Why Signal Latency is a Big Problem on Today’s Satellite Broadband?

Tue, Jan 3, 2012, by johndiaz

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Signal latency on today’s satellite broadband world is a very big problem. Some applications, like online games and remote surgery, fail and lose their ultimate use because they require a real-time user input. It is also irritating and incapacitating to those people who badly need to use the interactive applications such as VolP, videoconferencing, and other person-to-person communication.

Signal latency on today’s satellite broadband world is a very big problem. Some applications, like online games and remote surgery, fail and lose their ultimate use because they require a real-time user input. It is also irritating and incapacitating to those people who badly need to use the interactive applications such as VolP, videoconferencing, and other person-to-person communication.
Signal latency is the delay on requesting data and/or the response in a two-way communication on satellite broadband between the actual time of a signal’s broadcast and the time it was actually received caused by the distance (35,786 km/22,236 mi) the information is traveling from Earth to the satellite and back, common to all geostationary satellites. A theoretical minimum, this high level of latency is doubled before a reply is received for an Internet packet. The network sources divide among themselves the normal delays on a typical one-way connection latency of 500-700 ms from the user ISP, or about 1,000-1,400 ms latency for the total round trip time, or RTT, back to the user.
Looking motionless and fixed in the sky to ground observers, a geostationary orbit, or geostationary Earth orbit (GEO) satellite is not right for low-latency applications because of its geosynchronous orbit directly above the Earth’s equator with a period same to the Earth’s rotational period and an orbital eccentricity of approximately zero. Communication satellite and weather satellite usually use them so that the antennas trying to reach them need not to be moved to track them. They are just pointed permanently at a position in the sky where they stay. Their satellites differ in location by longitude only due to the constant zero degree latitude and circularity of geostationary orbits.
The lower speeds of lower orbits are acceptable latencies. Medium Earth orbit (MEO) and low Earth orbit (LEO) satellites do not have such great delays. After many schemes involving various types of aircraft proposed in the past, the ultralight atmospheric aircraft, the satellites that could fly along a circular path above a fixed ground location under the autonomous computer control at a height of about 20,000 m, are being pushed. Batteries on board would be charged during daylight hours by solar panels covering the wings and shall provide power to the plane during the night. Terrestrial satellite dishes will relay signals to and from the aircraft, reducing the round trip signal latency significantly of 0.25 ms. Aside from those, the planes can fly for long periods of time without refueling. Satellite broadband, after all, is on its way to being better.

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  1. Seth Says:

    I am not quite sure what the motivation for this post is but there a couple of points you just got wrong. A signal from either a land based dish a satellite travels at the speed of light, making the round trip in less than six tenths of a second. Is slower than terrestrial systems? Of course but in consideration of the geographic area served it is pretty amazing.

    Most VoIP calls made over satellite have less latency than cellular calls, and who is doing remote surgery?

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