Howard Eisenhauer <howarde@REMOVECAPShfx.eastlink.ca> wrote:>On Fri, 27 Oct 2006 20:38:37 -0800, floyd@apaflo.com (Floyd L. >Davidson) wrote: > >>Howard Eisenhauer <howarde@REMOVECAPShfx.eastlink.ca> wrote: >>>On Fri, 27 Oct 2006 10:29:06 -0500, no-top-post wrote: >>> >>>>It's common knowledge that digital technology gives more telephone >>>>[4 Khz wide] channels than analog technology - for the same spectrum >>>>width. This even with the steep-sided filters and SSB technology. >>>> >>>T'aint nesessarily so. As another poster pointed out FDM could >>>squeeze 24 channels os SSB 4kz voice into 96 KHz. where a T1 takes >>>over 1.5 megabits/sec to do the same thing. >> >>Comparing bandwidth to bit rate is nonsense! 96 KHz does not >>compare to 1.5 Mbps in any productive way. > >Lets define "Bandwidth"- Bandwidth properly refers to spectrum & is >measured in Hz. If you're talking "bitrates" then you're refering to >a system with a fixed transmission capacity. Whether or not it's >being used efficiently is measured by what % of the data stream >consists of overhead messages & empty data octets.Hence comparing bandwith (spectrum) to bitrate (capacity) is nonsense. Added prattle doesn't change that.>The OP was talking about "efficiency", more or less relating to voice >circuits. Without a doubt the standard reference of a 4 KHz voice >channel it's more efficient spectrally to use FDM than to move 24 >voice channels than to use a T1. In fact, as the T1 spec requires a >pulse shape that's more or less square that implies at least 3rd order >harmonics @ 4.5 MHz. You can fit 600 FDM voice channels in that >space.T1 does *not* require a square pulse shape. It requires 750 Khz bandwidth. It was not designed for efficient spectrum utilization, because that is not required on a twisted pair cable. However, since it was designed to replace a single 4 KHz voice circuit with 24 each 4 KHz voice circuits (granted with lower SNR), it is hard to accept your argument that a T1 represents bandwidth inefficency as such. Since nobody puts 600 FDM voice channels on a twisted pair, I can't see where you can claim that many will fit, eh?>>Keep in mind that a telco voice channel is 4 KHz analog, but >>over the same bandwidth one can easily send a 64 Kbps digital >>PAM signal (i.e., v.90) using the exact same codec in the >>telephone switch line card. > >Well, that sort of figures as a standard digital voice channel is >64K/sec anyhow. You certainly can't squeeze a higher bitrate from >your modem through there. & how much you can send depends on the >card, if its using robbed bit signalling (yes, its still in use here & >there) you're limited to 56K.Line cards know nothing about robbed bit signaling. And therefore robbed bit signaling has nothing to do with the bit rate for a PAM digital signal on the wire side of a line card.>If you have a crappy phone line with >poor S/N your rates going way down. A pointless quibble perhaps but >its late & I'm bored. > >> >>Bandwidth does not use more bitrate, it provides more! > >From the OP's question I'd say you're putting the cart before the >horse. Bitrate uses Bandwidth, spectrally speaking.Which is why bandwidth *provides* more bitrate. You are confused.>How much depends >on the modulation method, QAM, QPSK, FSK, FM, CW yadda yadda. >Bandwidth is not an unlimited resource, not everybody has the luxury >of multiple dark fibers in the ground between here & there. There are >very real- er, um, real world constraints with systems such as >satellite, terrestrial M/W & the previously mentioned wireless >systems.So?>>Shannon showed channel capacity to be relative to both bandwidth >>and signal-to-noise ratio. Anything you do to change one >>*requires* a change in the other to maintain the same maximum >>capacity. Different carrier systems do exactly that, balancing >>between SNR and bandwidth. > >I could have sworn thats what I was getting at by way of the examples >of cellular transmission standards, but what the hell do I know ???Swear all you like, but that isn't what you said.>>Bandwidth is not what makes digital more effective than analog. > >Agreed. Whole heartedly. > >>Above a minimum SNR digital systems are essentially error free >>while analog system have additive noise. > >Unfortunately bandwidth is never unlimited & the noise level can >occaisionally be out of your control.A useless statement of no significance.>Digital systems are far less >tolerent of noise when it *does* exceed the critical level. Analog >systems get "hissy", digitas ge& ..or_de^5T3+...Wrong. A digital system can function error free at an SNR so low that analog systems cannot function at all, much less simply get hissy.>>digital is usually prefered. The second most significant reason >>is the ease with which digital carrier systems can be designed >>to trade SNR for bandwidth by using multi-level encoding, which >>means well matched adaptions to anything from very noisy fiber >>optics to very quiet coax cable. > >True, although as I also alluded to encoding & error protection >schemes eat into the actual traffic throughput for a given system at >layer 1. You can over come a shit load of noise with the right setup, >but if you have to send a million bits to get one bit of payload >through to the customer you're better off hand delivering the message.More prattle? -- Floyd L. Davidson <http://www.apaflo.com/floyd_davidson> Ukpeagvik (Barrow, Alaska) floyd@apaflo.com
How can digital be more spectrum efficient than analog ?
Started by ●October 27, 2006
Reply by ●October 29, 20062006-10-29
Reply by ●October 29, 20062006-10-29
Howard Eisenhauer <howarde@REMOVECAPShfx.eastlink.ca> wrote:>On Fri, 27 Oct 2006 20:38:37 -0800, floyd@apaflo.com (Floyd L. >Davidson) wrote: > >>Howard Eisenhauer <howarde@REMOVECAPShfx.eastlink.ca> wrote: >>>On Fri, 27 Oct 2006 10:29:06 -0500, no-top-post wrote: >>> >>>>It's common knowledge that digital technology gives more telephone >>>>[4 Khz wide] channels than analog technology - for the same spectrum >>>>width. This even with the steep-sided filters and SSB technology. >>>> >>>T'aint nesessarily so. As another poster pointed out FDM could >>>squeeze 24 channels os SSB 4kz voice into 96 KHz. where a T1 takes >>>over 1.5 megabits/sec to do the same thing. >> >>Comparing bandwidth to bit rate is nonsense! 96 KHz does not >>compare to 1.5 Mbps in any productive way. > >Lets define "Bandwidth"- Bandwidth properly refers to spectrum & is >measured in Hz. If you're talking "bitrates" then you're refering to >a system with a fixed transmission capacity. Whether or not it's >being used efficiently is measured by what % of the data stream >consists of overhead messages & empty data octets.Hence comparing bandwith (spectrum) to bitrate (capacity) is nonsense. Added prattle doesn't change that.>The OP was talking about "efficiency", more or less relating to voice >circuits. Without a doubt the standard reference of a 4 KHz voice >channel it's more efficient spectrally to use FDM than to move 24 >voice channels than to use a T1. In fact, as the T1 spec requires a >pulse shape that's more or less square that implies at least 3rd order >harmonics @ 4.5 MHz. You can fit 600 FDM voice channels in that >space.T1 does *not* require a square pulse shape. It requires 750 Khz bandwidth. It was not designed for efficient spectrum utilization, because that is not required on a twisted pair cable. However, since it was designed to replace a single 4 KHz voice circuit with 24 each 4 KHz voice circuits (granted with lower SNR), it is hard to accept your argument that a T1 represents bandwidth inefficency as such. Since nobody puts 600 FDM voice channels on a twisted pair, I can't see where you can claim that many will fit, eh?>>Keep in mind that a telco voice channel is 4 KHz analog, but >>over the same bandwidth one can easily send a 64 Kbps digital >>PAM signal (i.e., v.90) using the exact same codec in the >>telephone switch line card. > >Well, that sort of figures as a standard digital voice channel is >64K/sec anyhow. You certainly can't squeeze a higher bitrate from >your modem through there. & how much you can send depends on the >card, if its using robbed bit signalling (yes, its still in use here & >there) you're limited to 56K.Line cards know nothing about robbed bit signaling. And therefore robbed bit signaling has nothing to do with the bit rate for a PAM digital signal on the wire side of a line card.>If you have a crappy phone line with >poor S/N your rates going way down. A pointless quibble perhaps but >its late & I'm bored. > >> >>Bandwidth does not use more bitrate, it provides more! > >From the OP's question I'd say you're putting the cart before the >horse. Bitrate uses Bandwidth, spectrally speaking.Which is why bandwidth *provides* more bitrate. You are confused.>How much depends >on the modulation method, QAM, QPSK, FSK, FM, CW yadda yadda. >Bandwidth is not an unlimited resource, not everybody has the luxury >of multiple dark fibers in the ground between here & there. There are >very real- er, um, real world constraints with systems such as >satellite, terrestrial M/W & the previously mentioned wireless >systems.So?>>Shannon showed channel capacity to be relative to both bandwidth >>and signal-to-noise ratio. Anything you do to change one >>*requires* a change in the other to maintain the same maximum >>capacity. Different carrier systems do exactly that, balancing >>between SNR and bandwidth. > >I could have sworn thats what I was getting at by way of the examples >of cellular transmission standards, but what the hell do I know ???Swear all you like, but that isn't what you said.>>Bandwidth is not what makes digital more effective than analog. > >Agreed. Whole heartedly. > >>Above a minimum SNR digital systems are essentially error free >>while analog system have additive noise. > >Unfortunately bandwidth is never unlimited & the noise level can >occaisionally be out of your control.A useless statement of no significance.>Digital systems are far less >tolerent of noise when it *does* exceed the critical level. Analog >systems get "hissy", digitas ge& ..or_de^5T3+...Wrong. A digital system can function error free at an SNR so low that analog systems cannot function at all, much less simply get hissy.>>digital is usually prefered. The second most significant reason >>is the ease with which digital carrier systems can be designed >>to trade SNR for bandwidth by using multi-level encoding, which >>means well matched adaptions to anything from very noisy fiber >>optics to very quiet coax cable. > >True, although as I also alluded to encoding & error protection >schemes eat into the actual traffic throughput for a given system at >layer 1. You can over come a shit load of noise with the right setup, >but if you have to send a million bits to get one bit of payload >through to the customer you're better off hand delivering the message.More prattle? -- Floyd L. Davidson <http://www.apaflo.com/floyd_davidson> Ukpeagvik (Barrow, Alaska) floyd@apaflo.com
Reply by ●October 29, 20062006-10-29
Howard Eisenhauer <howarde@REMOVECAPShfx.eastlink.ca> wrote:>On Fri, 27 Oct 2006 20:38:37 -0800, floyd@apaflo.com (Floyd L. >Davidson) wrote: > >>Howard Eisenhauer <howarde@REMOVECAPShfx.eastlink.ca> wrote: >>>On Fri, 27 Oct 2006 10:29:06 -0500, no-top-post wrote: >>> >>>>It's common knowledge that digital technology gives more telephone >>>>[4 Khz wide] channels than analog technology - for the same spectrum >>>>width. This even with the steep-sided filters and SSB technology. >>>> >>>T'aint nesessarily so. As another poster pointed out FDM could >>>squeeze 24 channels os SSB 4kz voice into 96 KHz. where a T1 takes >>>over 1.5 megabits/sec to do the same thing. >> >>Comparing bandwidth to bit rate is nonsense! 96 KHz does not >>compare to 1.5 Mbps in any productive way. > >Lets define "Bandwidth"- Bandwidth properly refers to spectrum & is >measured in Hz. If you're talking "bitrates" then you're refering to >a system with a fixed transmission capacity. Whether or not it's >being used efficiently is measured by what % of the data stream >consists of overhead messages & empty data octets.Hence comparing bandwith (spectrum) to bitrate (capacity) is nonsense. Added prattle doesn't change that.>The OP was talking about "efficiency", more or less relating to voice >circuits. Without a doubt the standard reference of a 4 KHz voice >channel it's more efficient spectrally to use FDM than to move 24 >voice channels than to use a T1. In fact, as the T1 spec requires a >pulse shape that's more or less square that implies at least 3rd order >harmonics @ 4.5 MHz. You can fit 600 FDM voice channels in that >space.T1 does *not* require a square pulse shape. It requires 750 Khz bandwidth. It was not designed for efficient spectrum utilization, because that is not required on a twisted pair cable. However, since it was designed to replace a single 4 KHz voice circuit with 24 each 4 KHz voice circuits (granted with lower SNR), it is hard to accept your argument that a T1 represents bandwidth inefficency as such. Since nobody puts 600 FDM voice channels on a twisted pair, I can't see where you can claim that many will fit, eh?>>Keep in mind that a telco voice channel is 4 KHz analog, but >>over the same bandwidth one can easily send a 64 Kbps digital >>PAM signal (i.e., v.90) using the exact same codec in the >>telephone switch line card. > >Well, that sort of figures as a standard digital voice channel is >64K/sec anyhow. You certainly can't squeeze a higher bitrate from >your modem through there. & how much you can send depends on the >card, if its using robbed bit signalling (yes, its still in use here & >there) you're limited to 56K.Line cards know nothing about robbed bit signaling. And therefore robbed bit signaling has nothing to do with the bit rate for a PAM digital signal on the wire side of a line card.>If you have a crappy phone line with >poor S/N your rates going way down. A pointless quibble perhaps but >its late & I'm bored. > >> >>Bandwidth does not use more bitrate, it provides more! > >From the OP's question I'd say you're putting the cart before the >horse. Bitrate uses Bandwidth, spectrally speaking.Which is why bandwidth *provides* more bitrate. You are confused.>How much depends >on the modulation method, QAM, QPSK, FSK, FM, CW yadda yadda. >Bandwidth is not an unlimited resource, not everybody has the luxury >of multiple dark fibers in the ground between here & there. There are >very real- er, um, real world constraints with systems such as >satellite, terrestrial M/W & the previously mentioned wireless >systems.So?>>Shannon showed channel capacity to be relative to both bandwidth >>and signal-to-noise ratio. Anything you do to change one >>*requires* a change in the other to maintain the same maximum >>capacity. Different carrier systems do exactly that, balancing >>between SNR and bandwidth. > >I could have sworn thats what I was getting at by way of the examples >of cellular transmission standards, but what the hell do I know ???Swear all you like, but that isn't what you said.>>Bandwidth is not what makes digital more effective than analog. > >Agreed. Whole heartedly. > >>Above a minimum SNR digital systems are essentially error free >>while analog system have additive noise. > >Unfortunately bandwidth is never unlimited & the noise level can >occaisionally be out of your control.A useless statement of no significance.>Digital systems are far less >tolerent of noise when it *does* exceed the critical level. Analog >systems get "hissy", digitas ge& ..or_de^5T3+...Wrong. A digital system can function error free at an SNR so low that analog systems cannot function at all, much less simply get hissy.>>digital is usually prefered. The second most significant reason >>is the ease with which digital carrier systems can be designed >>to trade SNR for bandwidth by using multi-level encoding, which >>means well matched adaptions to anything from very noisy fiber >>optics to very quiet coax cable. > >True, although as I also alluded to encoding & error protection >schemes eat into the actual traffic throughput for a given system at >layer 1. You can over come a shit load of noise with the right setup, >but if you have to send a million bits to get one bit of payload >through to the customer you're better off hand delivering the message.More prattle? -- Floyd L. Davidson <http://www.apaflo.com/floyd_davidson> Ukpeagvik (Barrow, Alaska) floyd@apaflo.com
Reply by ●October 29, 20062006-10-29
Howard Eisenhauer <howarde@REMOVECAPShfx.eastlink.ca> wrote:>On Fri, 27 Oct 2006 20:38:37 -0800, floyd@apaflo.com (Floyd L. >Davidson) wrote: > >>Howard Eisenhauer <howarde@REMOVECAPShfx.eastlink.ca> wrote: >>>On Fri, 27 Oct 2006 10:29:06 -0500, no-top-post wrote: >>> >>>>It's common knowledge that digital technology gives more telephone >>>>[4 Khz wide] channels than analog technology - for the same spectrum >>>>width. This even with the steep-sided filters and SSB technology. >>>> >>>T'aint nesessarily so. As another poster pointed out FDM could >>>squeeze 24 channels os SSB 4kz voice into 96 KHz. where a T1 takes >>>over 1.5 megabits/sec to do the same thing. >> >>Comparing bandwidth to bit rate is nonsense! 96 KHz does not >>compare to 1.5 Mbps in any productive way. > >Lets define "Bandwidth"- Bandwidth properly refers to spectrum & is >measured in Hz. If you're talking "bitrates" then you're refering to >a system with a fixed transmission capacity. Whether or not it's >being used efficiently is measured by what % of the data stream >consists of overhead messages & empty data octets.Hence comparing bandwith (spectrum) to bitrate (capacity) is nonsense. Added prattle doesn't change that.>The OP was talking about "efficiency", more or less relating to voice >circuits. Without a doubt the standard reference of a 4 KHz voice >channel it's more efficient spectrally to use FDM than to move 24 >voice channels than to use a T1. In fact, as the T1 spec requires a >pulse shape that's more or less square that implies at least 3rd order >harmonics @ 4.5 MHz. You can fit 600 FDM voice channels in that >space.T1 does *not* require a square pulse shape. It requires 750 Khz bandwidth. It was not designed for efficient spectrum utilization, because that is not required on a twisted pair cable. However, since it was designed to replace a single 4 KHz voice circuit with 24 each 4 KHz voice circuits (granted with lower SNR), it is hard to accept your argument that a T1 represents bandwidth inefficency as such. Since nobody puts 600 FDM voice channels on a twisted pair, I can't see where you can claim that many will fit, eh?>>Keep in mind that a telco voice channel is 4 KHz analog, but >>over the same bandwidth one can easily send a 64 Kbps digital >>PAM signal (i.e., v.90) using the exact same codec in the >>telephone switch line card. > >Well, that sort of figures as a standard digital voice channel is >64K/sec anyhow. You certainly can't squeeze a higher bitrate from >your modem through there. & how much you can send depends on the >card, if its using robbed bit signalling (yes, its still in use here & >there) you're limited to 56K.Line cards know nothing about robbed bit signaling. And therefore robbed bit signaling has nothing to do with the bit rate for a PAM digital signal on the wire side of a line card.>If you have a crappy phone line with >poor S/N your rates going way down. A pointless quibble perhaps but >its late & I'm bored. > >> >>Bandwidth does not use more bitrate, it provides more! > >From the OP's question I'd say you're putting the cart before the >horse. Bitrate uses Bandwidth, spectrally speaking.Which is why bandwidth *provides* more bitrate. You are confused.>How much depends >on the modulation method, QAM, QPSK, FSK, FM, CW yadda yadda. >Bandwidth is not an unlimited resource, not everybody has the luxury >of multiple dark fibers in the ground between here & there. There are >very real- er, um, real world constraints with systems such as >satellite, terrestrial M/W & the previously mentioned wireless >systems.So?>>Shannon showed channel capacity to be relative to both bandwidth >>and signal-to-noise ratio. Anything you do to change one >>*requires* a change in the other to maintain the same maximum >>capacity. Different carrier systems do exactly that, balancing >>between SNR and bandwidth. > >I could have sworn thats what I was getting at by way of the examples >of cellular transmission standards, but what the hell do I know ???Swear all you like, but that isn't what you said.>>Bandwidth is not what makes digital more effective than analog. > >Agreed. Whole heartedly. > >>Above a minimum SNR digital systems are essentially error free >>while analog system have additive noise. > >Unfortunately bandwidth is never unlimited & the noise level can >occaisionally be out of your control.A useless statement of no significance.>Digital systems are far less >tolerent of noise when it *does* exceed the critical level. Analog >systems get "hissy", digitas ge& ..or_de^5T3+...Wrong. A digital system can function error free at an SNR so low that analog systems cannot function at all, much less simply get hissy.>>digital is usually prefered. The second most significant reason >>is the ease with which digital carrier systems can be designed >>to trade SNR for bandwidth by using multi-level encoding, which >>means well matched adaptions to anything from very noisy fiber >>optics to very quiet coax cable. > >True, although as I also alluded to encoding & error protection >schemes eat into the actual traffic throughput for a given system at >layer 1. You can over come a shit load of noise with the right setup, >but if you have to send a million bits to get one bit of payload >through to the customer you're better off hand delivering the message.More prattle? -- Floyd L. Davidson <http://www.apaflo.com/floyd_davidson> Ukpeagvik (Barrow, Alaska) floyd@apaflo.com
Reply by ●October 29, 20062006-10-29
Howard Eisenhauer <howarde@REMOVECAPShfx.eastlink.ca> wrote:>On Fri, 27 Oct 2006 20:38:37 -0800, floyd@apaflo.com (Floyd L. >Davidson) wrote: > >>Howard Eisenhauer <howarde@REMOVECAPShfx.eastlink.ca> wrote: >>>On Fri, 27 Oct 2006 10:29:06 -0500, no-top-post wrote: >>> >>>>It's common knowledge that digital technology gives more telephone >>>>[4 Khz wide] channels than analog technology - for the same spectrum >>>>width. This even with the steep-sided filters and SSB technology. >>>> >>>T'aint nesessarily so. As another poster pointed out FDM could >>>squeeze 24 channels os SSB 4kz voice into 96 KHz. where a T1 takes >>>over 1.5 megabits/sec to do the same thing. >> >>Comparing bandwidth to bit rate is nonsense! 96 KHz does not >>compare to 1.5 Mbps in any productive way. > >Lets define "Bandwidth"- Bandwidth properly refers to spectrum & is >measured in Hz. If you're talking "bitrates" then you're refering to >a system with a fixed transmission capacity. Whether or not it's >being used efficiently is measured by what % of the data stream >consists of overhead messages & empty data octets.Hence comparing bandwith (spectrum) to bitrate (capacity) is nonsense. Added prattle doesn't change that.>The OP was talking about "efficiency", more or less relating to voice >circuits. Without a doubt the standard reference of a 4 KHz voice >channel it's more efficient spectrally to use FDM than to move 24 >voice channels than to use a T1. In fact, as the T1 spec requires a >pulse shape that's more or less square that implies at least 3rd order >harmonics @ 4.5 MHz. You can fit 600 FDM voice channels in that >space.T1 does *not* require a square pulse shape. It requires 750 Khz bandwidth. It was not designed for efficient spectrum utilization, because that is not required on a twisted pair cable. However, since it was designed to replace a single 4 KHz voice circuit with 24 each 4 KHz voice circuits (granted with lower SNR), it is hard to accept your argument that a T1 represents bandwidth inefficency as such. Since nobody puts 600 FDM voice channels on a twisted pair, I can't see where you can claim that many will fit, eh?>>Keep in mind that a telco voice channel is 4 KHz analog, but >>over the same bandwidth one can easily send a 64 Kbps digital >>PAM signal (i.e., v.90) using the exact same codec in the >>telephone switch line card. > >Well, that sort of figures as a standard digital voice channel is >64K/sec anyhow. You certainly can't squeeze a higher bitrate from >your modem through there. & how much you can send depends on the >card, if its using robbed bit signalling (yes, its still in use here & >there) you're limited to 56K.Line cards know nothing about robbed bit signaling. And therefore robbed bit signaling has nothing to do with the bit rate for a PAM digital signal on the wire side of a line card.>If you have a crappy phone line with >poor S/N your rates going way down. A pointless quibble perhaps but >its late & I'm bored. > >> >>Bandwidth does not use more bitrate, it provides more! > >From the OP's question I'd say you're putting the cart before the >horse. Bitrate uses Bandwidth, spectrally speaking.Which is why bandwidth *provides* more bitrate. You are confused.>How much depends >on the modulation method, QAM, QPSK, FSK, FM, CW yadda yadda. >Bandwidth is not an unlimited resource, not everybody has the luxury >of multiple dark fibers in the ground between here & there. There are >very real- er, um, real world constraints with systems such as >satellite, terrestrial M/W & the previously mentioned wireless >systems.So?>>Shannon showed channel capacity to be relative to both bandwidth >>and signal-to-noise ratio. Anything you do to change one >>*requires* a change in the other to maintain the same maximum >>capacity. Different carrier systems do exactly that, balancing >>between SNR and bandwidth. > >I could have sworn thats what I was getting at by way of the examples >of cellular transmission standards, but what the hell do I know ???Swear all you like, but that isn't what you said.>>Bandwidth is not what makes digital more effective than analog. > >Agreed. Whole heartedly. > >>Above a minimum SNR digital systems are essentially error free >>while analog system have additive noise. > >Unfortunately bandwidth is never unlimited & the noise level can >occaisionally be out of your control.A useless statement of no significance.>Digital systems are far less >tolerent of noise when it *does* exceed the critical level. Analog >systems get "hissy", digitas ge& ..or_de^5T3+...Wrong. A digital system can function error free at an SNR so low that analog systems cannot function at all, much less simply get hissy.>>digital is usually prefered. The second most significant reason >>is the ease with which digital carrier systems can be designed >>to trade SNR for bandwidth by using multi-level encoding, which >>means well matched adaptions to anything from very noisy fiber >>optics to very quiet coax cable. > >True, although as I also alluded to encoding & error protection >schemes eat into the actual traffic throughput for a given system at >layer 1. You can over come a shit load of noise with the right setup, >but if you have to send a million bits to get one bit of payload >through to the customer you're better off hand delivering the message.More prattle? -- Floyd L. Davidson <http://www.apaflo.com/floyd_davidson> Ukpeagvik (Barrow, Alaska) floyd@apaflo.com
Reply by ●October 29, 20062006-10-29
Howard Eisenhauer <howarde@REMOVECAPShfx.eastlink.ca> wrote:>On Fri, 27 Oct 2006 20:38:37 -0800, floyd@apaflo.com (Floyd L. >Davidson) wrote: > >>Howard Eisenhauer <howarde@REMOVECAPShfx.eastlink.ca> wrote: >>>On Fri, 27 Oct 2006 10:29:06 -0500, no-top-post wrote: >>> >>>>It's common knowledge that digital technology gives more telephone >>>>[4 Khz wide] channels than analog technology - for the same spectrum >>>>width. This even with the steep-sided filters and SSB technology. >>>> >>>T'aint nesessarily so. As another poster pointed out FDM could >>>squeeze 24 channels os SSB 4kz voice into 96 KHz. where a T1 takes >>>over 1.5 megabits/sec to do the same thing. >> >>Comparing bandwidth to bit rate is nonsense! 96 KHz does not >>compare to 1.5 Mbps in any productive way. > >Lets define "Bandwidth"- Bandwidth properly refers to spectrum & is >measured in Hz. If you're talking "bitrates" then you're refering to >a system with a fixed transmission capacity. Whether or not it's >being used efficiently is measured by what % of the data stream >consists of overhead messages & empty data octets.Hence comparing bandwith (spectrum) to bitrate (capacity) is nonsense. Added prattle doesn't change that.>The OP was talking about "efficiency", more or less relating to voice >circuits. Without a doubt the standard reference of a 4 KHz voice >channel it's more efficient spectrally to use FDM than to move 24 >voice channels than to use a T1. In fact, as the T1 spec requires a >pulse shape that's more or less square that implies at least 3rd order >harmonics @ 4.5 MHz. You can fit 600 FDM voice channels in that >space.T1 does *not* require a square pulse shape. It requires 750 Khz bandwidth. It was not designed for efficient spectrum utilization, because that is not required on a twisted pair cable. However, since it was designed to replace a single 4 KHz voice circuit with 24 each 4 KHz voice circuits (granted with lower SNR), it is hard to accept your argument that a T1 represents bandwidth inefficency as such. Since nobody puts 600 FDM voice channels on a twisted pair, I can't see where you can claim that many will fit, eh?>>Keep in mind that a telco voice channel is 4 KHz analog, but >>over the same bandwidth one can easily send a 64 Kbps digital >>PAM signal (i.e., v.90) using the exact same codec in the >>telephone switch line card. > >Well, that sort of figures as a standard digital voice channel is >64K/sec anyhow. You certainly can't squeeze a higher bitrate from >your modem through there. & how much you can send depends on the >card, if its using robbed bit signalling (yes, its still in use here & >there) you're limited to 56K.Line cards know nothing about robbed bit signaling. And therefore robbed bit signaling has nothing to do with the bit rate for a PAM digital signal on the wire side of a line card.>If you have a crappy phone line with >poor S/N your rates going way down. A pointless quibble perhaps but >its late & I'm bored. > >> >>Bandwidth does not use more bitrate, it provides more! > >From the OP's question I'd say you're putting the cart before the >horse. Bitrate uses Bandwidth, spectrally speaking.Which is why bandwidth *provides* more bitrate. You are confused.>How much depends >on the modulation method, QAM, QPSK, FSK, FM, CW yadda yadda. >Bandwidth is not an unlimited resource, not everybody has the luxury >of multiple dark fibers in the ground between here & there. There are >very real- er, um, real world constraints with systems such as >satellite, terrestrial M/W & the previously mentioned wireless >systems.So?>>Shannon showed channel capacity to be relative to both bandwidth >>and signal-to-noise ratio. Anything you do to change one >>*requires* a change in the other to maintain the same maximum >>capacity. Different carrier systems do exactly that, balancing >>between SNR and bandwidth. > >I could have sworn thats what I was getting at by way of the examples >of cellular transmission standards, but what the hell do I know ???Swear all you like, but that isn't what you said.>>Bandwidth is not what makes digital more effective than analog. > >Agreed. Whole heartedly. > >>Above a minimum SNR digital systems are essentially error free >>while analog system have additive noise. > >Unfortunately bandwidth is never unlimited & the noise level can >occaisionally be out of your control.A useless statement of no significance.>Digital systems are far less >tolerent of noise when it *does* exceed the critical level. Analog >systems get "hissy", digitas ge& ..or_de^5T3+...Wrong. A digital system can function error free at an SNR so low that analog systems cannot function at all, much less simply get hissy.>>digital is usually prefered. The second most significant reason >>is the ease with which digital carrier systems can be designed >>to trade SNR for bandwidth by using multi-level encoding, which >>means well matched adaptions to anything from very noisy fiber >>optics to very quiet coax cable. > >True, although as I also alluded to encoding & error protection >schemes eat into the actual traffic throughput for a given system at >layer 1. You can over come a shit load of noise with the right setup, >but if you have to send a million bits to get one bit of payload >through to the customer you're better off hand delivering the message.More prattle? -- Floyd L. Davidson <http://www.apaflo.com/floyd_davidson> Ukpeagvik (Barrow, Alaska) floyd@apaflo.com
Reply by ●October 29, 20062006-10-29
Howard Eisenhauer <howarde@REMOVECAPShfx.eastlink.ca> wrote:>On Fri, 27 Oct 2006 20:38:37 -0800, floyd@apaflo.com (Floyd L. >Davidson) wrote: > >>Howard Eisenhauer <howarde@REMOVECAPShfx.eastlink.ca> wrote: >>>On Fri, 27 Oct 2006 10:29:06 -0500, no-top-post wrote: >>> >>>>It's common knowledge that digital technology gives more telephone >>>>[4 Khz wide] channels than analog technology - for the same spectrum >>>>width. This even with the steep-sided filters and SSB technology. >>>> >>>T'aint nesessarily so. As another poster pointed out FDM could >>>squeeze 24 channels os SSB 4kz voice into 96 KHz. where a T1 takes >>>over 1.5 megabits/sec to do the same thing. >> >>Comparing bandwidth to bit rate is nonsense! 96 KHz does not >>compare to 1.5 Mbps in any productive way. > >Lets define "Bandwidth"- Bandwidth properly refers to spectrum & is >measured in Hz. If you're talking "bitrates" then you're refering to >a system with a fixed transmission capacity. Whether or not it's >being used efficiently is measured by what % of the data stream >consists of overhead messages & empty data octets.Hence comparing bandwith (spectrum) to bitrate (capacity) is nonsense. Added prattle doesn't change that.>The OP was talking about "efficiency", more or less relating to voice >circuits. Without a doubt the standard reference of a 4 KHz voice >channel it's more efficient spectrally to use FDM than to move 24 >voice channels than to use a T1. In fact, as the T1 spec requires a >pulse shape that's more or less square that implies at least 3rd order >harmonics @ 4.5 MHz. You can fit 600 FDM voice channels in that >space.T1 does *not* require a square pulse shape. It requires 750 Khz bandwidth. It was not designed for efficient spectrum utilization, because that is not required on a twisted pair cable. However, since it was designed to replace a single 4 KHz voice circuit with 24 each 4 KHz voice circuits (granted with lower SNR), it is hard to accept your argument that a T1 represents bandwidth inefficency as such. Since nobody puts 600 FDM voice channels on a twisted pair, I can't see where you can claim that many will fit, eh?>>Keep in mind that a telco voice channel is 4 KHz analog, but >>over the same bandwidth one can easily send a 64 Kbps digital >>PAM signal (i.e., v.90) using the exact same codec in the >>telephone switch line card. > >Well, that sort of figures as a standard digital voice channel is >64K/sec anyhow. You certainly can't squeeze a higher bitrate from >your modem through there. & how much you can send depends on the >card, if its using robbed bit signalling (yes, its still in use here & >there) you're limited to 56K.Line cards know nothing about robbed bit signaling. And therefore robbed bit signaling has nothing to do with the bit rate for a PAM digital signal on the wire side of a line card.>If you have a crappy phone line with >poor S/N your rates going way down. A pointless quibble perhaps but >its late & I'm bored. > >> >>Bandwidth does not use more bitrate, it provides more! > >From the OP's question I'd say you're putting the cart before the >horse. Bitrate uses Bandwidth, spectrally speaking.Which is why bandwidth *provides* more bitrate. You are confused.>How much depends >on the modulation method, QAM, QPSK, FSK, FM, CW yadda yadda. >Bandwidth is not an unlimited resource, not everybody has the luxury >of multiple dark fibers in the ground between here & there. There are >very real- er, um, real world constraints with systems such as >satellite, terrestrial M/W & the previously mentioned wireless >systems.So?>>Shannon showed channel capacity to be relative to both bandwidth >>and signal-to-noise ratio. Anything you do to change one >>*requires* a change in the other to maintain the same maximum >>capacity. Different carrier systems do exactly that, balancing >>between SNR and bandwidth. > >I could have sworn thats what I was getting at by way of the examples >of cellular transmission standards, but what the hell do I know ???Swear all you like, but that isn't what you said.>>Bandwidth is not what makes digital more effective than analog. > >Agreed. Whole heartedly. > >>Above a minimum SNR digital systems are essentially error free >>while analog system have additive noise. > >Unfortunately bandwidth is never unlimited & the noise level can >occaisionally be out of your control.A useless statement of no significance.>Digital systems are far less >tolerent of noise when it *does* exceed the critical level. Analog >systems get "hissy", digitas ge& ..or_de^5T3+...Wrong. A digital system can function error free at an SNR so low that analog systems cannot function at all, much less simply get hissy.>>digital is usually prefered. The second most significant reason >>is the ease with which digital carrier systems can be designed >>to trade SNR for bandwidth by using multi-level encoding, which >>means well matched adaptions to anything from very noisy fiber >>optics to very quiet coax cable. > >True, although as I also alluded to encoding & error protection >schemes eat into the actual traffic throughput for a given system at >layer 1. You can over come a shit load of noise with the right setup, >but if you have to send a million bits to get one bit of payload >through to the customer you're better off hand delivering the message.More prattle? -- Floyd L. Davidson <http://www.apaflo.com/floyd_davidson> Ukpeagvik (Barrow, Alaska) floyd@apaflo.com
Reply by ●October 29, 20062006-10-29
Howard Eisenhauer <howarde@REMOVECAPShfx.eastlink.ca> wrote:>On Fri, 27 Oct 2006 20:38:37 -0800, floyd@apaflo.com (Floyd L. >Davidson) wrote: > >>Howard Eisenhauer <howarde@REMOVECAPShfx.eastlink.ca> wrote: >>>On Fri, 27 Oct 2006 10:29:06 -0500, no-top-post wrote: >>> >>>>It's common knowledge that digital technology gives more telephone >>>>[4 Khz wide] channels than analog technology - for the same spectrum >>>>width. This even with the steep-sided filters and SSB technology. >>>> >>>T'aint nesessarily so. As another poster pointed out FDM could >>>squeeze 24 channels os SSB 4kz voice into 96 KHz. where a T1 takes >>>over 1.5 megabits/sec to do the same thing. >> >>Comparing bandwidth to bit rate is nonsense! 96 KHz does not >>compare to 1.5 Mbps in any productive way. > >Lets define "Bandwidth"- Bandwidth properly refers to spectrum & is >measured in Hz. If you're talking "bitrates" then you're refering to >a system with a fixed transmission capacity. Whether or not it's >being used efficiently is measured by what % of the data stream >consists of overhead messages & empty data octets.Hence comparing bandwith (spectrum) to bitrate (capacity) is nonsense. Added prattle doesn't change that.>The OP was talking about "efficiency", more or less relating to voice >circuits. Without a doubt the standard reference of a 4 KHz voice >channel it's more efficient spectrally to use FDM than to move 24 >voice channels than to use a T1. In fact, as the T1 spec requires a >pulse shape that's more or less square that implies at least 3rd order >harmonics @ 4.5 MHz. You can fit 600 FDM voice channels in that >space.T1 does *not* require a square pulse shape. It requires 750 Khz bandwidth. It was not designed for efficient spectrum utilization, because that is not required on a twisted pair cable. However, since it was designed to replace a single 4 KHz voice circuit with 24 each 4 KHz voice circuits (granted with lower SNR), it is hard to accept your argument that a T1 represents bandwidth inefficency as such. Since nobody puts 600 FDM voice channels on a twisted pair, I can't see where you can claim that many will fit, eh?>>Keep in mind that a telco voice channel is 4 KHz analog, but >>over the same bandwidth one can easily send a 64 Kbps digital >>PAM signal (i.e., v.90) using the exact same codec in the >>telephone switch line card. > >Well, that sort of figures as a standard digital voice channel is >64K/sec anyhow. You certainly can't squeeze a higher bitrate from >your modem through there. & how much you can send depends on the >card, if its using robbed bit signalling (yes, its still in use here & >there) you're limited to 56K.Line cards know nothing about robbed bit signaling. And therefore robbed bit signaling has nothing to do with the bit rate for a PAM digital signal on the wire side of a line card.>If you have a crappy phone line with >poor S/N your rates going way down. A pointless quibble perhaps but >its late & I'm bored. > >> >>Bandwidth does not use more bitrate, it provides more! > >From the OP's question I'd say you're putting the cart before the >horse. Bitrate uses Bandwidth, spectrally speaking.Which is why bandwidth *provides* more bitrate. You are confused.>How much depends >on the modulation method, QAM, QPSK, FSK, FM, CW yadda yadda. >Bandwidth is not an unlimited resource, not everybody has the luxury >of multiple dark fibers in the ground between here & there. There are >very real- er, um, real world constraints with systems such as >satellite, terrestrial M/W & the previously mentioned wireless >systems.So?>>Shannon showed channel capacity to be relative to both bandwidth >>and signal-to-noise ratio. Anything you do to change one >>*requires* a change in the other to maintain the same maximum >>capacity. Different carrier systems do exactly that, balancing >>between SNR and bandwidth. > >I could have sworn thats what I was getting at by way of the examples >of cellular transmission standards, but what the hell do I know ???Swear all you like, but that isn't what you said.>>Bandwidth is not what makes digital more effective than analog. > >Agreed. Whole heartedly. > >>Above a minimum SNR digital systems are essentially error free >>while analog system have additive noise. > >Unfortunately bandwidth is never unlimited & the noise level can >occaisionally be out of your control.A useless statement of no significance.>Digital systems are far less >tolerent of noise when it *does* exceed the critical level. Analog >systems get "hissy", digitas ge& ..or_de^5T3+...Wrong. A digital system can function error free at an SNR so low that analog systems cannot function at all, much less simply get hissy.>>digital is usually prefered. The second most significant reason >>is the ease with which digital carrier systems can be designed >>to trade SNR for bandwidth by using multi-level encoding, which >>means well matched adaptions to anything from very noisy fiber >>optics to very quiet coax cable. > >True, although as I also alluded to encoding & error protection >schemes eat into the actual traffic throughput for a given system at >layer 1. You can over come a shit load of noise with the right setup, >but if you have to send a million bits to get one bit of payload >through to the customer you're better off hand delivering the message.More prattle? -- Floyd L. Davidson <http://www.apaflo.com/floyd_davidson> Ukpeagvik (Barrow, Alaska) floyd@apaflo.com
Reply by ●October 29, 20062006-10-29
Howard Eisenhauer <howarde@REMOVECAPShfx.eastlink.ca> wrote:>On Fri, 27 Oct 2006 20:38:37 -0800, floyd@apaflo.com (Floyd L. >Davidson) wrote: > >>Howard Eisenhauer <howarde@REMOVECAPShfx.eastlink.ca> wrote: >>>On Fri, 27 Oct 2006 10:29:06 -0500, no-top-post wrote: >>> >>>>It's common knowledge that digital technology gives more telephone >>>>[4 Khz wide] channels than analog technology - for the same spectrum >>>>width. This even with the steep-sided filters and SSB technology. >>>> >>>T'aint nesessarily so. As another poster pointed out FDM could >>>squeeze 24 channels os SSB 4kz voice into 96 KHz. where a T1 takes >>>over 1.5 megabits/sec to do the same thing. >> >>Comparing bandwidth to bit rate is nonsense! 96 KHz does not >>compare to 1.5 Mbps in any productive way. > >Lets define "Bandwidth"- Bandwidth properly refers to spectrum & is >measured in Hz. If you're talking "bitrates" then you're refering to >a system with a fixed transmission capacity. Whether or not it's >being used efficiently is measured by what % of the data stream >consists of overhead messages & empty data octets.Hence comparing bandwith (spectrum) to bitrate (capacity) is nonsense. Added prattle doesn't change that.>The OP was talking about "efficiency", more or less relating to voice >circuits. Without a doubt the standard reference of a 4 KHz voice >channel it's more efficient spectrally to use FDM than to move 24 >voice channels than to use a T1. In fact, as the T1 spec requires a >pulse shape that's more or less square that implies at least 3rd order >harmonics @ 4.5 MHz. You can fit 600 FDM voice channels in that >space.T1 does *not* require a square pulse shape. It requires 750 Khz bandwidth. It was not designed for efficient spectrum utilization, because that is not required on a twisted pair cable. However, since it was designed to replace a single 4 KHz voice circuit with 24 each 4 KHz voice circuits (granted with lower SNR), it is hard to accept your argument that a T1 represents bandwidth inefficency as such. Since nobody puts 600 FDM voice channels on a twisted pair, I can't see where you can claim that many will fit, eh?>>Keep in mind that a telco voice channel is 4 KHz analog, but >>over the same bandwidth one can easily send a 64 Kbps digital >>PAM signal (i.e., v.90) using the exact same codec in the >>telephone switch line card. > >Well, that sort of figures as a standard digital voice channel is >64K/sec anyhow. You certainly can't squeeze a higher bitrate from >your modem through there. & how much you can send depends on the >card, if its using robbed bit signalling (yes, its still in use here & >there) you're limited to 56K.Line cards know nothing about robbed bit signaling. And therefore robbed bit signaling has nothing to do with the bit rate for a PAM digital signal on the wire side of a line card.>If you have a crappy phone line with >poor S/N your rates going way down. A pointless quibble perhaps but >its late & I'm bored. > >> >>Bandwidth does not use more bitrate, it provides more! > >From the OP's question I'd say you're putting the cart before the >horse. Bitrate uses Bandwidth, spectrally speaking.Which is why bandwidth *provides* more bitrate. You are confused.>How much depends >on the modulation method, QAM, QPSK, FSK, FM, CW yadda yadda. >Bandwidth is not an unlimited resource, not everybody has the luxury >of multiple dark fibers in the ground between here & there. There are >very real- er, um, real world constraints with systems such as >satellite, terrestrial M/W & the previously mentioned wireless >systems.So?>>Shannon showed channel capacity to be relative to both bandwidth >>and signal-to-noise ratio. Anything you do to change one >>*requires* a change in the other to maintain the same maximum >>capacity. Different carrier systems do exactly that, balancing >>between SNR and bandwidth. > >I could have sworn thats what I was getting at by way of the examples >of cellular transmission standards, but what the hell do I know ???Swear all you like, but that isn't what you said.>>Bandwidth is not what makes digital more effective than analog. > >Agreed. Whole heartedly. > >>Above a minimum SNR digital systems are essentially error free >>while analog system have additive noise. > >Unfortunately bandwidth is never unlimited & the noise level can >occaisionally be out of your control.A useless statement of no significance.>Digital systems are far less >tolerent of noise when it *does* exceed the critical level. Analog >systems get "hissy", digitas ge& ..or_de^5T3+...Wrong. A digital system can function error free at an SNR so low that analog systems cannot function at all, much less simply get hissy.>>digital is usually prefered. The second most significant reason >>is the ease with which digital carrier systems can be designed >>to trade SNR for bandwidth by using multi-level encoding, which >>means well matched adaptions to anything from very noisy fiber >>optics to very quiet coax cable. > >True, although as I also alluded to encoding & error protection >schemes eat into the actual traffic throughput for a given system at >layer 1. You can over come a shit load of noise with the right setup, >but if you have to send a million bits to get one bit of payload >through to the customer you're better off hand delivering the message.More prattle? -- Floyd L. Davidson <http://www.apaflo.com/floyd_davidson> Ukpeagvik (Barrow, Alaska) floyd@apaflo.com
Reply by ●October 29, 20062006-10-29
Howard Eisenhauer <howarde@REMOVECAPShfx.eastlink.ca> wrote:>On Fri, 27 Oct 2006 20:38:37 -0800, floyd@apaflo.com (Floyd L. >Davidson) wrote: > >>Howard Eisenhauer <howarde@REMOVECAPShfx.eastlink.ca> wrote: >>>On Fri, 27 Oct 2006 10:29:06 -0500, no-top-post wrote: >>> >>>>It's common knowledge that digital technology gives more telephone >>>>[4 Khz wide] channels than analog technology - for the same spectrum >>>>width. This even with the steep-sided filters and SSB technology. >>>> >>>T'aint nesessarily so. As another poster pointed out FDM could >>>squeeze 24 channels os SSB 4kz voice into 96 KHz. where a T1 takes >>>over 1.5 megabits/sec to do the same thing. >> >>Comparing bandwidth to bit rate is nonsense! 96 KHz does not >>compare to 1.5 Mbps in any productive way. > >Lets define "Bandwidth"- Bandwidth properly refers to spectrum & is >measured in Hz. If you're talking "bitrates" then you're refering to >a system with a fixed transmission capacity. Whether or not it's >being used efficiently is measured by what % of the data stream >consists of overhead messages & empty data octets.Hence comparing bandwith (spectrum) to bitrate (capacity) is nonsense. Added prattle doesn't change that.>The OP was talking about "efficiency", more or less relating to voice >circuits. Without a doubt the standard reference of a 4 KHz voice >channel it's more efficient spectrally to use FDM than to move 24 >voice channels than to use a T1. In fact, as the T1 spec requires a >pulse shape that's more or less square that implies at least 3rd order >harmonics @ 4.5 MHz. You can fit 600 FDM voice channels in that >space.T1 does *not* require a square pulse shape. It requires 750 Khz bandwidth. It was not designed for efficient spectrum utilization, because that is not required on a twisted pair cable. However, since it was designed to replace a single 4 KHz voice circuit with 24 each 4 KHz voice circuits (granted with lower SNR), it is hard to accept your argument that a T1 represents bandwidth inefficency as such. Since nobody puts 600 FDM voice channels on a twisted pair, I can't see where you can claim that many will fit, eh?>>Keep in mind that a telco voice channel is 4 KHz analog, but >>over the same bandwidth one can easily send a 64 Kbps digital >>PAM signal (i.e., v.90) using the exact same codec in the >>telephone switch line card. > >Well, that sort of figures as a standard digital voice channel is >64K/sec anyhow. You certainly can't squeeze a higher bitrate from >your modem through there. & how much you can send depends on the >card, if its using robbed bit signalling (yes, its still in use here & >there) you're limited to 56K.Line cards know nothing about robbed bit signaling. And therefore robbed bit signaling has nothing to do with the bit rate for a PAM digital signal on the wire side of a line card.>If you have a crappy phone line with >poor S/N your rates going way down. A pointless quibble perhaps but >its late & I'm bored. > >> >>Bandwidth does not use more bitrate, it provides more! > >From the OP's question I'd say you're putting the cart before the >horse. Bitrate uses Bandwidth, spectrally speaking.Which is why bandwidth *provides* more bitrate. You are confused.>How much depends >on the modulation method, QAM, QPSK, FSK, FM, CW yadda yadda. >Bandwidth is not an unlimited resource, not everybody has the luxury >of multiple dark fibers in the ground between here & there. There are >very real- er, um, real world constraints with systems such as >satellite, terrestrial M/W & the previously mentioned wireless >systems.So?>>Shannon showed channel capacity to be relative to both bandwidth >>and signal-to-noise ratio. Anything you do to change one >>*requires* a change in the other to maintain the same maximum >>capacity. Different carrier systems do exactly that, balancing >>between SNR and bandwidth. > >I could have sworn thats what I was getting at by way of the examples >of cellular transmission standards, but what the hell do I know ???Swear all you like, but that isn't what you said.>>Bandwidth is not what makes digital more effective than analog. > >Agreed. Whole heartedly. > >>Above a minimum SNR digital systems are essentially error free >>while analog system have additive noise. > >Unfortunately bandwidth is never unlimited & the noise level can >occaisionally be out of your control.A useless statement of no significance.>Digital systems are far less >tolerent of noise when it *does* exceed the critical level. Analog >systems get "hissy", digitas ge& ..or_de^5T3+...Wrong. A digital system can function error free at an SNR so low that analog systems cannot function at all, much less simply get hissy.>>digital is usually prefered. The second most significant reason >>is the ease with which digital carrier systems can be designed >>to trade SNR for bandwidth by using multi-level encoding, which >>means well matched adaptions to anything from very noisy fiber >>optics to very quiet coax cable. > >True, although as I also alluded to encoding & error protection >schemes eat into the actual traffic throughput for a given system at >layer 1. You can over come a shit load of noise with the right setup, >but if you have to send a million bits to get one bit of payload >through to the customer you're better off hand delivering the message.More prattle? -- Floyd L. Davidson <http://www.apaflo.com/floyd_davidson> Ukpeagvik (Barrow, Alaska) floyd@apaflo.com
