There is a need for a long haul communication process for cities or places that are far from reach by cables or any wireline technologies. Terrains may be a factor that other wireless technologies may not be efficient. So satellite communication comes in to minds of the carries to provide means of voice, data and other communication access.

Low Earth Orbit (LEO) refers to a satellite which orbits the earth at altitudes between (very roughly) 200 miles and 930 miles.

Low Earth Orbit satellites must travel very quickly to resist the pull of gravity — approximately 17,000 miles per hour. Because of this, Low Earth Orbit satellites can orbit the planet in as little as 90 minutes.

Low Earth Orbit has been used for both military and aeronautical purposes. Military rocketry and missiles have long taken advantage of this orbit to launch missiles and rockets over long distances. Other than lunar flights Low Earth Orbit defines the boundary of all human space exploration. This shows the major technical and financial obstacles that need to be overcome in order to make even nearby interplanetary travel possible. However there is promise in the technologies used to send satellites into Geostationary Orbit and beyond.

LEO provides features that other wireless technologies may not provide for remote areas.

There are two types of LEOs - little LEOs and Big LEOs.

Big LEO

Big LEOs are used for technology devices such as high-speed, high-bandwidth data communications, and video conferencing. They carry voice and high-speed data services. They are aimed at data communications and real-time voice into hand-held devices. Big LEO can also offer global services, which are also subject to regulatory requirements. There have been five Big LEO already licensed. The five Big LEO are Iridium, Global Star, Odyssey, ICO Global Communications, Teledesic.

Little LEO

Little LEOs are required to offer non-voice services for example vehicle tracking, environmental monitoring and two-way data communication. A little LEO is a constellation of small, low-earth orbiting satellites, used for short, narrowband communications. Little LEOs are a small, low-cost, class of satellites. LEOs are to use a spectrum allocated between 137-138MHz for space-to-Earth downlinks, and 148-150.05 MHz for Earth-to-space uplinks.

Advantages to LEO Satellite Telemetry

• Global applications in developing a remote environmental monitoring communication system.
• Two-way communications
• Easy to set up and low maintenance costs
• Low profile, non-directional whip helix antenna
• Easy access to data
• No FCC or other governmental agency requirements for data transmission
• Coverage in very remote areas
• Data is proprietary
• Stevens is able to quickly detect any problems with transmission of data
• Systems verifies that data has been transmitted which minimizes risk of missing data.
• Event notification on line, by pager, etc.
• Lower power transceivers compared to GEO transmitters.
• LEO Transceivers hardware system is lower in cost than a GEO transmitter system.

Disadvantages to LEO Satellite Telemetry

• Monthly service fee which could be expensive with frequent transmissions of data.
• Power outage at GCC would shut down the communication server, which could delay transmission of data to end user until power is restores. However, no data is lost.
• LEO satellites have a much shorter life span (five to eight years) than GEO satellites.

Reference:

http://www.stevenswater.com/telemetry_com/leo_info.aspx

http://www.tech-faq.com/low-earth-orbit.html