ADSL2+ exchange, but not ADSL2+ line!

yuloni

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Spear

Condi wrote: »

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At that attenuation ADSL2 won't make any difference, you're just too far for there to an improvement.

yuloni

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dub45

Condi wrote: »

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Not in my own experience - I am with Smart (crown alley exchange) and line is not great and have to keep speed around 3Mb to keep the SNR high otherwise lots of disconnects.

smellslikeshoes

As has been said it won't make much difference that far out. If you're getting a lot of disconnects you would probably be better asking them to restrict you to 1mbit.

yuloni

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roast

ADSL2+ will make absolutely no discernible difference at that distance.

Sponge Bob

Leaving aside the distance issue for the moment the key stat is the SNR Margin at around 6 or 7 db. Once the margin goes below that the modem cannot distinguish signal from noise on the line. If your margin were 30db there would be lots of room for speed increases.

Your line is more or less perfect _at that distance_ , even 1.5mbits is a veritable miracle.

Xennon

If you can get your hands on different modems you might try them as in my experience some deal with lower SNR margins better than others.

Bohrio

Several reason why Eircom wont upgrade your line to ADSL2+

First, its likely not to work, the least it will not to improve
Second it costs money

Maximum recommended distance for ADSL2+ is, with a few exceptions and depending on things as gauge, noise, attenuation, lb, etc, around 5.5km, g.dmt will be slightly longer.

hence stick to g.dmt and dont bother upgrading. I am surprised your line is synching at that speed, it'd be interesting to see what your transmit powers are.

Wouldnt touch anything if I were you. Where did you get those 8 km?

Nothingbetter2d

dsl sucks so much compared to cable

lucernarian

Bohrio wrote: »

Several reason why Eircom wont upgrade your line to ADSL2+

First, its likely not to work, the least it will not to improve
Second it costs money

Maximum recommended distance for ADSL2+ is, with a few exceptions and depending on things as gauge, noise, attenuation, lb, etc, around 5.5km, g.dmt will be slightly longer.

hence stick to g.dmt and dont bother upgrading. I am surprised your line is synching at that speed, it'd be interesting to see what your transmit powers are.

Wouldnt touch anything if I were you. Where did you get those 8 km?

The line will sync fine, once the signal margin allows for it. A line can sync with anything from 96/96 kpbs* upwards I believe, in 32 kbps steps. ADSL2+ would work slightly better. Mainly from aspects like allowing one bit per pin in ADSL2. READSL2 would work slightly better again than ADSL2+ but insignificantly so, and READSL2 requires changes to the power density values in the bandwidth used for syncing in and regulatory approval etc. READSL2 = Reach Extended ADSL2.


*I am not certain on this but it's been very hard to find reliable sources which give an answer, and not need a degree in electronic engineering to do so!

bkehoe

I've wondered about changing over to ADSL2+ modulation as well - has anyone actually accomplished this? I'm on an ADSL2+ exchange and the up to 8MBit business starter package, not NGB (no plans for NGB at my exchange).

yuloni

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lucernarian

That graph is not so relevant to compare to ADSL as deployed by eircom.

For the DSL line back home and for the OP's line, it shouldn't be possible for them to even reach 1 mbit download speed! In my case, it's 6.5 km long and even higher for the OP. Eircom seem to use some stronger transmit powers and DSLAMs more capable of dealing with noise than what's used Down Under. That graph may measure an attenuation at different frequencies to what eircom measure attenuation at in this country. I think it's 400 kHz? Anyway IIRC I've read a technical document which mentioned that ADSL2 resulted in a range increase of 200 metres (I'd suspect a bit more than that) or else an increase in downstream bitrate of 300 kbps.

Sponge Bob, you're mixing up SNR and signal margin. An SNR of 6dB does indeed cause loss of data/noise distinction, but the signal margin takes that into account. The modem should in theory only disconnect once it reaches a signal margin of 0 dB.

Bohrio

To_be_confirmed wrote: »

The line will sync fine, once the signal margin allows for it. A line can sync with anything from 96/96 kpbs* upwards I believe, in 32 kbps steps. ADSL2+ would work slightly better. Mainly from aspects like allowing one bit per pin in ADSL2. READSL2 would work slightly better again than ADSL2+ but insignificantly so, and READSL2 requires changes to the power density values in the bandwidth used for syncing in and regulatory approval etc. READSL2 = Reach Extended ADSL2.


*I am not certain on this but it's been very hard to find reliable sources which give an answer, and not need a degree in electronic engineering to do so!

The minimum and maximum tx rates are set at the dslam. Same as the 32 kbps intervals, you can set that value to whatever you want of course. I normally have it set up at 32 kbps myself but you rarely see a customer synching at that rate as for a customer to sync at 64 kbps it'd mean that he is using approx 8 bits out of the 512. At that point any small inference will cause the line to drop, and forget about the little margin RA has.

An ADSL2+ line can work no problem with a noise margin of 6 db, and even less if the line is stable enough. G.dmt is not so permissive, due to g.dmt characteristics and the way bit correction works you wanna increase that target to at least 9-12 dB or even more. This doesnt mean that a line can't work with TNM lower than 9 dB, it sure can but it will all depend on its conditions. But this is old news of course.

And this is the interesting part. ADSL2+ uses double the number of tones than g.dmt, this allows it to double the speed to "up to" 24 mb, but with those "extra" tone allocated on higher frequencies (g.dmt goes as high as 1.1 Mhz while adsl2+ goes as high as 2.2 Mhz) they are more susceptible to noise and attenuation, hence, if the line is a long loop your attenuation will also be high and this will affect your final speed.

ADSL2+ is only "effective" on lines up to 4.5 km (approx), after that it really doesnt make much of a difference as the line will be too attenuated to notice any improvement.

But here is the problem. To push ADSL2+ to the limit, to make it more "efficient" than g.dmt (in examples like this) you need to decrease the target noise margin (to as low as ~0 dB), leaving little margin for error. Any noise, interference, such as a faulty socket/filter, etc will cause the connection to drop. G.dmt doesnt care about this as is well use to this, g.dmt only looks at the condition of the line during showtime (with a few exceptions) while ADSL2+ will be constantly checking. Under normal circumstances this is a good thing but when you push the line too far this could turn against you, interleave can make your line laggy and slow.

Condi, I am not too sure your attenuation is 63.5 dB, I would think it should on the range of 50-55 dB, even less. I doubt much more your loop being 9.5 km. It might look like this to Eircoms ccr but I am sure that in reality it should be much less.

Unfortunately there is no way for me to tell unless I run a DMM test, and only Eircom can do that (only Eircom's NMC/3rd line as far as I know). your transmit power and dmt table could give me a clue but even if you get it wont really make much of a difference as is not me you need to convince!

If your house was, in fact, 9.5 km away this mean that your line will not be suitable for DSL (I repeat that 9.5 km is not your real loop length probably more like 6 km, maybe a bit more).

Despite how far you really are, on eircom's side your line is testing badly, and at the end of the day this is waht really matters. It is likely your prequal is amber, and we dont know how long this is going to last for. If things get worse it could go to red (unavailable).

And here is why I dont recommend you upgrading, based on my experience. To upgrade your line to ADSL2+ all they need to do is move you from one block to another, sometimes, this block could be on a different room or even floor, this "rejumpering" can add a good few extra meters to your already long loop (could be 50m , 100 m or could be less of course- unlikely tho!). So they finished upgrading you and jumpered you to your new block, but now your line doesnt work or it works at times. So you try moving back to your old line but now the system has generated a new prequal and voilá! you are testing red! So now you can't move back to your old DSL line but as eircom wont do it based on the fact that your line is not capable of handling broadband anymore... you might get it working again but this situation could turn out being a nightmare. This is probably the worse case scenario of course doesnt mean it will happen to you!!

My advice is stay as you are, although I have the feeling that, if you get your line stats again with nothing else connected to the phone line, just the modem directly into your main socket you might get better values (no filters, no phone, sky, etc). but even if you do get better values I wouldnt really matter, on the other hand, it might not make a difference whatsoever!!!!

Another reason why eircom wont upgrade you is because they could use that port on another customer with a better line.

Baneblade

Also eircom dont use adsl2+ for connections that sync < 8mb.
even if you were on an adsl2+ port it wont use adsl2+ unless you can sync at 9mb or higher

lucernarian

The DSLAM only sets a maximum, the point in RADSL being that the minimum is arbitrary and is according to line conditions.

The length of a line is very easy to quantify for those in rural areas. Generally the line can only go one or two ways to the exchange, usually. The locations of the exchanges can be found out relatively easily, some of this info is on boards and I have other information myself for most exchange locations.

The attenuation would be higher but for the fact that attenuation values for ADSL CPE modems are not defined above 63.5 dB in 0.5 dB steps. Similarly, one less bit is used for upstream attenuation and this means that values above 31.5 dB are not defined. Eircom themselves have told me my line's actual attenuation as 78dB but the modem tells me it's 53.5 dB. I trust eircom's answer:) Some people in my area have working adsl on lines that are 8km long. But 9.5km is rather extreme...

The point about rejumpering for ADSL2+ equipment doesn't apply for an exchange like Glencolumbcille, where a small MDF frame would be in use and the exchange "building" is probably a corrugated steel or concrete shed. Little bigger than the garage of a suburban house. Furthermore, all the DSL equipment is probably in the one rack, except with one ADSL2+ line card along with all the other ADSL cards. The second point, about using it for shorter lines/business lines is the reason why the OP won't see ADSL2 provisioned.

Bohrio

To_be_confirmed wrote: »

The DSLAM only sets a maximum, the point in RADSL being that the minimum is arbitrary and is according to line conditions.

Pretty sure that Eircom can, if I can do it on our exchanges they can too.

There is always a minimum. Eircom's G.dmt also has a minimum tx rate so I assume that their ADSL2+ equipment will be the same. This is not set by the DSLAM as such but by the NMS, so I might have created a bit of confussion there but the NMS is what sets those values on the DSLAM (more or less).

Eircom themselves have told me my line's actual attenuation as 78dB but the modem tells me it's 53.5 dB.

That's based on the attenuation value at 300 khz, Eircom will need to run a FR test, it is indeed the "real thing" but this doesnt represent the customer's real loop length, you can only get this information either by checking the pure cap results or through a TDR test.

The point about rejumpering for ADSL2+ equipment doesn't apply for an exchange like Glencolumbcille, where a small MDF frame would be in use and the exchange "building" is probably a corrugated steel or concrete shed.

You kind of made a good point there hehe, guess I am not used to dealing with such small exchanges, still, you will be amazed how much loop can be added even when moving from one block to the one beside. But I assume that, unlike ls, eircom are placing their new exchanges close to their old dsl1 dslams... unlike with other isps

yuloni

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Albert.gnet

Hi Guys,

Let me Seize the opportunity, how could I calculate my distance to the exchange?

Regards