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New Look at ADSL2
genrader writes "broadbandreports.com just posted a news article which had an interesting story about the new ADSL2, which should be approved in 2003. They say it should be backward compatible with current hardware. It seems pretty interesting. ISP-Planet has the featured in-depth look at it, so you might want to see if it is of any intrest to you."
Sure, ADSL2 is faster, but how many of us are running our DSL lines at close to the max speed now? I can do 3+ Mb/s on this line, but only get to use 640 Kb/s. New technology that allows me to go faster, yeah that'll come in handy! If it worked at a much longer range it might be useful for some who are out of range now, but it really isn't much of an advance there either. So why should we care, this is like getting excited because Macs are shipping with a gigabit ethernet port when your office is running on a shared 10 mbit hub!
The increases in performance and range are pretty minimal. An additional 50kbps and 600ft of range isn't all that impressive, although the fact that it is backwards compatible with some existing hardware is semi-promising.
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Anyway, here's some extra info on ADSL2, or G.bis that i dug up:
http://www.aware.com/products/DSL/gbisadsl2.htm
http://www.convergedigest.com/Silicon/siliconarti
http://www.dslprime.com/a/adsl21.pdf(sorry about the pdf)
Great one more thing for the telcos to screw up. I'm sure that ADSL2 means 2x the wait and 2x the cost. I'm already looking at my calendar and setting aside a week to wait for them to show up. I'm sure they'll have to make twice as many trips out for line tests and the techs will be twice as ignorant of the technology involved. In Soviet Russia, I bet they get it installed quicker.
Look - new, faster stuff that won't be available in my neighborhood!
"The real problem is that the guys in charge have so very little motivating them to implement new and better things..."
.. like 15-30 miles from the telco ...
"Why bother?
Do we actually think for a moment that US telcos will adopt anything decent? Please...if it's not a patented US currency printing press or a customer cornholing machine...they won't be interested."
And even better...
"For example, on longer phone lines, ADSL2 will provide a data rate increase of 50 kbps--a significant increase. This data rate increase also produces an increase in reach of about 600 feet, which translates to an increase in coverage area of about six percent, or 2.5 square miles."
Wooohooo...a whopping 50kbps, 600 feet...WOW...totally worthless! In about a zillion years they'll have enough range to reach me at 60,000ft from the nearest CO. Hell, telcos can even measure their copper runs accurate to 600ft. I'm serviced at my office at an actual copper length of 19,200ft...while Verizon originally estimated under 15,000ft.
Wow!
It's good for a total of 8,000 feet! Instead of screwing around with short length technologies, why don't they develope something that has far better range
Quidquid latine dictum sit altum viditur
First of all, the story at broadbandreports.com is nothing but a short blurb about the story at ISP-Planet.
Second, the people who posted comments didn't read it. Not sure what the original author meant by a 50kbps increase, but earlier in the article he mentions a doubling of the frequency used resulting in a doubling of the downstream bandwidth. That's significant to me.
I just signed up for a 12Mbit line here in Tokyo.
(I'm upgrading from 8Mbit - the 12 is actually a cheaper plan.)
Regular DSL, IIRC. Used the 30 year old wiring in my place, no problem.
Even on the 8, I've had Internet downloads stream in at better than 1500K.
A year or two ago, Japan was *way* behind in internet access - I was using ISDN (cheap here) and I was a bit of a rare case. Most people used dialup.
So what's really holding DSL back over there? I'd bet the reasons were more economic than engineering.
Just a thought,
Jim
-- My Weblog.
I can't see that this would be all that useful. While a very cool upgrade for the sake of very cool upgrades, how is it all that great?
My DSL connection is very high speed. I feel no net slowdown when listening to Shoutcast Radio on a 128Kbps station; even though I'm eating up 1/4 of my downlink, only rarely does it actually have an effect.
The slowdowns are at the other end. The servers are overloaded; its their T3s that need to be upgraded. Although 500,000 hits in the period of an hour would swamp anything, I suppose.
So while this idea has merit, a whole bunch of other stuff would have to improve too if this is to be particularly useful.
Warning: Poster of this comment is a nerd. Just like everybody else here.
I mean honestly, I am sure that someone here can explain why DSL is fundamentally going to be limited as far as bandwidth and range goes. Copper is a very lossy media, and we already have better stuff out there like fiber optic, and even fiberless communications versus mutliplexed wavelengths (eg Lucent) or even things such as wireless LAN's (although with a more limited range).
The point is that what we need is something that is a complete departure from the paradigm of cable and DSL modems. That is the only thing that is going to allow us to ALL have broadband, and for the cheap, at very high speeds. I have no idea what it will be, though I think it will have to be some wireless technology. Until then, I think we are going to be stuck in this rut of a small number of broadband users who get to use a flawed and unsatisfactory system (except for those that just surf and check e-mail) due to speed constraints and whatnot.
Any ideas of a new system, or how long one might take to engineer? I'm guessing around 20-35 years.
Remember your high-school geometry , area of a circle is pi(r^2)
So the 6% ( ? ) increase in range translates to a more than 12% increase in coverage area. It's not as small as first it appears.
The fact that no one understands you doesn't mean you're an artist.
The article says that there WILL be an increase in service radius by 6% from the telco loop to your home. Which translates into bigger area of service (~2.5 mi.)
Live for the present, learn from the past, and dream of the future!
Well this is all well and good, but lets keep in mind that dsl is expensive to roll-out, what is motivating the company I work for to go out and purchase this *new* wonderful equipment which is going to require upgrades at least in the DSLAM's / ATM switches, nothing is just "hook it in and it works", ever.
It's wonderful that they claim these super fast speeds, but what's the point right now? My company already has equipment in place to offer a few megabit to the home user, but we don't currently offer speeds faster then 768/768. Why? Because the demand isn't there, period. A few geeks here and there, or maybe a business or two, but most business that need something faster then 768 symetric are going to go with another dedicated telco soltion such as a T-1, or a DS3.
I'm happy that we have these wonderful systems, that promise super fast bandwidth, and I'm not saying I don't believe the speeds, I'm just skeptical that we're going to see them hitting the market anytime soon because phone companies aren't eager to roll them out, keep in mind they're all still trying to re-coup the costs to roll out the network in the first place.
For me to take advantage of this two things need to happen.
1. My internet provider is going to have to remove the 1 gig a month limit (if real expects to download movies).
2. Verizon is going to have to provide 1.5 m/bit or faster connection for the price of my current 768/128 k/bit connection..
"I bow to no man" - Riddick
I would imagine that telcos will start doing more of what they did for my neighborhood - install a box (looks like a large refridgerator on its side) that essentially functions as a mini Central Office. So even though we're 20,000 feet from the actual CO, we get DSL connections that are under 2,000 feet.
The telcos know they have to do something before they get their clocks cleaned by the cable companies and wireless T-1 providers (notwithstanding the limitations of those technologies - they do kick ass on price, which is all 85% of the market cares about). Expect to see more of these remote-CO things (pardon the technical description) in the future....
Help save the critically endangered Blue Iguana
Faster DSL is useless in the states until the telco's quit guarding and charging for broadband lines like it's their damn cherry. When that happens, ISPs might actually be able to afford to serve the "ulimited" service they claim without pruning off the people that actually use their share of bandwidth.
Example? T1 prices 5 years ago where $400 to $800 a month and T3 was about $8000 a month. Now? T1 is about $400 to $750 a month and T3 is about $6500 a month on up.
Any sufficiently advanced influence is indistinguishable from control.
All this stuff is down at the physical layer. There's no mention of the higher layers; apparently we're still stuck with PPPoE, a login mechanism, and client software.
The big win with this thing will be the improved diagnostics, along with slightly better noise immunity and the power-save modes.
..but still I can't get ANY form of broadband. And I'm not even living in the sticks - I live in a fairly large English town, which the government had the nerve to dub "IP-City", even though 90% of it lacks any form of connectivity above 56K. I know this is offtopic, but damn it, when I sit here with a connection which I pay more than broadband for, which also ties up the phone line and disconnects every 2 hours, I feel real mad and need to rant about it. Oh, and from my window I can see the BT lab where they develop new and exciting broadband technologies, and then fail to deploy them anywhere near.
This is what you get when you keep on electing a government led by a snivelling weasel who won't do anything unless Bush tells him to first.
Let's call the existing distance (not specified in the article), "r". So the original and new coverage areas ought to be (in terms of feet):
orig_coverage = pi * r * r
new_coverage = pi * (r + 600) * (r + 600)
The difference between these is claimed to be 2.5 square miles. Since there's 5280 feet in a mile, the difference between these two is supposed to be:
new_coverage - orig_coverage = 2.5 * 5280 * 5280
So, putting these together, and multiplying out the (r+600)*(r+600) part, it ought to be possible to deduce the original radius: ....adding some parens to make it easier to read
(pi * r * r) + (pi * 2 * 600 * r) + (pi * 600 * 600) - (pi * r * r) = 2.5 * 5280 * 5280
So, luckily the r squared terms subtract each other out, so this little bit of math won't requiring using a quadratic equation. Subracting the constant, it turns into:
pi * 2 * 600 * r = 2.5 * 5280 * 5280 - pi * 600 * 600
Now for anyone reading this far who's good at basic algerba, I'm going to appologize for yet a couple more simple steps spelled out....
r * 3769.9 = 69696000 - 1130972.4
r = 68565027.6 / 3769.9
r = 18187.5
So it looks like existing DSL goes 3.44 miles, and this new one goes 3.56 miles, and the increase from 37.276 square mile to 39.776 square miles really is 6% (actually 6.7%).
So it does really work out, and the existing DSL distance of 3.44 miles sounds reasonable.
Of course, it's all a moot point if the FCC allows the cable and baby bells to lock out competition. The only reason almost anyone has DSL within a 3.44 mile radius is because AT&T started rolling out high speed cable. What this new DSL _really_ needs (other than a real increase in distance) is a competing technology/business and a regulatory environment that allows that competition instead of squashing it. How likely is that? Too bad there's no easy formulas there.....
PJRC: Electronic Projects, 8051 Microcontroller Tools
Speaking as one of those in the UK sitting pretty much on the wrong side of the limit of the 5.5km restriction we have on British Telecom's ADSL implementation, the range increase may be more promising.
I'll hit the maths a bit -
Asssuming all the lines radiate directly out of the exchange so you can assume the range limit proscribes a circle with the exchange at the center (you can tell I'm a physicist can't you?)
The range increase talked about in the UK is 5.5km -> 6km of cable length. Now compare the areas of these 2 circles.
5.5 x 5.5 x 3.14 = 95 km squared (approx)
6.0 x 6.0 x 3.14 = 113 km squared (approx)
So this gives an extra 18 km squared coverage. If we assume one household per 100 metres squared (not unreasonable in the UK) then this bring 1800 homes in range of broadband.
Of course in the real world things will vary, but I've seen figures from BT suggesting 6km will bring 97% coverage of the population.
The irony for me is I live 30 miles from London, 4 miles from the end of the runway of one of our major airports, 3 miles from one of the major motorways and yet my broadband options are the same as someone on a remote island, no ADSL, no cable, just my trusty 56k jalopy...
The problem isn't really in the engineering or design, but the roll out.
The most significant bit of any telco's network is 'the last mile' where the copper leaves the exchange and gets to your office or home.
There is one heck of a lot of these local loops, and replacing them with another media is no small job. So the solutions that will succeed and can be rolled out in a reasonable time and at a cost the consumers will pay has to be ones that can make the best use of the established transmission media that goes past your house.
Now this means cable modems and ADSL.
Wireless has its own set of problems if it is to become ubiqoutous - do we have the bandwidth when we are all sharing it - maybe we can have local sub exchanges that feed signal to our houses by fibre?
I don't know the answers, but anything that involves replacing the media to every customers home is going to take a long period of time and money to roll out. Replacing the local loop physical media will not in anyway make broadband cheap, more likely the opposite.
Right now you can get fast reliable connections by buying in a T1 leased line - but most people can't because you have to bear the cost of the telco installing the dedicated line yourself.
We have plenty of technologies right now that can bring mega bit levels to your home - if we were starting from scratch.
I'm not convinced that there is enough frequency spectrum to get mega bit broadband wireless to all. My money would be on a hybrid structure pushing the fibre networks further out to your house as and when networks are updated, and using local nodes and short copper runs like cable modems, or ideally push fibre into your homes in metropolitan areas, moving to wireless links where replacing physical transmission media become cost ineffective.
This is going to be a bit long but bear with me, I hope I can explain it a little.
The fundamental limit of high bandwidth technologies is due to the physical nature of copper wire.
Any digital signal is essentially a composition of a series of sine waves. Don't worry if this doesn't make sense - what happens is that the sharp 'edges' of a digital pulse are effectively very high frequency. So although it is conventient to think of a digital signal having a single frequency that is effectively the data rate, its not actually true.
One of the properties of copper wire is that different frequencies travel at different speeds in the wire, and get attenuated (lose power) at different rates.
Now we combine these two thoughts and what happens is that the well defined pulse get smeared as the frequencies that make them up seperate as the pulse goes down the line, and misshaped as attenuation kicks in. At some point this smearing will make it impossible to reconstruct the pulse. Also every single joint in the cable causes reflection of the siganl to some point.
In a transmission system this is not a problem, as the great thing with a digital signal is we know it only has two states - 1 or 0 - so we can regenerate and clean up the signal and transmit it again. This is what repeaters in undersea cables do (even fibre has to have these, but at much greater lengths than copper). But to your house there is no point in the cable to put a repeater - if the signal can be read when it gets to where you are then it works, if not then it doesn't.
Now in reality digital signals are not transmitted as a single stream of on/off pulses, but encoding systems are used that turn the signals into ranges of tones - which is why when you listen to you modem you here a range of tones, rather than a single one.
All of these techniques aim to minimise the effect of the smearing due to the different speeds the different frequencies travel, and to make the signal more resiliant to noise issues. But at some point either the pulses will become so corrupted they cannot be recognised, or the signal to noise ratio will get so bad that they can't be distinguished from noise.
Generally the problems get worse as the frequency goes up, and in data terms this is roughly the same as baud rate. This is why faster DSL rates are only available nearer the exchnage.
The reasons why ADSL2 isnt a great improvement is we are hitting fundamental limitations of copper wire transmission systems as used for analogue telephones (and it is analogue in the local loop no matter what the exchnage is) and tweaking the encoding techniques is not bringing great increases.
Remember with normal modems we hit the limit at 36Kbaud due to the fact that normal voice is limited to 0-4Khz - a bit of clever engineering managed to boost this to 56Kbaud on the downlink because you avoid one of the anti aliasing filters in the exchange.
So modems are limited to 4Khz and Shannons Law tells us the maximum data rate we can do at 4Khz, and 56Kbaud modems are damn near the limit.
ADSL is carried as a piggy back signal on your analogue line - below 4khz is the normal voice signal, above 25Khz is the ADSL signals. There is no 'hard' upper limit to ADSL due to filters like there is for voice, but there is a 'soft' limit where the problems discussed above mean its not possible to get reliable transmission.
Current ADSL is pretty close to those 'soft' limits - ADSL2 tweaks it a bit to get more in and increase the range.
The bad news is its not going to get much better on copper wire - the modem limit was due to filtering, but ADSL is down to basic physics.
Explanation of the local loop technologies - mostly found via ADSLGuide (These guys do a great job of keeping on top of UK ADSL issues)
The Last Mile - personal site, but a good heads up. Significantly shows the bandwidth limits as related to the type of wire the signal is transmitted down.
The Trouble With DSL great well written article that summarises some of the technical and practical issues with DSL.
ADSL Techincal Summary
DSL Source Book - PDF (registration required) - very good for technical geeks.
Instead think of them in a larger scope.
Many Telcos are starting to roll out evironmentally hardened DSLAMs that they can pole or slab mount to serve areas that have demand but are too far from an existing DSLAM.
If a Telco can now reach a larger subscriber base without rolling out as many remote DSLAMs, that results in an increase in available infrastructure dollars, which could translate into fast or a greater number of remote DSLAM rollouts. I can also increase DSLAM rollouts by increasing revenue per DSLAM, since a given DSLAM can now service more customers, which might in turn make more DSLAM rollouts more affordable for Telcos.
"would imagine that telcos will start doing more of what they did for my neighborhood - install a box (looks like a large refridgerator on its side) that essentially functions as a mini Central Office. So even though we're 20,000 feet from the actual CO, we get DSL connections that are under 2,000 feet."
Your exactly right. I live out in what people would call the boonies. Cows, chickens and goats are my neighbors and I am waked up by howling dogs and roosters. However, I get very fast and reliable dsl access. I've had 1.5mb/s down and 256kbs up for a year now at $45 a month courtesy of my baby bell. It has only gone down 4x in the course of the year that I have had it, which is better than I can say about the dialup i used to have. I wish the bandwidth were higher, but I can't complain, because I don't get capped like so many cable users do. I live in an unencorporated town that is about 15 miles outside of Atlanta. They have one of those boxes not far from me, and the tech who had to repair my dsl told me that their little foray is doing well, we have 40 users on our Dslam. By extending the reach of DSL, they are able to capture the upper middle class market who live in the suburbs. Hopefully, your local telco will experiment in your area in a similar manner.
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