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

There is not much the user can do to improve SNR/Line Attenuation. It is all the characteristic of the phone line.

All that be done is check the phone line at the junction box. The contacts get oxidised in time. Cleaning the contacts can help. But you have to know which is your own line.

Some of the techies have claimed that switching mode from ADSL2+ to G.dmt improves the SNR slightly. No idea. In my case, it made no difference.

Tutorials - ADSL > Understanding Line Loss and Measurements

Improving your loss figures.

Tutorials - ADSL > Understanding Line Loss and Measurements

short extract : conclusions

Unfortunately there is little you can do about the actual line itself
other than get it maintained by BT. But you can take some steps
to ensure that you are not adding more than the minimum loss yourself:

1... Use good quality Splitter / Filters.

2. ...Use good quality extension cables.

3. .....Ensure that where you plug into cable sockets
......... that the pins are clean and bright.
.......... It has been known for the connections here to corrode with time
.............and you could try pulling out and re-inserting the plug into
..............the BT socket several times to polish the connections.

Hopefully the above information will have been useful to those
who wanted to know more about their ADSL connection

SNR is not simply the ratio of signal value to noise value. It is the ratio of signal power to noise power ratio. It is a unit less quantity.
Whenever a ratio is expressed in decibel it means 10 times the logarithm base of 10 of the ratio.

(Source Electronics Comm. Systems , George Kennedy 3ed)

Otherwise this thread is quite helpful & fabulous.

Thanks Luke.

--------

@all, I was checking "SNR+Line Attenuation" keywords in Google. A search result found many hits and Admin should be very happy to note that this article comes right on top of the search results (3rd).

There were many forum linkss, and many have given a link to this article.

Originally Posted by just4kix

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)

nice presentation!!!!! . really informative. CONGRATESSSSSSSS.....
still little more needed for me......... wht is the difference between local snr margin and remote snr margin. is there any significance by knowing these value ? also local line attenuation and remote line attenuation............... can these values help to identify the problem. my values i will give below please make a comment and direction.

local line attenuation: 47.5 dB
Remote line attenuation: 26.5 dB
local SNR margin: 20 dB
remote snr margin: 6 dB
Local Tx power: 12.4 dB
Remote tx power: 16.7 dB

Originally Posted by just4kix

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)

nice presentation!!!!! . really informative. CONGRATESSSSSSSS.....
still little more needed for me......... wht is the difference between local snr margin and remote snr margin. is there any significance by knowing these value ? also local line attenuation and remote line attenuation............... can these values help to identify the problem. my values i will give below please make a comment and direction.

local line attenuation: 47.5 dB
Remote line attenuation: 26.5 dB
local SNR margin: 20 dB
remote snr margin: 6 dB
Local Tx power: 12.4 dB
Remote tx power: 16.7 dB

Please take a look at the values. I am facing a minor disconnection problem. At times pages take time to load. I tried BSNL and OpenDNS.

SNR (Downstream) 42.0 dB
SNR (Upstream) 13.5 dB
Line Attentuation(Downstream) 13.0 dB
Line Attentuation(Upstream) 7.0 dB

I have Home 500 C plan. I cannot stay connected for more than 20 min.Suddenly while surfing my speed becomes 0 kB/s for no reason .When I look at my router I see the yellow DSL light blinking which means that its reconnecting(I'm using pppoe mode).The green internet light always blinks.I have read somewhere it means that my connection is out of sync. While surfing this site after every 10-20 min I get a message to log in again which may be because my IP changes after reconnection.Is my SNR too low ?



What are super frame errors ? Are they causing problem?

router:Siemens sl2_141
plan:500C
OS:Windows XP pro

Your SNR values are too low.

I complained to BSNL .They told me that my phone line is OK because they can't hear any noise in my phone
I don't think anybody at the office knows what SNR is.

what should I do now

Ask them to check your line completely, for faults like loop.

Check whether the line cable comming to your house is all right there should not be any cut and joints it should be a single direct cable.

Originally Posted by power_downloader

I have Home 500 C plan. I cannot stay connected for more than 20 min.Suddenly while surfing my speed becomes 0 kB/s for no reason .When I look at my router I see the yellow DSL light blinking which means that its reconnecting(I'm using pppoe mode).The green internet light always blinks.I have read somewhere it means that my connection is out of sync. While surfing this site after every 10-20 min I get a message to log in again which may be because my IP changes after reconnection.Is my SNR too low ?

What are super frame errors ? Are they causing problem?

router:Siemens sl2_141
plan:500C
OS:Windows XP pro

Super frame errors are also known as crc6 errors which means the data packet is corrupted enroute. This could mean a lot many things and going by the stats, the low SNR and high attenuation certainly signify line issues which may be inside the premises or out. You could start with the cables and connections and making sure they are plugged in proper. Make sure the adsl filter is not faulty and that the modem is plugged into the correct adsl port on the filter and not the phone port. If that doesn't resolve the problem it certainly is your provider's call. And on the modem GUI if it gives you an option which says something akin to "Connect on demand" and if it has a check box - leave that UNchecked. EMI can also cause such but I doubt that's what's happening here. But nevertheless you could make sure there is no electronic device too close to the dsl modem or cables as they could cause interference. This would include equipments like speakers, tv tubes, power amplifiers, power supplies, radio, microwaves, cordless phones etc

My last post in this thread was deleted. I'd appreciate if someone could let me in as to why. Thanks

^^ one cant know the reasons without asking the mods directly.. they always help..

Originally Posted by hexwiz

My last post in this thread was deleted. I'd appreciate if someone could let me in as to why. Thanks

None of your posts in this thread has been deleted. I checked.

Perhaps you posted somewhere else.

Rated this thread but kix .Please change definition from signal to noise ratio to power ratio between signal to noise as I said earlier. SNR long form is Signal to noise but it is not definition. It is 10 times log(base 10) of ratio of signal power to noise power.


PS: 1. I remember this as I have just studied it in March for my communication exam.
2.Dunno whether I gave rep or not don't want to give again for same. Tell me if I didn't , I will give to it.

Changing to Power Ratio will confuse a lot of people as everywhere it mentioned as SNR margin.

Changing to Power Ratio will confuse a lot of people as everywhere it mentioned as SNR margin.

Nice ! From what your comparision stats say .. my BSNL connection is outstanding
(Probably due to the local exchange being like 400 meters away and new telephone line)

(Downstream / Upstream)
SNR Margin (dB): 34.0 |7.5
Attenuation (dB): 18.0 |6.1

Output Power (dBm): 8.8 |1.5

Attainable Rate (Kbps): 13720|1028
Rate (Kbps):2048 |928

I am a bit confused about the Rate... it say 2048 or 2 Mbps and my plan is 512 kbps =\
which Rate does that number signify =\ ? I suppose attainable rate is the max supported speed by the router.

^ Attainable rate is the maximum achievable by the ADSL connection. Modem can achieve much more.

You actual speed is better ascertained by a speedtest. Do not depend upon the modem results.

Oh, speed test was at speedtest.net was around .9 mbps - .4 mbps (download) and .3-.5 upload. I am veeery happy with the speeds I am getting, although I am surprised by how the dl speed goes upto 80Kbps (max till now) on torrents at times. Even when I am sharing it with another PC on the network (which also downloads stuff quite a lot), the dl speeds are consistently around 50KBps-60KBps. I thought the speeds in UL plans don't go beyond the stated dl speed.

Originally Posted by just4kix

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)

I have upstream at a better range then downstream... Both use the same cable, if i am not wrong..

Originally Posted by just4kix

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)

I have upstream at a better range then downstream... Both use the same cable, if i am not wrong..

Originally Posted by NARENkill

I have upstream at a better range then downstream... Both use the same cable, if i am not wrong..

Yup you are right both use same cable.

can you please post your Statistics -- ADSL over here will make things easier.

The following are the values from my "modem status" page :

Modem Status

Connection Status Connected
Us Rate (Kbps) 508
Ds Rate (Kbps) 2042
US Margin 24
DS Margin 31
Trained Modulation ADSL_2plus
LOS Errors 0
DS Line Attenuation 13
US Line Attenuation 4
Peak Cell Rate 1198 cells per sec
CRC Rx Fast 0
CRC Tx Fast 0
CRC Rx Interleaved 0
CRC Tx Interleaved 0
Path Mode Interleaved


DSL Statistics
Near End F4 Loop Back Count 0
Near End F5 Loop Back Count 0


Please comment on whether the above values are ideal.
(esp. the US/DS Margins & US/DS Line Attenuation).

What US/DS Margins & US/DS Line Attenuation values
are the best ?

Thanks ...

Router : D-Link GLB-502T V2 ADSL2+
ISP & speed : BSNL DataOne; 256 kbps unlimited data transfer

Your values seem good.

Yes, they are pretty good...