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Routerstats Anomaly

Community Veteran
Posts: 4,821
Thanks: 117
Fixes: 23
Registered: 14-07-2009

Routerstats Anomaly

Even though I have eliminated the problem I had with a REIN source nearby, I have continued to run Routerstats.  Last night we had a short power cut and I have attached the routerstats trace for the duration of the cut (since my router and computer are on a UPS so kept going).  The downstream SNRM increases by about 4dB then drops back to normal a minute or two after the power is restored.  I have tried turning off my own mains and it makes no difference to the trace.  So can there really be an extra 4dB of noise coming from everywhere else?  If so, it never ever goes away.   
5 REPLIES
Community Veteran
Posts: 38,460
Thanks: 1,027
Fixes: 62
Registered: 15-06-2007

Re: Routerstats Anomaly

Very easily
That is why when my router reconnects after a power cut I get a much higher, and unmaintainable, sync speed
x47c
Grafter
Posts: 878
Registered: 14-08-2009

Re: Routerstats Anomaly

That jump is very typical of a power cut.
I see much the same when it happens - also on a UPS
It is just noise of all types from everywhere - all generated either by the mains itself or by items running off the mains.
What is actually rather interesting is the way the noise suddenly ceases upon the cut, but come back almost on an delayed exponential rise when the power come back on.
So some things are taking just a bit of time to re-energise and starting pumping out the cr*p across the airwaves.
One day when we get a long cut I swear I'm going to do a re-sync to see what the line will perform at without all the noise.
I do have somwhere a detailed spectrum trace in excel of the SNR margin at each tone extracted from the router with and without power locally.
As I recall the trace is lifted at all tones across the board by a bit.
The sudden odd minor dips in loading at certain points are still there suggesting they are RF interference from considerable distance away or are commercial installations also running off UPS's and giving out cr*p (mobile phone mast emergency generators for ex).
198kHz
Seasoned Pro
Posts: 3,285
Thanks: 294
Fixes: 9
Registered: 30-07-2008

Re: Routerstats Anomaly

Quote from: x47c
What is actually rather interesting is the way the noise suddenly ceases upon the cut, but come back almost on an delayed exponential rise when the power come back on.
So some things are taking just a bit of time to re-energise and starting pumping out the cr*p across the airwaves.

Which suggests that most of the 'noise' is crosstalk from other broadband lines?
Papyrus and Comic Sans walk into a bar. The bartender says, "Get out -- we don't serve your type."
hadden
Grafter
Posts: 486
Thanks: 2
Registered: 27-07-2007

Re: Routerstats Anomaly

I did have an 80 minute power cut back in May and was able to see what happens when powering up the router in that scenario...
Last March I had tweaked my SNR margin down from 6dB to 2dB resulting in a sync speed rise from about 5800 kbps to about 6200 kbps and this remained stable for 8 weeks then I had the power cut. Although I have a UPS, the router is currently not located conveniently for the UPS, so it had powered down.
After a bit of setting up I powered up my generator. There were certain domestic priorities to deal with first, but I then got round to powering up the router and connected via a tablet over wi-fi.
The router status page reported that the sync speed was 6880 kbps and the SNR margin at 6dB.
So comparing the sync speed with my "normal" sync speed, when the SNR margin was allowed to be 6dB, my connection was able to increase by about 1Mbps.
I didn't have sufficient time to power up my PC with Routerstats, so was not able to record any other data.
The area affected by the power cut was sufficient to include all of the premises that would be connected to the same cabinet as me, which would be very roughly a thousand houses and perhaps a dozen commercial premises.
Community Veteran
Posts: 4,821
Thanks: 117
Fixes: 23
Registered: 14-07-2009

Re: Routerstats Anomaly

Thanks for all the responses.  It's a bit of an eye-opener to see just how much 'background noise' goes away when the power goes out.