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uk.telecom.broadband (UK broadband) (uk.telecom.broadband) Discussion of broadband services, technology and equipment as provided in the UK. Discussions of specific services based on ADSL, cable modems or other broadband technology are also on-topic. Advertising is not allowed.

ADSL2 sync speed/SNR diurnal variation



 
 
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  #1  
Old September 6th 12, 09:20 AM posted to uk.telecom.broadband
Martin Brown
external usenet poster
 
Posts: 343
Default ADSL2 sync speed/SNR diurnal variation

Hello! What is the normal expected level of variation seen in sync speed
and noise level over a 24 hour period?

I just measured mine and was surprised by the results (numbers rounded).

In summary

Daytime sync is 5200+/-100 with 6dB noise
SNR starts to degrade from 18:00 to 20:00 roughly in line with local
sunset and when it hits 4dB retraining drops back to 4400 and steady.
Noise level 6dB again.

This persists continuously overnight.

The reverse happens leading up to local sunrise with SNR rising to 9dB
and sync speed climbing back up to 5100 and 7dB SNR. There is still
plenty of dew on the ground and yet SNR is already at daytime levels.

Is this normal and what is the cause?

For completeness daytime attenuation down/up are 50dB and 28dB
respectively and output powers 122dB and 199dB (upload sync is always
448kbps). I haven't measured these late at night but I will do tonight.

The Router is a Belkin F5D8633-4 in case it has any unusual quirks.
I could swap it for a WAG325 at a pinch to verify these results.

Thanks for any enlightenment. I am trying to glean the last ounce of
performance from my phone line since throughput is now just below the
threshold needed for reliable HD streaming on demand. In rural North
Yorks so I expect hell to freeze over before we see LLU up here!

--
Regards,
Martin Brown
  #2  
Old September 6th 12, 10:31 AM posted to uk.telecom.broadband
The Natural Philosopher
external usenet poster
 
Posts: 2,728
Default ADSL2 sync speed/SNR diurnal variation

Martin Brown wrote:
Hello! What is the normal expected level of variation seen in sync speed
and noise level over a 24 hour period?


noise level ariudn 3dB day to night here.

sync speed? normally stays the same.


I just measured mine and was surprised by the results (numbers rounded).

In summary

Daytime sync is 5200+/-100 with 6dB noise
SNR starts to degrade from 18:00 to 20:00 roughly in line with local
sunset and when it hits 4dB retraining drops back to 4400 and steady.
Noise level 6dB again.

This persists continuously overnight.


sounds about right,. You will in time get a 9dB target SNR and then you
should stabilise around 4500 with less disconnects.


The reverse happens leading up to local sunrise with SNR rising to 9dB
and sync speed climbing back up to 5100 and 7dB SNR. There is still
plenty of dew on the ground and yet SNR is already at daytime levels.

Is this normal and what is the cause?


MW radio.

After dark the long range stuff skips around the ionosphere - I forget why.

Ah. Wiki rescues

"The D layer is the innermost layer, 60 km to 90 km above the surface of
the Earth. Ionization here is due to Lyman series-alpha hydrogen
radiation at a wavelength of 121.5 nanometre (nm) ionizing nitric oxide
(NO). In addition, with high Solar activity hard X-rays (wavelength 1
nm) may ionize (N2, O2). During the night cosmic rays produce a residual
amount of ionization. Recombination is high in the D layer, the net
ionization effect is low, but loss of wave energy is great due to
frequent collisions of the electrons (about ten collisions every msec).
As a result high-frequency (HF) radio waves are not reflected by the D
layer but suffer loss of energy therein. This is the main reason for
absorption of HF radio waves, particularly at 10 MHz and below, with
progressively smaller absorption as the frequency gets higher. The
absorption is small at night and greatest about midday. The layer
reduces greatly after sunset; a small part remains due to galactic
cosmic rays. A common example of the D layer in action is the
disappearance of distant AM broadcast band stations in the daytime."

For completeness daytime attenuation down/up are 50dB and 28dB
respectively and output powers 122dB and 199dB (upload sync is always
448kbps). I haven't measured these late at night but I will do tonight.

The Router is a Belkin F5D8633-4 in case it has any unusual quirks.
I could swap it for a WAG325 at a pinch to verify these results.

Thanks for any enlightenment. I am trying to glean the last ounce of
performance from my phone line since throughput is now just below the
threshold needed for reliable HD streaming on demand. In rural North
Yorks so I expect hell to freeze over before we see LLU up here!


Very unlikely you will do better on that attenuation. Streaming HD will
have to wait...

--
Ineptocracy

(in-ep-toc'-ra-cy) - a system of government where the least capable to
lead are elected by the least capable of producing, and where the
members of society least likely to sustain themselves or succeed, are
rewarded with goods and services paid for by the confiscated wealth of a
diminishing number of producers.
  #3  
Old September 6th 12, 11:12 AM posted to uk.telecom.broadband
Peter Able
external usenet poster
 
Posts: 114
Default ADSL2 sync speed/SNR diurnal variation


"Martin Brown" wrote in message
...
Hello! What is the normal expected level of variation seen in sync speed
and noise level over a 24 hour period?

I just measured mine and was surprised by the results (numbers rounded).

In summary

Daytime sync is 5200+/-100 with 6dB noise
SNR starts to degrade from 18:00 to 20:00 roughly in line with local
sunset and when it hits 4dB retraining drops back to 4400 and steady.
Noise level 6dB again.

This persists continuously overnight.

The reverse happens leading up to local sunrise with SNR rising to 9dB and
sync speed climbing back up to 5100 and 7dB SNR. There is still plenty of
dew on the ground and yet SNR is already at daytime levels.

Is this normal and what is the cause?

For completeness daytime attenuation down/up are 50dB and 28dB
respectively and output powers 122dB and 199dB (upload sync is always
448kbps). I haven't measured these late at night but I will do tonight.


Sounds very typical, Martin.

For comparison, my -52dB line resyncs at 6dB speeds ranging from 4500
(currently, at about 1600h) to 3800kbps (during the night). The trick is to
find the right time of day for a manual resync that will then hold for 24
hours. For me it about one hour off the peak timing, i.e. 1500h or 1700h,
when I get about 4400kbps. My modem, once synced, can hold the connection
down to about 3dB. Your modem doesn't sound to be so tolerant, but the
process I've described is still valid.

The attenuation shouldn't vary diurnally. The diurnal effect is, as
mentioned elsewhere, due to the enhanced propagation of broadcast radio
stations during darkness hours. If you connect an oscilloscope to one of
the pair wires you'll be amazed that your broadband works at all. Connect a
differential oscilloscope to the pair and it is still pretty amazing that it
all works. The power of DSP!

PA


PA


  #4  
Old September 6th 12, 12:03 PM posted to uk.telecom.broadband
Martin Brown
external usenet poster
 
Posts: 343
Default ADSL2 sync speed/SNR diurnal variation

On 06/09/2012 10:31, The Natural Philosopher wrote:
Martin Brown wrote:
Hello! What is the normal expected level of variation seen in sync
speed and noise level over a 24 hour period?


noise level ariudn 3dB day to night here.
sync speed? normally stays the same.


OK. Thanks. Mine has been bouncing around ever since I did the bell wire
hack. It used to be stuck at about 2500 or less.

I just measured mine and was surprised by the results (numbers rounded).

In summary

Daytime sync is 5200+/-100 with 6dB noise
SNR starts to degrade from 18:00 to 20:00 roughly in line with local
sunset and when it hits 4dB retraining drops back to 4400 and steady.
Noise level 6dB again.

This persists continuously overnight.


sounds about right,. You will in time get a 9dB target SNR and then you
should stabilise around 4500 with less disconnects.


Since I don't much use it after midnight is there any way to keep a
slightly higher daytime sync rate and get the lines bRAS profile up to
4000kbps at the exchange instead of 3500 max?


The reverse happens leading up to local sunrise with SNR rising to 9dB
and sync speed climbing back up to 5100 and 7dB SNR. There is still
plenty of dew on the ground and yet SNR is already at daytime levels.

Is this normal and what is the cause?


MW radio.

After dark the long range stuff skips around the ionosphere - I forget why.


Thanks. I actually thought it was a coincidence but this explanation
makes perfect sense. The timing was remarkably consistent with the sun.

For completeness daytime attenuation down/up are 50dB and 28dB
respectively and output powers 122dB and 199dB (upload sync is always
448kbps). I haven't measured these late at night but I will do tonight.

The Router is a Belkin F5D8633-4 in case it has any unusual quirks.
I could swap it for a WAG325 at a pinch to verify these results.

Thanks for any enlightenment. I am trying to glean the last ounce of
performance from my phone line since throughput is now just below the
threshold needed for reliable HD streaming on demand. In rural North
Yorks so I expect hell to freeze over before we see LLU up here!


Very unlikely you will do better on that attenuation. Streaming HD will
have to wait...


It is so near though. I have a reliable 3300 streaming speed against a
profile limit on my line of 3500. I just need gain an extra 200 or so. I
suspect it is quantised in 500's rather than 250's.

I might have it too after rewiring the modem to a splitter this morning
at the master socket I am now syncing at 100 faster than before but with
no visible change in the noise figure. Oh for an extra digit in the
reported "6" dB noise (even half digit 0.5 steps would help)

--
Regards,
Martin Brown
  #5  
Old September 6th 12, 12:13 PM posted to uk.telecom.broadband
George Weston
external usenet poster
 
Posts: 467
Default ADSL2 sync speed/SNR diurnal variation

On 06/09/2012 10:31, The Natural Philosopher wrote:
Martin Brown wrote:
Hello! What is the normal expected level of variation seen in sync
speed and noise level over a 24 hour period?


noise level ariudn 3dB day to night here.

sync speed? normally stays the same.


I just measured mine and was surprised by the results (numbers rounded).

In summary

Daytime sync is 5200+/-100 with 6dB noise
SNR starts to degrade from 18:00 to 20:00 roughly in line with local
sunset and when it hits 4dB retraining drops back to 4400 and steady.
Noise level 6dB again.

This persists continuously overnight.


sounds about right,. You will in time get a 9dB target SNR and then you
should stabilise around 4500 with less disconnects.


The reverse happens leading up to local sunrise with SNR rising to 9dB
and sync speed climbing back up to 5100 and 7dB SNR. There is still
plenty of dew on the ground and yet SNR is already at daytime levels.

Is this normal and what is the cause?


MW radio.

After dark the long range stuff skips around the ionosphere - I forget why.

Ah. Wiki rescues

"The D layer is the innermost layer, 60 km to 90 km above the surface of
the Earth. Ionization here is due to Lyman series-alpha hydrogen
radiation at a wavelength of 121.5 nanometre (nm) ionizing nitric oxide
(NO). In addition, with high Solar activity hard X-rays (wavelength 1
nm) may ionize (N2, O2). During the night cosmic rays produce a residual
amount of ionization. Recombination is high in the D layer, the net
ionization effect is low, but loss of wave energy is great due to
frequent collisions of the electrons (about ten collisions every msec).
As a result high-frequency (HF) radio waves are not reflected by the D
layer but suffer loss of energy therein. This is the main reason for
absorption of HF radio waves, particularly at 10 MHz and below, with
progressively smaller absorption as the frequency gets higher. The
absorption is small at night and greatest about midday. The layer
reduces greatly after sunset; a small part remains due to galactic
cosmic rays. A common example of the D layer in action is the
disappearance of distant AM broadcast band stations in the daytime."


The occasional sporadic "E" layer can also cause problems when it kicks
in, usually during periods of high sunspot activity!
;-)


For completeness daytime attenuation down/up are 50dB and 28dB
respectively and output powers 122dB and 199dB (upload sync is always
448kbps). I haven't measured these late at night but I will do tonight.

The Router is a Belkin F5D8633-4 in case it has any unusual quirks.
I could swap it for a WAG325 at a pinch to verify these results.

Thanks for any enlightenment. I am trying to glean the last ounce of
performance from my phone line since throughput is now just below the
threshold needed for reliable HD streaming on demand. In rural North
Yorks so I expect hell to freeze over before we see LLU up here!


Very unlikely you will do better on that attenuation. Streaming HD will
have to wait...


  #6  
Old September 6th 12, 03:24 PM posted to uk.telecom.broadband
Mark
external usenet poster
 
Posts: 525
Default ADSL2 sync speed/SNR diurnal variation

On Thu, 06 Sep 2012 12:03:36 +0100, Martin Brown
wrote:

Since I don't much use it after midnight is there any way to keep a
slightly higher daytime sync rate and get the lines bRAS profile up to
4000kbps at the exchange instead of 3500 max?


I thought, with ADSL2+, that the bRAS/IP profile changes straight away
when the sync speed varies.
--
(\__/) M.
(='.'=) If a man stands in a forest and no woman is around
(")_(") is he still wrong?

  #7  
Old September 6th 12, 03:59 PM posted to uk.telecom.broadband
The Natural Philosopher
external usenet poster
 
Posts: 2,728
Default ADSL2 sync speed/SNR diurnal variation

Mark wrote:
On Thu, 06 Sep 2012 12:03:36 +0100, Martin Brown
wrote:

Since I don't much use it after midnight is there any way to keep a
slightly higher daytime sync rate and get the lines bRAS profile up to
4000kbps at the exchange instead of 3500 max?


I thought, with ADSL2+, that the bRAS/IP profile changes straight away
when the sync speed varies.


It may well do but that animal so far is only a rumoured fable at our
local exchange.


--
Ineptocracy

(in-ep-toc'-ra-cy) - a system of government where the least capable to
lead are elected by the least capable of producing, and where the
members of society least likely to sustain themselves or succeed, are
rewarded with goods and services paid for by the confiscated wealth of a
diminishing number of producers.
  #8  
Old September 6th 12, 11:17 PM posted to uk.telecom.broadband
Mike Tomlinson
external usenet poster
 
Posts: 285
Default ADSL2 sync speed/SNR diurnal variation

En el artículo , Martin Brown |||newspa
escribió:

For completeness daytime attenuation down/up are 50dB and 28dB
respectively


You're doing pretty well with that attenuation as it is. Presumably it's
a long line.

The Router is a Belkin F5D8633-4 in case it has any unusual quirks.
I could swap it for a WAG325 at a pinch to verify these results.


I'd try a couple of different routers for sure. Some cope better with
long lines. You can buy them used on fleabay for buttons.

Try a Netgear DG834GT with the DGTeam firmware. They're available on
ebay very cheap ex-$ky. I paid 2 quid delivered for mine, brand new and
unused. With the DGTeam firmware you can tweak the SNR down as far as
0dB, though I wouldn't recommend going lower than 3. This got my sync
speed up from 11200kbps to 18800kbps, pushing the line any harder than
that resulted in too many errors.

I've also heard reports that some 2Wire routers can get the most out of
a poor line.

Thanks for any enlightenment. I am trying to glean the last ounce of
performance from my phone line


Have you done the usual - disconnected any extension wiring, connected
the router to the master socket, disconnected the bell wire, fitted an
iPlate?

Lift the receiver and press any number to stop the dial tone. Any
noises - hisses, crackles, etc? If yes, report it as a VOICE fault.

--
(\_/)
(='.'=)
(")_(")
  #9  
Old September 6th 12, 11:34 PM posted to uk.telecom.broadband
Graham.
external usenet poster
 
Posts: 93
Default ADSL2 sync speed/SNR diurnal variation

On Thu, 6 Sep 2012 23:17:13 +0100, Mike Tomlinson
wrote:

En el artículo , Martin Brown |||newspa
escribió:

For completeness daytime attenuation down/up are 50dB and 28dB
respectively


You're doing pretty well with that attenuation as it is. Presumably it's
a long line.

The Router is a Belkin F5D8633-4 in case it has any unusual quirks.
I could swap it for a WAG325 at a pinch to verify these results.


I'd try a couple of different routers for sure. Some cope better with
long lines. You can buy them used on fleabay for buttons.

Try a Netgear DG834GT with the DGTeam firmware. They're available on
ebay very cheap ex-$ky. I paid 2 quid delivered for mine, brand new and
unused. With the DGTeam firmware you can tweak the SNR down as far as
0dB, though I wouldn't recommend going lower than 3. This got my sync
speed up from 11200kbps to 18800kbps, pushing the line any harder than
that resulted in too many errors.

I've also heard reports that some 2Wire routers can get the most out of
a poor line.

Thanks for any enlightenment. I am trying to glean the last ounce of
performance from my phone line


Have you done the usual - disconnected any extension wiring, connected
the router to the master socket, disconnected the bell wire, fitted an
iPlate?

Lift the receiver and press any number to stop the dial tone. Any
noises - hisses, crackles, etc? If yes, report it as a VOICE fault.


Buzzing or hum on long rural lines is common and is a sure sign of
earth leakage on one or both legs.

--
Graham.
%Profound_observation%
  #10  
Old September 7th 12, 09:01 AM posted to uk.telecom.broadband
Martin Brown
external usenet poster
 
Posts: 343
Default ADSL2 sync speed/SNR diurnal variation

On 06/09/2012 15:24, Mark wrote:
On Thu, 06 Sep 2012 12:03:36 +0100, Martin Brown
wrote:

Since I don't much use it after midnight is there any way to keep a
slightly higher daytime sync rate and get the lines bRAS profile up to
4000kbps at the exchange instead of 3500 max?


Looks from another post like a cheap Netgear DG834GT with the DGTeam
firmware may be worth a try and fib about SNR to the exchange in return
for a slightly flakier connection but more daytime speed. Have to see if
that pans out in mid-winter when there isn't much daylight.

I thought, with ADSL2+, that the bRAS/IP profile changes straight away
when the sync speed varies.


It probably would do if we actually had it in rural areas - a bit like
mains gas, LLU and cable TV. This is plain vanilla rural ADSL2 on very
old wire (not especially long but pretty lossy). 3km as the crow flies
and a bit further maybe 5km as the cable runs - some of it overhead.

BT refuse to install any new cable despite increased demand for real
copper circuits and DACS two grannies for every new ADSL circuit. The
only way we will get anything better is either by directed microwave
link or the government bribing BT to offer a service to rural users.

What was left of the minor junction box was buried underground after a
hedge flailer trashed it a few years back producing multicoloured
shorter spagetti that took them a fortnight and loads of blokes to sort
out. It does mean that all those connections are fairly fresh though.

Being on the wrong side of the beck from the exchange appears to be an
instant -1000kbps hit on the maximum sync rate and throughput.

Incidentally looks like my connection has at last settled on 4704 and a
varying SNR instead of hopping around like a demented Etch-a-Sketch.
Perhaps I was being impatient.

Incidentally is there any heuristic for line attenuation vs maximum
download speed to provide a guide as to what should be possible?
Datapoints for download speeds I have collected so far are
attn, iPLayer/diag
50dB, 3300
56dB, 2750
64dB, 1000

So a rough rule of thumb to me looks like +100 for every +1dB in SNR
(with bad things happening at the poor SNR end)

--
Regards,
Martin Brown
 




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