Routers and SNR: Last updated: 15th Sept 2011
This page documents my ADSL problems caused due to falling SNRM (Signal to Noise Ratio Margin) in the evening and my experiences with different routers.
My line stats are: Attenuation 50, Target SNR: 12db Sync:
around 4200kbps BRAS Profile: 3500
when my line was initially upgraded to a MAX product my
target SNR was the normal 6db and I sync'd at 5,200kbps.
I noticed the SNR dropped in the evening when it started to get dark, and would eventually lose sync if I didn't turn off manually to save my BRAS (IP) Profile). As this was around 9pm it didn't cause too much of a problem. Turning the router on the next morning I would enjoy my normal sync and speeds.
But since the days have been drawing in as we move in to
winter the SNR has been dropping earlier and earlier.
To ensure your internal wiring performs at it's best fit an ADSL Faceplate Filter:
As you can see soon after 5pm the SNR becomes pretty
It then re-syncs lower so as to increase the SNRM but the damage has already been done to my BT IP Profile - which would have been immediately reduced.
The SNR statistics are captured using RouterStats a useful and free application from www.vwlowen.co.uk This simple application lets you monitor and graph your SNR margin and connection speed, as well as other adsl statistics. With the latest version the current SNR value is also displayed in the System Tray icon so you can keep you eye on your SNRM as easliy as checking the time! The software also lets you run scripts or sounds an alarm if the SNRM drops too low etc. Highly recommended!
After being as happy as I could that the source of noise was not from within my house I started to look at changing my router to see if it would improve things. NB. I had already 'optimised' my line for ADSL as much as I could see ADSL page. After a lot of broadband forum reading it became obvious that quite a few people rated routers from both 2Wire and Thomson.
Seems to manage SNR well - but still losing synch in the evening for me.
The 2Wire 2700 router isn't easily available in the UK. BT supply it as their BT Business Hub - but it's locked to BT in an attempt to stop it being used with other providers. There are a few ways of getting round this - if you need to know how to unlock a 2Wire then an internet search will show you what's needed. I bought my 2Wire 2700HG-B second hand on eBay and had already been unlocked having been flashed with SBC firmware.
Interestingly this is the first router I've found where the
documentation actually references 'long noisy lines'.
From the 2Wire Router guide:
The 2Wire 2700 certainly seemed to manage SNR differently (better!) than the Netgear router.
Where SNRM with the Netgear would fluctuate between 8 and 12dbs during the day - the 2Wire would run completely stable at 12db (my target SNRM). But when night time came the SNR still dropped and the router lost sync when it had been running at around 6db. This happened a few hours later than the Netgear but didn't fix my problem.
I haven't got a SNR graph to hand for the 2Wire - if I should give this router a second try I'll update the page.
Fixed my adsl max problems - No more disconnections!
The Thomson Speedtouch 585v6 seems to have fixed my low
The ST585v6 from Thomson has proved to be the best router for coping with low SNR on my long and noisy BT line.
I'm connected to a Texas Instruments(TSTC) DSLAM in my exchange and it seems the chipset in the Speedtouch (TMMB/Broadcom) is a compatible combination for me. So I suggest if you are having similar problems with loss of internet connection in the evenings don't give up but try a new modem!
Update: 29th March 2008 - Target SNR reduced manually
My internet connection is still much improved after switching to the Thomson
Speedtouch 585 v6 router
See my ADSL page for tips to understand and improve your broadband connection: ADSL information
Update: 21st December 2008 - Target SNR reduced automatically
After seeing my connection run cleaner (less FEC/HEC/CRC errors) for a few weeks I was pleased to see on the 13th December I connected at 5504kbps around 1/2Mb faster than normal! Looking at my SNRM I found it was now 6db rather than my normal 9db - so BT's systems have automatically lowered my Target SNR to the default 6db.
Just for the record, I power my router off every evening and turn it back on first thing in the morning - so this shows that the Exchange equipment (DSLAM) does lower a Target SNR without seeing a continuous connection for 14 days or more as is often documented. The lowering of Target SNR is something of a 'black art' and the exact conditions are kept secret by BT unfortunately.
After running for 7 days syncing around 55xx my IP
Profile(BRAS) increased to 4500.
Update: 15th September 2011 Good internet speeds
Just to say I'm still doing well on my trusty Broadcom
chipset Thomson ST585v6.
Below is an up to date noise margin (SNR) graph from
RouterStats for my broadband connection using the Speedtouch 585.
This show things are running nice and smoothly connected with a 6db Target Noise