ADSL2+ What happens at the exchange?

Stick with me, this does make sense. :-)

I've got a long line which only gives 1Mb. For ages I had a 0.5Mb
connection which left me with an SNR of 11db. Pipex then shifted me to
Tiscali LLU for a laugh but the odd thing about that was I now had a 16db
SNR. Tiscali's kit is definately more recent that the BT kit in my exchange
and a 5db increase would almost double my sync speed (which would be very
welcome!).

My exchange has an ADSL2+ date of November this year and I was wondering if
this means brand new DSLAMs in the exchange? Would all customers get
shifted to this new kit automagically? I'm just wondering if in November
I'll get a nice SNR boost due to new equipment and maybe a bit extra at the
same time from ADSL2+?

--

WCZ

On Mon, 21 Apr 2008 08:24:20 +0100, WCZ wrote:

> Stick with me, this does make sense. :-)

No, it doesn't...

> I've got a long line which only gives 1Mb. For ages I had a 0.5Mb
> connection which left me with an SNR of 11db. Pipex then shifted me to
> Tiscali LLU for a laugh but the odd thing about that was I now had a
> 16db SNR. Tiscali's kit is definately more recent that the BT kit in my
> exchange and a 5db increase would almost double my sync speed (which
> would be very welcome!).

....because your sync speed will go down as the margin goes up. Have you
got them the wrong way round?

--
<http://ale.cx/> (AIM:troffasky) ((E-Mail Removed))
20:49:20 up 57 days, 3:43, 2 users, load average: 0.01, 0.35, 0.62
Convergence, n: The act of using separate DSL circuits for voice and data

alexd:
>...because your sync speed will go down as the margin goes up. Have you
>got them the wrong way round?

NO ! You have. More margin gets you more speed.

To WCZ:
Get hold of BT 1800 or BT 2700 (US made 2WIRE) router (they go cheap on
eBay). Mine keeps synch down to 1dB SNR, and I now get up to 2.8Mb/s, while
I previously struggled to get 1.5Mb/s with well known quality router.
Regards,
Martin

alexd wrote:
> On Mon, 21 Apr 2008 08:24:20 +0100, WCZ wrote:
>
>> Stick with me, this does make sense. :-)
>
> No, it doesn't...
>
>> I've got a long line which only gives 1Mb. For ages I had a 0.5Mb
>> connection which left me with an SNR of 11db. Pipex then shifted me
>> to Tiscali LLU for a laugh but the odd thing about that was I now
>> had a 16db SNR. Tiscali's kit is definately more recent that the BT
>> kit in my exchange and a 5db increase would almost double my sync
>> speed (which would be very welcome!).
>
> ...because your sync speed will go down as the margin goes up. Have
> you got them the wrong way round?

No, the sync speed was 0.5Mb in both cases as I wasn't on Max then. The
Tiscali kit gave a 5db increase in SNR which would roughly double my sync
speed now that I'm on Max. I'm still quite surprised that newer exchange
kit makes such a difference. I shall hope that the ADSL2+ kit does the
same.

--

WCZ

On Tue, 22 Apr 2008 02:52:34 +0100, Martin² wrote:

> alexd:
>>...because your sync speed will go down as the margin goes up. Have you
>>got them the wrong way round?
>
> NO ! You have. More margin gets you more speed.

No, it doesn't. If you increase the margin, you decrease the speed [but
get a more reliable connection]. You can test it for yourself with a tool
like DMT.

--
<http://ale.cx/> (AIM:troffasky) ((E-Mail Removed))
08:58:38 up 57 days, 15:52, 3 users, load average: 0.20, 0.40, 0.44
Convergence, n: The act of using separate DSL circuits for voice and data

alexd wrote:
> On Tue, 22 Apr 2008 02:52:34 +0100, Martin² wrote:
>
>> alexd:
>>> ...because your sync speed will go down as the margin goes up. Have
>>> you got them the wrong way round?
>>
>> NO ! You have. More margin gets you more speed.
>
> No, it doesn't. If you increase the margin, you decrease the speed
> [but get a more reliable connection]. You can test it for yourself
> with a tool like DMT.

No, you are wrong. In my case the sync speed was fixed at 0.5Mb. The SNR
margin comparison between the BT and Tiscali kit is valid with the Tiscali
kit being better. Bigger SNR == better == higher sync speed on Max.

--

WCZ

alexd wrote:
> On Mon, 21 Apr 2008 08:24:20 +0100, WCZ wrote:
>
>> Stick with me, this does make sense. :-)
>
> No, it doesn't...
>
>> I've got a long line which only gives 1Mb. For ages I had a 0.5Mb
>> connection which left me with an SNR of 11db. Pipex then shifted me to
>> Tiscali LLU for a laugh but the odd thing about that was I now had a
>> 16db SNR. Tiscali's kit is definately more recent that the BT kit in my
>> exchange and a 5db increase would almost double my sync speed (which
>> would be very welcome!).
>
> ...because your sync speed will go down as the margin goes up. Have you
> got them the wrong way round?
>
There is no general standard for SNR reporting in routers.

Whilst the routers GENERALLY report that they are stable at 6dB, some
report that they atre stable at 4dB or even less.

alexd wrote:
> On Tue, 22 Apr 2008 02:52:34 +0100, Martin² wrote:
>
>> alexd:
>>> ...because your sync speed will go down as the margin goes up. Have you
>>> got them the wrong way round?
>> NO ! You have. More margin gets you more speed.
>
> No, it doesn't. If you increase the margin, you decrease the speed [but
> get a more reliable connection]. You can test it for yourself with a tool
> like DMT.
>
He's right. Your ADLD MAX will go for the highest speed that nets you a
6DB margin, broadly. There are other issues in there, but that's more or
less how it works.

If you have a 1Mb fixed and a 10 dB noise margin, you can probably
expect about 1.5Mbps on ADSL max, at 6dB margin for example.

The Natural Philosopher wrote:
> alexd wrote:
>> On Tue, 22 Apr 2008 02:52:34 +0100, Martin² wrote:
>>
>>> alexd:
>>>> ...because your sync speed will go down as the margin goes up.
>>>> Have you got them the wrong way round?
>>> NO ! You have. More margin gets you more speed.
>>
>> No, it doesn't. If you increase the margin, you decrease the speed
>> [but get a more reliable connection]. You can test it for yourself
>> with a tool like DMT.
>>
> He's right. Your ADLD MAX will go for the highest speed that nets you
> a 6DB margin, broadly. There are other issues in there, but that's
> more or less how it works.
>
> If you have a 1Mb fixed and a 10 dB noise margin, you can probably
> expect about 1.5Mbps on ADSL max, at 6dB margin for example.

I think everyone has missed the point here.

I had a 0.5Mb fixed rate connection.

On the BT exchange kit my SNR was 11db at 0.5Mb
On the Tiscali exchange kit my SNR was 16db at 0.5Mb

This means that on Max I would get a faster sync on the Tiscali kit.

My question is, when ADSL2+ is deployed will new kit go into the exchange
and will everyone get put onto it.

I am hoping the new ADSL2+ kit, if it exists, will give me the better SNR
and hence faster Max speed.

I thought I was being clear. :-(

--

WCZ

On Tue, 22 Apr 2008 08:12:46 +0100, WCZ wrote:

>No, the sync speed was 0.5Mb in both cases as I wasn't on Max then. The
>Tiscali kit gave a 5db increase in SNR which would roughly double my sync
>speed now that I'm on Max. I'm still quite surprised that newer exchange
>kit makes such a difference. I shall hope that the ADSL2+ kit does the
>same.

It's more likely that the move meant a different routing of the wires
in the exchange and that lowered the interference from the other
cables. The noise comes from the cabling between the exchange kit and
your modem. Better kit may be able to operate with a lower noise margin
but I wouldn't expect it to alter the noise level of itself.

--
Regards - Rodney Pont
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