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Satellite to Satellite communication ?



 
 
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  #11  
Old December 8th 03, 11:38 PM
Gregory G Rose
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Default Satellite to Satellite communication ?

(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.
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  #12  
Old December 9th 03, 12:37 AM
Ken Taylor
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Default Satellite to Satellite communication ?

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



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  #14  
Old December 9th 03, 06:14 AM
Henry Spencer
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Default Satellite to Satellite communication ?

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.
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pointing, 10 Sept; first science, early Oct; all well. |
  #16  
Old December 9th 03, 08:06 PM
Stewart Smith
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Default Satellite to Satellite communication ?



Thanks for setting me straight Francois, you are correct


"(null)" wrote in message news:1070919774.530038@smirk...
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.



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  #17  
Old December 10th 03, 01:53 AM
Joann Evans
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Default Satellite to Satellite communication ?

"Greg D. Moore (Strider)" wrote:

"Norris Watkins" wrote in message
om...
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.


Generally ground to sat to ground and that's it.

Sat to sat communication is fairly rare.


It's been my imprression that there may be some military sat-to-sat
stuff going on at 60 gigahertz. This band is readily absorbed by oxygen,
making ground intercept of these signals impractical.

(Googling for a minute)

Here's a reference:

http://www.ydi.com/deployinfo/wp-benefits-60ghz.php



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You know what to remove, to reply....

  #18  
Old December 10th 03, 07:35 AM
David Lesher
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Default Satellite to Satellite communication ?

"Ken Taylor" writes:

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.



You need a thiotimoline injector to solve the delay issue.
--
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& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433
  #19  
Old December 10th 03, 08:20 PM
Hop David
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Default Satellite to Satellite communication ?



Paul F. Dietz wrote:

Cables are popular because they're *cheaper* than satellites
(per unit of delivered bandwidth) what with the incredible advances
in fiber optics.

Paul



Perhaps for large metropolitan areas. I live in a little podunk place 120
miles from Tucson or Phoenix. Folks on the nearby rez who'd have no way
of getting fiber optic or cable are getting dishes.

However the metropolitan markets are much more lucrative. Don't know if
reaching the planet's rural areas justifies comsats.

--
Hop David
http://clowder.net/hop/index.html

 




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