Wow

[g00dgirl]

If line attenuation indicates distance, does SNR margin indicate line quality?

I found the following useful:

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

An explanation of SNR and SNR Margin *

The SNR Margin is not the same as the Signal to Noise Ratio (SNR), although it is related.

The SNR is the signal-to-noise ratio. It is the ratio between the strength of the signal and the background noise on the line and is universally expressed as a logarithmic ratio (decibels or dB).

For a given line the SNR remains essentially fixed whatever the speed you are running.

ADSL routers and modems actually report the SNR Margin, and the term used to describe this varies but is generally “SNR Margin”, “Noise Margin”, “Margin”, “Receive Margin”.

The SNR Margin is the difference between the actual SNR and the SNR required to run at a given speed.

For example, if you need 20dB of SNR to run at 512Kbps, and the actual line SNR is 45dB, then the SNR Margin is 25dB.

The main reason why SNR margins fall as the line speed increases is that the required SNR increases.

For example, if increasing the speed from 512Kbps to 2MBps raises the required SNR from 20db to 30dB then the margin left will fall from 25dB to 15dB (as 45dB-30dB = 15dB.)

The one refinement is that if it is necessary for a faster speed to use some higher frequencies then these will have inherently lower SNRs and that will also contribute to the reduced SNR margin somewhat.

The SNR Margin is there to absorb fluctuations in interference on the line, and therefore to keep the service reliable. The figure of 6dB is normally accepted as enough headroom to make the link reliable, but some lines need more - 10dB is often accepted as a safer target.

Note that the target figures in the list are a reasonable summary, but it is the "SNR Margin" that is being talked about, not the "SNR". Despite this, it also does not invalidate the point that the most important factor on the reliability of a line at a given speed is the SNR Margin.

Also, as neither the SNR or SNR Margin can be established until a line is enabled (or validated with special test gear), then the estimated attenuation has to be used to come up with a viable speed. Once a line is enabled and working, it is possible - at least in theory - to gather information about the actual SNR and SNR Margin and use that to work out the actual speed the line will be able to sustain. This is essentially what will happen with the MaxDSL launch towards the end of the year.

* The above explanation has been slightly adapted from an original post made by Steve J (nopr0700) on adsl guide forums. - Due to the fact that forum posts are often archived, I have reproduced his information on this page. Thanks Steve.

SNR Margin

In general, a higher signal to noise ratio will result in less errors.

6bB. or below = Bad and will experience no line synchronisation or intermittent synchronisation problems.

7dB-10dB. = Fair but does not leave much room for variances in conditions.

11dB-20dB. = Good with little or no synchronisation problems

20dB-28dB. = Excellent

29dB. or above = Outstanding

Attenuation Rates

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

Distance

And for distance, the equation I have seen suggests that downstream attenuation divided by 13.81 will roughly equal KM from the exchange. For example; if you had a downstream attenuation of 40dB...

40dB / 13.81 = 2.896 KM

SNR can vary on an hour to hour basis, not only is it affected by the speed of your connection but there are other things may reduce your SNR. Hot weather can cause a long line to expand. Wet weather on a connection somewhere could cause dampness and deteriorate the signal. Even street lighting and flashing xmas tree lights have been known to affect SNR.

Your router or modem can either hear the signal from the exchange or it cant. If it cant "hear", or to put it correctly can't synchronise with the exchange, then your adsl connection is lost and you are said to have "lost sync".

[marcus]

Anyone knows how you can check if you have Indy or Premier ?

From your assigned IP address? I think Indy gets 117 or 222. But, not sure....

Yes... 117 or 222 and if your really unlucky 124.. 117 is the strongest 222 is close... and 124 is dead slow.. different routers and or different peering. if you get 58 or something in the 50's you are into premier. But Indy is much better then it has been.. though during the heavy use times of day you still loose the power to the USA. Premier seems to be consistent speed to offshore websites. This has been my experience anyway.

Strange, very strange.... My IP starts with 124, my router says upspead = 512 (so not the upgraded Premier which should be 1024) BUT the "Max Plack Test" says that my ISP isn't manipulating Bittorrent traffic at all... And the most funny : the Maxnet speedtest to BKK says that my speed sucks, but international speed right now (not the day before) is pretty good.

I have no idea what I have to think about it. Probably I will send them another email in a couple of days when my good intl. speed is gone.

[JetsetBkk]

Hmm, very nice and explains why I downloaded a "Spooks" episode at about 200 kB/s tonight.

[danfred]

Downstream SNR Margin: 12.2 db

Downstream Line Attenuation: 51.0 db

Downstream Data Rate: 1024 kbps

I take it I was upgraded last night:

Downstream SNR Margin: 7.1 db

Downstream Line Attenuation: 52.0 db

Downstream Data Rate: 2326 kbps

Your current bandwidth reading :

1.87 Mbps

Thank you TTT... I am very sorry for doubting you. Now how about the 4096 kbps upgrade as I'm paying you B1000 per month?

[g00dgirl]

I take it I was upgraded last night:

Downstream SNR Margin: 7.1 db

Downstream Line Attenuation: 52.0 db

Downstream Data Rate: 2326 kbps

Your current bandwidth reading :

1.87 Mbps

danfred that's a good speed 2326 kbps, can I ask you what model ADSL modem/router you are using for this?

I have done some testing with 3 different ADSL modems today on the same TT&T Maxnet line, all within 15 minutes with completely different results! Some hardware could negotiate a good speed, some other hardware could not:

Zyxel P660R-T1

============================

Downstream Speed: 2240 kbps

noise margin downstream: 5 db

attenuation downstream: 52 db

D-Link DSL-2640T

=============================

Downstream Speed: 1664 kbps

noise margin downstream: 5 db

attenuation downstream: 50 db

Billion BiPAC 5102S

=============================

Downstream Speed: 800 kbps

noise margin downstream: 6.5 db

attenuation downstream: 53 db

[Forkinhades]

Hmm, very nice and explains why I downloaded a "Spooks" episode at about 200 kB/s tonight.

how did you get that image??

[slackula]

Before the "upgrade" I was getting fairly uniform speeds across the globe from speedtest.net, now I am getting 2.5+ on the BKK server but this from the NY city one:

This is on a Maxnet Indy 1MB package that was upgraded to 1.5 and now is supposed to be 3.

Thanks for nothing Maxnet!

[JetsetBkk]

Hmm, very nice and explains why I downloaded a "Spooks" episode at about 200 kB/s tonight.

how did you get that image??

Have a look at Slackula's picture just below mine - on the left it says "Share your Result". You just copy the link by clicking on "Copy" and paste it into your post.

[slackula]

Have a look at Slackula's picture just below mine - on the left it says "Share your Result". You just copy the link by clicking on "Copy" and paste it into your post.

I didn't know if it was possible to directly upload a pic to thaivisa, so I did a screen grab of the relevant area and then put it into my photobucket.com account. JetsetBkk's answer is probably better.

[danfred]

danfred that's a good speed 2326 kbps, can I ask you what model ADSL modem/router you are using for this?

Hatari HW-AA101 (the same folks that manufacture all the fans in my house).

[JetsetBkk]

Have a look at Slackula's picture just below mine - on the left it says "Share your Result". You just copy the link by clicking on "Copy" and paste it into your post.

I didn't know if it was possible to directly upload a pic to thaivisa, so I did a screen grab of the relevant area and then put it into my photobucket.com account. JetsetBkk's answer is probably better.

Yes, your screen-grab was very handy in showing where the "Copy link" buttons are on the Speedtest.net page.

In fact, the links they provide are very similar to the ones that Photobucket provide.

[Ratsima]

D-Link DSL-500T

SNR Margin 20/20dB

Line Attenuation 28/30dB

Data Rate 3072/512kbps

Bangkok Server

US Server

[hereforgood]

Another Bxxxxxxt marketing campaign with no benefit.

When loading a website one won't see a big difference between 1 and 2 M. As long as they restrict speed on Torrents, FTP etc. the internet stays quite useless to me.

Doubling the speed for everybody will us more line capacity, which is already today not sufficient.

TiT.

If you are referring to TT&T, at least they state (in English, even when the rest of the brochure is in Thai) that the lowest-price range of packages (Indy) are restricted for torrents and VoIP. If that's what you find most important, then Indy would not be for you. I've never noticed any throttling of FTP on my Indy package, and I don't use VoIP or torrents, so I rationalize that when I first signed up for B1000/mo it was for 1Mbps. When it was working at full 2.5Mbps, I considered it a bonus. Now that I've downloaded a few files and noticed 400Bps+ download, I'm quite pleased.

Mind you, I do know what good internet access is: when I left Japan a few years ago I had 12Mbps ADSL, and it was the cheapest package I could get. Also available, even then, was 40Mbps, but I saw no reason to pay extra for it -- I found very few web sites that could deliver content much more than 4 or 5Mbps anyway.

I'm probably going to upgrade to the Premier 2Mbps/1Mbps package for an extra B90/month when my current 6-month Indy prepaid package is used up, the main attraction being the lower contention ratio.

I'm also grateful that the ISP model in Thailand is more like that in the US and Japan than like in Australia or England. I read features in computer magazines from those countries evaluating different ISPs, and it seems very rare or very expensive to have an "unlimited usage" plan like what we get here as standard. By "unlimited usage" I mean no maximum amount of download activity before the connection is "shaped" (reduced to 128kpbs or even 64kpbs) for the rest of the month.

I totally agree that what *really* needs to be worked on is a larger pipeline out of Thailand to the rest of the world...!

Yes that was the case for me not able to use P2P or voip services but since they doubled my speed on my indy plan can DL and at a great rate of speed and Voip now no problem and crystal clear as well all for 790 a month Thanks TT&T !!

[g00dgirl]

Just an interesting update I want to share.

I have been on the Maxnet Indy 2560/512 Kbps plan but only got 1536/512 Kpbs and I thought it was because I am too far from the DSLAM and because my signal to noise ratios were very low already.

But after seeing you guys getting upgraded, I complained and surprise, the low signal to noise ratios I had when synched on 1536/512 Kpbs didn't seem to matter, because now my modem synches with the DSLAM at

Upstream Speed: 506 kbps

Downstream Speed: 4096 kbps

and now my noise margin downstream is suddenly 24 db! (Check my previous posts in this thread for the poor noise margins I had before on the slower speed.)

My speedtests and downloads are great.

So don't think because your ADSL modem diagnostics are showing poor line quality you can not get the speed you pay for, it's worth to bug them to get you the speed you should get.

[jeffer]

So after reading this thread, the info in my router tells me I'm getting a good connection, yes?

okay, I give up trying to post an image on this forum, it used to be easy before.

Noise margin Up / 20.0db

Noise down / 47.0db

Attenuation Upstream, / 10.0db

Att. downstream / 20.0db

Edited July 23, 2008 by jeffer

[g00dgirl]

Yes your line quality looks good jeffer.

[woodyleonhard]

We've been seeing GREAT speeds in Phuket with TT&T Maxnet, on the Phuket Internet Speed reporting site.

I published an article in the Phuket Gazette about it last week. It hasn't been posted on the Gazette site yet, but you can check for it here.