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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.

adsl parameters: ideal readings?



 
 
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  #1  
Old July 21st 09, 11:44 AM posted to uk.telecom.broadband
tg
external usenet poster
 
Posts: 82
Default adsl parameters: ideal readings?

I've got a vonaq500 adsl tester but as a beginner doing a normal (UK) adsl
test I don't know what would constitute ideal readings.
The readings given by the tester a

LIne Rate (kb/sec)
Attainable rate (kb/sec)
SNR margin (dB)
Attenuation (dB)
Output Power (dBm)

the first two readings are obvious but for the rest of them I don't know
how to tell what's good ot bad.
my own broadband always works fine and the readings I got from that we

up down
LIne Rate (kb/sec) 448 5408
Attainable rate (kb/sec) 1120 5984
SNR margin (dB) 24.0 9.3
Attenuation (dB) 17.0 32.0
Output Power (dBm) 11.9 19.8

this gives me a rough idea but it would good to know what 100% ideal
readings should look like. My ISP said the SNR upstream was a bit high but
didn't say what it should be.
Thanks for any advice.




  #2  
Old July 21st 09, 12:11 PM posted to uk.telecom.broadband
Nick
external usenet poster
 
Posts: 43
Default adsl parameters: ideal readings?

tg wrote:
I've got a vonaq500 adsl tester but as a beginner doing a normal (UK) adsl
test I don't know what would constitute ideal readings.
The readings given by the tester a

LIne Rate (kb/sec)
Attainable rate (kb/sec)
SNR margin (dB)
Attenuation (dB)
Output Power (dBm)

the first two readings are obvious but for the rest of them I don't know
how to tell what's good ot bad.
my own broadband always works fine and the readings I got from that we

up down
LIne Rate (kb/sec) 448 5408
Attainable rate (kb/sec) 1120 5984
SNR margin (dB) 24.0 9.3
Attenuation (dB) 17.0 32.0
Output Power (dBm) 11.9 19.8

this gives me a rough idea but it would good to know what 100% ideal
readings should look like. My ISP said the SNR upstream was a bit high but
didn't say what it should be.
Thanks for any advice.


High SNR is a good thing.

The surprising thing about your stats is the low down line rate.

For an attenuation of 32.0 I would expect much better. You might want to
check your internal wiring to see if this is bringing down the down SNR
and hence the down line rate.

The best way to do this is to plug the router into the master socket
after you have disconnected your internal telephone extension lines.
  #3  
Old July 21st 09, 12:11 PM posted to uk.telecom.broadband
Ato_Zee
external usenet poster
 
Posts: 343
Default adsl parameters: ideal readings?


my own broadband always works fine and the readings I got from that we

up down
LIne Rate (kb/sec) 448 5408
Attainable rate (kb/sec) 1120 5984
SNR margin (dB) 24.0 9.3
Attenuation (dB) 17.0 32.0
Output Power (dBm) 11.9 19.8

this gives me a rough idea but it would good to know what 100% ideal
readings should look like. My ISP said the SNR upstream was a bit high but
didn't say what it should be.
Thanks for any advice.


Line rates are adaptive and depend on attenuation of the
physical copper line which obviously you can't alter, it's
BT plant, and SNR margin.
The SNR (Signal Noise Ratio) margin depends on
the lines inherent noise, due mainly to crosstalk from
other pairs in the cable from you to the exchange, and
some RF pickup from things like medium wave sources,
street lights, etc, and any noise you produce locally,
such as from commutator motors in washing machines,
vacuum cleaners, high frequency switch mode PSU's,etc.
Putting your router next to the master socket minimises
these.
The lower the SNR margin the faster your line will go,
but too low a SNR will result in instability.
Downstream 2 or 3dB SNR at night and 5-6dB during the
day seem to be optimal.
You can't with most modems alter you SNR margin,
with modems that support DMT tool you can, but
this capability needs to be used intelligently.
Some modems perform better, and give better speeds
than others.
  #4  
Old July 21st 09, 01:09 PM posted to uk.telecom.broadband
The Natural Philosopher
external usenet poster
 
Posts: 2,728
Default adsl parameters: ideal readings?

Nick wrote:
tg wrote:
I've got a vonaq500 adsl tester but as a beginner doing a normal (UK)
adsl
test I don't know what would constitute ideal readings.
The readings given by the tester a

LIne Rate (kb/sec)
Attainable rate (kb/sec)
SNR margin (dB)
Attenuation (dB)
Output Power (dBm)

the first two readings are obvious but for the rest of them I don't know
how to tell what's good ot bad.
my own broadband always works fine and the readings I got from that we

up down
LIne Rate (kb/sec) 448 5408
Attainable rate (kb/sec) 1120 5984
SNR margin (dB) 24.0 9.3
Attenuation (dB) 17.0 32.0
Output Power (dBm) 11.9 19.8

this gives me a rough idea but it would good to know what 100% ideal
readings should look like. My ISP said the SNR upstream was a bit high
but
didn't say what it should be.
Thanks for any advice.


High SNR is a good thing.

The surprising thing about your stats is the low down line rate.

For an attenuation of 32.0 I would expect much better. You might want to
check your internal wiring to see if this is bringing down the down SNR
and hence the down line rate.

Ah, but it critically depends in the SNR. That you can measure. Actual
attenuation merely estimates the actual power fed in at the far end,
compared with what you are seeing.

This would appear to be a fairly noisy line with some rather high noise
margin applied at the DSLAM in an attempt to gain stability: On a good
line you can receive down well below 5dB SNR. Mine here is running at
similar SNR - about 9 - and similar rates, but showing a 50dB attenuation.



The best way to do this is to plug the router into the master socket
after you have disconnected your internal telephone extension lines.


I doubt that would show any different.,. For whatever reason the noise
is highish.
  #5  
Old July 21st 09, 01:38 PM posted to uk.telecom.broadband
Nick
external usenet poster
 
Posts: 43
Default adsl parameters: ideal readings?

The Natural Philosopher wrote:
Nick wrote:
tg wrote:
I've got a vonaq500 adsl tester but as a beginner doing a normal (UK)
adsl
test I don't know what would constitute ideal readings.
The readings given by the tester a

LIne Rate (kb/sec)
Attainable rate (kb/sec)
SNR margin (dB)
Attenuation (dB)
Output Power (dBm)

the first two readings are obvious but for the rest of them I don't know
how to tell what's good ot bad.
my own broadband always works fine and the readings I got from that
we

up down
LIne Rate (kb/sec) 448 5408
Attainable rate (kb/sec) 1120 5984
SNR margin (dB) 24.0 9.3
Attenuation (dB) 17.0 32.0
Output Power (dBm) 11.9 19.8

this gives me a rough idea but it would good to know what 100% ideal
readings should look like. My ISP said the SNR upstream was a bit
high but
didn't say what it should be.
Thanks for any advice.


High SNR is a good thing.

The surprising thing about your stats is the low down line rate.

For an attenuation of 32.0 I would expect much better. You might want
to check your internal wiring to see if this is bringing down the down
SNR and hence the down line rate.

Ah, but it critically depends in the SNR. That you can measure. Actual
attenuation merely estimates the actual power fed in at the far end,
compared with what you are seeing.

This would appear to be a fairly noisy line with some rather high noise
margin applied at the DSLAM in an attempt to gain stability: On a good
line you can receive down well below 5dB SNR. Mine here is running at
similar SNR - about 9 - and similar rates, but showing a 50dB attenuation.


Ok I won't pretend to know what I'm talking about, but...

AIUI The DSLAM sets a high target SNR due to variations in SNR and
consequent LOS. Line Rate will come down with SNR I think ball park
figures are something like 1000 kb/sec increase in line rate for 6db
decrease in SNR.

Line rate tends to be correlated with attenuation. If you are a fair way
below the average it is worth checking internal wiring for something
that maybe adding noise to the line.



The best way to do this is to plug the router into the master socket
after you have disconnected your internal telephone extension lines.


I doubt that would show any different.,. For whatever reason the noise
is highish.


From a position of considerable ignorance I would say I do suspect
internal wiring may make a difference.

Hopefully the OP will post the results of my suggested investigation
and I can then either stick my tongue out at you or slink away quietly
and change my posting id ;o)
  #6  
Old July 21st 09, 02:15 PM posted to uk.telecom.broadband
PeeGee
external usenet poster
 
Posts: 311
Default adsl parameters: ideal readings?

Nick wrote:
The Natural Philosopher wrote:
Nick wrote:
tg wrote:
I've got a vonaq500 adsl tester but as a beginner doing a normal
(UK) adsl
test I don't know what would constitute ideal readings.
The readings given by the tester a

LIne Rate (kb/sec)
Attainable rate (kb/sec)
SNR margin (dB)
Attenuation (dB)
Output Power (dBm)

the first two readings are obvious but for the rest of them I don't
know
how to tell what's good ot bad.
my own broadband always works fine and the readings I got from that
we

up down
LIne Rate (kb/sec) 448 5408
Attainable rate (kb/sec) 1120 5984
SNR margin (dB) 24.0 9.3
Attenuation (dB) 17.0 32.0
Output Power (dBm) 11.9 19.8

this gives me a rough idea but it would good to know what 100% ideal
readings should look like. My ISP said the SNR upstream was a bit
high but
didn't say what it should be.
Thanks for any advice.


High SNR is a good thing.

The surprising thing about your stats is the low down line rate.

For an attenuation of 32.0 I would expect much better. You might want
to check your internal wiring to see if this is bringing down the
down SNR and hence the down line rate.

Ah, but it critically depends in the SNR. That you can measure. Actual
attenuation merely estimates the actual power fed in at the far end,
compared with what you are seeing.

This would appear to be a fairly noisy line with some rather high
noise margin applied at the DSLAM in an attempt to gain stability: On
a good line you can receive down well below 5dB SNR. Mine here is
running at similar SNR - about 9 - and similar rates, but showing a
50dB attenuation.


Ok I won't pretend to know what I'm talking about, but...

AIUI The DSLAM sets a high target SNR due to variations in SNR and
consequent LOS. Line Rate will come down with SNR I think ball park
figures are something like 1000 kb/sec increase in line rate for 6db
decrease in SNR.

The suggestion I saw was square-law based: a 2x change of line rate for
4x (6dB) change of SNR

Line rate tends to be correlated with attenuation. If you are a fair way
below the average it is worth checking internal wiring for something
that maybe adding noise to the line.



The best way to do this is to plug the router into the master socket
after you have disconnected your internal telephone extension lines.


I doubt that would show any different.,. For whatever reason the noise
is highish.


From a position of considerable ignorance I would say I do suspect
internal wiring may make a difference.

Hopefully the OP will post the results of my suggested investigation and
I can then either stick my tongue out at you or slink away quietly and
change my posting id ;o)



--
PeeGee

"Nothing should be able to load itself onto a computer without the
knowledge or consent of the computer user. Software should also be able
to be removed from a computer easily."
Peter Cullen, Microsoft Chief Privacy Strategist (Computing 18 Aug 05)
  #7  
Old July 21st 09, 04:07 PM posted to uk.telecom.broadband
Peter Crosland
external usenet poster
 
Posts: 1,463
Default adsl parameters: ideal readings?

I've got a vonaq500 adsl tester but as a beginner doing a normal (UK) adsl
test I don't know what would constitute ideal readings.
The readings given by the tester a

LIne Rate (kb/sec)
Attainable rate (kb/sec)
SNR margin (dB)
Attenuation (dB)
Output Power (dBm)

the first two readings are obvious but for the rest of them I don't know
how to tell what's good ot bad.
my own broadband always works fine and the readings I got from that we

up down
LIne Rate (kb/sec) 448 5408
Attainable rate (kb/sec) 1120 5984
SNR margin (dB) 24.0 9.3
Attenuation (dB) 17.0 32.0
Output Power (dBm) 11.9 19.8

this gives me a rough idea but it would good to know what 100% ideal
readings should look like. My ISP said the SNR upstream was a bit high but
didn't say what it should be.



There are no ideal readings as such. An ADSL circuit is a dynamic thing that
varies second by second so all you have is a snapshot at a particular
instant in time. The expensive kit you have does tell you much more than the
information given by a good ADSL router. In any case if there is a problem
then you will have to get BT or Openreach to investigate it because the
problem is in their equipment or line.

Peter Crosland


  #8  
Old July 21st 09, 04:28 PM posted to uk.telecom.broadband
Peter Crosland
external usenet poster
 
Posts: 1,463
Default adsl parameters: ideal readings?

Correction. Does NOT tell you.......


  #9  
Old July 21st 09, 04:57 PM posted to uk.telecom.broadband
martin goose
external usenet poster
 
Posts: 2
Default adsl parameters: ideal readings?

On Tue, 21 Jul 2009 16:07:25 +0100, Peter Crosland wrote:

There are no ideal readings as such. An ADSL circuit is a dynamic thing
that varies second by second so all you have is a snapshot at a
particular instant in time.


Therein lies the problem unless you monitor the S/N ratio and sync speed.
Even then what sort of variation in S/N is 'normal'?

I am currently monitoring these values and finding wide swings in S/N
both up and down. I have done all the usual in house stuff to eliminate
problems with my kit, but looking at a trace for the last 36 hours shows
a 15dB improvement to 27 dB at one point and two drops from 15dB to about
6 dB which caused a resync in each case.

--
Martin Goose --- "Engineering is the art of modelling materials we do not
wholly understand, into shapes we cannot precisely analyse, so as to
withstand forces we cannot properly assess, in such a way that the public
has no reason to suspect the extent of our ignorance"
Dr A H Dykes I Structural E 1976

  #10  
Old July 21st 09, 05:46 PM posted to uk.telecom.broadband
Graham J
external usenet poster
 
Posts: 389
Default adsl parameters: ideal readings?


"martin goose" wrote in message
o.uk...
On Tue, 21 Jul 2009 16:07:25 +0100, Peter Crosland wrote:

There are no ideal readings as such. An ADSL circuit is a dynamic thing
that varies second by second so all you have is a snapshot at a
particular instant in time.


Therein lies the problem unless you monitor the S/N ratio and sync speed.
Even then what sort of variation in S/N is 'normal'?

I am currently monitoring these values and finding wide swings in S/N
both up and down. I have done all the usual in house stuff to eliminate
problems with my kit, but looking at a trace for the last 36 hours shows
a 15dB improvement to 27 dB at one point and two drops from 15dB to about
6 dB which caused a resync in each case.


Therein lies the fundamental problem with ADSL. Telephone wires were never
designed to carry data so the electronics at each end have to adapt to suit
the varying line conditions. It's a credit to clever engineering that it
works at all.

If you need a reliable connection (i.e one that is designed to be reliable,
and meet a performance specification) then you will have to install optical
fibre.

--
Graham J


 




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