390 MDS Orbit MCR/ECR Technical Manual MDS 05-6632A01, Rev. F
5.0 Glossary of Terms and Abbreviations
If you are new to wireless communications systems, some of the terms used in this guide may be
unfamiliar. The following glossary explains many of these terms and will prove helpful in understanding
the operation of the unit. While some of these terms may not appear in the text, they are included here to
promote a more complete understanding of wireless technology.
Antenna System Gain: A figure, normally expressed in dB, representing the power increase resulting
from the use of a gain-type antenna. System losses (from the feedline and coaxial connectors, for
example) are subtracted from this figure to calculate the total antenna system gain.
Bit: The smallest unit of digital data, often represented by a one or a zero. Eight bits (plus start, stop, and
parity bits) usually comprise a byte.
Bits-per-second: See BPS.
BPS (Bits-per-second): A measure of the information transfer rate of digital data across a
communication channel.
Bridging: (see Ethernet Bridging)
Byte: A string of digital data usually made up of eight data bits and start, stop and parity bits.
CLI: Command Line Interface. A method of user control where commands are entered as character
strings to set configuration and operating parameters.
CTS: Clear to Send
Decibel (dB): A measure computed from the ratio between two signal levels. Frequently used to express
the gain (or loss) of a system.
Data Circuit-terminating Equipment: See DCE.
Data Communications Equipment: See DCE.
Data Terminal Equipment: See DTE.
dBi: Decibels referenced to an “ideal” isotropic radiator in free space, frequently used to express antenna
gain.
dBm: Decibels referenced to one milliwatt. An absolute unit used to measure signal power, as in
transmitter power output, or received signal strength.
DCE (Data Circuit-terminating Equipment) (or Data Communications Equipment): In data
communications terminology, this is the “modem” side of a computer-to-modem connection. The unit
described in this manual is hardwired as a DCE device.
DTE (Data Terminal Equipment): A device that provides data in the form of digital signals at its
output. DTE connects to the DCE device.
ETH: Ethernet
Ethernet Bridging: Involves combining an Ethernet interface with one or more other interfaces under a
single interface.
Fade Margin: The greatest tolerable reduction in average received signal strength that will be anticipated
under most conditions. It provides an allowance for reduced signal strength due to multipath, slight
antenna movement or changing atmospheric losses. A fade margin of 20 to 30 dB is usually sufficient in
most systems.
Frame: A segment of data that adheres to a specific data protocol and contains definite start and end
points. It provides a method of synchronizing transmissions.
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