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#21
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Stewart Smith wrote:
"Paul F. Dietz" wrote in message ... Marc 182 wrote: Multi-jump communications would create unacceptable delay in a voice conversation due to the speed of light and the distance to the satellites. Even a single jump causes a noticeable and annoying delay. That's why trans-Atlantic/Pacific cables remain popular. Cables are popular because they're *cheaper* than satellites (per unit of delivered bandwidth) what with the incredible advances in fiber optics. Has anybody ever heard of Echo-Cancelling devices? These can mitigate the effect of the "bounce" to a great degree. Also, to compensate further, "Reverb" can be added to flesh out tone and timbre. Echo cancelling does nothing to reduce time-of-flight issues. A half-second delay is still a half-second delay. Adding reverb is contraindicated for telephone communications, as it tends to reduce intelligibility. Check out speakerphones for examples thereof. As a matter of fact, there is a fair bit of research for _reducing_ reverberation in speakerphones. Signal processing techniques are not useful for fixing problems due to speed of light causing delays. 300,000 km/second: not just a good idea, it's the law. Francois. |
#22
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(replying to wrong article -- didn't see the
original.) In article , Marc 182 wrote: In article , says... Hello: 1. When you make an international phone call - say from NY to China - how does the voice data travel ? Does it have to be send to the satellite and then received at teh ground, some distance away, then sent to another satellite till it reaches the destination country. ? I mean is there any direct satellite to satellite communication. Or is it always bouncing between teh satellite and the ground at an angle. 2. Is this true for international television programming too ? I know there are live television from Arab countries, Japan etc, in US. Multi-jump communications would create unacceptable delay in a voice conversation due to the speed of light and the distance to the satellites. Even a single jump causes a noticeable and annoying delay. That's why trans-Atlantic/Pacific cables remain popular. Note that I didn't actually answer your question, because I don't know. The "unacceptable delays" come from Geostationary satellites. Iridium for example does do satellite-to-satellite switching in the sky. That turns out to be a bad idea for other reasons (basically the satellites are little telephone switches in the sky), but in LEO it doesn't add noticeable delays. Greg. -- Greg Rose 232B EC8F 44C6 C853 D68F E107 E6BF CD2F 1081 A37C Qualcomm Australia: http://www.qualcomm.com.au |
#23
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(replying to wrong article -- didn't see the
original.) In article , Marc 182 wrote: In article , says... Hello: 1. When you make an international phone call - say from NY to China - how does the voice data travel ? Does it have to be send to the satellite and then received at teh ground, some distance away, then sent to another satellite till it reaches the destination country. ? I mean is there any direct satellite to satellite communication. Or is it always bouncing between teh satellite and the ground at an angle. 2. Is this true for international television programming too ? I know there are live television from Arab countries, Japan etc, in US. Multi-jump communications would create unacceptable delay in a voice conversation due to the speed of light and the distance to the satellites. Even a single jump causes a noticeable and annoying delay. That's why trans-Atlantic/Pacific cables remain popular. Note that I didn't actually answer your question, because I don't know. The "unacceptable delays" come from Geostationary satellites. Iridium for example does do satellite-to-satellite switching in the sky. That turns out to be a bad idea for other reasons (basically the satellites are little telephone switches in the sky), but in LEO it doesn't add noticeable delays. Greg. -- Greg Rose 232B EC8F 44C6 C853 D68F E107 E6BF CD2F 1081 A37C Qualcomm Australia: http://www.qualcomm.com.au |
#24
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Echo cancellation reduces echo, it doesn't do anything to delay except
potentially add to it. Delay doesn't show up as an echo - echo is due to mismatches; delay is due to propagation delays, processing delays, and similar time-wasters. Ken "Stewart Smith" wrote in message y.com... Has anybody ever heard of Echo-Cancelling devices? These can mitigate the effect of the "bounce" to a great degree. Also, to compensate further, "Reverb" can be added to flesh out tone and timbre. just some info S Smith "Paul F. Dietz" wrote in message ... Marc 182 wrote: Multi-jump communications would create unacceptable delay in a voice conversation due to the speed of light and the distance to the satellites. Even a single jump causes a noticeable and annoying delay. That's why trans-Atlantic/Pacific cables remain popular. Cables are popular because they're *cheaper* than satellites (per unit of delivered bandwidth) what with the incredible advances in fiber optics. Paul --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.548 / Virus Database: 341 - Release Date: 12/5/03 |
#25
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Echo cancellation reduces echo, it doesn't do anything to delay except
potentially add to it. Delay doesn't show up as an echo - echo is due to mismatches; delay is due to propagation delays, processing delays, and similar time-wasters. Ken "Stewart Smith" wrote in message y.com... Has anybody ever heard of Echo-Cancelling devices? These can mitigate the effect of the "bounce" to a great degree. Also, to compensate further, "Reverb" can be added to flesh out tone and timbre. just some info S Smith "Paul F. Dietz" wrote in message ... Marc 182 wrote: Multi-jump communications would create unacceptable delay in a voice conversation due to the speed of light and the distance to the satellites. Even a single jump causes a noticeable and annoying delay. That's why trans-Atlantic/Pacific cables remain popular. Cables are popular because they're *cheaper* than satellites (per unit of delivered bandwidth) what with the incredible advances in fiber optics. Paul --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.548 / Virus Database: 341 - Release Date: 12/5/03 |
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#27
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#28
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In article ,
Ken Taylor wrote: ...Satellite to satellite can be done, as in the Iridium system, but I don't know of any other system off-hand which is commercial and made it to service. There's generally not actually a need. Iridium does it, and there is some use of GSO comsats to talk to stuff in low orbit (notably but not exclusively, NASA's TDRS system), but nobody's done GSO comsats with intersatellite links, yet. It's been talked about for some special purposes -- e.g., at one time, the DSP missile-warning satellites in GSO were going to have laser cross-links so that White Sands could talk to all of them without needing overseas ground stations -- but it hasn't actually happened yet. At least, not on anything unclassified. -- MOST launched 30 June; first light, 29 July; 5arcsec | Henry Spencer pointing, 10 Sept; first science, early Oct; all well. | |
#29
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In article ,
Ken Taylor wrote: ...Satellite to satellite can be done, as in the Iridium system, but I don't know of any other system off-hand which is commercial and made it to service. There's generally not actually a need. Iridium does it, and there is some use of GSO comsats to talk to stuff in low orbit (notably but not exclusively, NASA's TDRS system), but nobody's done GSO comsats with intersatellite links, yet. It's been talked about for some special purposes -- e.g., at one time, the DSP missile-warning satellites in GSO were going to have laser cross-links so that White Sands could talk to all of them without needing overseas ground stations -- but it hasn't actually happened yet. At least, not on anything unclassified. -- MOST launched 30 June; first light, 29 July; 5arcsec | Henry Spencer pointing, 10 Sept; first science, early Oct; all well. | |
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