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Topic: Dsl |
Ken Lang
From:
Simi Valley, Ca
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Posted 3 Jul 2000 3:46 pm |
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I don't know how many folks here have DSL or can get it. I understand it depends on location. I just thought I'd post this for information. We've been fortunate to have DSL for over a year now at about $50 a month.
Last night my wife decided to download something. It said at the standard modem speed it would take 5 hours. At cable it would take something less, maybe 3-4 hours.
She clicked the download button. It took 5 minutes.
I think all services are searching for that kind of speed and better. Hopefully it will soon be avialable to all. |
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Cairo Zoots
From:
Moville, Iowa ,next to the west fork of the Little Sioux River
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Posted 3 Jul 2000 4:43 pm
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Hi Ken! I envy ur position there. My buddy in Riverside, Ca. recently got his DSL connection and what a difference! We use instant messenger quite a bit, and my 56K modem pales in comparison to his DSL. My brother and I are served by the same central office here in Iowa, and the Calif. connection makes it here a lot faster than my bro who is only about 5mi. down the road! No more waiting on downloads-I can't wait *L
Cz
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ree-oo-dee-doo
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Bobby Lee
From:
Cloverdale, California, USA
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Posted 5 Jul 2000 2:23 pm
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| DSL is great! I can download the entire Forum web site in less than 15 minutes. I've never actually timed it, but it is fast! The compressed backup file is 78 MB. |
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Jim Smith
From:
Midlothian, TX, USA
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Posted 5 Jul 2000 5:59 pm
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I'm still happy with my "old fashioned" cable modem. Yesterday I downloaded a 28.3 MB file in 2 minutes and 31 seconds at 192 KB/sec.  |
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Bill Llewellyn
From:
San Jose, CA
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Posted 6 Jul 2000 6:58 am
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I just bought a 56k modem (upgrading from 28k) to hold off getting DSL for maybe a year. I'm fortunate in that I get about 48k from the new modem (noticably better than the 31/28k I used to get with the older modem).
You guys will be surprised at this.... I got the chance to work with a DSL modem and a central office line card (basically, a rack-mount modem for PacBell's switching offices) hooked together in a lab with 2,000 feet of cable in between. That DSL modem could negotiate a connection of up to 10,000 kpbs. Yes, that's 10 megabits per second. Mind you, the conditions were ideal (the cable was on two spools, not out in the real world hanging between telephone poles with tons of electromagnetic interference wafting around). But the 384kbps they let you have within the 3-mile radius between their switching office and your home is nothing compared to what that technology is capable of.
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Bill * MSA Classic U12 * email * my online music
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Bill Terry
From:
Bastrop, TX
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Posted 6 Jul 2000 10:32 am
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Hi Bill,
I do software for the DMT based DSLAM line cards that Cisco sells, and you are absolutely correct. We've found that most DSL capable loops within 6 or 7 kft of the CO are capable of 'several' Mbps data rates, even with noise and interferers, a real world environment. The theoretical limit is 12+Mbps in a perfect world, so your 10 Mbps was getting pretty close.
I'm not part of the marketing group, but I do know that 'throttling' the bit rate is how the DSL providers will differentiate the $50 mo. accounts from the $150 mo. accounts, even though in most cases there is absolutely NO difference in the equipment, you just tell it how fast to go in software.
Interesting side note; with all the emphasis that is made in the market about being close to the CO, 2 to 3 kft of loop is more likely to give you optimum rates than living next door to a CO would. Zero length loops are some of the toughest cases for DMT due to the fact that the typically high TX power reflected back into the RX side of the CO is much greater than on longer loops. Sorta' like you can't hear what the other end is saying because you're yelling so loud in your own ear. Most DSL chip vendors provide a TX power cutback mode to help get around this problem, but it's still tough.
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bterry.home.netcom.com
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Jack Stoner
From:
Kansas City, MO
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Posted 6 Jul 2000 11:42 am
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Can somebody 'splain how DSL works. I've worked with analog modems, and dedicated stuff up to T1, but I've been retired for almost four years and the DSL wasn't around (or not practical) back then.
(My screen name on AOL Instant Manager is "Fireberd" that I got from the TTC T1 test set).
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Bill Llewellyn
From:
San Jose, CA
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Posted 6 Jul 2000 11:59 am
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Bill T.,
I figured there was throttling going on as soon as I saw those two modems hit even 8Mbps. But what what would PacBell do if everybody had that kinda BW? Their backbones would choke. It will have to come someday, however....
Bill, since you're a code writer, could you scratch out some lines which will make my 56k modem go 1-2Mbps? That would be really nice. If you could do that, you could not only move to Tahiti, you could buy Tahiti.
My little company is working toward the DSL chipset area. I'll pass along your power reduction comments. (Did you work for Netspeed?)
How does all this relate to PSG? Well, in a past thread I proposed that someday all new steel guitars will need to be Internet-ready. There... that's it!
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Bill * MSA Classic U12 * email * my online music
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Bill Terry
From:
Bastrop, TX
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Posted 6 Jul 2000 2:23 pm
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Hi Jack,
Check this tutorial out: http://www.adsl.com/adsl_tutorial.html This is specifically about ADSL but there are a variety of other protocols (SDSL, HDSL) that I'm not that familiar with.
The 10 cent DMT tour:
If you've worked with analog modems you're probably familiar with QAM encoding. Think about 256 QAM modems (in the DMT world they are called carriers or bins) all running at equally spaced frequencies, about 4kHz apart starting above the voice band and going up to about 1.1MHz, a bandwidth that most loops can probably support.
Each carrier is capable of supporting up to 16 bits of information, depending on the SNR at the particuar frequency. During training or activation, the CO and the CPE (customer premise equipment) generate some spectral test tones and exchange information about what the line model looks like from each end's perspective. An agreement is negotiated on how many bins can be used, how many bits per bin can be supported based on SNR, and some other parameters regarding the configured service parameters (throttling ).
Once the two ends agree on the parameters, the link is brought up, the incoming data is framed as DMT symbols, and shipped to the other end. The Asymmetric aspect refers to the fact that you have a lot more bins (bandwidth) dedicated to traffic from CO to CPE, than are used from CPE to CO.
As you might guess, the DMT scheme was around for a while before technology (DSPs that is) got to the point that it was economically feasible. Imagine how much processing is going on with that many carriers being demodulated/decoded, not to mention the other overhead involved with framing, error correction, etc.
I couldn't find the other links I had but if you just do a web search on discrete multitone, ADSL, etc. you'll find tons of stuff. Lots of academic papers are around, you might look up John Cioffi, I think he's the Stanford guy that started this stuff.
Bill,
I'd love to help out with your 56k modem pal, but see above ...
I worked at Motorola SPS for about 4 years, where we developed the CopperGold ADSL transceiver. I was fortunate enough to get a lot of experience in the software and the hardware aspects and it turned out to be the right skillset at the right time. Here at Cisco I work with a bunch of ex-Netspeed people. When Cisco bought Netspeed a lot of those folks stayed around. I came along after that.
Bill
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bterry.home.netcom.com
[This message was edited by Bill Terry on 06 July 2000 at 03:27 PM.] |
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Jack Stoner
From:
Kansas City, MO
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Posted 6 Jul 2000 3:37 pm
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Bill, thanks for the info. I've worked with Codex and Racal Datacom modems (and the diagnostic systems) and DSU's and with muxes and channel banks so I have enough knowledge to be in the danger zone 
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Bill Terry
From:
Bastrop, TX
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Posted 7 Jul 2000 6:22 am
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Jack, it's really just knowing the right acronyms......
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bterry.home.netcom.com
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Rich Paton
From:
Santa Maria, CA.,
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Posted 7 Jul 2000 8:01 am
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I remember running Netscape 3.0 under Windows 3.11, with a 14.4 modem. Several munites to load a web page, and half of anything I clicked on caused a complete system crash.
Now my V90 Robotics Sportster modem connecting at 49.333Kbps and Netscape 4.6 under Win98SE seems a luxury.
Your DSL service sounds very nice! |
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Bobby Lee
From:
Cloverdale, California, USA
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Posted 7 Jul 2000 9:27 am
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My first modem was a Hayes S-100 card that ran at 300 bps. I wrote a terminal program for it in Forth to dial bulletin boards. One of the hot topics of the time was "Is 1200 bps too fast?". (People found 300 bps to be a comfortable reading speed, and were afraid that things would scroll off their screen before they could read them.) Another hot topic was "Which side of the toilet paper roll...". And of course there were political discussions.
Today my DSL modem runs about 5,000 times faster than that early Hayes, but the human interaction on this Forum isn't really much different from the BBSs of old. I'm addicted to the people, not the technology.
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 Bobby Lee - email: quasar@b0b.com - gigs - CDs
Sierra Session S-12 (E9), Speedy West D-10 (E9, D6),
Sierra 8 Laptop (D13), Fender Stringmaster D-8 (D13, A6) |
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Jack Stoner
From:
Kansas City, MO
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Posted 7 Jul 2000 10:03 am
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| The first "modem" that I worked on was a Stelma modem that ran at 150/300/600 baud and was in a 24" high chassis in a 19"rack. It was a tweakers paradise with all the plug in descrete component cards. When I retired in late 96, I had circuits with everything from 9600 baud multi-point analog modems up to T1 links and a 28.8 dialup modem bank. |
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