The orbiting satellite transmits and receives its information to a location on Earth called the Network Operations Center (NOC). NOC is connected to the Internet so all communications made from the customer location (satellite dish) to the orbiting satellite will flow through the NOC before they reached the Internet and the return traffic from the Internet to the user will follow the same path.
How does Satellite Internet work?
Data over satellite travels at the speed of light and Light speed is 186,300 miles per second. The orbiting satellite is 22,300 miles above earth (This is true for the GEO-based satellite)
The data must travel this distance 4 times:
1. Computer to satellite
2. Satellite to NOC/Internet
3. NOC/Internet to satellite
4. Satellite to computer
Satellite Adds latency
This adds a lot of time to the communication. This time is called “Latency or Delay” and it is almost 500 milliseconds. This may not be seen so much, but some applications like financial and real-time gaming don’t like latency.
Who wants to pull a trigger, and wait for half a second for the gun to go off?
But, latency is related to which orbit the satellite is positioned.
Let’s have a look at different Satellite Orbits to understand the satellite latency and its effect on the communication
Geostationary (GEO) Satellites
Geostationary satellites are earth-orbiting about 22,300 miles (35,800 Kilometers) directly above the equator
Picture – GEO-Based Satellite Distance
They travel in the same direction as the rotation of the Earth. This gives the satellites the ability to stay in one stationary position relative to the Earth
Communication satellites and weather satellites are often given geostationary orbits so that the satellite antennas that communicate with them do not have to move to track them, so they can be pointed permanently at the position in the sky where they stay.
The latency in GEO Satellites is very high compared to MEO and LEO Satellites.
The geostationary orbit is useful for communication applications, because ground-based antennas, which must be directed toward the satellite, can operate effectively without the need for expensive equipment to track the satellite’s motion.
There are hundreds of GEO satellites in orbit today, delivering services ranging from weather and mapping data to distribution of digital video-on-demand, streaming, and satellite TV channels globally.
The higher orbit of GEO based satellite means greater signal power loss during transmission when compared to a lower orbit
Medium Earth Orbit Satellites
MEO is the region of space around the Earth above low Earth orbit and below the geostationary orbit.
Historically, MEO constellations have been used for GPS and navigation applications, but in the past five years, MEO satellites have been deployed to provide broadband connectivity to service providers, government agencies, and enterprises.
Current applications include delivering 4G LTE and broadband to rural, remote, and underserved areas where laying fiber is either impossible or not cost-effective – such as a cruise or commercial ships, offshore drilling platforms, backhaul for cell towers, and military sites, among others
In addition, Service Providers are using managed data services from these MEO satellites to quickly restore connectivity in regions where the service has been lost due to undersea cable cuts or where major storms have occurred
MEO satellite constellations can cover the majority of Earth with about eight satellites. Because MEO satellites are not stationary, a constellation of satellites is required to provide continuous service.
This means that antennas on the ground need to track the satellite across the sky, which requires ground infrastructure which is more complex compared to GEO-based satellites
Low Earth Orbit (LEO) Satellites
Unlike geostationary satellites, low and medium Earth orbit satellites do not stay in a fixed position in the sky.
Consequently, ground-based antennas cannot be easily locked into communication with any one specific satellite. Low Earth orbit satellites, as their name implies, orbit much closer to earth.
LEOs tend to be smaller in size compared to GEO satellites, but require more LEO satellites to orbit together at one time to be effective. Lower orbits tend to have lower latency for time-critical services because of the closer distance to earth.
It’s important to reiterate that many LEO satellites must work together to offer sufficient coverage to a given location
Although many LEOs are required, they require less power to operate because they are closer to earth
Picture – Low Earth Orbit – LEO Satellite
Choosing to go with more satellites in the LEO orbit on less power, or using fewer larger satellites in GEO, is the biggest decision to make here
Due to the high number of satellites required in LEO constellations, LEO satellites systems are expected to be high initial manufacturing and launch costs and more expensive ground hardware compared to GEO