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Telecommunications Stub‑class

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Provider Section

The Suppliers section seems to be very short. I will be adding more Suppliers of ADSL/DSL services. Ishmael Rufus 16:18, 1 June 2007 (UTC)

vs DSL

Is this better than DSL? What abuot cable? Whats the difference? Is it big or small?

That is not true. The theoretical maximum for G.992.1 for example is 13Mbps (224 downstream carriers * 15bit/carrier * 4kHz symbol frequency). --69.105.224.209

Can someone elucidate DSLAM? I suppose it's DSL access apparatus, but abbreviations should be defined before use.

It's explained here --Tolien 3 July 2005 20:17 (UTC)

I understand that "Annex A" is for ADSL over analog lines while "Annex B" is for ISDN lines. Could someone enter this into the article with some info on how likely you are to need one or the other? Or other compatibilities or non-compatibilites to watch out for? Thanks. ---Ransom/CG

Spectrum allocation not quite right

The spectrum breakdown is not entirely accurate in this article. CAP did allocate spectrum the way that the diagram indicates it, but DMT doesn't - it defines 247 (from memory - this figure might be a bit out) subchannels, each of which can be either upstream or downstream (dynamically). --DaveSymonds 06:11, 21 September 2005 (UTC)

Yep, just looked it up: DMT splits the channel into 247 subchannels, each 4kHz wide. This is the standard way it's done now. --DaveSymonds 06:15, 21 September 2005 (UTC)

Faxes

Out of interest, how does ADSL affect faxes? can you send or receive a fax on an ADSL line? - Ta bu shi da yu 05:34, 14 January 2006 (UTC)

A fax is just a low-speed modem, so it uses the voice band. This band is protected by a splitter from the DSL signal. Biot 09:10, 14 January 2006 (UTC)

That's what I though. Cheers Biot! - Ta bu shi da yu 13:53, 15 January 2006 (UTC)

Asynchronous

ADSL is a syncronous protocol at the lowest data layer. Amusingly enough, it runs ATM (async transfer mode) on top of this layer, but it still used syncronised clocks at the sending and receiving end.

That is, I think, true of most layers atop which ATM runs. Guy Harris 23:22, 25 November 2006 (UTC)

Upload speeds

"Upstream rates start at 64 kbit/s and typically reach 256 kbit/s but can go as high as 1024 kbit/s." Is this also true for ADSL2 and ADSL2+? Or do they allow higher upstream rates? --ozzmosis 10:26, 26 February 2006 (UTC)

Upload

The site only mentions the word "upload" once, maybe more information should be provided about uploading on ADSL, the uploading speed, and if uploading is affected by downloading. etc.--82.152.138.225 01:29, 8 March 2006 (UTC)

What I think you are referring to is "link saturation", where the maximum upload speed obtainable reduces during a high speed download, or vice versa. But this behaviour is not restricted to ADSL. --ozzmosis 12:24, 8 March 2006 (UTC)

Actually, can ADSL upload and download data at the same time, or is it effectively one or the other? --geoff_o 20:35, 11 April 2006 (UTC)

I thought I should point out that in Japan, download speeds for ADSL go as high as 47Mbps, and upload speeds up to 5Mbps. Without the proper technical background, I wouldn't want to alter this article, but I thought it might be useful info to add. For evidence of this see the NTT page, in English, on this: http://www.ntt-east.co.jp/product_e/05/2.html

I believe that the 47/5 Mbps line is propably a bonded ADSL2+ line, in otherwords, two ADSL2+ lines used together for the connection. This is covered in the ADSL2/2+ ITU-standard. But I cannot support this claim with any evidence, it's only a guess because the speeds would match pretty nicely.

This is not correct - in japan "adsl2++" is used , which extends the adsl spectrum to 3.75MHz, thus roughly doubling the downstream rate to 50Mbps. 5 Mbps upstream is with triple upstream - the upstream band is three times the US bandwidth of regular adsl. ~~===

ADSL backbone network

I was wondering, if its approriate to mention that the shift from ATM backbone networks to Ethernet is also because of the future possibilities of using the same backbone network for other services like POTS or mobile phone networks?

..."or lower signal to noise (SNR)ratios"... Shouldn't this be lower Signal to Noise Ratios(SNR)? Cruxit 15:59, 14 June 2006 (UTC)

Updating ADSL and DSL entries

CarlosRibeiro 17:23, 21 October 2006 (UTC). I've dropped a note at the DSL history. I moved some notes on DSL installation that applied specifically to ADSL here. It refers to some history on the usage of splitters, that is not longer absolutely required but is still of interest, both historically and also to understand some practical aspects of the technology.

Is it an analogue or digital technology?

Hello

Is it correct to describe it as a digital technology since it modulates analogue carriers?

Thanks

I.I.A —The preceding unsigned comment was added by 195.130.120.24 (talk) 09:03, 21 December 2006 (UTC).

Annex M

The page here states the download speed is 28mbit, but the page says 24mbit... which is it? 125.236.153.184 09:05, 31 January 2007 (UTC)

Capitalization

Reading I think it means this article is incorrectly capitalised, while Digital subscriber line is correctly titled. Does anyone agree that only the first word should be capitalized? Disagree? Think both styles are correct for their respective article? Jim.henderson 20:29, 19 March 2007 (UTC)

• I agree, it should be Asymmetric digital subscriber line. But what links here is overwhelmingly in favour of the capitaised version. I will give it a week then move it. -- RHaworth 10:14, 15 October 2007 (UTC)

S=1/2?

My USR router specs says that with S=1/2, it can do 12Mbps, up from 8. What does S=1/2 mean and how does it extend the download speed? Any info appreciated, cheers! 84.9.32.226 14:47, 25 June 2007 (UTC)

OFDM system comparison table

Feel free to add an ADSL column to the OFDM#OFDM system comparison table. Mange01 11:46, 17 July 2007 (UTC)

History

I came to this page to find out when ADSL was invented and rolled out. If someone knows, can they add it to the article? It would also be good to know who invented it. exterminator 11:06, 8 August 2007 (UTC)

How Much Faster is ADSL compared to Dialup?

I came here hoping to find a definitive answer, because Verizon's claims make no sense ("768 kbit/s DSL is 21 times faster than 56k dialup"). 768/56 == 13 which is nowhere near Verizon's claim. (It's even less when you consider 56K modems use compression to increase effective thoughput to ~150 kbps).) I'd like to find an actual study that's not biased by salesmanship. - Theaveng 17:37, 14 September 2007 (UTC)

Given that ADSL can run from 768Kb/s (or possibly even lower) to 6Mb/s (or possibly even higher), there isn't a single definitive answer to your question. I've gotten 1.5Mb/s; 1500/56 = 26. Guy Harris (talk) 19:21, 20 November 2007 (UTC)

Typical marketing flim-flam, probably. Remember that the max tech speed of this segment of the SYSTEM that you are using is only one factor in the response you experience. Your computer is a factor. Latencies anywhere along the way are a factor, that remains no matter how fast the peak speeds. As a practical matter, you can hope that DSL will be about ten times faster than dial-up, in real life. -69.87.200.195 (talk) 11:17, 24 March 2008 (UTC)

Does DSL use V.42, V.44, or some other data compression?

My dialup modem uses V.44 to compress text 6-to-1 (effective throughput of 300 kbit/s) and executables like flash programs 3-to-1 (effective throughput of 150 kbit/s). Does DSL use a similar technology to squash data on the fly? - Theaveng (talk) 18:30, 20 November 2007 (UTC)

Installation issues

I think this part is about how it is done in the USA? This can be very different depending on local telephone installations in other parts of the world.

Example: ADSL is very in wide use in Germany now and local installation is usually done by the customer, but I have never heard of a microfilter. When you order ADSL you get a spitter from your provider and you install it yourself by pluging it into the telephone jack. The splitter is the only device directly connected to the public network. The splitter itself has two outputs, one for a DSL modem and one for a telephone or an ISDN network termination device. Since the combination of ADSL+ISDN is very common in Germany , there are combined spliiter/termination boxes (called "NTSplit" or something), sometimes there is even a small ISDN PBX inside that box.

I think microfilters make sense if you have multiple telefone jacks that are simply wired parallel. This kind of installation is not even allowed here. If you want more than one telefone you use a small PBX (or ISDN devices connectes to a S0 bus) with the ADSL splitter in front.

Christian —Preceding unsigned comment added by 80.133.139.40 (talk) 15:51, 15 January 2008 (UTC)

Filters are not necessary for ISDN lines, which do not have a large ringer condenser producing echoes. ISDN is rare in the USA, and almost non existent in American homes. Are the German DSL splitters separately marked with a phone socket and a modem socket?

Yes, the splitter has 3 Connections: An input for the old phone jack (the splitter is the only device connected to the public network) and 2 Outputs: One is for the modem, the other one is for telephone equipment.

Is the German arrangement different when DSL is applied to an old analog line?

No, as far as I know all providers in Germany use ANNEX-B DSL ("DSL over ISDN") even when there is no ISDN but an analog phone line. One of the reasons is historic, for several years you could only get DSL in combination with ISDN. Now you can also get it with analog, but they use the same equipment.

Most splitters have a small switch ("ISDN - ANALOG") so the same device could be used for ANNEX-A on an analog line, giving some more bandwidth, but the telcos don't use that and the devices are shipped configured to ISDN (ANNEX-B). I think they also want to avoid customer confusion. (Christian)

OSI Model

Where in the OSI model do (A)DSL and ADSL+ fit? In the link layer? —Preceding unsigned comment added by 194.251.240.114 (talk) 12:42, 7 February 2008 (UTC)

768Kbps

It is great to have all this tech info about the range of possible speeds. But it would be good to also have a table of the most common marketed speeds. In the US 2008 at the low end for Verizon that is 768 Kbps / 128 Kbps. It would be interesting to see a table of the most common low-end DSL speeds current around the world, and the average price. -69.87.200.195 (talk) 11:11, 24 March 2008 (UTC)

Annex L footnote

The footnote for Annex L seems to be ineditable. I was one of the contributors to that bit of text, and I think it should probably be changed a bit by now, but that doesn't seem to be possible anymore, or am I missing something? KryzMasta (talk) 21:55, 8 April 2008 (UTC)

I just clicked on the Edit key for the table, and shortened the footnote without diffuclty. Maybe someone fixed the problem and didn't say. Jim.henderson (talk) 21:31, 14 April 2008 (UTC)

Bitrates

What is the source for the downstream/upstream bitrates of the various modulations and annexes? The G.99* documents don't specify a theoretical maximum that I can see. Kisch (talk) 11:29, 20 November 2008 (UTC)

Original research tag

On 3 December 2008 Mikeblas tagged this article as possibly containing original research or unverified claims. I have searched and cannot find any evidence for this, and Mikeblas has not explained his reasons on this talk page. Can anyone indicate where the possible original research is?
On the same date Mikeblas also tagged the article as citing no references or sources. Certainly it would be good to have sources cited, but is this the reason for the original research tag too?
The following is quoted from the Misplaced Pages Verifiability policy:

This page in a nutshell: Material challenged or likely to be challenged, and all quotations, must be attributed to a reliable, published source.

It is worth noting that this refers quite explicitly to "material challenged or likely to be challenged", and does not support the view which seems to be held by many Misplaced Pages editors that articles must always cite references, even if the information given is quite uncontroversial.
JamesBWatson (talk) 14:45, 9 December 2008 (UTC)

(1) After almost 2 months nobody has supported the original research/unverified claims tag, so I have removed it.

(2) Some references to sources are now included, so I have removed the unreferenced tag.

(3) On 28 January 2009 an anonymous editor operating from IP address 87.78.35.109 tagged the article with "The external links in this article may not follow Misplaced Pages's content policies or guidelines." Having looked at the links in question I agree, and I have removed a few links which I regard as particularly marginal. However, it seems to me that several more of the links given might not be justifiable under the terms of Misplaced Pages's external links policy, in particular "...one should avoid: Any site that does not provide a unique resource beyond what the article would contain if it became a Featured article." Does anyone wish to either defend any of the remaining links or propose removing them? JamesBWatson (talk) 12:55, 4 February 2009 (UTC)

Asymmetric Digital Subscriber Line (ADSL) is a form of DSL, a data communications technology that enables faster data transmission over copper telephone lines than a conventional voiceband modem can provide. It does this by utilizing frequencies that are not used by a voice telephone call. A splitter - or microfilter - allows a single telephone connection to be used for both ADSL service and voice calls at the same time. Because phone lines vary in quality and were not originally engineered with DSL in mind, it can generally only be used over short distances, typically less than 4km.

At the telephone exchange the line generally terminates at a DSLAM where another frequency splitter separates the voice band signal for the conventional phone network. Data carried by the ADSL is typically routed over the telephone company's data network and eventually reaches a conventional internet network. In the UK under British Telecom the data network in question is its ATM network which in turn sends it to its IP network IP Colossus. —Preceding unsigned comment added by 125.21.240.2 (talk) 11:29, 14 February 2009 (UTC)

Rain and ADSL speed

I have noticed that my ADSL connection slows down during a thunderstorm. I did some searching using the terms "rain slow dsl" and I discovered that there have been many cases of people complaining (on message boards)of loosing their ADSL connections due to rain and thunderstorms. I can not find any solid resources that would warrant an article edit. Anyone know of any good resources on this issue? Dreammaker182 03:52, 13 April 2009 (UTC)

No I don't. However, I should think the thunder would be more likely to be the cause than the rain. JamesBWatson (talk) 10:25, 15 April 2009 (UTC)

My call??? My call is that it is perfectly understandable that your ADSL signal degrades when it rains or when there is a thunderstorm - it's like when you talk on your telephone and there is a thunderstorm and you hear static - the signal degrades - why? - because ADSL is NOT digital - it is analogue - just like when you talk over the phone - the only difference that I know of is that ADSL operates well above the 20kHz frequency spectrum that humans can hear. But it's still plain old analogue. Thus your signal degredation. See my entry below titled "But then why is it called Digital???" —Preceding unsigned comment added by 86.143.154.57 (talk) 05:16, 8 May 2009 (UTC)

Any signal on these wires suffers in storms, mostly due to two causes:

1. Lightning induces currents. The receiver mistakes them for signals.
2. Wetness diminishes impedance. Even when both wires of the balanced pair are equally affected the resulting impedance mismatch can make signal reflections but usually it isn't equal, thus the imbalance allows crosstalk.

In the case of analog signals, we hear the click, buzz or other noise. For digital signals a packet is corrupted and the receiving modem requests retransmissions, possibly many retransmissions, possibly at lower speed, until an uncorrupted version arrives.

If you have old external wiring, even here in Brooklyn where all other utilities are buried, cable service and phone are above-ground, dampness tends to permeate into the cable, so the longer it stays wet outside, the more likely you are to have problems, in my personal experience. It's the main reason we upgraded to cable Internet service originally, not the increase in speed (or cost!). If your service junction box is outside, it may be that the oldest phone wiring on the outside of your house is the wire that goes from the junction box to inside, if that's old, I would start with replacing that segment with cable sheathed and rated for external use and go from there. PЄTЄRS J VЄСRUМВА ►TALK 15:02, 18 September 2010 (UTC)

But then why is it called "Digital"???????

I realise that there is a paragraph above where somebody asked if this technology was digital or analogue - and it was never answered. I came to the ADSL page to find that out. It turns out that the Wiki page on ADSL does not answer this. I'm pretty sure that ADSL is NOT digital - it is just analogue way above the 20kHz that humans can hear. Can somebody that knows this technology STATE THAT in the first couple of sentences of this Misplaced Pages entry???? If not, I am going to have to do that in the next week or so - I would prefer not to do that - I am not an expert on this technology. But I think it is not a good Wiki article if you go to ADSL and never read that "it is NOT digital - it is an ANALOGUE technology". Please help me out here. Thanks. —Preceding unsigned comment added by 86.143.154.57 (talk) 05:13, 8 May 2009 (UTC)

It is a digital technology. All digital communications techniques modulate some analogue quantity (current, voltage, electromagnetic field, acoustic pressure); that doesn't make them inherently analogue. What makes them digital is the nature of the data being communicated. Oli Filth 09:01, 8 May 2009 (UTC)

ok, but if I am allowed to ask, for the shake of conversation: plain old modems up to V.90 would also be referred as digital technology? why do we refer to dial-up modems as analog and to ISDN as digital? based on the same assumption I would still refer to ADSL as analog (versus ISDN as digital) (since ADSL also uses QAM as the last dial up modems did) isn't the signal that "travels" in the wire analog for ADSL and digital for ISDN? 195.130.120.24 (talk) 10:07, 18 September 2010 (UTC)

All the above are digital transmissions on carrier wave. You may prefer to restrict the term digital signal to only baseband signals. In that case you will count none of the above as digital, nor will you count other carrier wave transmissions including digital television and optical fiber connections as digital. That's your private choice; just don't confuse this private meaning with public ones. Jim.henderson (talk) 11:37, 18 September 2010 (UTC)

Criticisms of ADSL

Suggestion: A section criticisms of ADSL be added

Rationale: I have plenty of field experience of ADSL and have experienced problems personally. Where the local loop has few ADSL subscribers, the quality and reliability of service tends to be excellent. I have observed that over time, the quality of service on many lines has degraded.

I imagine this is caused by crosstalk. Crosstalk is a well known and well defined property of wires in close proximity. The local loop was designed with 4Khz voice bands in mind, and with relatively few lines active at once. If the frequency is pushed from 4Khz to 138Khz (lowest downstream), the level of crosstalk for those high frequency transmissions will be orders of magnitude greater.

Local loop wiring will have a pair of wires for each subscriber, in a bundle, laid under the pavement from the local end-of-street box to the exchange. That bundle may contain hundreds of individual pairs over perhaps many miles. ADSL tends to become a victim of it's success; as more subscribers opt for ADSL, the proportion of those pairs which carry HF ADSL frequencies increases leading to the noise induced into each wire in that bundle increasing. Once saturation is reached, a new subscriber will result in an existing subscriber, further from the exchange, experience the ADSL HF noise on their line increase beyond the maximum threshold. In effect, there is a maximum number of ADSL signals which can be carried by a bundle. Those further away from the exchange will be knocked off ADSL first. A local loop bundle of wires will generally have an ADSL carrying capacity of far less than the number of phone lines carried.

The criticism so far is that of the local loop infrastructure when it applies to the ADSL coding scheme. This criticism could extend to the ADSL coding scheme as follows:

1) Lines which can carry voice calls will often not sync an ADSL signal at all; if ADSL were more flexible in choosing upstream and downstream frequency bands, ADSL would presumably sync on very poor lines by establishing both an upstream and downstream path close to audio frequencies. If not providing broadband, at least an always-on internet service.

2) Related to 1) above, ADSL tends to fail abruptly rather than gracefully. Once noise has reduced the sync to 700Kbit, a slight increase in noise has, in my experience, broken the connection completely rather than the preferred behaviour of the system continually lowering the data rate. A better design would exploit any usable clear frequency bands the line has, to maintain some sort of bi-directional connection. Both attenuation and crosstalk-induced noise will tend to be higher at higher frequencies.

3) ADSL always noisy: Given the issues so far seem not to have been fully factored in the ADSL system design, it may be that ADSL generates a lot of HF noise on lines even when data is not being communicated. If the system tended towards minimum hf signal generation, the local loop capacity may not be limited by number of subscribers, but by data volume carried, aggregated across subscribers served by the bundle of wires. Given most ADSL modems are not transferring data at max rate 24/7, a 'quiet' ADSL system may lead to a much higher local loop capacity.

These problems could potentially be solved by re-defining the ADSL specification, and perhaps minor (if any) equipment hardware modification, to have a more flexible frequency choice and for ADSL to make less noise when not actively transferring data. Overall, the best approach would be for telecoms companies to change the topology of the local loop to terminate a line closer to the home or premises.(Fiber_to_the_x). Nick R Hill (talk) 11:04, 5 July 2009 (UTC)

There is abuse on the page

"CJ Currie Overview

CJ can run at 3MPH over a distance of 1KM, in terms of fibre hes a fat bastered" —Preceding unsigned comment added by 41.132.178.11 (talk) 11:25, 21 April 2010 (UTC)

• Stub-Class Telecommunications articles
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