Glossary Terms

Time Division Multiple Access (TDMA)

A method of accessing a satellite using time separation; sending simultaneous data streams interleaved using a clock to separate the various data packets.

Synchronous transmission

Digital transmission in which the time interval between any two similar significant instants in the overall bit stream is always an integral number of unit intervals. Note: Isochronous and anisochronous are characteristics, while synchronous and asynchronous are relationships.

Spot beams

The focusing of energy from a satellite to the ground to concentrate the limited available effective radiated power (EIRP).


The process of interconnecting a number of individual networks to provide a path from a terminal or a host on one network to a terminal or a host on another network. The networks involved may be of the same type, or they may be of different types. However, each network is distinct, with its own …

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Echo suppression

Refers to the cancellation of any reflected signal in a communications channel.


Transmissions from a satellite to a ground station; also, the dish used for reception.

Digital voice

Analog voice signals that have been converted into digital signals.


Decibel; an analog unit of measure of signal strength, volume, or signal loss due to resistance as expressed in logarithmic form.

Data Encryption Standard (DES)

A cryptographic algorithm for the protection of unclassified computer data, issued as Federal Information Processing Standard Publication 46-1.


Representation of facts, concepts, or instructions in a formalized manner suitable for communication, interpretation, or processing by humans or by automatic means.


A unit measuring the rate of information flow, with five baud roughly equivalent to one alphanumeric character.


Point-to-point transmission from a remote site back to a central site for further distribution.


Amplitude Modulation


Wide Area Network

Packet mode

A packet switched operational mode for transferring (transporting and switching) user information through a network without establishing a connection. The packets do not necessarily arrive at their destination in the order they were sent, unlike the circuit mode of transmission. See packet switching.


In data communication, a grouping of a sequence of binary digits, including data and control signals, that is transmitted and switched as a composite whole. The data, control signals, and possibly error control information, are arranged in a specific format. The packet can be of either fixed or variable length.


Using the electronic media to reach a specific audience

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