DICTIONARY OF SATELLITE COMMUNICATION TERMS
Analog
The representation of information in variable intensity and/or frequency by a continuous signal.
Antenna
Equipment that sends and/or receives signals from a satellite.
Aperture
A cross sectional area of an antenna exposed to the satellite signal.
Apogee
The highest point in the satellite’s orbit (km); the point in the orbit of a satellite where it is farthest from the object about which it revolves.
Asynchronous Transmission
Data transmission in which each information character or byte is individually synchronized, usually by the use of start or stop elements.
ATP
Acceptance Test Procedure
Attenuation
The loss in power of electromagnetic signals between transmission and reception points.
AZ-EL Mount
Antenna mount that requires two separate adjustments-of azimuth and elevation-to move from one satellite to another.
Azimuth
The angle between an antenna beam and the meridian plane, measured along a horizontal plane.
Bandwidth
The range of frequencies utilized for the transmission of a signal or group of inter-related signals expressed in Hertz (Hz).
ADSL
See Asymmetric Digital Subscriber Line.
algorithm
A specific procedure used to modify a signal. For example, the key to a digital compression system is the algorithm that eliminates redundancy.
American National Standards Institute (ANSI)
An official body within the United States delegated with the responsibility of defining standards.
American Standard Code for Information Interchange (ASCII)
Assigns specific letters, numbers, and control codes to the 256 different combinations of 0s and 1s in a byte.
American wire gauge (AWG)
A measurement of wire diameter - the lower the AWG number, the larger the wire diameter. Copper phone wiring usually comes in 24 or 26 AWG.
analog
A continuously varying signal or wave. As with all waves, analog waves are susceptible to interference which can change the character of the wave.
Asymmetric digital subscriber line (ADSL)
A group of DSL technologies that reserve more bandwidth in one direction than the other, which is advantageous for users that do not need equal bandwidth in both directions. See DSL.
Asynchronous
Occurring at different times. For example, electronic mail is asynchronous communication because it does not require the sender and receiver to be connected at the same time.
Asynchronous transfer mode (ATM)
A method of data transportation whereby fixed length packets are sent over a switched network. The ability to ensure reliable delivery of packets at a high rate makes it suitable for carrying voice, video, and data.
audio on demand
A type of media that delivers sound programs in their entirety whenever a listener requests the delivery.
B
Bandwidth
The range of frequencies utilized for the transmission of a signal or group of inter-related signals expressed in Hertz (Hz).
Base band
A video or audio signal transmitted at its original frequency.
BER (Bit Error Rate)
The percentage of received bits that are in error during transmission; expressed as a number referenced to a power of ten.
Beam width
The angular coverage of an antenna beam. Earth station beams are usually specified at the half-power (or -3 dB) point. Satellite beams are based on the area to be covered.
Bisync
Binary Synchronous Communications (BSC).
Bit
A single unit of information.
BPSK
Binary Phase Shift Keying.
BTV (Business Television)
Corporate communications tool involving video transmissions of information via satellite. Common uses of business television are for meetings, product introductions and training.
backbone
The part of a communications network that handles the major traffic using the highest-speed, and often longest, paths in the network.
basic rate ISDN (BRI-ISDN)
The basic rate ISDN interface provides two 64 Kb/s channels (called B channels) to carry voice or data and one 16 Kb/s signaling channel (the D channel) for call information.
broadband - An adjective used to describe large-capacity networks that are able to carry several services at the same time, such as data, voice, and video.
broadband integrated services digital network (BISDN)
A second-generation ISDN technology that uses fiber optics for a network that can transmit data at speeds of 155 megabits per second and higher.
byte
A compilation of bits, seven bits in accordance with ASCII standards and eight bits in accordance with EBCDIC standards.
C
Carrier
A continuous frequency capable of being modulated with a second data-carrying signal.
Cassegrain
Antenna comprised of two reflectors, the parabolic reflector and an hyperbolic sub reflector at the focus point, which reflects signals back into the feed.
C-Band
Frequencies of approximately 4 to 6 GHz for satellite downlink and uplink transmission, respectively.
Channel
Path for electrical communication between two facilities.
Circular Polarization
A mode of transmission in which signals are down linked in a rotating corkscrew pattern. A satellite’s transmission capacity can be doubled by using both right-hand and left-hand circular polarization.
CPU
Central Processing Unit.
C/N (Carrier-to-Noise Ratio)
Refers to the ratio of the satellite carrier (or signal) to noise level in a given channel. Usually measured in dB at the LNA output.
Colocation
Placement of several satellites near each other in orbit. This allows a single fixed antenna to receive signals from all of the satellites without tracking.
Bandwidth
The range of frequencies utilized for the transmission of a signal or group of inter-related signals expressed in Hertz (Hz).
Base band
A video or audio signal transmitted at its original frequency.
BER (Bit Error Rate)
The percentage of received bits that are in error during transmission; expressed as a number referenced to a power of ten.
Beam width
The angular coverage of an antenna beam. Earth station beams are usually specified at the half-power (or -3 dB) point. Satellite beams are based on the area to be covered.
Bisync
Binary Synchronous Communications (BSC).
Bit
A single unit of information.
BPSK
Binary Phase Shift Keying.
BTV (Business Television)
Corporate communications tool involving video transmissions of information via satellite. Common uses of business television are for meetings, product introductions and training.
backbone
The part of a communications network that handles the major traffic using the highest-speed, and often longest, paths in the network.
basic rate ISDN (BRI-ISDN)
The basic rate ISDN interface provides two 64 Kb/s channels (called B channels) to carry voice or data and one 16 Kb/s signaling channel (the D channel) for call information.
broadband - An adjective used to describe large-capacity networks that are able to carry several services at the same time, such as data, voice, and video.
broadband integrated services digital network (BISDN)
A second-generation ISDN technology that uses fiber optics for a network that can transmit data at speeds of 155 megabits per second and higher.
byte
A compilation of bits, seven bits in accordance with ASCII standards and eight bits in accordance with EBCDIC standards.
C
Carrier
A continuous frequency capable of being modulated with a second data-carrying signal.
Cassegrain
Antenna comprised of two reflectors, the parabolic reflector and an hyperbolic sub reflector at the focus point, which reflects signals back into the feed.
C-Band
Frequencies of approximately 4 to 6 GHz for satellite downlink and uplink transmission, respectively.
Channel
Path for electrical communication between two facilities.
Circular Polarization
A mode of transmission in which signals are down linked in a rotating corkscrew pattern. A satellite’s transmission capacity can be doubled by using both right-hand and left-hand circular polarization.
CPU
Central Processing Unit.
C/N (Carrier-to-Noise Ratio)
Refers to the ratio of the satellite carrier (or signal) to noise level in a given channel. Usually measured in dB at the LNA output.
Colocation
Placement of several satellites near each other in orbit. This allows a single fixed antenna to receive signals from all of the satellites without tracking.
CAP
carrier - an electromagnetic wave or alternating current which is modulated to carry signals in radio, telephonic, or telegraphic transmission.
carrierless amplitude phase (CAP)
A type of quadrature amplitude modulation, used for some types of DSL, that stores pieces of a modulated message signal in memory and then reassembles the parts in the modulated wave.
central office (CO)
A telephone company facility that handles the switching of telephone calls on the public switched telephone network (PSTN) for a small regional area.
circuit-switched network
A type of network in which a continuous link is established between a source and a receiver. Circuit switching is used for voice and video to ensure that individual parts of a signal are received in the correct order by the destination site.
common carrier
A business, including telephone and railroads, which is required by law to provide service to any paying customer on a first-come, first-serve basis.
competitive local exchange carrier (CLEC)
An American term for a telephone company that was created after the Telecommunications Act of 1996 made it legal for companies to compete with the ILECs. Contrast with ILEC.
compression
The process of reducing the amount of information necessary to transmit a specific audio, video, or data signal. core network - The combination of telephone switching offices and transmission plant connecting switching offices together. In the U.S. local exchange network, core networks are linked by several competing Inter exchange networks; in the rest of the world the core network extends to national boundaries.
customer premises equipment (CPE)
Any piece of equipment in a communication system that resides within the home or office. Examples include modems, television set-top boxes, telephones and televisions.
D
DAMA
Demand Assignment Multiple Access.
dB
Decibel. A unit of signal measurement that expresses a ratio between two electrical signals or levels logarithmically.
dBW
An expression of power in dB relative to one watt.
D/C (Down Converter)
Equipment that performs frequency conversion to a lower (IF) band.
DCE
Data Circuit Terminating Equipment.
Delay
The time it takes for a signal to go from the sending station through the satellite to the receiving station.
Demodulator
Equipment that converts the RF signal from the carrier into base band signals (video, audio, or data) for further processing or amplification.
Digital
The representation of information in binary form (ones and zeros), discontinuous in time.
Downlink
Transmission of information from a satellite to earth for reception by earth stations.
DPSK
Differential Phase Shift Keying.
Driver
A software module that manages an I/O port to an external device.
DTE
Data Terminal Equipment.
DTMF (Dual Tone Multifrequency)
A method of signaling and basis for operation of push-button telephone sets.
Duplex Operation
Method in which transmission is possible simultaneously in both directions of a telecommunications channel. Generally, two frequencies in radio communications are required.
dedicated connection
A communication link that operates constantly.
dial-up connection
A data communication link that is established when the communication equipment dials a phone number and negotiates a connection with the equipment on the other end of the link.
digital signal
A signal that takes on only two values, off or on, typically represented by "0" or "1." Digital signals require less power but (typically) more bandwidth than analog, and copies of digital signals can be made exactly like the original.
digital subscriber line (DSL)
A data communications technology that transmits information over the copper wires that make up the local loop of the public switched telephone network (See local loop).) It bypasses the circuit-switched lines that make up that network and yields much faster data transmission rates than analog modem technologies
digital subscriber line access multiplexor (DSLAM)
A device found in telephone company central offices that takes a number of DSL subscriber lines and concentrates these onto a single ATM line.
direct broadcast satellite (DBS)
A broadcast technology that uses satellites orbiting the Earth to broadcast television or data signals to an 18" dish antenna.
discrete multi-tone modulation (DMT)
A method of transmitting data on copper phone wires that divides the available frequency range into 256 sub-channels or tones, and which is used for some types of DSL
discrete wavelet multitone (DWMT)
A variation of DMT modulation that improves performance by using wavelets rather than tones to provide additional isolation of sub-channels.
DMT
See discrete multi-tone modulation.
DNS
See domain name system. domain name system (DNS) - The protocol used for assigning text addresses (such as www.2wire.com) for specific computers and computer accounts on the Internet.
DSLAM
See digital subscriber line access multiplexor.
DWMT
See discrete wavelet multitone.
E
Earth Station
Any system (combination of satellite antenna, amplification, conversion, and reception electronics) that can either transmit to or receive signals from orbiting satellites.
Eclipse
When a satellite passes through the line between the earth and the sun or the earth and another satellite.
EIRP (Effective Isotropic Radiated Power)
Refers to measure of satellite signal strength on the ground.
Elevation
The angle between an antenna beam and the horizontal plane.
Encoder
Equiment that converts a baseband analog input into a digital data stream.
Encryption
The process of coding, "scrambling," or altering a signal electronically so it can only be decoded by recipients who have the equipment and knowledge to reverse the encryption code.
Eclipse
When a satellite passes through the line between the earth and the sun or the earth and another satellite.
EIRP (Effective Isotropic Radiated Power)
Refers to measure of satellite signal strength on the ground.
Elevation
The angle between an antenna beam and the horizontal plane.
Encoder
Equiment that converts a baseband analog input into a digital data stream.
Encryption
The process of coding, "scrambling," or altering a signal electronically so it can only be decoded by recipients who have the equipment and knowledge to reverse the encryption code.
E-1
A dedicated digital communication link provided by a European telephone company that offers 2.048 megabits per second of bandwidth, commonly used for carrying traffic to and from private business networks and Internet service providers
echo cancellation
The elimination of reflected signals ("echoes") in a two-way transmission created by some types of telephone equipment, used in data transmission to improve the bandwidth of the line.
F
F/D
Ratio of antenna focal length to antenna diameter. A higher ration means a shallower dish.
FDMA (Frequency Division Multiple Access)
Refers to the use of multiple carriers within the same transponder where each uplink has an assigned frequency slot and bandwidth.
FEC (Forward Error Correction)
A technique that ensures the transmitted message is received at the receiving end without error.
Feeds
Device mounted at the focus point of the antenna that gathers signals reflected from the dish.
FEP
Front End Processor.
Focal Length
Distance from the feed to the center of the dish.
Footprint
The area of the earth's surface that a satellite's signal is expected to cover. Shown as an EIRP contour map expressed in dBW.
fiber-to-the-cabinet (FTTCab)
network architecture where an optical fiber connects the telephone switch to a street-side cabinet where the signal is converted to feed the subscriber over a twisted copper pair.
fiber-to-the-curb (FTTC)
The deployment of fiber optic cable from a central office to a platform serving numerous homes. The home is linked to this platform with coaxial cable or twisted pair (copper wire). Each fiber carries signals for more than one residence, lowering the cost of installing the network versus fiber to the home.
fiber-to-the-home (FTTH)
The deployment of fiber optic cable from a central office to an individual home. This is the most expensive broadband network design, with every home needing a separate fiber optic cable to link it with the central office.
frame relay
A high-speed packet switching protocol used in wide area networks (WANs), often to connect local area networks (LANs) to each other, with a maximum bandwidth of 44.725 megabits per second.
frequency
The number of oscillations in an alternating current that occur within one second, measured in Hertz (Hz).
frequency division multiplexing (FDM)
The transmission of multiple signals simultaneously over a single transmission path by dividing the available bandwidth into multiple channels that each cover a different range of frequencies.
FTTC
See fiber-to-the-curb.
full-motion video
The projection of 20 or more frames (or still images) per second to give the eye the perception of movement. Broadcast video in the United States uses 30 frames per second, and most film technologies use 24 frames per second.
F/D
Ratio of antenna focal length to antenna diameter. A higher ration means a shallower dish.
FDMA (Frequency Division Multiple Access)
Refers to the use of multiple carriers within the same transponder where each uplink has an assigned frequency slot and bandwidth.
FEC (Forward Error Correction)
A technique that ensures the transmitted message is received at the receiving end without error.
Feeds
Device mounted at the focus point of the antenna that gathers signals reflected from the dish.
FEP
Front End Processor.
Focal Length
Distance from the feed to the center of the dish.
Footprint
The area of the earth's surface that a satellite's signal is expected to cover. Shown as an EIRP contour map expressed in dBW.
fiber-to-the-cabinet (FTTCab)
network architecture where an optical fiber connects the telephone switch to a street-side cabinet where the signal is converted to feed the subscriber over a twisted copper pair.
fiber-to-the-curb (FTTC)
The deployment of fiber optic cable from a central office to a platform serving numerous homes. The home is linked to this platform with coaxial cable or twisted pair (copper wire). Each fiber carries signals for more than one residence, lowering the cost of installing the network versus fiber to the home.
fiber-to-the-home (FTTH)
The deployment of fiber optic cable from a central office to an individual home. This is the most expensive broadband network design, with every home needing a separate fiber optic cable to link it with the central office.
frame relay
A high-speed packet switching protocol used in wide area networks (WANs), often to connect local area networks (LANs) to each other, with a maximum bandwidth of 44.725 megabits per second.
frequency
The number of oscillations in an alternating current that occur within one second, measured in Hertz (Hz).
frequency division multiplexing (FDM)
The transmission of multiple signals simultaneously over a single transmission path by dividing the available bandwidth into multiple channels that each cover a different range of frequencies.
FTTC
See fiber-to-the-curb.
full-motion video
The projection of 20 or more frames (or still images) per second to give the eye the perception of movement. Broadcast video in the United States uses 30 frames per second, and most film technologies use 24 frames per second.
G
Gain
Increased signal power usually the result of amplification; measured in decibels.
Geostationary
Refers to a geosynchronous satellite angle with zero inclination, so the satellite appears to hover over one spot on the earth’s equator.
Geosynchronous
Refers to the orbit in which the speed of a satellite’s orbit is synchronized with the speed of the earth’s rotation so that they are always positioned above the same spot on the earth. For this to occur, the satellite must be in orbit 22,300 miles over the equator, Most communications satellites are in geosynchronous orbit.
GHz (Gigahertz)
One billion cycles per second.
G/T (Gain-to-Noise Temperature)
Ratio of the gain of an antenna compared to the receive system noise temperature; expressed in dB per degree K.
Gain
Increased signal power usually the result of amplification; measured in decibels.
Geostationary
Refers to a geosynchronous satellite angle with zero inclination, so the satellite appears to hover over one spot on the earth’s equator.
Geosynchronous
Refers to the orbit in which the speed of a satellite’s orbit is synchronized with the speed of the earth’s rotation so that they are always positioned above the same spot on the earth. For this to occur, the satellite must be in orbit 22,300 miles over the equator, Most communications satellites are in geosynchronous orbit.
GHz (Gigahertz)
One billion cycles per second.
G/T (Gain-to-Noise Temperature)
Ratio of the gain of an antenna compared to the receive system noise temperature; expressed in dB per degree K.
G.dmt
A kind of asymmetric DSL technology, based on DMT modulation, that offers up to 8 megabits per second downstream bandwidth, 1.544 Megabits per second upstream bandwidth. "G.dmt" is actually a nickname for the standard officially known as ITU-T Recommendation G.992.1. (See International Telecommunications Union.)
G.lite [pronounced "G-dot-light"]
A kind of asymmetric DSL technology, based on DMT modulation, that offers up to 1.5 megabits per second downstream bandwidth, 384 Kilobits per second upstream, does not usually require a splitter and is easier to install than other types of DSL. "G.lite" is a nickname for the standard officially known as G.992.2. (See International Telecommunications Union.)
general switched telephone network (GSTN)
See public switched telephone network.
gigabyte
1,000,000,000 bytes, or 1,000 megabytes (see Byte).
graphical user interface (GUI)
A computer operating system that is based upon icons and visual relationships rather than text. Windows and the Macintosh computer use GUIs because they are more user friendly.
H
Hertz (Hz)
One cycle per second.
HPA (High-Power Amplifier)
Earth station equipment that amplifies the transmit RF signal.
HPC (High-Power Converter)
VSAT RF equipment that up converts and amplifies transmit signals.
Hub
The central earth station satellite transmission facility that is the focal point for communicating to remote locations within a satellite communications network.
A kind of asymmetric DSL technology, based on DMT modulation, that offers up to 8 megabits per second downstream bandwidth, 1.544 Megabits per second upstream bandwidth. "G.dmt" is actually a nickname for the standard officially known as ITU-T Recommendation G.992.1. (See International Telecommunications Union.)
G.lite [pronounced "G-dot-light"]
A kind of asymmetric DSL technology, based on DMT modulation, that offers up to 1.5 megabits per second downstream bandwidth, 384 Kilobits per second upstream, does not usually require a splitter and is easier to install than other types of DSL. "G.lite" is a nickname for the standard officially known as G.992.2. (See International Telecommunications Union.)
general switched telephone network (GSTN)
See public switched telephone network.
gigabyte
1,000,000,000 bytes, or 1,000 megabytes (see Byte).
graphical user interface (GUI)
A computer operating system that is based upon icons and visual relationships rather than text. Windows and the Macintosh computer use GUIs because they are more user friendly.
H
Hertz (Hz)
One cycle per second.
HPA (High-Power Amplifier)
Earth station equipment that amplifies the transmit RF signal.
HPC (High-Power Converter)
VSAT RF equipment that up converts and amplifies transmit signals.
Hub
The central earth station satellite transmission facility that is the focal point for communicating to remote locations within a satellite communications network.
hybrid fiber/coax (HFC)
A type of network that includes coaxial cables to distribute signals to a group of individual locations (typically 500 or more), and a fiber optic backbone to connect these groups.
high bit rate digital subscriber line (HDSL)
A symmetric DSL technology that provides a maximum bandwidth of 1.5 megabits per second in each direction over two phone lines, or 2 Megabits per second over three phone lines.
high bit rate digital subscriber line II (HDSL II)
A descendant of HDSL which offers the same performance over a single phone line.
high-definition television (HDTV)
Any television system that provides a significant improvement in picture quality over existing television systems. Most HDTV systems offer more than 1,000 scan lines, in a wider aspect ratio, with superior color and sound fidelity.
HTML
See hypertext markup language.
HTTP
See hypertext transfer protocol.
hypertext
Documents or other information with embedded links that enable a reader to access tangential information at specific points in the text.
hypertext markup language (HTML)
The computer language used to create hypertext documents, allowing connections from one document or Internet page to numerous others. HTML is the primary language used to create pages on the World Wide Web.
hypertext transfer protocol (HTTP)
The first part of an address (URL) of a site on the Internet, signifying a document written in Hypertext Markup Language (HTML).
Hz
See frequency.
I
IF (Intermediate Frequency)
The frequency of a satellite receiver after down conversion or a satellite modulator before up conversion.
IFL (Interfacility Link)
A cable that provides communication between the ODU and IDU.
I/O
Input/Output
IP (Internet Protocol)
The standard signaling method used for all communication over the Internet
IDSL
See ISDN digital subscriber line.
incumbent local exchange carrier (ILEC)
A large telephone company that has been providing local telephone service in the United States since the divestiture of the AT&T telephone monopoly in 1982.
Institute of Electrical and Electronics Engineers (IEEE)
A membership organization comprised of engineers, scientists and students that sets standards for computers and communications.
integrated services digital network (ISDN)
A circuit-switched communication network, closely associated with the public switched telephone network, that allows dial-up digital communication at speeds up to 128 kilobits per second.
inter-exchange carrier (IXC)
A long-distance telephone carrier.
International Organization of Standardization (ISO)
Develops, coordinates, and promulgates international standards that facilitate world trade.
International Telecommunication Union (ITU)
A United Nations organization that coordinates use of the electromagnetic spectrum and creation of technical standards for telecommunication and radio communication equipment.
International Telecommunication Union/Telecommunication Standardization Sector (ITU-T)
The branch of the ITU that is responsible for telecommunication standardization.
Internet Engineering Task Force (IETF)
The standards organization that standardizes most Internet communication protocols, including Internet protocol (IP) and hypertext transfer protocol (HTTP).
Internet service provider (ISP)
IF (Intermediate Frequency)
The frequency of a satellite receiver after down conversion or a satellite modulator before up conversion.
IFL (Interfacility Link)
A cable that provides communication between the ODU and IDU.
I/O
Input/Output
IP (Internet Protocol)
The standard signaling method used for all communication over the Internet
IDSL
See ISDN digital subscriber line.
incumbent local exchange carrier (ILEC)
A large telephone company that has been providing local telephone service in the United States since the divestiture of the AT&T telephone monopoly in 1982.
Institute of Electrical and Electronics Engineers (IEEE)
A membership organization comprised of engineers, scientists and students that sets standards for computers and communications.
integrated services digital network (ISDN)
A circuit-switched communication network, closely associated with the public switched telephone network, that allows dial-up digital communication at speeds up to 128 kilobits per second.
inter-exchange carrier (IXC)
A long-distance telephone carrier.
International Organization of Standardization (ISO)
Develops, coordinates, and promulgates international standards that facilitate world trade.
International Telecommunication Union (ITU)
A United Nations organization that coordinates use of the electromagnetic spectrum and creation of technical standards for telecommunication and radio communication equipment.
International Telecommunication Union/Telecommunication Standardization Sector (ITU-T)
The branch of the ITU that is responsible for telecommunication standardization.
Internet Engineering Task Force (IETF)
The standards organization that standardizes most Internet communication protocols, including Internet protocol (IP) and hypertext transfer protocol (HTTP).
Internet service provider (ISP)
An organization offering and providing
Internet access to the public using computer servers connected directly
to the Internet.
Intranet
A network serving a single organization or site that is modeled after the Internet, allowing users access to almost any information available on the network. Unlike the Internet, intranets are typically limited to one organization or one site, with little or no access to outside users.
ISDN digital subscriber line (IDSL)
A type of DSL that uses ISDN transmission technology to deliver data at 128kbps into an IDSL "modem bank" connected to a router.
J
Joint Photographic Experts Group (JPEG)
A committee formed by the International Organization of Standardization to set standards for digital compression of still images. Also refers to the digital compression standard for still images created by this group.
K
kbps
One thousand bits per second.
kHz (Kilohertz)
One thousand cycles per second.
Ku-Band
Frequencies approximately in the 12 to 14 GHz range for satellite reception and transmission, respectively.
Intranet
A network serving a single organization or site that is modeled after the Internet, allowing users access to almost any information available on the network. Unlike the Internet, intranets are typically limited to one organization or one site, with little or no access to outside users.
ISDN digital subscriber line (IDSL)
A type of DSL that uses ISDN transmission technology to deliver data at 128kbps into an IDSL "modem bank" connected to a router.
J
Joint Photographic Experts Group (JPEG)
A committee formed by the International Organization of Standardization to set standards for digital compression of still images. Also refers to the digital compression standard for still images created by this group.
K
kbps
One thousand bits per second.
kHz (Kilohertz)
One thousand cycles per second.
Ku-Band
Frequencies approximately in the 12 to 14 GHz range for satellite reception and transmission, respectively.
L
LAN
Local Area Network. A network connecting a number of computers to each other or to a central server so that the computers can share programs and files.
LLC
Logical Link Control.
LNA (Low Noise Amplifier)
Equipment that receives the satellite signal reflected by the antenna and amplifies it to the level needed by the satellite receiving equipment.
LNB (Low Noise Block Down converter)
Satellite receiving equipment that converts all signals from the LNA to the lower IF frequencies.
LNC (Low Noise Converter)
Part of the earth station transmission subsystem consisting of an LNA and down converter.
Laser
From the acronym for "Light Amplification by Stimulated Emission of Radiation." A laser usually consists of a light-amplifying medium placed between two mirrors. Light not perfectly aligned with the mirrors escapes out the sides, but light perfectly aligned will be amplified. One mirror is made partially transparent. The result is an amplified beam of light that emerges through the partially transparent mirror.
local access transport area (LATA)
The geographical areas defining local telephone service. Any call within a LATA is handled by the local telephone company, but calls between LATAs must be handled by long-distance companies, even if the same local telephone company provides service in both LATAs.
Local exchange carrier (LEC)
A local telephone company. LECs provide telephone service for phone calls originating and terminating within a single LATA.
local loop
The copper lines between a customer's premises and a telephone company's central office (See central office).
M
Mbps
One million bits per second.
LAN
Local Area Network. A network connecting a number of computers to each other or to a central server so that the computers can share programs and files.
LLC
Logical Link Control.
LNA (Low Noise Amplifier)
Equipment that receives the satellite signal reflected by the antenna and amplifies it to the level needed by the satellite receiving equipment.
LNB (Low Noise Block Down converter)
Satellite receiving equipment that converts all signals from the LNA to the lower IF frequencies.
LNC (Low Noise Converter)
Part of the earth station transmission subsystem consisting of an LNA and down converter.
Laser
From the acronym for "Light Amplification by Stimulated Emission of Radiation." A laser usually consists of a light-amplifying medium placed between two mirrors. Light not perfectly aligned with the mirrors escapes out the sides, but light perfectly aligned will be amplified. One mirror is made partially transparent. The result is an amplified beam of light that emerges through the partially transparent mirror.
local access transport area (LATA)
The geographical areas defining local telephone service. Any call within a LATA is handled by the local telephone company, but calls between LATAs must be handled by long-distance companies, even if the same local telephone company provides service in both LATAs.
Local exchange carrier (LEC)
A local telephone company. LECs provide telephone service for phone calls originating and terminating within a single LATA.
local loop
The copper lines between a customer's premises and a telephone company's central office (See central office).
M
Mbps
One million bits per second.
M&C (Monitor and Control)
Equipment that monitors and controls Skystar network traffic and hub and VSAT equipment status.
MHz (Megahertz)
One million cycles per second.
Modem (Modulator/Demodulator)
Equipment that converts between digital data and audio tones for transmission and reception over analog channels.
Modulator
Equipment that converts audio, video, or data signals (baseband) into an RF signal.
MSK
Minimum Shift Keying.
MTBF (Mean Time Between Failure)
Average length of time for which a system, or a component of a system, works without fault.
MTTR (Mean Time To Respond)
Average time taken to arrive on site to correct a fault in a system or component.
Multiplexing
A technique that combines multiple data channels on a single transmission channel.
MUX
Multiplexer equipment.
Mb/s
Megabits per second.
Megabit
One million bits.
Megabyte
1,000,000 bytes, or 1,000 kilobytes (see Byte).
millions of instructions per second (MIPS)
This is a common measure of the speed of a computer processor.
Moving Pictures Experts Group (MPEG)
A committee formed by the ISO to set standards for digital compression of full-motion video. Also stands for the digital compression standard created by this committee.
MPEG-1 - An international standard for the digital compression of VHS-quality, full-motion video.
MPEG-2 - An international standard for the digital compression of broadcast-quality, full-motion video.
MPEG-3 - An international standard for the digital compression of broadcast-quality, audio.
Multicast
The transmission of information over the Internet to two or more users at the same time.
Equipment that monitors and controls Skystar network traffic and hub and VSAT equipment status.
MHz (Megahertz)
One million cycles per second.
Modem (Modulator/Demodulator)
Equipment that converts between digital data and audio tones for transmission and reception over analog channels.
Modulator
Equipment that converts audio, video, or data signals (baseband) into an RF signal.
MSK
Minimum Shift Keying.
MTBF (Mean Time Between Failure)
Average length of time for which a system, or a component of a system, works without fault.
MTTR (Mean Time To Respond)
Average time taken to arrive on site to correct a fault in a system or component.
Multiplexing
A technique that combines multiple data channels on a single transmission channel.
MUX
Multiplexer equipment.
Mb/s
Megabits per second.
Megabit
One million bits.
Megabyte
1,000,000 bytes, or 1,000 kilobytes (see Byte).
millions of instructions per second (MIPS)
This is a common measure of the speed of a computer processor.
Moving Pictures Experts Group (MPEG)
A committee formed by the ISO to set standards for digital compression of full-motion video. Also stands for the digital compression standard created by this committee.
MPEG-1 - An international standard for the digital compression of VHS-quality, full-motion video.
MPEG-2 - An international standard for the digital compression of broadcast-quality, full-motion video.
MPEG-3 - An international standard for the digital compression of broadcast-quality, audio.
Multicast
The transmission of information over the Internet to two or more users at the same time.
N
Noise
Extraneous and unwanted signal disturbances.
NAP (network access provider)
Another name for a provider of networked telephone and associated services, usually in the U.S.
narrowband
A designation of bandwidth less than 56 kilobits per second.
network service provider (NSP)
A high-level Internet provider that offers high-speed backbone services.
network termination equipment (NTE)
The equipment at the ends of the communication path.
N-ISDN
See narrowband ISDN.
O
ONU
See optical network unit.
optical carrier 3 (OC-3)
An fiber optic line carrying 155 megabits per second; a U.S. designation generally recognized throughout the telecommunications community worldwide.
optical network unit (ONU)
A form of access node that converts optical signals transmitted via fiber to electrical signals that can be transmitted via coaxial cable or twisted pair copper wiring to individual subscribers. (See hybrid fiber/coax.)
Noise
Extraneous and unwanted signal disturbances.
NAP (network access provider)
Another name for a provider of networked telephone and associated services, usually in the U.S.
narrowband
A designation of bandwidth less than 56 kilobits per second.
network service provider (NSP)
A high-level Internet provider that offers high-speed backbone services.
network termination equipment (NTE)
The equipment at the ends of the communication path.
N-ISDN
See narrowband ISDN.
O
ONU
See optical network unit.
optical carrier 3 (OC-3)
An fiber optic line carrying 155 megabits per second; a U.S. designation generally recognized throughout the telecommunications community worldwide.
optical network unit (ONU)
A form of access node that converts optical signals transmitted via fiber to electrical signals that can be transmitted via coaxial cable or twisted pair copper wiring to individual subscribers. (See hybrid fiber/coax.)
P
PA/TDMA
Permanent Assignment Time Division Multiple Access.
POP
Point of Presence.
POS
Point of Sale.
Protocol
Formal set of rules governing the format, timing, sequence, and error control of messages on a data network.
PSK
Phase Shift Keying.
PVC
Permanent Virtual Circuit.
PA/TDMA
Permanent Assignment Time Division Multiple Access.
POP
Point of Presence.
POS
Point of Sale.
Protocol
Formal set of rules governing the format, timing, sequence, and error control of messages on a data network.
PSK
Phase Shift Keying.
PVC
Permanent Virtual Circuit.
packet-switched network
A network that allows a message to be broken into small "packets" of data that are sent separately by a source to the destination. The packets may travel different paths and arrive at different times, with the destination sites reassembling them into the original message. Packet switching is used in most computer networks because it allows a very large amount of information to be transmitted through a limited bandwidth.
passive optical network (PON)
A fiber-based transmission network containing no active electronics.
peripheral
An external device that increases the capabilities of a communication system.
plain old telephone service (POTS)
An acronym identifying the traditional function of a telephone network to allow voice communication between two people across a distance. In most contexts, POTS is synonymous with the public switched telephone network (PSTN).
Postal, Telegraph and Telephone (PTT)
The generic European name usually used to refer to state-owned telephone companies.
POTS splitter
A device that uses filters to separate voice from data signals when they are to be carried on the same phone line, required for several types of DSL service.
primary-rate ISDN (PRI-ISDN)
The primary rate ISDN interface provides 23 64 Kb/s channels (called B channels) to carry voice or data and one 16 Kb/s signaling channel (the D channel) for call information.
PTT
See Postal, Telegraph and Telephone.
public switched telephone network (PSTN)
The worldwide communications network that carries phone calls and data.
Q
QPSK
Quadrature Phase Shift Keying.
QPSK
Quadrature Phase Shift Keying.
R
RA
Random Access.
RA/TDMA
Random Access Time Division Multiple Access.
RF (Radio Frequency)
Electromagnetic carrier waves upon which audio, video, or data signals can be superimposed for transmission.The frequency range from 10 kHz to 100 GHz used for transmitting data, audio, or video.
Redundancy
A secondary system of backup equipment that performs similarly to a primary system, thereby preventing network downtime and system outages.
Response Time
The elapsed time between the end of an inquiry and the beginning of the response.
RFI
Radio Frequency Interference.
RFT (Radio Frequency Terminal)
Equipment including an antenna, U/C, D/C, HPA, and LNA which provides the up and down conversion of signals in a satellite-based network.
R/O (Receive Only)
Referring to an earth station that receives transmissions only and does not transmit.
Routing
The process of selecting the correct circuit path for a message.
rate-adaptive digital subscriber line (RADSL)
A variation of DSL that uses carrierless amplitude phase modulation, divides the available frequencies into discrete sub-channels and also maximizes performance by adjusting the transmission to the quality of the phone line while in use.
RBOC
One of the seven local telephone companies formed upon the divestiture of AT&T in 1984. The seven are: NYNEX, Bell Atlantic, BellSouth, Southwestern Bell, U S WEST, Ameritech, and Pacific Telesis.
Router
The central switching device in a packet-switched computer network that directs and controls the flow of data through the network.
RA
Random Access.
RA/TDMA
Random Access Time Division Multiple Access.
RF (Radio Frequency)
Electromagnetic carrier waves upon which audio, video, or data signals can be superimposed for transmission.The frequency range from 10 kHz to 100 GHz used for transmitting data, audio, or video.
Redundancy
A secondary system of backup equipment that performs similarly to a primary system, thereby preventing network downtime and system outages.
Response Time
The elapsed time between the end of an inquiry and the beginning of the response.
RFI
Radio Frequency Interference.
RFT (Radio Frequency Terminal)
Equipment including an antenna, U/C, D/C, HPA, and LNA which provides the up and down conversion of signals in a satellite-based network.
R/O (Receive Only)
Referring to an earth station that receives transmissions only and does not transmit.
Routing
The process of selecting the correct circuit path for a message.
rate-adaptive digital subscriber line (RADSL)
A variation of DSL that uses carrierless amplitude phase modulation, divides the available frequencies into discrete sub-channels and also maximizes performance by adjusting the transmission to the quality of the phone line while in use.
RBOC
One of the seven local telephone companies formed upon the divestiture of AT&T in 1984. The seven are: NYNEX, Bell Atlantic, BellSouth, Southwestern Bell, U S WEST, Ameritech, and Pacific Telesis.
Router
The central switching device in a packet-switched computer network that directs and controls the flow of data through the network.
S
SAC(Satellite Access Controller)
Skystar equipment that contains the satellite transmission facility components and data network components.
SCPC
Single Channel Per Carrier.
SDLC
Synchronous Data Link Control.
SNA
System Network Architecture.
S/N (Signal-to-Noise Ratio)
Relative power of the signal to the noise in a channel.
SSPA (Solid-State Power Amplifier)
A lower powered transmitter used for amplification of RF signals at a remote site.
SVC
Switched Virtual Circuit.
Synchronous
When characters or bits are transmitted at a fixed rate with the transmitting and receiving devices synchronized.
small computer system interface (SCSI) [pronounced "scuzzy"]
A type of interface between computers and peripherals that allows faster communication than most other interface standards, often used to connect PCs to external disk drives.
sdsl - Symmetric Digital Subscriber Line
This technology provides the same bandwidth in both directions, upstream and downstream. That means whether you're uploading or downloading information, you have the same high-quality performance. SDSL provides transmission speeds within a T1/E1 range, of up to 1.5 Mbps at a maximum range of 12,000 - 18,000 feet from a central office, over a single-pair copper wire. This option is ideal for small and medium sized businesses that have an equal need to download and upload data over the Internet.
SAC(Satellite Access Controller)
Skystar equipment that contains the satellite transmission facility components and data network components.
SCPC
Single Channel Per Carrier.
SDLC
Synchronous Data Link Control.
SNA
System Network Architecture.
S/N (Signal-to-Noise Ratio)
Relative power of the signal to the noise in a channel.
SSPA (Solid-State Power Amplifier)
A lower powered transmitter used for amplification of RF signals at a remote site.
SVC
Switched Virtual Circuit.
Synchronous
When characters or bits are transmitted at a fixed rate with the transmitting and receiving devices synchronized.
small computer system interface (SCSI) [pronounced "scuzzy"]
A type of interface between computers and peripherals that allows faster communication than most other interface standards, often used to connect PCs to external disk drives.
sdsl - Symmetric Digital Subscriber Line
This technology provides the same bandwidth in both directions, upstream and downstream. That means whether you're uploading or downloading information, you have the same high-quality performance. SDSL provides transmission speeds within a T1/E1 range, of up to 1.5 Mbps at a maximum range of 12,000 - 18,000 feet from a central office, over a single-pair copper wire. This option is ideal for small and medium sized businesses that have an equal need to download and upload data over the Internet.
T
TDMA (Time Division Multiple Access)
Refers to a form of multiple access where a single carrier is time shared by many users. Signals from earth stations reaching the satellite consecutively are processed in time segments without overlapping.
Teleconference
A meeting involving at least one uplink and a number of downlinks at different locations.
Telemetry
The use of telecommunications for automatically indicating or recording measurements at a distance from the measuring instrument.
Terrestrial Interference
Interruptions in a satellite signal caused by high power land-based microwave links in the 4 GHz band.
Tracking
Using earth-based equipment to follow a satellite’s position.
Transfer Orbit
An intermediate elliptical orbit used to reach geosynchronous orbit, where the apogee is the same altitude as the final operating orbit.
Transponder
The circuitry on a satellite that receives the uplink signal, amplifies it, then retransmits it as the downlink signal.
TWTA
Traveling Wave Tube Amplifier. Satellite electronic components that provide power for the transponders (in watts).
T1.413
The American National Standards Institute (ANSI) standard for asymmetric digital subscriber line using discrete multitone modulation, which the G.dmt standard is based on.
T-1
Also known as DS1 and T1, a T-1 is dedicated digital communication link provided by a telephone company that offers 1.544 megabits per second of bandwidth, commonly used for carrying traffic to and from private business networks and Internet service providers.
T-3
Also known as DS3 and T3, a T-3 is a dedicated digital communication link provided by a telephone company that offers 44.75 megabits per second of bandwidth, commonly used for carrying traffic to and from private business networks and Internet service providers.
telecommuting
The practice of using telecommunication technologies to facilitate work at a site away from the traditional office location and environment. teleconference - Interactive, electronic communication among three or more people at two or more sites. Includes audio-only, audio and graphics, and video-conferencing.
terabyte
1,000,000,000,000 bytes, or 1,000 gigabytes (see Byte).
time division multiplexing (TDM)
A digital data transmission method that takes signals from multiple sources, divides them into pieces which are then placed periodically into time slots, transmits them down a single path and reassembles the time slots back into multiple signals on the remote end of the transmission.
transmission control protocol/Internet protocol (TCP/IP)
A method of packet-switched data transmission used on the Internet. The protocol specifies the manner in which a signal is divided into parts, as well as the manner in which "address" information is added to each packet to ensure that it reaches its destination and can be reassembled into the original message.
twisted pair
The set of two copper wires used to connect a telephone customer with a switching office, loosely wrapped around each other to minimize interference from other twisted pairs in the same bundle. Synonymous with 2-wire line.
TDMA (Time Division Multiple Access)
Refers to a form of multiple access where a single carrier is time shared by many users. Signals from earth stations reaching the satellite consecutively are processed in time segments without overlapping.
Teleconference
A meeting involving at least one uplink and a number of downlinks at different locations.
Telemetry
The use of telecommunications for automatically indicating or recording measurements at a distance from the measuring instrument.
Terrestrial Interference
Interruptions in a satellite signal caused by high power land-based microwave links in the 4 GHz band.
Tracking
Using earth-based equipment to follow a satellite’s position.
Transfer Orbit
An intermediate elliptical orbit used to reach geosynchronous orbit, where the apogee is the same altitude as the final operating orbit.
Transponder
The circuitry on a satellite that receives the uplink signal, amplifies it, then retransmits it as the downlink signal.
TWTA
Traveling Wave Tube Amplifier. Satellite electronic components that provide power for the transponders (in watts).
T1.413
The American National Standards Institute (ANSI) standard for asymmetric digital subscriber line using discrete multitone modulation, which the G.dmt standard is based on.
T-1
Also known as DS1 and T1, a T-1 is dedicated digital communication link provided by a telephone company that offers 1.544 megabits per second of bandwidth, commonly used for carrying traffic to and from private business networks and Internet service providers.
T-3
Also known as DS3 and T3, a T-3 is a dedicated digital communication link provided by a telephone company that offers 44.75 megabits per second of bandwidth, commonly used for carrying traffic to and from private business networks and Internet service providers.
telecommuting
The practice of using telecommunication technologies to facilitate work at a site away from the traditional office location and environment. teleconference - Interactive, electronic communication among three or more people at two or more sites. Includes audio-only, audio and graphics, and video-conferencing.
terabyte
1,000,000,000,000 bytes, or 1,000 gigabytes (see Byte).
time division multiplexing (TDM)
A digital data transmission method that takes signals from multiple sources, divides them into pieces which are then placed periodically into time slots, transmits them down a single path and reassembles the time slots back into multiple signals on the remote end of the transmission.
transmission control protocol/Internet protocol (TCP/IP)
A method of packet-switched data transmission used on the Internet. The protocol specifies the manner in which a signal is divided into parts, as well as the manner in which "address" information is added to each packet to ensure that it reaches its destination and can be reassembled into the original message.
twisted pair
The set of two copper wires used to connect a telephone customer with a switching office, loosely wrapped around each other to minimize interference from other twisted pairs in the same bundle. Synonymous with 2-wire line.
U
U/C (Up converter)
Equipment that performs frequency conversion to a higher (RF) band.
Uplink
Transmission of information from an earth station to a geostationary communications satellite.
U/C (Up converter)
Equipment that performs frequency conversion to a higher (RF) band.
Uplink
Transmission of information from an earth station to a geostationary communications satellite.
Uniform Resource Locator (URL)
A text-based address used to identify specific resources on the Internet, such as web pages. URLs are arranged in a hierarchical form that specifies the name of the server on which a resource is located (such as www.2wire.com) and the name of the file on that server (www.2wire.com/index.html).
Universal ADSL Working Group (UAWG)
An organization composed of leading personal computer industry, networking and telecommunications companies with the goal of creating an interoperable, consumer-friendly ADSL standard titled the G.992.2 standard, and commonly referred to as the G.lite standard.
Universal Serial Bus (USB)
A computer interface with a maximum bandwidth of 1.5 Megabytes per second used for connecting computer peripherals such as printers, keyboards and scanners.
universal service provider (USP)
A company that sells access to phone, data, and entertainment services and networks.
V
VSAT (Very Small Aperture Terminal)
A small earth station, usually less than 2.4 meters, used for satellite communications.
variable bit rate (VBR)
A data transmission that can be represented by an irregular grouping of bits or cell payloads followed by unused bits or cell payloads.
VDSL
See very high bit rate digital subscriber line. very high bit rate digital subscriber line (VDSL) - An asymmetric DSL that delivers from 13 to 52 megabits per second downstream bandwidth and 1.5 to 2.3 megabits per second upstream.
video on demand (VOD)
A pay-per-view television service in which a viewer can order a program from a menu and have it delivered instantly to the television set, typically with the ability to pause, rewind, etc.
Video conference
Interactive, audiovisual communication among three or more people at two or more sites.
Virtual Reality Markup Language (VRML)
A computer language that provides a three-dimensional environment for traditional Internet browsers, resulting in a simple form of virtual reality available over the Internet.
VSAT (Very Small Aperture Terminal)
A small earth station, usually less than 2.4 meters, used for satellite communications.
variable bit rate (VBR)
A data transmission that can be represented by an irregular grouping of bits or cell payloads followed by unused bits or cell payloads.
VDSL
See very high bit rate digital subscriber line. very high bit rate digital subscriber line (VDSL) - An asymmetric DSL that delivers from 13 to 52 megabits per second downstream bandwidth and 1.5 to 2.3 megabits per second upstream.
video on demand (VOD)
A pay-per-view television service in which a viewer can order a program from a menu and have it delivered instantly to the television set, typically with the ability to pause, rewind, etc.
Video conference
Interactive, audiovisual communication among three or more people at two or more sites.
Virtual Reality Markup Language (VRML)
A computer language that provides a three-dimensional environment for traditional Internet browsers, resulting in a simple form of virtual reality available over the Internet.
W
wide area network (WAN)
A network that interconnects geographically-distributed computers or LANs.
X
X.25 data protocol
A packet switching standard developed in the mid-1970s for transmission of data over twisted pair copper wire.
* Published Glossary from http://www.solveforce.com/internet-glossary.html with the permission of Dr. Augie Grant, author of "Communication Technology Update (Ninth Edition)"
and an Associate Professor in the College of Mass Communications and Information Studies University of South Carolina Columbia, SC 29208
wide area network (WAN)
A network that interconnects geographically-distributed computers or LANs.
X
X.25 data protocol
A packet switching standard developed in the mid-1970s for transmission of data over twisted pair copper wire.
* Published Glossary from http://www.solveforce.com/internet-glossary.html with the permission of Dr. Augie Grant, author of "Communication Technology Update (Ninth Edition)"
and an Associate Professor in the College of Mass Communications and Information Studies University of South Carolina Columbia, SC 29208
