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Satellite Internet Glossary

Below is but a snap shot of the terms used to discribe this technology.

Acceleration:
In the satellite Internet world, it's the overall name for specific techniques used to optimize satellite service. We have include a special section on satellite internet acceleration under both platforms: Aetheron and Aetheron Plus. For Enterprise Wildblue. All acceleration is hangled in the Teleports directly as a fuction of the broadcast (Note: Unique to KA).

Aperture:
A cross sectional area of the antenna, which is exposed to the satellite signal.

Attenuation:
The loss in power of electromagnetic signals between transmission and reception points.

Attitude Control:
The orientation of the satellite in relationship to the earth and the sun.

Asymmetrical:
Devoting more bandwidth to downstream (downloads) traffic than upstream (uploads).

Azimuth:
The angle of rotation (horizontal) that a ground based parabolic antenna must be rotated through to point to a specific satellite in a geosynchronous orbit. The azimuth angle for any particular satellite can be determined for any point on the surface of the earth giver the latitude and longitude of that point. It is defined with respect to due north as a matter of easy convenience.

Conus:
Contiguous United States. All the states in the U.S. except Hawaii and Alaska.

Clarke Belt:
Science-fiction legend Arthur C. Clarke invented the geo-synchrous orbit, upon which satellite communications is based, more than a half century ago. The mathematical question was how high would a satellite have to be in orbit to appear to be stationary over the same spot on the Earth at all time. The answer, in aproximate terms, is 23,000 miles high and flying west-to-east.
3DES:
Sometimes called Triple DES. A method of triple-securing data (encrypt-decrypt-encrypt) for ensuring privacy in satellite VSAT transmissions. Security experts went to three-way encryption to foil what are known as meet-in-the-middle cipher attacks.

Elevation:
The upward tilt to a satellite antenna measured in degrees required to aim the antenna at the communications satellite. When. aimed at the horizon, the elevation angle is zero. If it were tilted to a point directly overhead, the satellite antenna would have an elevation of 90 degrees.

Feed:
This term has at least two key meanings within the field of satellite communications. It is used to describe the transmission of video programming from a distribution center. It is also used to describe the feed system of an antenna. The feed system may consist of a subreflector plus a feedhorn or a feedhorn only.

Forward Error Correction (FEC):
Adds unique codes to the digital signal at the source so errors can be detected and corrected at the receiver.

Gigahertz (GHz):
One billion cycles per second. Signals operating above 3 Gigahertz are known as microwaves. above 30 GHz they are know as millimeter waves. As one moves above the millimeter waves signals begin to take on the characteristics of Iight waves.

Inclination:
The angle between the orbital plane of a satellite and the equatorial plane of the earth.

IPSec:
Short for Internet Protocol Security. IPSec is a framework for a set of protocols for security at the network or at the packet-processing layer of the network communication. Used in virtual private networks, one advantage of IPSec is that security arrangements can be handled without requiring changes to individual computers.

Ku Band:
The frequency range from 10.9 to 17 GHz.

Link Budget:
The term for correctly sizing uplink and downlink paths. Factors include antenna size, satellite transmission power and potential atmospheric effects (from weather to sunspots).

Latency:
Sometimes called "Ping Time," it refers to the number of milliseconds (ms) it takes to send a data packet and receive an acknowledgement. Latency across the Internet is generally 100ms or less. In the satellite world, even with transmission speeds approaching the speed of light, the round-trip off the satellite can create roughly 700ms - 900ms of round-trip latency. Satellite service providers use advanced techniques to minimize latency, but some applications -- most notably interactive gaming -- will perform poorly.

NetBIOS:
An acronym for Network Basic Input Output System. It's an application program interface (API) used in local-area networks (LANs). Mentioned here because custom-software relying on NetBIOS, which was never designed for WANs, cannot be accelerated for better performance over satellite.

Parabolic Antenna:
The most frequently found satellite TV antenna; it takes its name from the shape of the dish described mathematically as a parabola. The function of the parabolic shape is to focus the weak microwave signal hitting the surface of the dish into a single focal point in front of the dish. It is at this point that the feed horn is usually located.

Satellite Footprint:
A satellite Internet footprint diagram will show a picture of the signal level received at a particular location in terms of the Effective Isotropic Radiated Power (EIRP) received from the satellite. Areas of common reception are linked by lines that look like isobars on a weather map; when numbers are included on the banded lines, the higher the number, the greater the signal strength.

TCP/IP:
Transmission Control Protocol / Internet Protocol. The IP standard controls how packets of information travel on the Internet and TCP enables two hosts to establish a connection and exchange streams of data. Mentioned here because TCP/IP applications can work beautifully on a satellite.

TDMA:
Time division multiple access. Refers to a form of multiple access where a single carrier is the shared by many users. Signals from earth stations reaching the satellite consecutively are processed in time segments without overlapping.

UDP:
User Datagram Protocol. Used primarily for broadcasting messages over local networks. It is a connectionless protocol and therefore cannot be accelerated for use on satellite Internet connections.

VSAT: Stands for Very Small Aperture Terminal. Term describes a ground unit to receive (or send) data via satellite. Generally consists of an ODU (Outdoor Unit) and IDU (Indoor Unit). ODU components include an antenna equipped with a feed system capable of receiving and transmitting, a microwave radio known as a BUC (Block-Up-Converter) and an LNB (low noise block down converter) used to convert the signal gathered by the feed. The IDU is typically a modem and it converts the data, video, or voice generated by the customer application for transmission over satellite. The power of a BUC is measured in watts of transmitting power.

 

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