SNR margin and Line Attenuation

curieux2

Hi gurus

Just a quick one ... I've ordered 2Mb with BT and am waiting to receive their modem
As I have an old Eircom modem ( in fact I have 4 ... ) , I had a nice surprise today when my modem synced up

Here are the stats but could someone explain what SNR and attenuation stand for ? Sorry of the question has allready been posted

ADSL Line State: Up
ADSL Startup Attempts: 1
ADSL Modulation: DMT
Datapump Version: 3.38.2
Downstream Upstream

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SNR Margin: 24.34 14.00 dB
Line Attenuation: 37.27 25.00 dB
Output Power: 19.51 11.97 dB
Errored Seconds: 0 0
Loss of Signal: 0 0
Loss of Frame: 0 0
CRC Errors: 1 0
Data Rate: 2048 128

juliuspret

Your stats look pretty much the same as mine and I get, on 2Mbit BT, 1.71M/105K on the http://www.irishisptest.com/myspeed java prog.

Line Attenuation: 37.27 is probable the most important piece of data.
37.27 db is your download attenuation and is well within the range for full 2Mbit broadband.
BT UK quote a figure of less than 45 db for 2Mbit BB!

Dont worry...you will get full 2Mbit BB!!!

SNR - Signal to noise Ratio
Signal divided by noise...so a higher value is better.
Attenuation
Resistance/loss in the transmission of data on your line.

zap

so i should def get full 2meg then


Max Allowed Speed (kbps) 2048 128
SN Margin (dB) 27.05 28.00
Line Attenuation (dB) 19.89 13.00
CRC Errors 0 0

curieux2

juliuspret wrote:

Your stats look pretty much the same as mine and I get, on 2Mbit BT, 1.71M/105K on the http://www.irishisptest.com/myspeed java prog.

Line Attenuation: 37.27 is probable the most important piece of data.
37.27 db is your download attenuation and is well within the range for full 2Mbit broadband.
BT UK quote a figure of less than 45 db for 2Mbit BB!

Dont worry...you will get full 2Mbit BB!!!

SNR - Signal to noise Ratio
Signal divided by noise...so a higher value is better.
Attenuation
Resistance/loss in the transmission of data on your line.

Cheers

AdMMM

Attainable Line Rate (AKA Synch Rate)
This is the maximum rate at which your modem can connect to the DSLAM if there was no service provisioning limiting the bandwidth. Anything over 2,000Kbps is considered good. The higher the number the better.

Used Line Rate
Your Used ATM Rate (actual service rate) plus bandwidth to cover the overhead and provisioning of the service.

Fast Used ATM Rate
Actual bandwidth at which your service has been provisioned. The actual number can vary a little depending how you are physically serviced. If there is a number here that also means your connection is "fastpathed".

Interleaved Used ATM Rate
Actual bandwidth at which your service has been provisioned. The actual number can vary a little depending how you are physically serviced. If there is a number here that also means your connection is "interleaved".

Relative Capacity (AKA Line Capacity)
Percentage of your overall available bandwidth used to obtain your service ATM rate. For example; if your max line synch rate was 5888Kbps and you were provisioned on a 1472Kbps service you would be using 25% capacity. 1472/5888=25% capacity. The lower the relative capacity the better, but you can still get maximum speeds (although a less stable connection) even with a very high relative capacity. In other words you could be synching at 1472Kbps with 98% relative capacity and achieve maximum speeds, but you may experience more disconnects.

Noise Margin (AKA Signal to Noise Margin or Signal to Noise Ratio)
Relative strength of the DSL signal to Noise ratio. 6dB is the lowest dB manufactures specify for modem to be able to synch. In some instances interleaving can help raise the noise margin to an acceptable level. The higher the number the better for this measurement.
6dB or below is bad and will experience no synch or intermittent synch problems
7dB-10dB is fair but does not leave much room for variances in conditions
11dB-20dB is good with no synch problems
20dB-28dB is excellent
29dB or above is outstanding

Line Attenuation
Measure of how much the signal has degraded between the DSLAM and the modem. Maximum signal loss recommendation is usually about 60dB. The lower the dB the better for this measurement.
20dB and below is outstanding
20dB-30dB is excellent
30dB-40dB is very good
40dB-50dB is good
50dB-60dB is poor and may experience connectivity issues
60dB or above is bad and will experience connectivity issues

Output Power
How much power modem (upstream) or DSLAM (downstream) is using. Maximum recommended is about 15dB. The lower the power the better for this measurement.

CRC Errors (Cyclic Redundancy Check)
CRC is a method of detecting errors in data transmission. A high CRC count in inself is not really cause for alarm. However, any increase in CRCs after your initial connection is established is a problem and usually points to a physical issue somewhere.

Source: http://www.dslreports.com/faq/6734

kaizersoze

Very informative. Thanks