Wired Broadband and Related Industry Glossary of Terms with Acronyms As of 13 June 2011 Compiled By: Conrad L. Young, Director, Broadband Technical Strategy

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Gap Channel

A channel within the encompassed spectrum which is not active; this occurs with non-contiguous channel frequency assignments on an RF output port. [Cab112]
Gap Loss

Loss resulting from the end separation of two axially aligned fibers. [Fib111]

Gap Loss Diagram courtesy of Fiber Optics Info, http://www.fiber-optics.info/fiber_optic_glossary/g


1) A device having one output channel and one or more input channels, such that the output channel state is completely determined by the input channel states, except during switching transients. 2) One of the many types of combinational logic elements having at least two inputs. [Fib111]

Gate Controller (GC)
In a PacketCable 1.0-based network, the GC is responsible for authorizing the enhanced quality of service for the media stream.

Gateway (GW)
A function or server that acts as a point of interconnection between two different networks. For example, a Public Switched Telephone Network (PSTN) gateway would interconnect a PacketCable-based network with the PSTN. A computing machine which is both connected to one or more networks and is capable of passing network information from one network to another.

Gaussian Beam

A beam pattern used to approximate the distribution of energy in a fiber core. It can also be used to describe emission patterns from surface-emitting LEDs. Most people would recognize it as the bell curve (illustrated). The Gaussian beam is defined by the equation:

E(x) = E (0) e-x2/w02 [Fib111]

Gaussian Beam Diagram courtesy of Fiber Optics Info, http://www.fiber-optics.info/fiber_optic_glossary/g


One billion bits of data per second or 109 bits. Equivalent to 1 for binary signals. [Fib111]

Gate Controller


A process of sync generator locking. This is usually performed by introducing a composite video signal from a master source to the subject sync generator. The generator to be locked has circuits to isolate vertical drive, horizontal drive and subcarrier. The process then involves locking the subject generator to the master subcarrier, horizontal, and vertical drives so that the result is that both sync generators are running at the same frequency and phase. [Fib111]

Geostationary Orbit

The orbit of a satellite approximately 22,300 miles above the equator, revolving around the earth with an angular velocity equal to that of the earth's rotation on its own axis. The satellite's position is constant in relation to the earth's surface. Synonymous with geosynchronous. [Arr11]
Geostationary Transfer Orbit

This orbit is in the equatorial plane. This type of orbit has an elliptical form, with a perigee at 200 km and an apogee at 35870 km. [Sat07]

Generally used in detectors. Good for most fiber optic wavelengths (e.g., 800-1600 nm). Performance is inferior to InGaAs. [Fib111] A brittle, crystalline, gray-white metalloid element, widely used as a semiconductor, as an alloying agent and catalyst, and in certain optical glasses. Atomic number 32; atomic weight 72.59; melting point 937.4°C; boiling point 2,830°C; specific gravity 5.323 (at 25°C); valence 2, 4. [Fre11]


Ground Fault Circuit Interrupter; an electrical circuit breaker device used for protection against shock hazard. GFCIs are usually used where AC outlets will be exposed to moisture. [Arr11]
A shadowy or weak image in the received picture offset either to the left or right of the primary image, the result of transmission conditions which create secondary signals that are received earlier or later than the main or primary signal. A ghost displaced to the left of the primary image is designated as “leading” and one displaced to the right is designated as “following” (lagging). When the tonal variations of the ghost are the same as the primary image, it is designated as “positive” and when it is in reverse, it is designated as “negative.”


GigaHertz; one billion Hertz (cycles per second) or 10
9 Hertz. [Fib111]
Gigacycle (Gc)

See Gigahertz

GigaHertz (GHz)

One billion cycles of electrical frequency per second.

Gigabit Ethernet

Global Beam

An antenna down-link pattern used by the Intelsat satellites, which effectively covers one-third of the globe. Global beams are aimed at the center of the Atlantic, Pacific and Indian Oceans by the respective Intelsat satellites, enabling all nations on each side of the ocean to receive the signal. Because they transmit to such a wide area, global beam transponders have significantly lower EIRP outputs at the surface of the Earth as compared to a US domestic satellite system which covers just the continental United States. Therefore, earth stations receiving global beam signals need antennas much larger in size (typically 10 meters and above (i.e.30 feet and up). [Sat07]

A mobile satellite system that deploys a network of 48 satellites to create a global voice and data service. This system is backed by Qualcomm, Loral, and Alcatel. [Sat07]
Global System for Mobility (GSM)
A digital cellular service designed for world-wide implementation; uses a combination of TDMA and FDMA. Or Global System for Mobile Communications (GSM)—An international standard, developed in Europe, for digital mobile communications.

Global Title Translation (GTT)
Network routing functionality required to offer customers advanced features such as local number portability (LNP), toll-free, calling card, calling name delivery, and roaming support, as well as other advanced network services.


Generalized Multiprotocol Label Switching; an extension of the signaling protocols of MPLS to lower-layer entities in the network, including optical and physical layer devices. GMPLS-enabled photonic switches allow automated provisioning and bandwidth-on-demand services, as well as new services like optical virtual private networks. [IEC06]
Government Channel
FCC rules require cable systems in the top 100 markets to set aside one channel for local government use, to be available without cost for the “developmental period.” That period runs for five years from the time that subscriber service began, or until five years after the completion of the basic trunk line.


GPON is specified by ITU G.984 and is an evolution of the BPON standard. It supports higher rates, enhanced security, and choice of Layer 2 protocol (ATM, GEM, and Ethernet). By early 2011, Verizon had installed over three million (3M) lines. It is the primary PON architecture employed within Verizon FiOS™ networks. It is the successor to G.983.

PON Category:


Downstream (DS) Data Rates

Upstream (US) Data Rates


BPON (Broadband PON)

ITU-T G.983

622 Mbps

155 Mbps

RF Overlay using 1550nm optical λ

GPON (Gigabit PON) successor to BPON; provides for transport of asynchronous transfer mode (ATM), time division multiplexing (TDM) & Ethernet

ITU-T G.984

2.488 Gbps

1.244 Gbps

RF Overlay using 1550nm optical λ

EPON (Ethernet PON)

IEEE 802.3ah

100 Mbps

100 Mbps


GE-PON (Gigabit Ethernet PON)

IEEE 802.3ah

1 Gbps (std)

2.5 Gbps (dual speed)

1 Gbps (std)

1 Gbps (dual speed)


10GE-PON (10 Gigabit Ethernet PON)

IEEE 802.3av

10 Gbps

1 Gbps

RF Overlay using 1550nm optical λ

DOCSIS over EPON (DePON) – a combination of EPON & DOCSIS leveraging a cable operator’s DOCSIS network & OSSs (operational support systems). A DePON OLT looks & acts like a CMTS (cable modem termination system).


125 Mbps (32 passive optical split)

125 Mbps (32 passive optical split)

RF Overlay using 1550nm optical λ
DOCSIS 3.0 supports IPTV (internet protocol television)

RFoG (RF over Glass); associated with specific FTTP products & an emerging standard; RF is transmitted over fiber, instead of coaxial cable, through splitters to a node or R-ONT @ the premises; requires the addition of an EDFA (erbium doped fiber amplifier) & return receiver in the hub or headend (HE) to support bi-directional optical transport on a FTTH P2MP plant. Use of existing HE/hub CMTS, eQAM, &/or CMAP along with CPE is required.

SCTE 174 2010

160 Mbps (4-channel bonding)

160 Mbps (4-channel bonding)

DS RF Overlay using 1550nm & US RF Overlay using 1310nm or 1610nm optical λ
DOCSIS 3.0 supports IPTV (internet protocol television)

PON Categories as of 01 March 2011

Global Positioning System; a constellation of geo-synchronous satellites that provide navigation and time information. [Arr11]
Grade A Contour

The area in which the quality of television broadcast reception is satisfactory at least 70% of the time for at least 90% of the receiving locations. [Arr11]
Grade B Contour

The area in which the quality of television broadcast reception is satisfactory at least 90% of the time for at least 50% of the receiving locations. [Arr11]
Graded Index Fiber

An optical fiber which has a refractive index that gets progressively lower away from the center. This characteristic causes the light rays to be continually refocused by refraction in the core. A fiber type wherein the core refractive index decreases almost parabolically radially outward toward the cladding. This type of fiver combines high-bandwidth capacity with moderately high coupling efficiency. [Arr11]

Graded Index Fiber Diagram courtesy of Fiber Optics Info, http://www.fiber-optics.info/fiber_optic_glossary/g

Grainy Picture

A poor picture condition, usually the result of weak signal strength and a uniform distribution of noise, appearing as spots or streaks throughout the picture. [Arr11]


Exempting cable systems from the federal rules because 1) they were in existence or operation before the rules, or 2) substantial investments were made in the system construction before the rules. Grandfathering applies to signal carriage, access channels and the certification process.


Dual-reflector antenna system employing a paraboloidal main reflector and a concave ellipsoidal subreflector. [Sat07]

Gradient Index; generally refers to the “self focusing” SELFOC lens often used in fiber optics. [Fib111]


An electrical connection to the earth. Also a common return to a point of zero potential, such as the metal chassis in radio equipment. [Arr11]
Ground Noise

Unwanted microwave signals generated from ground and detected by a dish. [Arr11]

Ground Communication Equipment
Satellite earth station electronic equipment.

Group Delay

The difference in transmission time between the highest and lowest of several frequencies through a device, circuit or system.

Group Index

Also called group refractive index. In fiber optics, for a given mode propagating in a medium of refractive index (n), the group index (N), is the velocity of light in a vacuum (c), divided by the group velocity of the mode. [Fib111]
Group Velocity

1) The velocity of propagation of an envelope produced when an electromagnetic wave is modulated by, or mixed with, other waves of different frequencies. 2) For a particular mode, the reciprocal of the rate of change of the phase constant with respect to angular frequency. 3) The velocity of the modulated optical power. [Fib111]

Guaranteed Service Domain

Global System for Mobility


A figure of merit of an antenna and low noise amplifier combination expressed in dB. "G" is the net gain of the system and "T" is the noise temperature of the system. The higher the number, the better the system. [Sat07]
G/T Ratio

Gain to noise temperature ratio; figure of merit of a receiving system, expressed in dB/k. G is the net gain of the antenna referenced to the point of measurement and T is the noise temperature of the system in Kelvins referenced to the same point. The value of G/T is independent of the point measured. [Arr11]

Global Title Translation

Guard Band

Minimum time allocated between bursts in the upstream referenced from the symbol center of the last symbol of a burst to the symbol center of the first symbol of the following burst. The guard band should be at least the duration of five symbols plus the maximum system timing error.

Guard Channel

Television channels are separated in the frequency spectrum by spacing them several megahertz apart. This unused space serves to prevent the adjacent television channels from interfering with each other. [Sat07]

Guard Time

The term guard time is similar to the guard band, except that it is measured from the end of the last symbol of one burst to the beginning of the first symbol of the preamble of an immediately following burst. Thus, the guard time is equal to the guard band - 1.




An ITU-T standard for transmitting and controlling audio and video information. The H.323 standard requires the use of the H.225/H.245 protocol for communication control between a “gateway” audio/video endpoint and a “gatekeeper” function.


Refers to a communications system or equipment capable of communications in both directions, but in only one direction at a time. [Arr11]
Half Duplex Transmission

A bidirectional link that is limited to one-way transfer of data, i.e., data cannot be sent both ways at the same time. Also referred to as simplex transmission. [Fib111]
Half Transponder

A method of transmitting two TV signals through a single transponder through the reduction of each TV signal's deviation and power level. Half-transponder TV carriers each operate typically 4 dB to 7 dB below single-carrier saturation power. [Sat07]
Most commonly, a dark area surrounding an unusually bright object, caused by overloading of the camera tube. Reflection of studio lights from a piece of jewelry, for example, might cause this effect. With certain camera tube operating adjustments, a white area may surround dark objects.

Hard-clad Silica fiber

An optical fiber having a silica core and a hard polymeric plastic cladding intimately bounded to the core. [Fib111]
Hard Line Cable

In an all coaxial cable system, the transmission cable from the headend to the trunk amplifier. In an HFC network the coaxial cable from the optical node to a trunk or trunk/bridger amplifier. [Arr11]
The equipment involved in production, storage, distribution or reception of electronic signals. In cable television it means the headend, the coaxial cable network, amplifiers, the television receiver and production equipment like cameras and videotape recorders.

Harmonic Distortion

A form of interference caused by the generation of signals according to the relationship N times f (N * f), where N is an integer greater than one and f is the original signal's frequency. [Arr11]
Harmonic Related Carrier (HRC)
A method of spacing television channels on a cable television system in exact 6- MHz increments, with all carrier frequencies harmonically related to a common reference.

Hashed Message Authentication Code (HMAC)
A message authentication algorithm, based on either SHA-1 or MD5.


Home Audio/Video Interoperability


High-bandwidth Digital Content Protection

High Definition Copy Protection

High Definition Multimedia Interface

High-speed Digital Subscriber Line

High Definition Television; television that has approximately twice the horizontal and twice the vertical emitted resolution specified by the NTSC standard. [Fib111]

Headend (HE)

The control center of a cable television system, where incoming signals are amplified, converted, processed and combined into a common cable along with any original cablecasting, for transmission to subscribers. The system usually includes antennas (off-air and satellite), satellite receivers, LNAs and LNBs, processors, demodulators, modulators, preamplifiers, frequency converters, processors and other related equipment which receives, amplifies, filters and converts off-air television and satellite signals to cable system channels.. [Arr11] Also known as the central location on the cable network that is responsible for injecting broadcast video and other signals in the downstream direction. See also Master Headend, Distribution Hub, and Super Headend (HE).

Excerpt from ANSI/SCTE 87-1 2008,

Graphic Symbols For Cable Systems Part 1: HFC Symbols

Headend Diagram courtesy of Fiber Optics Info, http://www.fiber-optics.info/fiber_optic_glossary/h

Headend Cable

A coaxial cable designed for use in a headend application. It generally has a silver-plated copper center conductor for better conduction. [Arr11]
Headend Router
The computer, at the cable headend, responsible for gateway operations between the headend and the internet.


Protocol control information located at the beginning of a protocol data unit.

Heliosynchronous Orbit

At an altitude of 600 to 800 km and situated in a quasi-polar plane. The satellite is permanently visible from that part of the Earth in sunlight. Heliosynchronous orbits are used for Earth observation or solar-study satellites. [Sat07]

High Electron Mobility Transistor; a type of III-V compound semiconductor device within the field effect transistor (FET) class of devices. HEMTs are also called MODFETs, TEGFETs and SDHTs (modulation doped FETs, two-dimensional electron gas FETs and selectively doped heterojunction transistors). [Fre11]

Highly Elliptical Orbit; This is type of orbit used by the Russian Molniya Satellite system. It is also referred to as Extremely Elliptical Orbit (EEO). [Sat07]
Hero Experiments

Experiments performed in a laboratory environment to test the limits of a given technology. [Fib111]

Hertz (Hz)
A unit of frequency equivalent to one cycle per second. See also Megahertz and Gigahertz.


A process of the shifting of a signal of interest down to a frequency at which it may be processed more easily to extract information.

Heterodyne Signal Processor

A unit employed in CATV systems to convert a carrier frequency to an intermediate frequency (IF). The intermediate frequency carrier may then be filtered, regulated, or otherwise conditioned, and then heterodyned back to either the original carrier frequency, or to a completely new carrier frequency. [Arr11]
High Frequency

Hybrid Fiber/Coaxial Cable; a transmission system or cable construction (illustrated) that incorporates both fiber optic transmission components and copper coax transmission components. [Fib111]

HFC Cable Cross-Sectional Diagram courtesy of Fiber Optics Info, http://www.fiber-optics.info/fiber_optic_glossary/h

HFC Network

A telecommunication technology in which optical fiber and coaxial cable are used in different sections of the network to carry broadband content. The network allows a CATV company to install fiber from the cable headend to serve nodes located close to business and homes, and then from these fiber nodes, use coaxial cable to individual businesses and homes. [Fib111]

High Head Room amplifier; used in high performance off air antenna or uni-directional CATV systems. [Lin07]

That portion of the electromagnetic spectrum from 174 to 216 MHz, television channels 7 through 13. [Arr11]
High-Definition Television (HDTV)

Television with over 1,000 lines of resolution per screen, approximately double the resolution of standard NTSC analog systems. [Arr11]
High Electron Mobility Transistor (HEMT)
A transistor that yields the lowest noise figures in single FET devices.

High Frequency (HF)
Used here to refer to the entire subsplit (5-30 MHz) and extended subsplit (5-42 MHz) band used in reverse channel communications over the cable television network.

High-Pass Filter

A filter which passes frequencies above a given frequency and attenuates all others. [Arr11]
High-Power Satellite

Satellite with 100 watts or more of transponder RF power. [Sat07]
High Q
A fiber circuit with a great deal of selectivity.

High Return

A frequency division scheme that allows bi-directional traffic on a single coaxial cable. Reverse channel signals propagate to the headend above the downstream passband.

High Split

When the upstream frequencies are 5-150/174-750 MHz; this split provides the greatest amount of return path.

High VHF Band
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