How Satellite Internet Works

Topics

The following topics are discussed:

What Is Satellite Internet? 

Satellite Internet provides the ability to connect a remote user in virtually any location in the United States to the Internet.

The path the data will follow to and from the Internet is described and illustrated below:

  1. At the remote end is a relatively small satellite dish (Very Small Aperture Terminal/VSAT) that communicates with an orbiting geostationary satellite.
  2. The orbiting satellite transmits (and receives) its information through a location on Earth called the Network Operations Center (NOC).
  3. The NOC is connected to the Internet, so all communication from a VSAT must flow through the NOC, to the Internet.
  4. Data will follow the same path back.

Graphic of data path for satellite Internet

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What is a Geostationary Satellite? 

There is a location in space where you can place a satellite in orbit so that from the ground, the satellite appears stationary. What is happening is that the satellite is actually orbiting the Earth at the same speed the Earth is rotating. The satellite makes a complete orbit around the Earth in 24 hours.

Geostationary or geosynchronous satellites are located approximately 22,300 miles above the Earth's equator!

Graphic illustrates geosynchronous orbit.

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Satellite Name and Longitude

Geostationary satellites have a name. For Ka-band services, HughesNet primarily uses a satellite called Echostar 17. It is also referred to as Jupiter. HughesNet Ka-band services are also deliverd by an older satellite called Spaceway 3

The satellites also have a longitude position. As a review, longitude refers to the imaginary long lines that travel down the Earth for global mapping.  There are 360 degrees of longitude readings for Earth (360 degrees is a full circle).  If one knows the longitude of a satellite, one knows where the satellite is located in the sky, since all Geostationary satellites are located above the equator (at zero latitude).

Longitude is divided into the western hemisphere and the eastern hemisphere and all orbital "Slots" for satellites are between 0° to 180° in either the Eastern Hemisphere or the Western Hemisphere.

HughesNet's primary satellite, Echostar 17, has an orbital slot of 107.1° West Longitude. Spaceway 3 is located at 95° W.

The graphic below shows approximate longitudes (across the top) and latitudes (down the right side) for the Continental US.

Longitudes and latitudes in the US

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Satellite Pointing Parameters

It is important that there are no obstacles between the location of the satellite dish and the orbiting satellite. In other words, you must have a clear "line-of-sight" to the satellite. There are many utilities available for determining the pointing parameters:

  • azimuth
  • elevation
  • polarization, (also called skew or tilt)

The pointing parameters are illustrated below.

Azimuth, elevation and skew/polarization are shown.

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Satellite Latency 

Latency refers to how long it takes a single piece of information to make a round trip back and forth over a satellite connection. Since data travels at the speed of light (186,000 miles per second), the orbiting satellite is 22,300 miles above earth, and the data must travel that distance four times (computer to satellite ... satellite to NOC ... NOC to satellite ... satellite to computer), this adds up to a lot of additional time.

This time is called "Latency" and it is roughly 1/2 of a second or 500 milliseconds. This is not a lot of time to you or me, but some applications like real-time gaming don’t like this delay.

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CIR - Committed Information Rate 

Committed Information Rate (CIR) is the rate of download or upload speed (typically expressed as Kbps or Mbps) that a service provider promises to deliver. With consumer satellite Internet services, there is typically no CIR. How fast it is depends on how many subscribers the provider has and how many of them are online at any time. Commercial services offer CIR, but they cost significantly (many times) as much!

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Contention Ratios 

Contention Ratios are the number of subscribers that can share the bandwidth at any point in time. Contention ratios of consumer satellite Internet services are as high as 400 to 1 (written as 400:1). Commercial services will have contention ratios closer to 20 to 1 (or 20:1) or less. Contention Ratios are not CIRs, but if you know what the contention ratio is, you can calculate the lowest speeds you can expect.

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Satellite Footprint - Ka-band 

The coverage map or footprint of a satellite shows the areas in which a satellite dish may be located to communicate with the satellite. Below are the coverage areas for HughesNet Ka-band consumer services. The darker green areas are for Echostar 17 at 107.1 W; the lighter color is for Spaceway 3 at 95 W. See Satellite Coverage Maps for more information about satellite footprints.

Satellite coverage map of Echostar 9 at 121 W

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