PinoyBIX Engineering Problem Solving and Reference

CHAPTER 26

SATELLITE MULTIPLE ACCESSING ARRANGEMENTS

Items

Definitions

Terms

1

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)

Multiple Accessing

2

A given number of the available voice-band channels from each earth station are assigned a dedicated destination.

Pre-assignment (dedicated)

3

Voice channels are assigned on an as-needed basis.

Demand Assignment

4

The method of assigning adjacent channels different electromagnetic polarizations and is possible by using orthogonal polarization and spacing adjacent channels 20 MHz apart.

Frequency Reuse

5

Eskimo word meaning “little brother”.

Anik

6

Domestic Satellites operated by Telsat Canada.

Anik-E communications Satellite

7

A method of multiple accessing where a given RF bandwidth is divided into smaller frequency bands.

FDMA

8

Multiple channels per carrier formats assigned and remain fixed for a long Period of time.

Fixed-Assignment, Multiple

Access (FAMA)

9

Assigning carrier frequency on temporary basis using a statistical assignment process.

Demand-Assignment

Multiple Access

10

An acronym for Single-channel-per-carrier PCM multiple Access Demand-assignment Equipment.

SPADE

11

Stands for Single-Carrier-Per-Channel.

SCPC

12

A time division-multiplexed transmission that is frequency division multiplexed.

Common Signaling Channel

(CSC)

13

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.

TDMA

14

An RF-to-RF repeater that simply receives the earth station transmissions, amplifies them, and then retransmits them in a downlink beam that is received by all other participating station.

Transponder

15

It is where transmissions from all earth stations are synchronized.

Reference Burst

16

It is where all receiving stations recover a frequency and phase coherent carrier for PSK demodulation.

Carrier Recovery Sequence

(CRS)

17

An acronym for, Conference of European Postal and Telecommunications Administrations, is commonly used TDMA frame format for digital satellite system.

CEPT

18

Sometimes referred to as Spread-Spectrum Multiple entire allocated bandwidth Access, the transmissions can spread throughout.

Code-Division Multiple Access

CDMA)

19

A unique binary word that each earth station’s transmissions are encoded.

Chip Code

20

It compares two signals and recover the original data.

Correlator

21

It assigns an individual terrestrial channel (TC) to a particular satellite channel (SC) for the duration of the call.

Digital non interpolated Interface

22

It assigns a terrestrial channel to a satellite channel only when speech energy is present on the TC.

Digital Speech Interpolated Interface

23

A form of analog channel compression that has been used for sub oceanic cables for many years.

Time-Assignment Speech Interpolation

(TASI)

24

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.

Navigation

25

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.

Wandering

26

Earliest effective means of navigation wherein direction and distance are determined from precisely timed sightings of celestial bodies, including the stars and moon.

Celestial Navigation

27

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.

Piloting

28

A navigation technique that determines position by extrapolating a series of measured velocity increments.

Dead Reckoning

29

The term derived from the word “deduced” and not necessarily from the fate of the people who used the technique.

Dead

30

He used dead reckoning successfully in 1927 during his historic 33-hour transatlantic journey.

Charles Lindbergh

31

She attempted to make the first around-the-world in 1937 using the dead reckoning technique.

Amelia Earhart

32

Navigation technique wherein the position is determined by measuring the travel time of an electromagnetic wave as it moves from a transmitter to a receiver.

Radio Navigation

33

A radio Navigation system for terrestrial surface broadcast.

Decca

34

Radio Navigation system that provides global coverage and terrestrial surface broadcast.

Omega

35

Also a terrestrial surface broadcast.

LORAN

36

Low-orbit satellite broadcast that provides global coverage.

Navy Transit GPS

37

Medium-orbit satellite broadcast also provides global coverage.

Navstar GPS

38

Means of radio navigation in which receivers acquire Coded signals from two pairs of high-powered, land based transmitters whose locations are precisely known.

LORAN

39

An acronym for Navigation System with Time and Ranging.

Navstar

40

An abbreviation for Global Positioning System.

Two levels of service or accuracy:

·         Standard Positioning Service

·         Precise Positioning Service

GPS

41

A satellite-based open navigation system which simply means that it is available to anyone equipped with a GPS receiver.

Consists of three segments:

·         a space segment

·         a ground control segment

·         user segment

Navstar GPS

42

It was when the Navstar declared as fully operational by the U.S. Air Force Space Command.

April 27, 1995

43

It was completed in 1994 and is maintained by the United States Air Force.

Navstar Satellite System

44

A positioning and timing service that is available to all GPS users on a continuous, worldwide basis with no direct change.

Standard Positioning

Service

45

Sometimes called Space Segment, consists of 24operational satellites revolving around Earth in six orbital planes approximately 60° apart with four satellites in each plane.

Satellite Segment

46

It produces highly accurate timing signals for satellites.

Cesium Atomic Clock

47

A unique integer number that is used to encrypt the signal from that satellite.

Pseudorandom Noise

(PRN)

Code Number

48

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.

Ephemeris

49

Error in the receiver’s clock which affects the accuracy of the time-difference measurement.

Clock Bias Error

50

The Navstar control segment.

It consists of :

·         Fixed-location ground based monitor stations

·         Master Control Station

·         uplink transmitter

Operational Control

System

51

It makes standard GPS more accurate. It works by cancelling out most of the natural and man-made errors that creep into normal GPS measurements.

Differential GPS

CHAPTER 25

SATELLITE COMMUNICATIONS

Items

Definitions

Terms

1

A celestial body that orbits around a planet.

Satellite

2

Man-made satellites that orbit earth, providing a multitude of communication functions to a wide variety of consumers, including military, governmental, private and commercial subscriber.'

Communications

Satellites

3

A satellite radio repeater which

Consists of :

·         input Bandlimiting device (BPF)

·         input low-noise amplifier (LNA)

·         frequency translator

·         low level amplifier

·         output bandpass filter

Transponder

4

It consists of one or more satellite space vehicles, a ground-based station to control the operation of the system, and a user network of earth stations that provides the interface facilities for the transmission and reception of terrestrial communications traffic through the satellite system.

Satellite System

5

It includes control mechanism that supports the payload operation.

Bus

6

The actual user information conveyed through the system.

Payload

7

A type of satellite wherein it simply “bounces” signals from one place to another.

Passive Reflector

8

A natural satellite of Earth, visible by reflection of sunlight having a slightly elliptical orbit.

Moon

9

Used by passive satellites for tracking and ranging purposes.

Radio Beacon

Transmitters

10

Launched by Russia, the first active earth satellite in 1957. It transmitted telemetry for 21 days.

Sputnik I

11

A type of satellite capable of receiving, amplifying, reshaping, regenerating and retransmitting information.

Active Satellite

12

Satellite launched by U.S., it transmitted telemetry information for nearly five months.

Explorer I

13

Satellite launched by NASA in 1958, a 150-pound conical-shaped satellite. It was the first artificial satellite used for relaying terrestrial communications.

Score

14

The first active satellite to simultaneously receive and transmit radio signals.

Telstar I

15

Launched in 1963, and was used for telephone television, facsimile and data transmission and accomplished the first successful transatlantic video transmission.

Telstar II

16

Launched in February 1963, was the first attempt to place a geosynchronous satellite into orbit.

Syncom I

17

It was the first commercial telecommunications satellite. It launched from Cape Kennedy in 1965 and used two transponders. Also called as Early Birds. It stands for International Telecommunications Satellite.

Intelsat I

18

Domestic satellite launched by former Soviet Union in 1966. It means “lighting”.

Molya

19

A German astronomer who discovered the laws that governs satellite motion.

Johannes Kepler

20

It may be simply stated as:

The planets move in ellipses with the sun at one focus

The line joining the sun and the planet sweeps out equal intervals of time.

The square of the time of revolution of a planet divided by the cube of its mean distance from the sun gives a number that is the same for all planets.

Kepler’s Law

21

The point in an orbit closest to earth.

Perigee

22

The point in an orbit farthest from the earth.

Apogee

23

It states that the square of the periodic time of orbit is proportional to the cube of the mean distance between the primary and the satellite.

Harmonic Law

24

High-altitude earth-orbit satellites operating primarily in the 2-GHz to 18 GHz frequency spectrum with orbits Satellite 22,300 miles above earth’s surface.

Advantages of Geosynchronous Satellite:

·         It remain almost stationary in respect to a given earth station.

·         Available to earth within their shadows 100% of the time.

·         No need to switch from one geosynchronous satellite to another as they orbit overhead

·         The effects of Doppler shift are negligible

Disadvantages of geosynchronous Satellite:

·         It requires sophisticated and heavy propulsion device onboard to keep them in a fixed orbit

·         Much longer propagation delays

·         Requires higher transmit power and more sensitive receivers because of the longer distances and greater path loss.

·         High precision spacemanship is required.

Geosynchronous

Satellite

25

The angle between the earth’s equatorial plane and the orbital plane of a satellite measured counter clockwise at the point in the orbit where it crosses the equatorial plane traveling from south to north called the ascending node.

Angle of Inclination

26

The point where the polar or inclines orbit crosses the equatorial plane travelling from north to south.

Descending Node

27

The line joining the ascending and descending node.

Line of Nodes

28

It is when the satellite rotates in an orbit directly above the equator, usually in a circular path.

Equatorial Orbit

29

It is when the satellite rotates in path that takes over the North and the South poles in an orbit that is close to earth and passes over and very close to both the North and South Poles.

Polar Orbit

30

The noise power normalized to a 1 Hz bandwidth, or the noise power present in a 1Hz bandwidth.

Noise Density

31

It identifies the system parameters and is used to determine the projected carrier-to-noise ratio and energy Bit-to-noise density ratio at both the satellite and earth station receivers for a given modulation scheme.

Link Budget