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[Floydoid]

Sorry for really being thick, but I still don't understand what the terms 'downstream margin' or 'interleaved' mean.

[mr_chris]

Downstream margin is another way of saying Downstream SNR (Signal-To-Noise) Margin.

Downstream is from the exchange to you.. i.e. coming 'down' into your house.
Margin or SNR Margin is an indication of how strong the good (ADSL) signal is compared to noise (i.e. interference, unwanted signals) on the line, expressed in decibels (dB).

For a better understanding read this ---> http://www.kitz.co.uk/adsl/linestats.htm

I can't explain interleaving better than linking to kitz's page on it. ---> http://www.kitz.co.uk/adsl/interleaving.htm

If there's a particular point you don't understand after reading those, just ask

[Floydoid]

It's getting past first line that is becoming more and more of an issue these days

Anyway I reckon someone has bumped up your margin. 19dB downstream margin AND interleaved is taking the proverbial really.

So based on that, if I put in a support ticket to Tiscali, what should I ask for and how should it be worded?

(by contacting tech support that way you get straight to the second line chaps)

[guest]

I would suggest something like :

"I've noticed that my line only synchronises a little above 6Mbps now. It used to sync at the full 8Mbps until a recent fault in the exchange equipment* but now only synchronises at 6Mbps. My downstream noise margin seems rather high (19dB) and I'm interleaved as well. I wonder if you would be kind enough to set a target noise margin of 9dB as that looks likely to give me the full 8Mbps and shouldn't cause stability problems with the line."

I'm suggesting 9dB as that should take you to the maximum 8Mbps. If it works well (give it a couple of weeks) then I'd be inclined to ask for interleaving to be taken off the line as it uses some of your bandwidth (speed if you like) as error correction. If you don't have some sort of local wiring problem or electrical noise then there's no point in having it on a line as good as yours - well certainly not on an 8Mbps service anyway. There is little point in dropping the margin to 6dB unless you are on a >8Mbps service, and your USB modem probably can't handle >8Mbps anyway. I strongly suspect that you'd get the full 8Mbps on a margin of 12dB, but you will definitely get it on 9dB.

If that doesn't make sense then just ask

*quote the ticket number of the problems you had.

[Floydoid]

Rizla, I've sent the support ticket worded exactly as you wrote it, and enclosed my Dr Speedtouch results.  Hopefully that will make them break wind... I'll keep you informed.

And yeah, it's slowly starting to make sense thanks to you guys.

[guest]

Fingers crossed you get some sense back from Tiscali then

[soms]

Dont know about LLU providers but as far as I know all new BT provides for a while now have been with interleaving turned on by default, regardless of line conditions.

The reason I think is as simple as hoping it wil reduce the number of faults reported, especially on marginal lines.

Obviously for those fortunate enough to recieve high speeds on good quality lines or who require especially low latency data tranmission it could be considered an incovenience to use or to have to arrange for it to be turned off.

[kitz]

>> BTW Kitz, on the speedtouch page that you link to, there is no mention of Dr Speedtouch

ty - it looks like theyve changed the page and added some info re vista - I'll change it when I get a mo.  - thanks

>> I think about it now... and certainly the ones on Roseway's link look reasonably priced (remembering I tend to go for the cheap & cheerful)

I did a mini-review of that particular router here
http://forum.kitz.co.uk/index.php/topic,529.0.html



>> I can't help wondering if the limiting factor on his connection is actually the USB device

Im only quickly scanning this thread (still in catchup mode)... but the stats did look slightly odd to me... and the first thing I thought was that line should be capable of more than its getting.

DownstreamMaxBitRate= 6144000
ReceiveAttenuation_dB= 25
ReceiveMargin_dB= 19

A 25db atten line should sync at the full 8Mb..  Theres also plenty of spare margin - a heck of a lot.
Practically  no errors so I wouldnt expect it to have a high target SNR either.
Perhaps a resync during the early part of the day may help.

Have a look at your ReceiveMargin immediately after a resync to guage your target SNR.

>> 19dB downstream margin AND interleaved is taking the proverbial really.

Does seem very steep for that line..  Ive managed to find a bit of info about the tiscali LLU profiles which are posted at the bottom of the page here...  but the target SNRs arent that clear.  9dB seens to be the norm..  although they do do a 6dB, 12db and probably the 15dB which is the high too.

Oops just noticed a page 3 - think the others have covered all I wanted to say.

[guest]

Yeah I think Tiscali/BT/whoever bumped the SNR up to see if that would be a quick fix - I can see this becoming the standard practice really. Hopefully a 9dB profile won't cause problems (it shouldn't) but I do have to say I'd be happier giving that advice to someone with a router/modem rather than a USB modem.

I doubt anything will happen all that rapidly anyway

[kitz]

>> Yeah I think Tiscali/BT/whoever bumped the SNR up to see if that would be a quick fix ....

I hope not:/   

>> giving that advice to someone with a router/modem

Yeah - but shouldnt harm to try a resync to see if it does alter things... and at least attempt to get a reading of the magin immediately after.   As soon as I saw those stats my immediate thought was perhaps the USB limitation, but if floydy has been able to sync higher in the past then perhaps not.

A router would give way more control..  and the nice thing about the ST routers is the DMT tool seems to work pretty well with them if you want to tweak bits

[kitz]

Floydy - just thought.

Try seeing if you can do the tiscali connection test.
If you can log in there and the adsl checker says tiscali LLU is at your exchange then it is a sure bet that youre on tiscali LLU

[guest]

I was sort of assuming he must be - or is the BT system so brain-dead it'd go up to 19dB margin interleaved for a 6Mbps sync? I genuinely don't know - having dodged that particular bullet

[kitz]

tbh Ive not heard of a 19dB target at all before- either  BT or tiscali.   Hence why I think a resync to check.

[guest]

Tis a USB modem kitz so unless the man runs the PC 24/7 he resyncs at least once a day

[Floydoid]

However, the following test can help check if you are on Tiscali LLU, but please bear in mind that the test will also work if you are on a Tiscali DataStream service.

You will need to change your router or modem settings to the following:-

    username: testing@dslconnect.co.uk
    password: testing

From there you may also be able to navigate to: http://www.dslconnect.co.uk

What on earth does that mean - I'm totally confused about what I'm supposed to do?

However the ADSL checker gives these results:

BT Exchange Information
Exchange: Norwich City.    BT Code: EANCC
Location: St Andrews Street,    NR2 4AE.
ADSL enabled :    June 30, 2001
dsl Max enabled:    March 31, 2006
SDSL enabled :    Enabled
21CN due :    Q4 2009
Distance:-    Direct:          821 metres
          (appx)*    By Road:    1.13 km

adsl button     Fixed ADSL:      2048 kbps      (2 Mb)
adsl button    DSL Max :      6000 kbps    (6 Mb)

Fixed:  1Mbps and 2Mbps available
radsl:    512Kbps and 256Kbps available
MAX:    ADSL Max is available
SDSL:    2 Mbps available
TPON:    TPON/Fibre not recorded
Check:    The check identified another service on your line which may prevent you from ordering a new ADSL connection. Examples are : Existing adsl connection, DACs, LLU, TPON

Other Broadband Technology & LLU Providers
AOL   Available   
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Tiscali   Available   25.07.07
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Now Wireless   Not available