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SNR Margin and Line Attenuation - What do they mean?

This is a discussion on SNR Margin and Line Attenuation - What do they mean? within the Broadband How to forums, part of the Indian Broadband Forums category; Originally Posted by power_downloader I have Home 500 C plan. I cannot stay connected for more than 20 min.Suddenly while ...

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Old 08-05-09, 04:48 AM   #61
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Quote:
Originally Posted by power_downloader View Post
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
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Old 08-15-09, 10:04 PM   #62
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My last post in this thread was deleted. I'd appreciate if someone could let me in as to why. Thanks
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Old 08-15-09, 10:05 PM   #63
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^^ one cant know the reasons without asking the mods directly.. they always help..
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Old 08-16-09, 12:27 PM   #64
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Quote:
Originally Posted by hexwiz View Post
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.
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Old 08-17-09, 10:54 AM   #65
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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.

Last edited by Luke Skywalker; 08-17-09 at 11:11 AM.
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Old 08-17-09, 01:28 PM   #66
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Changing to Power Ratio will confuse a lot of people as everywhere it mentioned as SNR margin.
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Old 08-17-09, 01:28 PM   #67
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Changing to Power Ratio will confuse a lot of people as everywhere it mentioned as SNR margin.
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Old 08-31-09, 02:12 PM   #68
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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.
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Old 08-31-09, 08:49 PM   #69
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^ 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.
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Old 08-31-09, 09:28 PM   #70
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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.
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Old 09-02-09, 07:55 PM   #71
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Quote:
Originally Posted by just4kix View Post
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..

Quote:
Originally Posted by just4kix View Post
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..

Last edited by NrN Kill; 09-02-09 at 07:55 PM. Reason: Automerged Doublepost
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Old 09-03-09, 02:24 AM   #72
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Quote:
Originally Posted by NARENkill View Post
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.
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Old 11-13-09, 09:10 PM   #73
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Default Are my router values ideal ?

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
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Old 11-13-09, 09:45 PM   #74
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Your values seem good.
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Old 11-15-09, 12:37 AM   #75
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Yes, they are pretty good...
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Old 11-17-09, 10:59 PM   #76
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My SNR margin varies. it is generally 7.1 downstram and 19 upstram. attenuation is 21.5(500 combo--speed Upto 2 MBPS plan). But when it rains, it goes don and starts to disconnect. What should I do? sometimes I get SNR of 14 when its not raining. So I think rain is the culprit. What will I do in monsoon yaar!
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Old 11-17-09, 11:37 PM   #77
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Quote:
Originally Posted by appy.djuetce View Post
My SNR margin varies. it is generally 7.1 downstram and 19 upstram. attenuation is 21.5(500 combo--speed Upto 2 MBPS plan). But when it rains, it goes don and starts to disconnect. What should I do? sometimes I get SNR of 14 when its not raining. So I think rain is the culprit. What will I do in monsoon yaar!
Mention your modem model and make.
Check all contacts for oxidisation /high resistance contacts /blackening
Use short cables.
Change MOd mode to GDMT. Uncheck adsl2 +
Check SNR/ATTN when it rains.
Hasty conclusion.
SNR will increase and ATTN will reduce !!
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