Changes to BT's ADSL

Russ · 14-09-2004, 20:55

BT's conditions for ADSL used to be that if you were within 3.5km of a BT exchange then you could get 1Mb broadband. Following recent work on their exchanges, they can now offer 2mb to those within 3.5km and 1mb to those within 6km which now means more people will be able to take up their service.

However another aspect to this is that BT can now guarantee 500k BB to anyone who lives near a recently-upgraded exchange (this means they must have a DSLAM device fitted which extends the range of their BB). Not sure what percentage of the population this now covers but around 1500 exchanges have been upgraded this way.

The only thing is it's not ADSL - it's RAADSL which is Rate Adaptive ADSL. This means they will guarantee 500k down at the expense of the upload which will be anything from 64k to 256, depending on how much of the downstream you're using. It's not perfect but it means BB is available to more people.

paulyoung666 · 14-09-2004, 21:10

and good news for ppl who are not in a cabled area , it is just a shame that it has taken so long for it to happen

, but i suppose anything is an improvement

Ignition · 15-09-2004, 07:47

Quote:

Originally Posted by Russ D

BT's conditions for ADSL used to be that if you were within 3.5km of a BT exchange then you could get 1Mb broadband. Following recent work on their exchanges, they can now offer 2mb to those within 3.5km and 1mb to those within 6km which now means more people will be able to take up their service.

No, the limit for 2Mbit has always been approximately 3.5km, or 41dB of line attenuation at 300khz with no DSL CPE installed.

Quote:

Originally Posted by Russ D

However another aspect to this is that BT can now guarantee 500k BB to anyone who lives near a recently-upgraded exchange (this means they must have a DSLAM device fitted which extends the range of their BB). Not sure what percentage of the population this now covers but around 1500 exchanges have been upgraded this way.

What? DSLAMs are DSL Aggregation Modules, the bit that goes in the exchange where all the incoming lines terminate. These do not extend ADSL range in any way, shape or form, they are an essential part of providing ADSL, they are the equivalent of the uBR on a cable network. BT still can't guarantee service to those livuing near the exchange, it's still dependent on the line synchronising properly. What they will do if service cannot be achieved is send an engineer to a customer's site to fit a noise filtering face plate onto the main telephone socket to try and get service to work.

What part of this is new technically? None - those face plates were used in the original ADSL installs in 2000. Policy wise it's a considerable shift, even if it is so that BT can get as many on DSL as possible for efficiency reasons.

Quote:

Originally Posted by Russ D

The only thing is it's not ADSL - it's RAADSL which is Rate Adaptive ADSL. This means they will guarantee 500k down at the expense of the upload which will be anything from 64k to 256, depending on how much of the downstream you're using. It's not perfect but it means BB is available to more people.

Rate Adaptive DSL has been used for a while, ever since the limit for 512k ADSL was extended from 3.5km to 5.5km. It also doesn't actually care how much of the downstream you are using. ADSL is modulated using GDMT, this system involved use of 255 different discrete frequency bins. RF types will know that higher frequencies encounter more resistance and attenuation when transmitted over copper. DSL rate adapts when a line can't maintain the required downstream SNR, the DSLAM at the exchange removes a 'buffer zone' that sits between the upstream frequencies and the downstream ones, which means that you lose the higher upstream frequencies but gain some hopefully cleaner bins for downstream usage. Doesn't really care how much bandwidth you are using.

Oh and it's RADSL not RAADSL, Rate Adaptive Digital Subscriber Line.

Russ · 15-09-2004, 07:54

Quote:

Originally Posted by JustAnotherN00b

No, the limit for 2Mbit has always been approximately 3.5km, or 41dB of line attenuation at 300khz with no DSL CPE installed.

Maybe but it was not the official line. Now it's confirmed.

Quote:

Originally Posted by JustAnotherN00b

What? DSLAMs are DSL Aggregation Modules, the bit that goes in the exchange where all the incoming lines terminate. These do not extend ADSL range in any way, shape or form, they are an essential part of providing ADSL, they are the equivalent of the uBR on a cable network. BT still can't guarantee service to those livuing near the exchange, it's still dependent on the line synchronising properly. What they will do if service cannot be achieved is send an engineer to a customer's site to fit a noise filtering face plate onto the main telephone socket to try and get service to work.

The exchanges have still been upgraded. Obviously no-one can guarantee service but considering the network BT use, this will be the best change for a lot of people yet to get BB.

Quote:

Originally Posted by JustAnotherN00b

Rate Adaptive DSL has been used for a while, ever since the limit for 512k ADSL was extended from 3.5km to 5.5km. It also doesn't actually care how much of the downstream you are using. ADSL is modulated using GDMT, this system involved use of 255 different discrete frequency bins. RF types will know that higher frequencies encounter more resistance and attenuation when transmitted over copper. DSL rate adapts when a line can't maintain the required downstream SNR, the DSLAM at the exchange removes a 'buffer zone' that sits between the upstream frequencies and the downstream ones, which means that you lose the higher upstream frequencies but gain some hopefully cleaner bins for downstream usage. Doesn't really care how much bandwidth you are using.

As above. It's not perfect but it means more people can get BB than before.

Quote:

Originally Posted by JustAnotherN00b

Oh and it's RADSL not RAADSL, Rate Adaptive Digital Subscriber Line.

oooOOOooo, the pedantics are out in force this morning

Ignition · 15-09-2004, 08:23

Quote:

Originally Posted by Russ D

Maybe but it was not the official line. Now it's confirmed.

Umm no, the limit for 2Mbit has always been 41dB. (Actually it's now 43dB reasons for that unknown but looks accidental

)

Quote:

The exchanges have still been upgraded. Obviously no-one can guarantee service but considering the network BT use, this will be the best change for a lot of people yet to get BB.

Well yeah, DSLAMs have been put into exchanges to allow people to get DSL full stop but that has nothing to do with longer reach.

RADSL is a setting on the DSLAM, hardly an upgrade.

Quote:

oooOOOooo, the pedantics are out in force this morning

So be more careful next time you try a big techy post about something you aren't sure about

**Paul** · 15-09-2004, 08:37

Quote:

Originally Posted by JustAnotherN00b

So be more careful next time you try a big techy post about something you aren't sure about

Now now, be gentle with him, he's only been there two days.

Ignition · 15-09-2004, 08:40

Quote:

Originally Posted by Paul M

Now now, be gentle with him, he's only been there two days.

Oooo where, where, where? Not big bad BT?!?!

Russ · 15-09-2004, 08:55

Quote:

Originally Posted by JustAnotherN00b

So be more careful next time you try a big techy post about something you aren't sure about

If you think that was my attempt at sounding techy then you really haven't been around this site long enough

I was passing on information, just as I've always done

But nice try at belittling me though

**Paul** · 15-09-2004, 08:55

Quote:

Originally Posted by JustAnotherN00b

Oooo where, where, where? Not big bad BT?!?!

http://www.cableforum.co.uk/board/sh...ad.php?t=17201

Ignition · 15-09-2004, 09:23

Quote:

Originally Posted by Russ D

If you think that was my attempt at sounding techy then you really haven't been around this site long enough

I was passing on information, just as I've always done

But nice try at belittling me though

Been around this site for upwards of 2 years

IF you think that was my attempt at belittling you haven't been around this site long enough

Russ · 15-09-2004, 10:35

Quote:

Originally Posted by JustAnotherN00b

Been around this site for upwards of 2 years

Oh well that beats me then, I've only been here 15 months, you know, since the site started

Quote:

Originally Posted by JustAnotherN00b

IF you think that was my attempt at belittling you haven't been around this site long enough

Well how about the next time I pass information on intended to help people you keep your cynical eye out of it?

Ignition · 15-09-2004, 10:43

Quote:

Originally Posted by Russ D

Well how about the next time I pass information on intended to help people you keep your cynical eye out of it?

How about next time you pass information you make it accurate not BT marketing material?

I don't criticise for no reason, but have no time for someone people trust passing on market droid information, any more than you would have patience with me saying how great ntl are over mythical upgrades which were nothing more than a change of policy and involved no 'upgrades' in technology at all.

www.adslguide.org.uk

Anyone wanting to look into what is actually going on with ADSL should have a look at that, very informative.

Russ · 15-09-2004, 10:45

Quote:

Originally Posted by JustAnotherN00b

How about next time you pass information you make it accurate not BT marketing material?

Accurate? That's exactly what I've done. I'd rather source my info from the people who understand it, thank you

Quote:

Originally Posted by JustAnotherN00b

I don't criticise for no reason, but have no time for someone people trust passing on market droid information, any more than you would have patience with me saying how great ntl are over mythical upgrades which were nothing more than a change of policy and involved no 'upgrades' in technology at all.

Ok, whatever, that's your opinion.

Now no more of this as it's dragging the thread off topic. You can discuss/argue this with me in PM if you want.

Bifta · 15-09-2004, 10:52

Quote:

Originally Posted by Russ D

Accurate? That's exactly what I've done. I'd rather source my info from the people who understand it, thank you

No offense Russ, but the information he countered with was actually correct.

Ignition · 15-09-2004, 10:53

Quote:

Originally Posted by Russ D

Accurate? That's exactly what I've done. I'd rather source my info from the people who understand it, thank you

Shame they don't understand what a DSLAM is, that they don't extend range but settings on them can, nor the difference between RADSL and RAADSL whatever that is.

Duly noted, I'll keep quiet on this from now. Hope the new job goes well and the training improves.