Re: 56 kbps modems
-----BEGIN PGP SIGNED MESSAGE----- Mime-Version: 1.0 Content-Type: text/plain Content-Transfer-Encoding: 7bit To: cypherpunks@toad.com Date: Mon Sep 16 15:59:53 1996 I think I have to throw in some words here, too: 1. BAUD is one distingushable signal form. 2. BPS is bits per second 3. NO transmission over a standard phoneline can have more than 3100 baud, because the frequency of anything transmitted over that line is band limited to 300hz - 3400hz. (If you have ISDN it's not relevant anyway, since you are fixed with 8000hz or 64000 bps->in europe :), 56000 bps in usa) 4. Most modern transmission schemes work with multiple bits per baud. I.e. you transmit 10 bits in one baud if you have a 31000 bps modem. the only limitation in transmission speed is the amount of binary values you can pack into one baud. that on the other hand is limited by the S/N (signal to noise) ratio of your line. If you have a noise of 0.9%, you can't use more than 100 steps or you have ambiguous signals. since people talk about 56000 bps modems (we tried 34000 modems here and they couldn't produce more than 28800 on a very good connection) that would mean, that you have to transmit 18 bits = 262144 (!) distinguishable signal forms per baud. Comments? Remo Pini - ------< fate favors the prepared mind >------ Remo Pini rp@rpini.com PGP: http://www.rpini.com/crypto/crypto.html - ----< words are what reality is made of >---- -----BEGIN PGP SIGNATURE----- Version: 2.6.3i Charset: noconv iQEVAwUBMj1dWhFhy5sz+bTpAQHmVAgAqRHydyZdElXlwMSgdKB6hg1fDBCMfhia JoI5W8n0JLcKe9HYN/H0DPqFHHDIATEhlN3b3OIhYCw52cNJ/e3b9Nbp5RQo+sDX zAogz5wZiDV7EA/gL589lNQZ9VKHlgTYBLzu1tqyJ5cD2KhWEUjvXyN4lYuxcEQT NIaiNPeYXrC0BeoLa/AE8mCrtu+7nhxy5HlSjDiu3lEYaVygKIPQHM3+Ljzq0jkq bmbqJbTyZshos+5gxHyXLsbL8rkpST53YT4Z3clL6PCv1ntNGXtb/loWgIDallYJ bHgfh/bAS5Utg7fpzuVNS8AJV8L2VLirScBd4Bq5RAXZxnoTVVQxOw== =9JSI -----END PGP SIGNATURE-----
Speaking of ISDN, how many people, can afford to have a personal ISDN line in there house? And then afford to connect to something/someone else on a next to permanent basis monthly?
As I write this message I'm in the last day of my ISDN service for now. When I was doing independent consulting work I installed ISDN at my office. This was to facilitate connectivity to work in California from Minnesota. After taking a job working for a company locally in Minneapolis I succumbed to the temptation of installing ISDN at my home and moved my Combinet router home. I won't deny that I'll be giving up considerable convenience since the ISDN connection has the ability to come up quickly and automatically as I send packets to external destinations (that's in theory, your mileage can vary considerably). But the price per month is ridiculous for the marginal improvement in connectivity I get over my U of M account that only costs me about $100 per year. For the price I'm paying for ISDN Internet connectivity I could buy 32 meg of memory or a gigabyte drive every month. The driving force in my decision is the continuing improvement in modem speeds. When I started with ISDN, my modem speed was 9600 and plenty finicky at that. Now you can get 33.6 modems for less than $200. _________________ Steve Bryan sbryan@gofast.net
I personally, am not much for this, I am just one with various ideas, and questiosn and such, so here goes. On Mon, 16 Sep 1996, Remo Pini wrote:
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To: cypherpunks@toad.com Date: Mon Sep 16 15:59:53 1996 I think I have to throw in some words here, too:
1. BAUD is one distingushable signal form. 2. BPS is bits per second
Ok, I agree with those.
3. NO transmission over a standard phoneline can have more than 3100 baud, because the frequency of anything transmitted over that line is band limited to 300hz - 3400hz. (If you have ISDN it's not relevant anyway, since you are fixed with 8000hz or 64000 bps->in europe :), 56000 bps in usa)
Personally, by saying that no transmission on a standard phoneline can have more than 3100 baud, is a statement saying that technology and science, shall never advance, to a point where things are possible. If you remember right, just 10 or so years ago, we stated that 2400 baud was the highest possible baud, and we would never go over. My modem, running on a standard phone line, is a 28.8 USRobotics modem, with the software, and hardware upgrades to a 3400 baud, I get on an average day anywhere from 3500 to 3600 baud for send/receive. On a bad day, I only get 3100 to 3200. SO I would say, that my phone lines, are cleaner than most eh? And Yes, I am in the US. Speaking of ISDN, how many people, can afford to have a personal ISDN line in there house? And then afford to connect to something/someone else on a next to permanent basis monthly?
4. Most modern transmission schemes work with multiple bits per baud. I.e. you transmit 10 bits in one baud if you have a 31000 bps modem. the only limitation in transmission speed is the amount of binary values you can pack into one baud. that on the other hand is limited by the S/N (signal to noise) ratio of your line. If you have a noise of 0.9%, you can't use more than 100 steps or you have ambiguous signals. since people talk about 56000 bps modems (we tried 34000 modems here and they couldn't produce more than 28800 on a very good connection) that would mean, that you have to transmit 18 bits = 262144 (!) distinguishable signal forms per baud.
Comments?
What about new ways of splitting the steps and baud more so that it shows less at a higher level.... Just a question.. Ahh well, I'm getting a page so I shall finish this now... Answer appreciated..
Remo Pini
- ------< fate favors the prepared mind >------ Remo Pini rp@rpini.com PGP: http://www.rpini.com/crypto/crypto.html - ----< words are what reality is made of >---- -----BEGIN PGP SIGNATURE----- Version: 2.6.3i Charset: noconv
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Erp
On Mon, 16 Sep 1996, Jay Gairson wrote:
Speaking of ISDN, how many people, can afford to have a personal ISDN line in there house? And then afford to connect to something/someone else on a next to permanent basis monthly?
No problem here. My ISDN bill is a small fraction of my regular phone bill. --Lucky
Jay Gairson
Personally, by saying that no transmission on a standard phoneline can have more than 3100 baud, is a statement saying that technology and science, shall never advance, to a point where things are possible. If you remember right, just 10 or so years ago, we stated that 2400 baud was the highest possible baud, and we would never go over.
Baud denotes the number of state changes made by the modem on the line per second. The possible states generally form some sort of regular pattern in frequency/phase space, with each state being maintained long enough to reliably determine it on the other end. Before the advent of V32 and V32.bis modems, the underlying symbol rate was substantially lower than it is now. Then it was determined that it was possible to overdrive the line cards on digital switches to equalize them over a wider range of frequencies, without smoking them down. The newer modems take advantage of this kludge. Since the underlying digital data stream is eight thousand 8-bit u-law samples per second, there are genuine theoretical limits in terms of symbols per second which cannot be crossed.
My modem, running on a standard phone line, is a 28.8 USRobotics modem, with the software, and hardware upgrades to a 3400 baud, I get on an average day anywhere from 3500 to 3600 baud for send/receive. On a bad day, I only get 3100 to 3200. SO I would say, that my phone lines, are cleaner than most eh? And Yes, I am in the US.
Don't confuse "baud" in terms of characters per second through your modem with the low level symbol rate of the modem's analog output into the phone line. The "baud" you see is a function not only of the low level symbol rate, but of framing, the V.42 compression/error correction process, and other factors.
Speaking of ISDN, how many people, can afford to have a personal ISDN line in there house? And then afford to connect to something/someone else on a next to permanent basis monthly?
The price of ISDN is a function of phone company marketing, not the cost of providing the service. Domestic US service is almost entirely digital now, and moving the subscriber line interface to the consumer end, so the digital aspects of the network may be fully exploited, is not a conceptually expensive process. (Yes I know the software upgrade to ESS for ISDN costs a bundle.) -- Mike Duvos $ PGP 2.6 Public Key available $ mpd@netcom.com $ via Finger. $
participants (5)
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Jay Gairson -
Lucky Green -
mpd＠netcom.com -
Remo Pini -
Steve Bryan