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From: Muzaffer Kal on 6 Apr 2010 02:24 On Tue, 06 Apr 2010 00:31:36 -0500, Vladimir Vassilevsky <nospam(a)nowhere.com> wrote: > > >steveu wrote: > >> If someone tells an >> investor the channel capacity expression, which it quite easy to remember, >> they might well (and quite reasonably) discount as bogus any claim that two >> boxes can communicate faster than that. > >Hmm. I can still remember old time arguments that it is impossible to >communicate more then 2400 bits per second over the phone line. > >VLV I think one reason for that is over time what constitues a 'phone line' has also changed. 2400 bps might as well be the limit for a end to end analog line. -- Muzaffer Kal DSPIA INC. ASIC/FPGA Design Services http://www.dspia.com
From: glen herrmannsfeldt on 6 Apr 2010 02:40 Muzaffer Kal <kal(a)dspia.com> wrote: (snip, someone wrote) >>Hmm. I can still remember old time arguments that it is impossible to >>communicate more then 2400 bits per second over the phone line. > I think one reason for that is over time what constitues a 'phone > line' has also changed. 2400 bps might as well be the limit for a end > to end analog line. Also on how much computational resources you put to the task. At the time of the 2400 bits/second claim it would likely take more processing power than was available at even the largest computers. -- glen
From: Steve Pope on 6 Apr 2010 02:42 glen herrmannsfeldt <gah(a)ugcs.caltech.edu> wrote: >Muzaffer Kal <kal(a)dspia.com> wrote: >(snip, someone wrote) >>>Hmm. I can still remember old time arguments that it is impossible to >>>communicate more then 2400 bits per second over the phone line. > >> I think one reason for that is over time what constitues a 'phone >> line' has also changed. 2400 bps might as well be the limit for a end >> to end analog line. > >Also on how much computational resources you put to the task. > >At the time of the 2400 bits/second claim it would likely take >more processing power than was available at even the largest >computers. Another thing to remember... if it's worth remembering, is that before turbo codes were developed, many people felt it was impossible to communicate beyond the rate-distortion limit. Steve
From: steveu on 6 Apr 2010 07:06 >glen herrmannsfeldt <gah(a)ugcs.caltech.edu> wrote: > >>Muzaffer Kal <kal(a)dspia.com> wrote: > >>(snip, someone wrote) > >>>>Hmm. I can still remember old time arguments that it is impossible to >>>>communicate more then 2400 bits per second over the phone line. >> >>> I think one reason for that is over time what constitues a 'phone >>> line' has also changed. 2400 bps might as well be the limit for a end >>> to end analog line. >> >>Also on how much computational resources you put to the task. >> >>At the time of the 2400 bits/second claim it would likely take >>more processing power than was available at even the largest >>computers. > >Another thing to remember... if it's worth remembering, is that >before turbo codes were developed, many people felt it was >impossible to communicate beyond the rate-distortion limit. What relevance does that have? Turbo codes played no part in taking 2 wire telephone line modems way beyond 2400bps. Steve
From: Jerry Avins on 6 Apr 2010 10:55
On 4/6/2010 2:24 AM, Muzaffer Kal wrote: > On Tue, 06 Apr 2010 00:31:36 -0500, Vladimir Vassilevsky > <nospam(a)nowhere.com> wrote: > >> >> >> steveu wrote: >> >>> If someone tells an >>> investor the channel capacity expression, which it quite easy to remember, >>> they might well (and quite reasonably) discount as bogus any claim that two >>> boxes can communicate faster than that. >> >> Hmm. I can still remember old time arguments that it is impossible to >> communicate more then 2400 bits per second over the phone line. >> >> VLV > > I think one reason for that is over time what constitues a 'phone > line' has also changed. 2400 bps might as well be the limit for a end > to end analog line. I don't think so. The unstated assumption behind that line of reasoning is binary signaling (and a signal robust enough not to need error correction). Keep that assumption valid, and the limit really is about 2400. Jerry -- "It does me no injury for my neighbor to say there are 20 gods, or no God. It neither picks my pocket nor breaks my leg." Thomas Jefferson to the Virginia House of Delegates in 1776. ��������������������������������������������������������������������� |