Technical Discussion
  >> Technical Issues


Register (or login) on our website and you will not see this ad.


Pages in this thread: 1 | 2 | (show all)   Print Thread
Standard User pvfpvf
(newbie) Wed 29-Aug-12 10:35:42
Print Post

ADSL upload faster than download


[link to this post]
 
In connection with the BDUK rural broadband plans, I've been soliciting speed measurements from people who live more than 3 Km from our village exchange, as the lines go. Most of them look sensible, but I've had three where the upload speed is higher than the download:-
Download 0.133 Upload 0.357 Mbps, Distance 6.6 Km
Download 0.220 Upload 0.350 Mbps, Distance 3.5 Km
Download 0.125 Upload 0.345 Mbps, Distance 4.1 Km

My exchange does not have WBC or ADSL2 so this is plain ADSL. The bandwidth that ADSL technology allocates to download is about 11 times that for upload, so I'd expect the download was always faster than upload. I suppose a strong RF noise source in the house might preferentially affect download?

Has anyone had experience of ADSL upload being faster than download, and what are the possible causes of it?

Edited by pvfpvf (Wed 29-Aug-12 10:36:37)

Standard User StephenTodd
(member) Wed 29-Aug-12 10:51:07
Print Post

Re: ADSL upload faster than download


[re: pvfpvf] [link to this post]
 
Even though more tones are allocated to download, they are the higher frequency tones. It is these that suffer worst from long lines.

If any of them have appropriate routers, try using a program like DMT to have a look at the frequency spectrum in use. http://dmt.mhilfe.de/ The webpage is in German, but if you find the right version, the code is mainly in English and easyish to understand.

--
Moved (with trepidation) to BT Infinity 2 for upload speed. Happy BE user for several years.
Standard User shtu
(experienced) Wed 29-Aug-12 11:21:57
Print Post

Re: ADSL upload faster than download


[re: pvfpvf] [link to this post]
 
In reply to a post by pvfpvf:
Has anyone had experience of ADSL upload being faster than download, and what are the possible causes of it?


In my experience, that is a sign of there being other faults, be it poorly wired or there being a fault on the line.

I would expect to find an audible line fault.


Register (or login) on our website and you will not see this ad.

Administrator MrSaffron
(staff) Wed 29-Aug-12 17:33:21
Print Post

Re: ADSL upload faster than download


[re: pvfpvf] [link to this post]
 
You need to look also at attenuation e.g. if the 3.5km line is actually a 50dB attenuation line then something is wrong, very likely the telephone wiring inside the property, or they just have a bad choice of ISP.

If you can get the stats from them, then type them in at http://www.coolwebhome.co.uk/calc/calculator.php and if its a good line you'll get three sets of green traffic lights.

If things are slow, then fixing their speeds, e.g. remove ring wire or fit an i-plate. Remove unused or substandard extension wiring, can improve speeds with perhaps 30 minutes of fiddling, rather than wait 12 to 36 months for BDUK to deliver.

Andrew Ferguson, andrew@thinkbroadband.com
www.thinkbroadband.com - formerly known as ADSLguide.org.uk
The author of the above post is a thinkbroadband staff member. It may not constitute an official statement on behalf of thinkbroadband.
Standard User pvfpvf
(newbie) Wed 29-Aug-12 18:17:40
Print Post

Re: ADSL upload faster than download


[re: StephenTodd] [link to this post]
 
Thanks. Yes it makes sense to me that higher frequencies suffer greater attenuation.

Had a look at DMT and was not aware that some ADSL modems give so much info, but it seems not all.

I'm dealing mainly with non-technical users so there's a limit as to shat I can push them to do.
Standard User pvfpvf
(newbie) Wed 29-Aug-12 18:22:50
Print Post

Re: ADSL upload faster than download


[re: MrSaffron] [link to this post]
 
Thanks. Yes, I did send out an explanation of the ring wire/I-plate scenario, but not sure who will take it up. Users are mainly non-technical.

Unfortunately, I forgot to ask them to tell me their ISP, so don't know that.

Probably have to visit them to see the attenuation/SNR. Surprised you say house wiring could affect the attenuation: I can see it might pick up noise and hence affect SNR, but attenuation surely is mainly affected by impedance of the long line from exchange to house?
Administrator MrSaffron
(staff) Wed 29-Aug-12 18:27:21
Print Post

Re: ADSL upload faster than download


[re: pvfpvf] [link to this post]
 
The house wiring will not affect the attenuation (or should not to a significant effect). but it does allow you to estimate the range of speeds you would expect from a line.

e.g. if the attenuation is 61dB and they are getting 1.8 Meg from speedtests, then probably not much more if any to be squeezed from the line.

Andrew Ferguson, andrew@thinkbroadband.com
www.thinkbroadband.com - formerly known as ADSLguide.org.uk
The author of the above post is a thinkbroadband staff member. It may not constitute an official statement on behalf of thinkbroadband.
Standard User MHC
(legend) Wed 29-Aug-12 20:32:43
Print Post

Re: ADSL upload faster than download


[re: pvfpvf] [link to this post]
 
You already have several useful comments, but a few other points.

The distances you refer to - are they straight line, by road, or actual line length?

Secondly, I have seen quite a few lines where the upload is faster than download - always on long lines where the higher frequencies just cannot be used.

The customer side equipment and wiring can affect the attenuation - for example if there are too many master sockets, or too many phones, or cheap phones ... they can adversely load the line, changing teh termination impedance which could result on several dB of additional attenuation.

When taking line stats, do it with just the modem connected to the test socket behind the removable front of the master - that disconnects everything else. Also try it wit the modem located in its normal place and see what the differences are in Attenuation, SNR and Sync ...


~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

M H C


taurus excreta cerebrum vincit
Standard User pvfpvf
(newbie) Wed 29-Aug-12 20:40:51
Print Post

Re: ADSL upload faster than download


[re: MHC] [link to this post]
 
Thanks. My distances are actual BT line lengths (I wandered around and traced all the lines. There are only a few places where the route of buried cables is conjectural.)

Yes, I can see that if equipment is actually connected to the extension wiring then it could indeed affect the attenuation, and thanks for pointing that out.

I'll bear in mind the other advice should anyone invite me into their home to investigate!
Administrator MrSaffron
(staff) Wed 29-Aug-12 22:50:26
Print Post

Re: ADSL upload faster than download


[re: pvfpvf] [link to this post]
 
If someone on a 3.5km line is really only getting under 0.5 Meg, then something is seriously wrong with the line length or something else.

Why? Because back in 2000, BT specced ADSL as giving 2Meg at 3.5km line length, and plenty of lines now show it running at 7 to 8Meg now that BT has relexed the various limits.

Also as its an IPStream exchange, rather than WBC, best to get people to check what their IP Profile is, via www.speedtester.bt.com

Andrew Ferguson, andrew@thinkbroadband.com
www.thinkbroadband.com - formerly known as ADSLguide.org.uk
The author of the above post is a thinkbroadband staff member. It may not constitute an official statement on behalf of thinkbroadband.
Pages in this thread: 1 | 2 | (show all)   Print Thread

Jump to