Line attenuation. What is it?

Thrill

Cork City center
Eircombb 2mb

I have noticed that over the last few weeks my "line attenuation"
has gone from 31/13 dB to 28/13 dB.

Can someone please tell me what line attenuation is and if the lower
number is good or bad?

Thanks in advance.

Boston

In general attenuation means to cut-off/reduce something. db is just the decibel scale, and more then likely those numbers are a measure of the power on your line, signal to noise ratio, or some such.

Based on the information, I'd go with lower numbers being bad, though I'm not an expert on Eircoms adsl offering.

Boston

Having looked up something, it says 45db is standard for 2mbit line.

dub45

thrill wrote:

Cork City center
Eircombb 2mb

I have noticed that over the last few weeks my "line attenuation"
has gone from 31/13 dB to 28/13 dB.

Can someone please tell me what line attenuation is and if the lower
number is good or bad?

Thanks in advance.

http://www.kitz.co.uk/adsl/linestats.htm

kaizersoze

In short, for attenuation,the lower the better. So yours is going in the right direction.
With SNR the opposite is the case, the higher the better.

Good link Dub.

Thrill

Thanks for the info guys. That site explained everything.:D:D:D

Thanks for that link.

dub45

kaizersoze wrote:

In short, for attenuation,the lower the better. So yours is going in the right direction.
With SNR the opposite is the case, the higher the better.

Good link Dub.

May as well thrown in this one as well so!:)

http://www.kitz.co.uk/adsl/lowSNR.htm

Dingatron

So I supose this sh*te so?

Max Allowed Speed (kbps) 3072 384
SN Margin (dB) 7.50 10.00
Line Attenuation (dB) 63.50 31.50
CRC Errors 3 2

rc28

Dingatron wrote: »

So I supose this sh*te so?

Max Allowed Speed (kbps) 3072 384
SN Margin (dB) 7.50 10.00
Line Attenuation (dB) 63.50 31.50
CRC Errors 3 2

I'm surprised eircom approved you the 3mb package considering your line attenuation(i've come across others on here who were told their line doesn't support 3mb). How far away do you live from the exchange and can you take a speedtest on www.speedtest.net and post your results on here?

Dingatron

Yeah I'm not too happy at the minute with my connection. I've been getting the odd disconection, bad pings etc. The exchange is around 1.2 miles as the crow flies (need to check this) I think. Stats are ok tonight but usually a lot worse.



Not sure what I can do about it so any advice would be welcome?

Dingatron

This would be more the norm....

nilhg

Dingatron wrote: »

This would be more the norm....

Hi peak usage time is hardly going to be the best time to test the absolute speed of your connection later on tonight or early in the morning would be much better.

Contention would easily explain your last test.

Skyuser

Attenuation.............Approximate Line Length............Potential Connection Speed
32db...................................2.3km.....................................16000kbps
35db...................................2.5km.....................................14500kbps
40db...................................2.9km.....................................11800kbps
45db...................................3.2km.......................................8500kbps
50db...................................3.6km.......................................6500kbps
55db...................................4.0km.......................................4500kbps
60db...................................4.3km.......................................3200kbps
65db...................................4.7km.......................................2000kbps

Dingatron

Interesting. I'm at most 3km from the exchange and getting 63db. Would the internal wiring in the house affect this? I have 3 lines coming off the main phone line and my router is in one of the the split lines.

Snaga

Dingatron wrote: »

Interesting. I'm at most 3km from the exchange and getting 63db. Would the internal wiring in the house affect this? I have 3 lines coming off the main phone line and my router is in one of the the split lines.

Disconnect all the lines - plug the modem in on the first phone point and see what your attenuation reading is then - at least you'll answer that question

Dont forget - tha cable path to your premises may well be significantly longer than the crow-flies distance.

Dingatron

Snaga wrote: »

Disconnect all the lines - plug the modem in on the first phone point and see what your attenuation reading is then - at least you'll answer that question

Dont forget - tha cable path to your premises may well be significantly longer than the crow-flies distance.

True I'll give it a check at the weekend. Need to try and get this sorted with the impending speed increases from eircom on the way.

long_b

Very interesting ... I have similarly crap attenuation and was only approved for a 1 MB line.
The modem syncs at anything from 360 ~ 700 kbs.
Would I get a better speed if I insist on a 2MB package ?

fatboymsport

what are these like how much faster can i go ??

Downstream Upstream
Max Allowed Speed (kbps) 2048 256
SN Margin (dB) 13.50 22.00
Line Attenuation (dB) 26.00 13.00
CRC Errors 75 5

dub45

long_b wrote: »

Very interesting ... I have similarly crap attenuation and was only approved for a 1 MB line.
The modem syncs at anything from 360 ~ 700 kbs.
Would I get a better speed if I insist on a 2MB package ?

You will most likely get more frequent disconnects. If you have crap attenuation there is absolutely no point in insisting on a a faster speed. Have you checked all your internal connections etc etc.

The Real B-man

Dingatron wrote: »

Interesting. I'm at most 3km from the exchange and getting 63db. Would the internal wiring in the house affect this? I have 3 lines coming off the main phone line and my router is in one of the the split lines.

No i have the same 63db internal wiring wont affect it too much just line quality and distance from the exchange will.

Jason Ryan

I'm on the 3mb package, and consistently get full 3mb download speeds.
But would these line stats agree?

Thanks.

Downstream Upstream
Max Allowed Speed (kbps) 3072 384
SN Margin (dB) 21.00 6.50
Line Attenuation (dB) 51.00 31.50

Snaga

Yup - but you wont get much better than that.

I assume the SNR Margin of 6.5 is your downstream margin? If thats so then you are right on the edge as it is at your current speeds. (I would guess that your ISP has you on a target SNR of 6db which is low but ok for a stable (not very noisy) line).

Your line is capable of a higher upload speed however.

kaizersoze

The Real B-man wrote: »

No i have the same 63db internal wiring wont affect it too much just line quality and distance from the exchange will.

True enough but crap copper and/or internal wiring will affect your SNR which can affect your connection aswell.

kaizersoze

Snaga wrote: »

Yup - but you wont get much better than that.

I assume the SNR Margin of 6.5 is your downstream margin? If thats so then you are right on the edge as it is at your current speeds. (I would guess that your ISP has you on a target SNR of 6db which is low but ok for a stable (not very noisy) line).

Your line is capable of a higher upload speed however.

The SN Margin of 6.50 is upstream.

Snaga

kaizersoze wrote: »

The SN Margin of 6.50 is upstream.

Arp, yup that'd make more sense given the attenuation figure order.

You should squeeze another couple of Mb download out of your line according to that SNR margin of 20+db.

Its unusual to see your upload SNR margin lower than your download though.

Dingatron

kaizersoze wrote: »

True enough but crap copper and/or internal wiring will affect your SNR which can affect your connection aswell.

Well it looks like it's crappy internal wiring in my case. Unplugged everything and moved my router down to the main line in. Plugged in the router on its own and 'Hey Presto!' 36db downstream. Now all I need to figure out what way the current mess of wiring is done and do it right this time.

Thanks for the help guys!

Henry O'Henry

Am getting these stats with BT 3mb. How will this fare with the alleged 8mb upgrade in June?

Port Status TxPkts RxPkts Collisions Tx B/s Rx B/s Up Time
WAN PPPoA 5745 7363 0 509 4005 00:27:30
LAN 10M/100M 8858 6890 0 4214 650 00:28:51
WLAN 11M/54M/270M 933 733 0 144 68 00:28:47

ADSL Link Downstream Upstream
Connection Speed 3072 kbps 384 kbps
Line Attenuation 30.0 db 10.0 db
Noise Margin 17.1 db 19.0 db

jleavy

Hi Guys,
I understand my line attenuation is good/fair (if i read the posts correctly), but my question is- does my SN Margin look ok?

Downstream Upstream
Max Allowed Speed (kbps) 3072 384
SN Margin (dB) 16.00 16.00
Line Attenuation (dB) 30.50 13.50
CRC Errors 0 0

Many thanks,
Joe



EDIT:

This kinda explains everything:

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 sync. 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 sync 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.

Duiske

Statistics Downstream Upstream
Line Rate 3072 Kbps 384 Kbps
Noise Margin 30.2 dB 14.0 dB
Line Attenuation 2.0 dB 3.0 dB
Output Power 2.2 dBm -3.9 dBm

I live 3 doors away from the exchange, which explains the above.

slx

I re-wired my phone lines, using CAT5e cable. Removed all the old extensions and wired in a new line to where the eircom cables come in.

Coming up at 7.5db Line Attenuation now!

It was over 40!

Connection's been great.

firefly123

Hi All,

Ive been reading this post and checked some of the stats. A friend has an eircom line at the very limit of the exchanges reach. She is only getting 160kbps downstream. The line attenuation is 41 / 24 (which as far as I can see is good) and the SNR is 31 down (also acceptable).

I cant figure how the stats are good yet her speed is so low - I think eircom limited it to this speed as it wasnt syncing at higher speeds - the question is would we see more noise and attenuation if the line was set to a higher speed??

Thanks,

FF.