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#1
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Modem development question...
Okay,
This may seem like a lame question but... Is ANYONE doing any research to increase the performance of a "dial-up" modem beyond the so-called 56kbps limit? TIA |
#2
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"rdlebreton" wrote in message
om... Okay, This may seem like a lame question but... Is ANYONE doing any research to increase the performance of a "dial-up" modem beyond the so-called 56kbps limit? With the speading use of broadband it wouldn't be considered a good investment TIA |
#3
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rdlebreton wrote:
Okay, This may seem like a lame question but... Is ANYONE doing any research to increase the performance of a "dial-up" modem beyond the so-called 56kbps limit? If I recall correctly, speeds above 28.8 (or maybe even 14.4) are not a consequence of more rapid transmission, but from compression of the data. Because the compressibility of the data is dynamic, I suspect that means that 56K is possible, but not sustainable in practical use. Perhaps better compression schemes will come along, but I wouldn't hope for a dramatic improvement. Another issue is line quality. I can't really say much about the practical limit imposed by line quality, other than there is one. |
#4
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"rdlebreton" wrote in message om... Okay, This may seem like a lame question but... Is ANYONE doing any research to increase the performance of a "dial-up" modem beyond the so-called 56kbps limit? the real limitation is the line itself... |
#5
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Your question suggest you don't yet know the basic science
nor the reason why these limits exist. In simplest times, the naive complained that copper wire was a speed limiting factor. They were wrong. Speed limiting factor for modems (on POTS systems) is the switching computer inside the telco's toll station. The fundamental science was defined by Claude Shannon in the Bell Labs in 1948 (back when the Labs were run by people who had science backgrounds). To you, this means that 56K will be the best speed theoretically possible without completely changing hardware in that switching station computer. BTW, what made 56K modems able to do up to 53K? Eliminate only some hardware in the switching computer - an A/D converter. Of course Clayton Christensen defined the underlying concept in his book Innovator's Dilemma. Disruptive innovations simply change your question to be myopic and irrelevant. British Telephone was demonstrating DSL in 1981. IOW long before even 56K existed the telephone switching computer was being obsoleted by a disruptive technology. That means scrapping the entire $multi-million computer that most switching stations only replaced in the 1980s and 1990s. You can see why Baby Bells so feared broadband and why Congress had to pass the 1996 Communications Act to force them to innovate. Isenberg best defined this in his AT&T Bell Labs paper about the 'Smart and Dumb' networks. The Dumb network being a superior solution. But again, AT&T so routinely stifled innovation that Isenberg could not even put that paper on his own web site. You can find it through http://www.isen.com . IOW that 'easy to read' paper may better demonstrate why your 56K modem question is about promoting obsolete technology. I can't say enough about the concepts promoted by both Isenberg and Christensen. Concepts that too many computer users still don't appreciate. But underlying your original question are technical limits defined by Shannon's epic paper "A Mathematical Theory of Communication". So understated and yet so revolutionary to digital communication. rdlebreton wrote: Okay, This may seem like a lame question but... Is ANYONE doing any research to increase the performance of a "dial-up" modem beyond the so-called 56kbps limit? TIA |
#6
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I recall that for a long time 1200 baud modems were considered the
maximum speed theoretically possible, then 2.4, 14.4, 28.8 and then 56k. It is somewhat off-point to talk about central-office equipment since dialup modems are POTS devices; only the ISP's CO gear needed upgrading to support 56K, not the end users'. Did Shannon actually say that 56k was the best POTS could do? Speeds have gone up as compression and modulations schemes have been improved (and the cost of implementing them has gone down.) I agree that there's not much incentive to up POTS modem speed with DSL now available though I'd guess that lots of work is always being done on better modulation and compression schemes for all sorts of wired, wireless and optical communications. w_tom wrote: Your question suggest you don't yet know the basic science nor the reason why these limits exist. In simplest times, the naive complained that copper wire was a speed limiting factor. They were wrong. Speed limiting factor for modems (on POTS systems) is the switching computer inside the telco's toll station. The fundamental science was defined by Claude Shannon in the Bell Labs in 1948 (back when the Labs were run by people who had science backgrounds). To you, this means that 56K will be the best speed theoretically possible without completely changing hardware in that switching station computer. BTW, what made 56K modems able to do up to 53K? Eliminate only some hardware in the switching computer - an A/D converter. Of course Clayton Christensen defined the underlying concept in his book Innovator's Dilemma. Disruptive innovations simply change your question to be myopic and irrelevant. British Telephone was demonstrating DSL in 1981. IOW long before even 56K existed the telephone switching computer was being obsoleted by a disruptive technology. That means scrapping the entire $multi-million computer that most switching stations only replaced in the 1980s and 1990s. You can see why Baby Bells so feared broadband and why Congress had to pass the 1996 Communications Act to force them to innovate. Isenberg best defined this in his AT&T Bell Labs paper about the 'Smart and Dumb' networks. The Dumb network being a superior solution. But again, AT&T so routinely stifled innovation that Isenberg could not even put that paper on his own web site. You can find it through http://www.isen.com . IOW that 'easy to read' paper may better demonstrate why your 56K modem question is about promoting obsolete technology. I can't say enough about the concepts promoted by both Isenberg and Christensen. Concepts that too many computer users still don't appreciate. But underlying your original question are technical limits defined by Shannon's epic paper "A Mathematical Theory of Communication". So understated and yet so revolutionary to digital communication. rdlebreton wrote: Okay, This may seem like a lame question but... Is ANYONE doing any research to increase the performance of a "dial-up" modem beyond the so-called 56kbps limit? TIA |
#7
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rdlebreton wrote:
This may seem like a lame question but... Is ANYONE doing any research to increase the performance of a "dial-up" modem beyond the so-called 56kbps limit? It's only lame if you don't know the underlying facts. Most telephone service today is conducted over digital links, operating at 56kb. There is no added capacity available. The modem is already doing magical things by getting your signal over the highly variable POTS pair to the telephone exchange, where that voice signal is converted to digital. The modem has been able to figure out what to do to get that capacity over that 2 wire analog pair. Going any further won't do anything. That is why you don't get 56 kb connections if you live too far from the exchange (or the exchange isn't digital), and also why the actual limit is about 53 kb (because otherwise excessive power would be needed for the transmission, and exceed FCC regulations). BTW, the specified bandwidth on that POTS line is about 3.5 kHz. So the answer is that, given the existing telephone network, higher speeds are impossible. -- Some useful references about C: http://www.ungerhu.com/jxh/clc.welcome.txt http://www.eskimo.com/~scs/C-faq/top.html http://benpfaff.org/writings/clc/off-topic.html http://anubis.dkuug.dk/jtc1/sc22/wg14/www/docs/n869/ (C99) http://www.dinkumware.com/refxc.html (C-library} http://gcc.gnu.org/onlinedocs/ (GNU docs) |
#8
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This is where wikipedia is better first consulted.
http://en.wikipedia.org/wiki/Information_theory Signal to noise ratio is one concept. To make 56K possible, the noise from one A/D converter was eliminated. So the sever had to make a direct connection to a telco switching station without that A/D converter. IOW hardware had to be removed from the switching computer to make 56K possible - to eliminate a source of noise - to meet criteria defined by Shannon. http://en.wikipedia.org/wiki/Analog-...ital_converter Bennett Price wrote: I recall that for a long time 1200 baud modems were considered the maximum speed theoretically possible, then 2.4, 14.4, 28.8 and then 56k. It is somewhat off-point to talk about central-office equipment since dialup modems are POTS devices; only the ISP's CO gear needed upgrading to support 56K, not the end users'. Did Shannon actually say that 56k was the best POTS could do? Speeds have gone up as compression and modulations schemes have been improved (and the cost of implementing them has gone down.) I agree that there's not much incentive to up POTS modem speed with DSL now available though I'd guess that lots of work is always being done on better modulation and compression schemes for all sorts of wired, wireless and optical communications. w_tom wrote: Your question suggest you don't yet know the basic science nor the reason why these limits exist. In simplest times, the naive complained that copper wire was a speed limiting factor. They were wrong. Speed limiting factor for modems (on POTS systems) is the switching computer inside the telco's toll station. The fundamental science was defined by Claude Shannon in the Bell Labs in 1948 (back when the Labs were run by people who had science backgrounds). To you, this means that 56K will be the best speed theoretically possible without completely changing hardware in that switching station computer. BTW, what made 56K modems able to do up to 53K? Eliminate only some hardware in the switching computer - an A/D converter. Of course Clayton Christensen defined the underlying concept in his book Innovator's Dilemma. Disruptive innovations simply change your question to be myopic and irrelevant. British Telephone was demonstrating DSL in 1981. IOW long before even 56K existed the telephone switching computer was being obsoleted by a disruptive technology. That means scrapping the entire $multi-million computer that most switching stations only replaced in the 1980s and 1990s. You can see why Baby Bells so feared broadband and why Congress had to pass the 1996 Communications Act to force them to innovate. Isenberg best defined this in his AT&T Bell Labs paper about the 'Smart and Dumb' networks. The Dumb network being a superior solution. But again, AT&T so routinely stifled innovation that Isenberg could not even put that paper on his own web site. You can find it through http://www.isen.com . IOW that 'easy to read' paper may better demonstrate why your 56K modem question is about promoting obsolete technology. I can't say enough about the concepts promoted by both Isenberg and Christensen. Concepts that too many computer users still don't appreciate. But underlying your original question are technical limits defined by Shannon's epic paper "A Mathematical Theory of Communication". So understated and yet so revolutionary to digital communication. rdlebreton wrote: Okay, This may seem like a lame question but... Is ANYONE doing any research to increase the performance of a "dial-up" modem beyond the so-called 56kbps limit? TIA |
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