High-Power
Amplifiers
It is used in earth station transmitters and the traveling-wave tubes typically used in satellite transponders.
Back-off loss The amount the output level is backed off from rated level is equivalent to a loss and is appropriately called?
Saturated output power
The output power of a typical satellite earth station transmitter is much higher than the output power from terrestrial microwave power amplifiers.
CHAPTER 26:
SATELLITE MULTIPLE ACCESSING ARRANGEMENTS
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TERMS DEFINITIONS
Multiple Accessing
Also called as Multiple Destination, It implies that more than one user has access to one or more radio channels within a satellite communications channel.
Multiple Accessing Arrangement:
Frequency-division multiple accessing (FDMA)
Time-division multiple accessing (TDMA)
Code-division multiple accessing (CDMA)
Pre-assignment(dedicated)
A given number of the available voice-band channels from each earth station are assigned a dedicated destination.
Demand Assignment Voice channels are assigned on an as-needed basis.
Frequency Reuse
The method of assigning adjacent channels different
electromagnetic polarizations and is possible by using orthogonal polarization and spacing adjacent channels 20 MHz apart.
Anik Eskimo word meaning “little brother”.
Anik-E communications
Satellite
Domestic Satellites operated by Telsat Canada.
FDMA A method of multiple accessing where a given RF bandwidth is divided into smaller frequency bands.
Fixed-Assignment, Multiple Access (FAMA)
Multiple channels per carrier formats assigned and remain fixed for a long Period of time.
Demand-Assignment Multiple Access
Assigning carrier frequency on temporary basis using a statistical assignment process.
iclvi SPADE An acronym for Single-channel-per-carrier PCM multiple Access
Demand-assignment Equipment.
SCPC Stands for Single-Carrier-Per-Channel.
Common Signaling Channel
(CSC)
A time division-multiplexed transmission that is frequency division multiplexed.
TDMA
The predominant Multiple-access method of time-division multiplexing digitally modulated carriers between participating earth stations within a satellite network through a common satellite transponder.
Transponder
An RF-to-RF repeater that simply receives the earth station transmissions, amplifies them, and then re-transmits them in a downlink beam that is received by all other participating station.
Reference Burst
It is where transmissions from all earth stations are synchronized.
Carrier Recovery Sequence
(CRS)
It is where all receiving stations recover a frequency and phase coherent carrier for PSK demodulation
CEPT An acronym for Conference of European Postal and
Telecommunications Administrations, is commonly used TDMA frame format for digital satellite system
Code-Division Multiple Access (CDMA)
Sometimes referred to as Spread-Spectrum Multiple entire allocated bandwidth Access, the transmissions can spread throughout
Chip Code A unique binary word that each earth station’s transmissions are encoded.
iclvii Correlator
It compares two signals and recovers the original data.
Digital non interpolated
Interface It assigns an individual terrestrial channel (TC) to a particular satellite channel (SC) for the duration of the call.
Digital Speech Interpolated Interface
It assigns a terrestrial channel to a satellite channel only when speech energy is present on the TC.
Time-Assignment Speech Interpolation
(TASI)
A form of analog channel compression that has been used for sub oceanic cables for many years.
Navigation
The art or science of plotting, ascertaining or directing the course of movements, in other words, knowing where you are and being able to find your way around.
Wandering It is the most ancient and rudimentary method of navigation and simply continuing to travel about until you reach your destination, assuming of course that you have one.
Celestial Navigation
Earliest effective means of navigation wherein direction and distance are determined from precisely timed sightings of celestial bodies, including the stars and moon.
Piloting Method of navigation by means of fixing a position and direction with respect to familiar, significant landmarks such as railroad tracks, water towers, barns, mountains and bodies of water.
Dead Reckoning A navigation technique that determines position by extrapolating a series of measured velocity increments.
Dead The term derived from the word “deduced” and not necessarily from the fate of the people who used the technique.
Charles Lindbergh
iclviii He used dead reckoning successfully in 1927 during his historic 33-hour transatlantic journey.
Amelia Earhart She attempted to make the first around-the-world in 1937 using the dead reckoning technique.
Radio Navigation
Navigation technique wherein the position is deter-mined by measuring the travel time of an electromagnetic wave as it moves from a transmitter to a receiver.
Decca A radio Navigation system for terrestrial surface broadcast.
Omega Radio Navigation system that provides global coverage and terrestrial surface broadcast.
LORAN Also a terrestrial surface broadcast.
Navy Transit GPS Low-orbit satellite broadcast provides global coverage.
Navstar GPS Medium-orbit satellite broadcast also provides global coverage.
LORAN
Means of radio navigation in which receivers acquire coded signals from two pairs of high-powered, land based transmitters whose locations are precisely known.
Navstar
An acronym for Navigation System with Time and Ranging.
GPS
An abbreviation for Global Positioning System.
Two levels of service or accuracy:
Standard Positioning Service
Precise Positioning Service
Navstar GPS
A satellite-based open navigation system which simply means that it is available to anyone equipped with a GPS receiver.
Consists of three segments:
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a space segment
a ground control segment
user segment
April 27, 1995 It is when the Navstar was declared as fully operational by the U.S.
Air Force Space Command.
Navstar Satellite
System It was completed in 1994 and is maintained by the United States Air Force.
Standard Positioning
Service A positioning and timing service that is available to all GPS users on a continuous, worldwide basis with no direct change.
Satellite Segment Sometimes called Space Segment, consists of 24operational satellites revolving around Earth in six orbital planes approximately 60° apart with four satellites in each plane.
Cesium Atomic Clock It produces highly accurate timing signals for satellites.
Pseudorandom Noise (PRN) Code Number
A unique integer number that is used to encrypt the signal from that satellite.
Ephemeris A term associated with a table showing the position of a heavenly body on a number dates in a regular sequence, in essence, an astronomical almanac.
Clock Bias Error Error in the receiver’s clock which affects the accuracy of the time-difference measurement.
Operational Control System
The Navstar control segment.
It consists of :
Fixed-location ground based monitor stations
Master Control Station
uplink transmitter Differential GPS
It makes standard GPS more accurate. It works by canceling out most of the natural and man-made errors that creep into normal GPS measurements.
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