised? If yes, note it down.

Make a written complaint in duplicate to the exchange about frequent disconnections (even if you are not suffering that). Tell them the wire/connection is weathered/corroded/oxidised.

A promise of Rs.100 baksheesh to the linesman will work wonders.

p/s. I have assumed that the splitter is correctly splitting the voice and data circuits at the point of entry.

Originally Posted by just4kix

Assuming that your SNR is low, you can do the following to increase your SNR are the following:

A promise of Rs.100 baksheesh to the linesman will work wonders.

p/s. I have assumed that the splitter is correctly splitting the voice and data circuits at the point of entry.

Thx J4X...
I'll check. I am sure there is corrosion in line but not much exposure to weather..
The J.Box has a chaos like condition .... Rs. 200/- chai paani has already worked wonders !!

Originally Posted by just4kix

Assuming that your SNR is low, you can do the following to increase your SNR are the following:

a) Identify where the telephone wire runs into your home
b) Trace it all the way back to the junction box
c) Check whether the cable is in good shape - not too much weathered, etc.
d) At the junction box, check the connection. Is it corroded, oxidised? If yes, note it down.

From the junction box,the telephone wire directly runs to my house. Its a new wire,I got it changed recently.
I dont have any paralled connection.
But still the SNR value is around 7~8.
Attn Value is around 40~45.
I do experience frequent disconnection for 10 sec...
When the connection is there...I get the expected speed & I dont face any issues.

Then there is a problem with the port at the exchange. Make a written complaint in duplicate. Get the duplicate signed by the DE of the circle.

Ok..THanks....will do that....

Originally Posted by just4kix

Then there is a problem with the port at the exchange. Make a written complaint in duplicate. Get the duplicate signed by the DE of the circle.

Hey you found what port your BSNL guy was talking about ??? Is this the same you had problem with ??

I have no idea about what port? After repeated queries they would not clarify. They said that the BB connection runs to the exchange and to the port of the DSLAM. Probably something similar like an ethernet port.

Originally Posted by lovelyMe

You are really generous on Reps Mad.... we must admit !! (Rep from my side to you. Like the Way !!)

What exactly you played with your router to increase SNR ?

Yeah... I don't mind giving reps... if a person has done some work to help others on this forum... I'm always 1st to rep him...
Any1 feels nice to get recognition for his work.... so, in a way its a small appreciation from my side...

thanx for ur rep...

I changed router's mode from ADSL2+ to G.DMT... it worked wonders... downstream rocketed from 9 to 41... u can give it a try too... but if it doesn't work... revert back to ADSL 2+...

This post derserves REP points, Thanks "just4kix".

Originally Posted by just4kix

Then there is a problem with the port at the exchange. Make a written complaint in duplicate. Get the duplicate signed by the DE of the circle.

To whom should I write the written complaint & to whom should I submit...

Originally Posted by jee.ramesh1983

To whom should I write the written complaint & to whom should I submit...

To the divisional engineer at the exchange.

how do I measure / check my SNR & line attenuation ?
is some software / hardware required for the same ?

my ADSL comes through Copper cable , joints galore along the way from around a distance for abt 4 -5 km frm the Exchange , after the Dp Pole it goes directly to the splitter and then to the modem (UT Star 300 r2 ) ....

can I know if this would lead to extreme drop isn Signal ? My tel line is faily clear , scratchy only when it rains !

pls advise


thnks

toolman/~