WDRM, 2nd edition - Falcon Electronics

Transcription

Falcon Electronics Pty Ltd.
Wireless Design Glossary
This Glossary provides concise and up-to-date terminology
that reflects the wireless industry worldwide. It includes
specific definitions from standards bodies where
appropriate, in an effort to harmonize terms within the
industry.
Falcon Electronics Pty Ltd
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Glossary
Terms
µ
micro; one millionth of a unit of measure (0.000001).
Ω
ohm; the Greek capital letter omega traditionally used to represent the electrical unit.
0dBm
The standard-level ratio of measurement that represents a zero decibel reading
from one milliwatt of power. Initially was introduced for copper systems and was
specified at a frequency of 1000 hertz (Hz) across an impedance of 600 ohms.
1G
The first generation (1G) of systems for mobile telephony was analog circuit switched
and only carried voice traffic. The analog phones used in 1G were less to secure and
prone interference where the signal is weak. Analog systems include advanced mobile
phone service (AMPS), Nordic Mobile Telephone (NMT), and extended total access
communications system (TACS). Second generation (2G) and third generation (3G)
networks are replacing 1G networks. These advanced networks support richer
applications, such as short message service (SMS), multimedia messaging service (MMS),
and games. (Jupitermedia Corporation)
1xEV-DO
One times evolution—data optimized (IS-856)
1xEV-DV
One times evolution—data and voice
1xRTT
Single-carrier radio transmission technology. A third generation (3G) wireless
technology that is the code division multiple access (CDMA) version of the International
Telecommunication Union’s (ITU) International Mobile Telecommunications (IMT)-2000
standard.
2G
The second generation (2G) of mobile telephony systems uses digital encoding. 2G
networks support high bit-rate voice, limited data communications, and different levels of
encryption. 2G networks include Global System for Mobile Communications (GSM),
digital advanced mobile phone service (DAMPS [time division multiple access (TDMA)]),
and code division multiple access (CDMA). 2G networks can support short message
service (SMS) applications. (Jupitermedia Corporation)
2.5 generation (2.5G) mobile telephony
An evolution of second generation (2G)
mobile telephony (digital) cellular mobile telephone systems, adding features such as
packet-switched connections and enhanced data rates to the 2G core network
architecture.
3 dB rule
The relationship of decibel (dB) loss and gain to power is known as the
3dB rule. The rule simply states that for every 3dB of gain the power is doubled and
for every 3dB of loss the power is halved.
3G
The third generation of mobile systems provides high-speed data transmissions of
144 kilobits per second (kb/s) and higher. 3G will support multimedia applications such
as full-motion video, video conferencing, and Internet access. (Jupitermedia Corporation)
3GPP
Third Generation Partnership Project.
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Glossary
3GPP2
Third Generation Partnership Project Two.
3xRTT
Three-carrier radio transmission technology.
6 dB rule
A link loss budget relationship in which each 6 decibel (dB) increase in
effective isotropic radiated power (EIRP) or antenna gain equates to a doubling of range
and each 6 dB reduction equates to cutting the range in half.
A
A
The Global System for Mobile Communications (GSM) interface between the basic
service set (BSS) and network substation (NS).
A3
A stream cipher used for authentication in the Global System for Mobile
Communications (GSM) authentication center (AuC) database subsystem.
A5
A stream cipher used for encryption of transmissions in the Global System for Mobile
Communications (GSM) authentication center (AuC) database subsystem.
A-bis
The Global System for Mobile Communications (GSM) interface if the base station
controller (BSC) is not collocated with the base transceiver station (BTS).
absorption
1. A phenomenon causing attenuation of a radio signal passing through a
medium. It occurs when gaseous molecules or suspended water molecules in the
atmosphere absorb the signal energy and convert it into heat due to molecular resonance.
2. In the transmission of electrical, electromagnetic, or acoustic signals, the conversion
of the transmitted energy into another form, usually thermal. Absorption is one cause of
signal attenuation.
access
The process of connecting to a network.
access control
The manner in which devices are granted or denied access to a resource
in cases where two or more devices simultaneously attempt to use a shared resource
(e.g., telecommunications circuit between two sites, specific printer).
access control list (ACL)
A database that keeps track of privileges to network services.
access control mechanism
The way devices on a local area network (LAN) are
granted or denied access to the network.
access point (AP)
A stand-alone hardware device or a computer wireless adaptor with
software that acts as a wireless communication hub for users of wireless devices to
connect with each other and to bridge those devices to the cabled portion of the network.
access protocol
The set of procedures that enables a user to obtain services from a
network (e.g., carrier sense multiple access with collision detection [CSMA/CD] and
token passing for local area networks [LAN]). Also called media access control (MAC)
protocol.
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Glossary
acknowledgment (ACK)
A frame used in the Institute of Electrical and Electronics
Engineers, Inc.® (IEEE®) 802.11 standard to acknowledge that an error-free, data-free,
frame has been received.
active tracking
A method of compensation for alignment variations in antennas.
address
1. A unique identification code assigned to a network device, used to associate
a message with its source and destination. See device address, medium access control
(MAC) address, and network address. 2. A unique location in a computer’s memory or
other electronic storage medium.
ad hoc network
A peer-to-peer network characterized by communication between nodes
without the need for an infrastructure. Also known as independent basic service set
(IBSS).
adjacent channel discrimination
A measure of the ability of a receiver to successfully
receive a wanted frequency channel in the presence of unwanted signals on adjacent
frequency channels, which are being picked up by the antenna.
adjacent channel interference
Radio frequency interference (RFI) caused by residual
energy outside the nominal bandwidth of an adjacent channel signal spilling into the
wanted channel signal on two systems operating in close proximity on side by side
channels.
adjacent channel rejection
The ability of a receiver to reject interference caused by a
transmitter operating on an adjacent channel.
administration
1. The methodology defining the documentation requirements of a cabling
system and its containment, the labeling of functional elements and the process by which
moves, additions, and changes are recorded. (ISO) See cable labeling system. 2. See
network administration.
alternating current (ac)
1. Current flow that alternates periodically (usually sinusoidal)
in magnitude and direction. 2. The letters ac are used generically to refer to any
periodically alternating (e.g., sinusoid) waveform or signal (e.g., power line voltage of
115 volt alternate current [Vac]). Contrast with direct current (dc).
American National Standards Institute (ANSI)
A private, nonprofit membership
organization focused on meeting the standards and conformity assessment requirements
of its diverse constituency. It provides a neutral forum for the development of consensus
agreements on issues relevant to voluntary standardization. The United States (U.S.)
representative to the International Organization for Standardization (ISO), and through
the U.S. National Committee, to the International Electrotechnical Commission (IEC).
amplifier
An electronic device that increases signal strength.
amplitude modulation (AM)
Modulation in which the amplitude of a carrier wave
is varied in accordance with some characteristic of the modulating signal.
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Glossary
analog signal
A signal in the form of a wave that uses continuous physical variables
(e.g., voltage amplitude or frequency variations) to transmit information. Contrast with
digital signal.
antenna
A conductive structure specifically designed to couple or radiate electromagnetic
energy. In radio frequency (RF) systems, the antenna may be used to both transmit and
receive electromagnetic energy.
antenna array (including panel)
An antenna made up of a number of elements including
an active or driven element, a reflector, and a director. Array antennas may be
narrowband or broadband, and are used in all frequency bands.
antenna gain
1. A term used to describe the capability of an antenna to direct signal
energy in a particular direction. 2. The ratio of the power required at the input of a lossfree reference antenna (usually an isotropic radiator or dipole) to the power supplied to
the input of the given antenna to produce, in a given direction, the same field strength at
the same distance. Antenna gain is usually expressed in decibels relative to an isotropic
radiator (dBi) (isotropic reference) or half wavelength dipole reference (dBd).
aperture size
1. The effective capture area of an antenna. The term is commonly used
in connection with microwave horn antennas and waveguides. 2. The physical size of the
opening in a camera lens, expressed as F-stops.
application address
An address used to uniquely identify each software process running
on a network device. See medium access control (MAC)address and network address.
Application layer
The Open Systems Interconnection (OSI) Reference Model layer
responsible for providing mechanisms that enable software applications on different
systems to use the services of a network to exchange information. Also called Layer 7.
asynchronous transfer mode (ATM)
A high-speed switching transmission protocol that
utilizes payload packages organized into cells to carry all types of traffic (e.g., voice, data,
still image, audio/video).
ATM Forum, The
An international organization of manufacturers, service suppliers, and
users of asynchronous transfer mode (ATM) networking products.
attenuation
The decrease in magnitude of transmission signal strength between points,
expressed in dB as the ratio of output to input signal level. (TIA) See insertion loss.
attenuator
A device used to reduce the amplitude of voltage, current, or power (signal
strength) without appreciable distortion.
AuC
The Global System for Mobile Communications (GSM) authentication center
database.
audio frequency (AF)
The band of frequencies (approximately 20 hertz [Hz] to 20
kilohertz [kHz]) that when transmitted as acoustic waves can be heard by the normal
human ear. Contrast with voice frequency (VF).
authentication
the network.
A security mechanism that confirms the identity of a user accessing
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Glossary
authorization
The process of establishing and enforcing the network activities that are
permitted for a given user.
automatic gain control (AGC)
A process or means by which gain is automatically
adjusted in a specified manner as a function of a specified parameter, such as received
signal level.
availability
A measure of network response time or freedom from operating failure
(downtime) during a given period of time.
availability attack
The disruption of network operations by maliciously generating
enough traffic to cause bad congestion and thereby rendering the network unavailable
to intended users.
B
back end equipment
The equipment component of a distributed antenna system (DAS)
that is located in an area of coverage and receives and transmits signals to the headend.
balloon float A helium filled balloon device used to assist in the verification of line of sight
(LoS) in point-to-point (PTP) radio communications.
bandwidth
1. A measure of the range of frequencies associated with a given signal or
communications channel, typically expressed in hertz (Hz). It is used to denote the
potential capacity of the medium, device, or system. 2. The information-handling capability
of a medium, expressed in units of frequency (Hz).
baseband
The bandwidth or interface containing the original basic information of a signal
before it is subject to multiplexing or modulation processes.
base station
The fixed part of a mobile radio frequency (RF) network through which
mobile and portable terminals (or stations) communicate. In the cellular industry, this also
may be called a base transceiver station (BTS).
basic service set (BSS)
A single wireless local area network (WLAN) access point
(AP) and its associated clients, loosely equivalent to a wireless collision domain.
baud
1. The signal-change rate on the line. 2. The rate at which the signal changes from
one state to the other.
beacon
1. A device used to mark tower for aircraft avoidance. 2. A frame transmitted
by wireless local area network (WLAN) access points (APs) at regular intervals to let
its presence be known to clients within its transmit range.
beacon frame
A special token ring frame that is transmitted by a network device when
it detects a ring failure. The device sending the frame is said to be beaconing.
beamwidth
On an antenna radiation pattern for a particular plane, the angle between
the half-power (3 decibels [dB]) points of the main lobe, when referenced to the peak
effective radiated power of the main lobe. Beamwidth is usually expressed in degrees.
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Glossary
bel
A logarithmic ratio of analog signal strengths; named in honor of telephone pioneer
Alexander Graham Bell.
bias tee
A type of connection used to inject direct current (dc) power to combine the
alternating current (ac) radio frequency (RF) signal on one end of a coaxial cable, and
tap it off at the other end, thereby allowing remote powered devices to operate without
a separate local power source.
BICSI®
An international association supporting the information transport systems (ITS)
industry with training, conferences, publications, and registration programs for cabling
distribution designers, as well as commercial and residential installers.
binary digit (bit)
1. The smallest unit of binary data in digital systems. 2. Zeros and
ones used to represent binary data processed by digital devices.
binary phase shift keying (BPSK)
A modulation scheme using phase-shift keying
between two phase states, normally 180 degrees apart.
biometrics
Authentication techniques based on measurable physical characteristics
of individual users (e.g., fingerprints).
bit
1. The basic unit of digital information, used to indicate the existence of one of two
binary states or conditions (e.g., current flow or no current flow, on or off). 2. A digital
pulse representing a one (1) or a zero (0); contracted from the phrase binary digit.
3. A binary digit; the smallest element of information in binary systems. It is either
a logical one (1) or zero (0), also known as “an on or an off bit” of binary data.
bit error rate (BER)
1. The ratio of incorrectly transmitted bits to total transmitted bits.
A primary specification for all transmission systems, it is usually expressed as a power
of 10. 2. The fraction of bits transmitted incorrectly. See attenuation-to-crosstalk ratio
(ACR) and signal-to-noise ratio (SNR).
bit per second (b/s)
A unit of measure used to express the binary data rate of a device,
system, or communications channel. Commonly used rates include kilobit per second
(kb/s), megabit per second (Mb/s), and gigabit per second (Gb/s). Also called bit rate.
bit rate
Transmission of a binary signal measured in bits per second.
A low-power radio frequency (RF) personal area network (PAN) technology
Bluetooth®
that enables cordless data transfer between Bluetooth equipped devices at short range.
bounded medium
A term used to describe cabling or waveguide. Contrast with
unbounded medium.
bridge
1. A Layer 2 networking device used to connect separate local area network
(LAN) collision domains (or network segments) to extend network reach or selectively
isolate network traffic. Data frames may be either forwarded or discarded (filtered) by
the bridge, depending on their source or destination media access control address. The
data rate through the bridge may be lower than the data rate at its LAN interfaces.
Ethernet switches perform the function of a multi-port bridge. 2. Connecting hardware
used to connect multiple devices or cables to a single appearance of a signal.
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Glossary
broadband signaling
See broadband transmission.
broadband transmission
A transmission with bandwidth typically many times that
required to carry a single voice signal (4 kilohertz [kHz] or 64 kilobits [kb/s]). The
bandwidth boundary between narrowband and broadband depends on the industry
sector context.
broadcast
A technique for sending data simultaneously to all devices affiliated to a
network with a single transmission. See multicast and unicast.
broadcast domain
The span of a local area network (LAN) as represented by the
devices capable of receiving a Network layer datagram addressed to all.
byte
A data unit comprising eight bits. Also called an octet.
C
cable loss
The attenuation of a signal as it passes through a cable medium. Cable loss
is normally expressed in decibels (dB) and increases with frequency.
campus
1. The buildings and grounds having legal contiguous interconnection. (TIA)
Some examples include a college, university, industrial park, or military base. 2. A
premises containing one or more buildings. (ISO, CENELEC)
campus area network (CAN)
area.
A data communications network that spans a campus
carrier
A signal modulated by an information source, thereby making it carry the
information.
carrier sense multiple access with collision avoidance (CSMA/CA)
The Institute
of Electrical and Electronics Engineers, Inc.® (IEEE®) 802.11 listen-before-talk protocol.
carrier sense multiple access with collision detection (CSMA/CD)
The protocol for
carrier transmission access in Ethernet networks. CSMA/CD is specified in the Institute
of Electrical and Electronics Engineers, Inc.® (IEEE®) 802.3 standard.
carrier sensing
The monitoring of a communications channel to check if it is free before
transmitting (i.e., to see if any network devices are transmitting).
cdma2000
An air interface, developed under Third Generation Partnership Project Two
(3GPP2) that evolved from second generation (2G) mobile telephony code division
multiple access (CDMA) interim standard (IS)-95.
cell
1. A single raceway of a cellular or underfloor duct system. (TIA) 2. A 53-byte data
transfer unit used by asynchronous transfer mode (ATM) networks. 3. The fixed area in
which a wireless base station (BS) is configured to operate. See zone. 4. A single wireless
local area network (WLAN) access point (AP) and its associated clients.
central processing unit (CPU)
performed.
That part of a computer in which logical operations are
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Glossary
channel
The end-to-end transmission path connecting interfaces of any two pieces of
application-specific equipment. Equipment cords and work area cords are included in
the channel. (CENELEC)
checksum
A value calculated from the binary content of a message. It is used by the
receiving device to verify that the data has not been altered during its transfer from
source to receiver. See frame check sequence (FCS).
chipping sequence
A specific sequence of bits created by converting each bit in the
message stream. Used in direct sequence spread spectrum (DSSS) signaling and referred
to as a chipping code.
chip rate
The rate of the spreading code factor in code division multiple access
(CDMA).
churn
The rate that customers move from one service provider (SP) or system to
another.
circulators
See isolators.
clear to send (CTS)
A frame type used as a reply to the request to send (RTS)
component when the wireless medium is available for transmission.
closed-circuit television (CCTV)
A private video distribution system (DS), typically
used for security surveillance camera purposes, in which the signal is transmitted to a
limited number of receivers or monitoring points.
coax
See coaxial cable.
coaxial cable
A cable consisting of a central metallic inner conductor separated from
an enclosing outer conductor by a dielectric material. This material may be solid, foam,
a suitable gas, or dry air. The outer conductor comprises a metallic braid, a foil layer,
combination of braid and foil, or a solid metallic sleeve. The cable may be protected by
an outer jacket of nonconducting material.
code
A rule intended to ensure safety during the installation and use of materials,
components, fixtures, systems, premises, and related subjects. Codes are typically invoked
and enforced through government regulation.
codec
1. Transforms analog signals into a digital bit stream (coder) and digital signals into
an analog signal (decoder). 2. Converts a digital bit stream from one format or digital
medium to another. 3. Compresses audio and video files for more efficient storage and
transmission. Files are decompressed prior to playback.
coder/decoder
See codec.
communications protocol
See protocol.
complementary code keying (CCK)
A single carrier modulation technique used in the
Institute of Electrical and Electronics Engineers, Inc.® (IEEE®) 802.11b and IEEE 802.11g
networks.
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Glossary
compressor/decompressor
expander).
confidentiality attack
See codec. Also called a compander (compressor/
Another term for data theft.
Consumer Electronics Bus (CEBus®)
An open architecture set of specification
documents that defines protocols for making home products and appliances communicate.
content filtering
The process of restricting the entry or exit of unauthorized or unwanted
data (e.g., e-mail attachments) to and from a network.
coverage density
The number of stations in a wireless network coverage zone.
cross-polar discrimination (XPD)
The difference in antenna gain or device response
between a signal arriving on one polarization and one arriving on the opposite polarization
(expressed in decibels [dB]).
cryptography
The field of study associated with encryption.
customer
An individual or company that has employed contractors to install their
telecommunications system(s).
customer premises
Building(s), grounds, and appurtenances (belongings) under the
control of the customer. (TIA)
customer premises equipment (CPE)
the customer’s premises. (TIA)
Telecommunications equipment located on
cyclic redundancy check (CRC)
An error-detection technique based on polynomial
division that adds bits to a transmitted data stream for the purpose of error detection
at the receiver. See frame check sequence (FCS).
D
datagram
A data unit created at the Network layer of the Open Systems Interconnection
(OSI) Reference Model. It contains the data and control information necessary to transfer
a message from one network to another. Also called a packet.
data integrity
1. The assurance that a given data file has not been deleted, modified,
duplicated, or forged without detection. 2. The degree to which a collection of data is
complete, consistent, and accurate.
Data Link layer
Open Systems Interconnection (OSI) Reference Model layer
responsible for providing reliable data transfer in the form of frames on a local area
network (LAN). Also called Layer 2.
data rate
The rate at which electronically encoded information is transferred between
network devices over a communications channel. Also called throughput or operating
speed.
dBi
Decibel levels referenced to a theoretical isotropic antenna. Used to express
antenna gain.
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Glossary
dBm
1. Decibel referenced to 1 milliwatt (mW); 0 decibel milliwatt (dBm) is equal to
1 mW; -10 dBm corresponds to 0.1 mW; -20 dBm corresponds to 0.01 mW; -30 dBm
corresponds to 0.001 mW. 2. Psophometrically weighted noise power in decibels, with
respect to a power level equivalent to an 800 hertz (Hz) test done at 0 dBm.
dead zone
A space on an optical fiber trace following a Fresnel reflection in which no
measurement can be made.
decibel (dB)
A logarithmic unit for measuring the relative power or strength of a signal.
A decibel is one tenth of a bel. See bel.
delay spread
The standard deviation of the delay of reflections of a radio frequency (RF)
wave that is weighted proportional to the energy in the reflected waves.
demodulation
The recovery from a modulated carrier of a signal having substantially the
same characteristics as the original modulating signal.
demodulator
An electronic device that removes the modulation from signals.
Department of Commerce/National Telecommunications and Information
Administration (NTIA)
The Department of Commerce/NTIA regulates
communications by radio, television, wire, satellite, and cable for all governmental
organizations within the United States (federal, state, and local). Frequency management
and approval for use of spectrum by noncommercial government agencies is provided by
the NTIA.
detector (optical)
An optoelectronic transducer that converts light to an electrical signal.
device address
An address to uniquely identify each device on a network. The address
is coded in the physical hardware. See network address and medium access control
(MAC) address.
diffraction
The bending of radio, sound, or light waves around an object, barrier, or
aperture edge.
digital certificate
A security tool used to authenticate a message. It ensures the recipient
that the message originated from a source whose identity has been verified by the issuer
of the certificate.
digital enhanced cordless telecommunications (DECT)
A standard developed by
the European Telecommunications Standards Institute (ETSI). DECT defines the radio
connection between two points and can be used for remote access to public and private
networks.
digital key
A security tool used to encrypt a message prior to transmission to keep its
contents confidential. Also used by the recipient to restore encrypted messages into
readable content. See key.
digital signal
A signal that changes from one state to another in discrete steps. Contrast
with analog signal.
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Glossary
digital signature
A security tool used to authenticate a message. It ensures the recipient
that the message was not modified after being transmitted by the sender.
digital subscriber line (DSL)
A type of digital technology designed to use existing
(legacy) cabling to support high data rate applications. See xDSL.
diplexer
A three-port frequency-dependent device that may be used as a separator or
a combiner of signals into a single antenna system while achieving the desired signal
strength and system performance (e.g., 150 megahertz [MHz] and 450 MHz).
dipole
An antenna formed by splitting two wires of a two-wire transmission line, and
bending them back to form a single straight line. The antenna feed is in the middle of
the dipole antenna, where the split occurs. A dipole antenna is a resonant antenna. The
optimal length of a dipole antenna is one half of the wavelength of the signal being
received or transmitted by the antenna. A dipole antenna is a narrowband antenna,
operating efficiently in only a narrow band of frequencies.
dipole array
See antenna array.
direct broadcast satellite (DBS)
A service that uses satellites to broadcast multiple
channels of television programming directly to a small-dish antenna.
direct current (dc)
1. Current flow that has a constant magnitude and direction.
2. The letters dc also are used generically to refer to any constant waveform or
signal (e.g., battery voltage of 3 volt direct current [Vdc]). Contrast with alternating
current (ac).
directivity
The ratio of the maximum sensitivity of an antenna to its average sensitivity.
It varies directly as the effective aperture of the antenna and inversely as the square of
the wavelength.
direct ray
In the ray theory analysis of light propagation, the direct ray connects the
source and receiver in a straight line.
direct sequence spread spectrum (DSSS)
1. A technique used to structure signal
process utilizing a digital code sequence having a chip rate much higher than the
information signal bit rate. Each information bit within a digital signal is transmitted as a
pseudorandom sequence of chips. 2. Using a spreading code, the transmitted signal is
spread over a wide frequency band. The spreading code is reapplied to the transmitted
signal at the receiver.
direct wave
Direct wave is the portion of the wave that travels from transmitting to
receiving antenna. It is limited to the distance from the transmitter to the horizon, plus
a small distance added by the wave’s attempt to bend with the surface of the Earth.
directional antenna
An antenna characterized by a broad coverage zone that
preferentially sends or receives signals in a specific direction. See omnidirectional antenna
and unidirectional antenna.
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Glossary
directional coupler
Directional couplers are linear devices that use induction or another
method to differentially split downlink power from an input connector to two or more
output connectors.
discone antenna
A development of the ground-plane antenna in which a circular disc is
substituted for the monopole so that the antenna has a broadband response.
distributed antenna system (DAS)
Systems that transmit or relay radio frequency (RF)
signals (e.g., signals from cellular/personal communications system [PCS] telephones, text
pagers, wireless local area networks [WLANs]) within buildings, structures, tunnels, or
other areas where wireless services cannot be otherwise provided.
distribution system (DS)
A bridging engine in access points (APs) that is used to
connect APs together. The network used to link APs in a wireless environment.
diversity reception
A technique used to improve the reception ability of a wireless
network device (e.g., access point [AP]). A second antenna is built into the wireless
device, which uses the antenna with the best reception.
donor signal
A radio frequency (RF) signal retransmitted on the same or a different
frequency by a distributed antenna system (DAS).
downlink
1. Signals transmitted from satellites to ground stations. 2. In demand priority
access method, the communications channel between a repeater and a connected end
node or between a repeater and a lower-level repeater.
downtime
The interval during which a functional system is inoperable.
dual-duplex signaling
A form of bidirectional signaling in which data transfer can flow
in both directions at the same time over a single communications channel. See full-duplex
signaling, half-duplex signaling, and simplex signaling.
duplex
A simultaneous two-way independent transmission in both directions. See halfduplex and full-duplex signaling.
duplexer
A device that isolates the receiver from the transmitter while permitting them
to share a common antenna.
E
Earth curvature (Earth bulge)
The curvature of the Earth and its effect on line of sight
(LoS) communications links that are more than 10 kilometers (km [6.2 miles (mi)]) apart.
effective isotropic radiated power (EIRP)
The arithmetic product of the power
supplied to an isotropic (ideal [imaginary] spherical omnidirectional) antenna and its gain.
effective radiated power (ERP)
The power supplied to an antenna multiplied by the
antenna gain in a given direction.
electromagnetic emission
The phenomenon by which electromagnetic energy
emanates from a source. Emissions can be either radiated or conducted.
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Glossary
electromagnetic environment
in a transmission medium.
The electromagnetic field(s) and/or signals existing
electromagnetic field
The energy field radiating from a source and containing both
electric and magnetic field components. An electric field is a field surrounding a charged
object. A magnetic field is the field surrounding any current-carrying conductor.
electromagnetic radiation (EMR)
Radiation made up of oscillating electric and
magnetic fields and propagated with the speed of light. Includes gamma radiation, X rays,
ultraviolet, visible, and infrared (IR) radiation, including radar and radio waves.
electromagnetic spectrum
all light and radio waves.
electromagnetic wave
magnetic fields.
The full range of electromagnetic emissions, which include
A wave produced by the interaction of time-varying electric and
Electronic Industries Alliance (EIA)
An alliance organized along specific electronic
product and market lines, and, as a standards association, develops and publishes industry
guidelines.
electronic serial number (ESN)
A unique 32-bit serial number permanently stored in
the mobile station or cellular equipment by the manufacturer. The ESN is transmitted
during the authentication process.
emission
The phenomenon by which electromagnetic energy emanates from a source.
Emission can be either radiated or conducted.
encryption
1. A security mechanism that transforms the readable content in a message
into a seemingly random collection of characters, numbers, and/or symbols to provide
confidentiality. 2. A modification of a bit stream to make it appear randomly controlling
the readability of the emissions.
encryption key
See key.
A standard symbol for signal-to-noise
energy per bit/spectral noise density (Eb/N0)
ratio (SNR); measured at the input to the receiver to quantify signal strength. The
wireless system designer should consult the available curves of theoretical bit error rates
(BERs) to determine the best possible ratio based on the type of modulation.
equipment room (ER) (telecommunications)
An environmentally controlled
centralized space for telecommunications equipment that usually houses a main
or intermediate cross-connect. (TIA)
error
Any unwanted change in the original contents of a transmission.
Ethernet
A local area network (LAN) protocol using a logical bus structure and carrier
sense multiple access with collision detection (CSMA/CD).
European Radio Message System (ERMES)
A paging protocol defined by the
European Telecommunications Standards Institute (ETSI).
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Glossary
extended service set (ESS)
A collection of access points (APs) that are tied together
by a wired backbone in a single collision domain, or by virtual local area networks
(VLANs), to allow Layer 2 (Link layer) roaming.
extra high frequency (EHF)
300 GHz.
Frequencies in the range of 30 gigahertz (GHz) to
F
fade bandwidth
The narrow bandwidth where fading is witnessed.
fade margin
A design allowance that provides for sufficient system gain or sensitivity
to accommodate expected fading for the purpose of ensuring that the required quality
of service is maintained.
fading
The variation of the amplitude or relative phase, or both, of one or more of the
frequency components of the received signal. It is caused by changes in the
characteristics of the propagation path with time fade.
fallback
The ability of an access point (AP) to lower the transfer rate as the signal level
from the mobile station drops below the level required to maintain a reliable connection.
Faraday’s Law A law stating that an oscillating magnetic flux field will lead to the
generation of an oscillating voltage in a conductive loop placed in that field.
Federal Communications Commission (FCC)
A regulatory body for U.S. interstate
telecommunications services and international service originating in the United States.
feed horn
A device that concentrates radio frequency (RF) energy into a waveguide,
antenna radiator, or antenna reflector.
firewall
1. A continuous barrier used to prevent fire spreading from one fire zone or area
to another. 2. One or more security mechanisms (hardware and/or software) designed to
prevent, detect, suppress, and/or contain unauthorized access to a network.
first generation (1G)
flex
See 1G.
Flexible wide-area synchronous protocol.
forward packet data channel (F-PDCH)
forward link.
cdma2000 1xEV-DV data channel on the
frame
A data unit created at the Data Link layer of the Open Systems Interconnection
(OSI) Reference Model. It contains the data and control information necessary to transfer
a message from one device to another on the same network.
frame check sequence (FCS)
The product of an error-detecting code normally inserted
as the final field in a block of transmitted data. Also referred to as a checksum or a cyclic
redundancy check (CRC).
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Glossary
frame synchronization (FS)
A 32-bit post office code standardization advisory group
paging code used to identify the beginning of each message batch.
free space loss
The signal loss that occurs between two isotropic antennas in free space,
unaffected by blocking, refraction, diffraction, or absorption.
free space optics (FSO)
Low-power laser beam used for outdoor point-to-point (PTP)
high-rate, protocol independent transmission.
frequency
The number of cycles or sine waves occurring in a given time; if the unit of
time is one second, the frequency is stated in hertz (Hz); one Hz is equal to one cycle
per second.
frequency band
A range of frequencies for the operation of different radio
communications classes. The International Telecommunication Union (ITU) recognizes
12 bands from 30 hertz (Hz) to 3000 gigahertz (GHz).
frequency converter
Integrated component assemblies required for converting signals
into lower (or intermediate) or higher frequency ranges for further processing.
frequency-hopping spread spectrum (FHSS)
A modulation technique that employs
rapid changing of the transmission frequency in a predetermined, pseudorandom pattern.
Communication is accomplished by synchronizing the transmitter and receiver.
frequency modulation (FM)
Modulation in which the instantaneous frequency of a sine
wave carrier is caused to depart from the center frequency by an amount proportional to
the instantaneous value of the modulating signal. In FM, the carrier frequency is called
the center frequency.
Fresnel reflection
Whenever light traveling in a material encounters a different density
material, some of the light is reflected back to the light source, while the rest continues.
Fresnel zone
The circular zone about the direct path between an electromagnetic wave
transmitter and receiver in an unbounded transmission medium free of radiation sources.
Within the signal span, there are other zones where deflected signals are generally out of
phase with the center lobe signal.
full-duplex signaling
The transmission of data in two directions simultaneously. See
dual-duplex signaling, half-duplex signaling, and simplex signaling.
G
gain
The increase in output current, voltage, or power relative to input current, voltage,
or power, respectively. Gain is usually expressed in decibels (dB).
gateway
An internetworking service used to connect dissimilar applications running on
different networks with different communications protocols. Gateways normally operate
at one or more of the top four layers of the Open Systems Interconnection (OSI)
Reference Model. See portal and wireless local area network (WLAN) gateway.
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Glossary
Gigabit Ethernet
A local area network (LAN) protocol with a 100 times higher
transmission rate (1000 megabits per second [Mb/s]) than Ethernet. See Ethernet.
gigabit per second (Gb/s)
gigahertz (GHz)
A transmission rate denoting one billion bits per second.
A unit of frequency denoting one billion cycles per second (hertz).
ground plane
A system of conductors placed beneath an elevated antenna as a near field
reflective point serving as an earth ground.
ground-reflected wave
The portion of a wave that reaches a receiving antenna after it
has reflected off the Earth’s surface.
ground wave
A low-frequency (LF) radio wave that bends along the Earth’s surface
rather than traveling through the atmosphere because of different refractive indexes.
H
half-duplex channel
A communications channel that can transfer signals in either
direction, but not at the same time.
half-duplex signaling
A bidirectional signaling method in which data transfer can occur
place in either direction, but in only one direction at a time. Contrast with dual-duplex
signaling, full-duplex signaling, and simplex signaling.
handoff
1. The process that occurs when a mobile user moves from one cell (thereby
terminating communications) to another cell (thereby initiating communications) in a
cellular network. The handoff is accomplished without disruption of the exiting connection.
2. The transfer of control from one cell to another in cellular wireless networks.
handover
See handoff.
hardware address
See device address and medium access control (MAC) address.
harmonic distortion
Disruption of a signal caused by an integral multiple of the
fundamental frequency of the signal’s sinusoidal wave. The frequency of a sine wave
is called the fundamental frequency or the first harmonic. The second harmonic is twice
the fundamental frequency, the third is three times the fundamental frequency.
harmonics
Frequencies in an output signal that are not present in the input signal. See
harmonic distortion.
headend
The equipment located at the start of a coaxial cable distribution system where
the signals are processed and combined prior to distribution. (Heneveld’s Pocket Guide
to Residential Technology Terms and Definitions)
headend equipment
The equipment component of a distributed antenna system (DAS)
that consists of active components, power supplies, processors, antennas, and interfaces
to connect the donor signals and backend equipment.
Henry
The unit used to measure magnetic inductance of electromagnetic fields.
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Glossary
hertz (Hz)
1. A unit of measure used to express the range of frequencies associated with
a given signal or communications channel. This range also is called bandwidth. 2. A unit
of frequency equal to one cycle per second. A commonly used rate is megahertz (MHz).
heterodyning
To generate new frequencies by mixing two or more signals in a nonlinear
device (e.g., vacuum tube, transistor, diode mixer).
hidden node (HN)
An instance where two or more nodes in a wireless local area
network (WLAN) are within transmission range of the same access point (AP), but not
within transmission range of each other. Such nodes are said to be hidden from each
other.
high frequency (HF)
Frequencies in the range of 3 megahertz (MHz) to 30 MHz.
high rate direct sequence spread spectrum (HR/DSSS)
A form of wireless signaling
similar to DSSS, but employing a more advanced coding scheme to enable higher data
rates.
high-speed downlink packet access (HSDPA)
A third generation (3G) mobile
telephony digital cellular standard based on the evolution of wideband code division
multiple access (WCDMA) technologies.
hub
A network device that provides a centralized point for Ethernet local area network
(LAN) communications, media connections, and management activities of a physical star
topology cabling system.
hybrid coupler
A component used to combine two wireless bands to a single antenna
feed or distribution cable.
hybrid optical fiber cable
A cable containing two or more types of optical fiber
(e.g., multimode, singlemode) or optical fiber combined with copper.
I
illuminator
A device that concentrates radio frequency (RF) energy at the focal point
of a satellite dish. Also referred to as a feed horn.
image rejection
The discarding of signal images by a receiver. Such images are
produced due to mixing in the intermediate frequency (IF) section of the receiver,
resulting in desired signals and undesired signal images.
impedance
A unit of measure expressed in ohms. The total opposition (resistance,
capacitance, and inductance) a circuit, cable, or component offers to the flow of
alternating current.
incidental radiators
A device that generates radio frequency (RF) energy during
operations although it has not been intentionally designed to do so (e.g., direct current
[dc] motors, mechanical light switches).
independent basic service set (IBSS)
A group of stations in a wireless local area
network (WLAN) that communicate directly with each other (without the use of a central
access point [AP]). This type of network is also known as an ad-hoc network.
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Glossary
industrial, scientific, and medical (ISM)
Unlicensed frequency band in the 900
megahertz (MHz), 2.4 gigahertz (GHz), and 5.8 GHz range. Many devices, including the
Institute of Electrical and Electronics Engineers, Inc.® (IEEE®) 802.11a, IEEE 802.11b,
and IEEE 802.11g wireless local area networks (WLANs), operate in this band. Devices
in close proximity using the same band (e.g., microwave ovens, cordless phones,
Bluetooth®-enabled cell phones) can interfere with network operations.
infrared (IR)
The electromagnetic spectrum having wavelengths between 0.75 and
1000 micrometers (7.5 × 10–7 meters [m] – 1 × 10–3 m) or between 30 and 40,000
microinches (3 × 10–5 inches [in] – 4 × 10–2 in). Used as an alternative to radio-based
communications between devices in close proximity (line of sight [LoS]).
Infrared Data Association® (IrDA®)
The organization responsible for producing the
specifications for infrared (IR)-based connections over very short distances.
infrastructure (telecommunications)
1. A collection of those telecommunications
components, excluding equipment, that together provide the basic support for the
distribution of all information within a building or campus. (TIA) 2. Substructure of system
used to support the cable plant being installed.
Institute of Electrical and Electronics Engineers, Inc.® (IEEE®)
The organization
responsible for the standardization of most networking technologies at Layer 1 (Physical)
and Layer 2 (Data Link) of the seven-layer Open Systems Interconnection (OSI)
Reference Model.
integrated digital enhanced network (iDEN®)
A wireless technology that provides
digital cellular telephone, two-way radio, alphanumeric pager, and data/fax modem
services in a single network.
integrated services digital network (ISDN)
A fully digital communications facility
designed to provide transparent end-to-end transmission of voice, data, audio/video, and
still images across the public switched telephone network.
integrity attack
An unauthorized attempt to modify the contents of one or more files
on a network. See data integrity.
intentional radiator
A device designed to generate and emit radio frequency (RF)
energy during operations using radiation or induction.
inter-access point protocol (IAPP)
A protocol developed by the Institute of Electrical
®
and Electronics Engineers, Inc. (IEEE®) to enable interoperability between access points
(APs) manufactured by different vendors. Adopted as IEEE 802.11f in 2003.
intermediate cross-connect (IC) [building distributor (BD)]
The connection point
between a backbone cable that extends from the main cross-connect (MC [campus
distributor (CD)] first-level backbone) and the backbone cable from the horizontal
cross-connect (HC [floor distributor (FD)] second-level backbone). Building distributor
is the international equivalent term for intermediate cross-connect (IC).
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Glossary
intermediate frequency (IF)
The frequency to which a carrier frequency is shifted as
an intermediate step in signal transmission or reception.
International Electrotechnical Commission (IEC)
international electronics standards.
International Organization for Standardization (ISO)
for defining international cabling standards.
The commission responsible for
The organization responsible
Internet
A worldwide internetwork using transmission control protocol/Internet protocol
(TCP/IP).
Internet Engineering Task Force (IETF)
One of the organizations responsible for
the overall development of the Internet and the standardization of internetworking
technologies.
Internet protocol (IP)
The protocol most often used for communications at Layer 3
(Network layer) of the seven-layer Open Systems Interconnection (OSI) Reference
Model. Required for communications over the Internet.
Internet protocol (IP) address
The Layer 3 (Network layer) address assigned to
devices using the IP. Also referred to as an Internet address.
Internet service provider (ISP)
access to the Internet.
An entity that provides or sells Internet services or
intranet
A collection of users/servers designed to provide content, via methods similar to
the World Wide Web (www), to a limited group of users, defined by security restrictions,
on an internal network. The content is viewed using a Web browser.
intrusion detection
The process of tracking actual or attempted unauthorized access
to a network or protected device.
ionosphere
A section of the atmosphere that extends from about 70 kilometers (km)
to 500 km (43.5 miles [mi] to 311 mi) in altitude, in which ions and free electrons exist
in sufficient quantities to reflect and/or refract electromagnetic waves.
isolator, radio frequency
A passive device used to control the propagation of a radio
frequency (RF) signal by allowing the signal to pass in one direction while providing high
isolation to reflected energy in the reverse direction.
isotropic radiator
A theoretical model antenna that radiates power with identical and
constant intensity in all directions from a point source. Used as a reference standard to
compare the radiation properties of all other types of antennas.
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Glossary
J
J-STD-008
A second generation (2G) narrowband code division multiple access
(CDMA) digital cellular standard for operations in the 1900 megahertz (MHz) band.
K
Kerberos
A network authentication protocol designed to provide strong authentication
for client and server applications by using secret key cryptography. (Massachusetts
Institute of Technology)
key
A unique value (digital signature) associated with a specific user on a network for
the purposes of network security. See also digital key.
k-factor
In tropospheric radio propagation, the ratio of the effective Earth radius to the
actual Earth radius. The k-factor is approximately 4:3.
kilobits per second (kb/s)
per second (b/s).
A data rate denoting one thousand bits per second. See bit
kilohertz (kHz)
A measurement of frequency equivalent to one thousand cycles per
second (hertz).
L
last mile
Generally referred to as the last leg of network transport from the point of
presence or local exchange switch to a home or business.
Layer 1
See Physical layer.
Layer 2
See Data Link layer.
Layer 3
See Network layer.
Layer 4
See Transport layer.
Layer 5
See Session layer.
Layer 6
See Presentation layer.
Layer 7
See Application layer.
leaky coax (LCX)
A colloquial term for radiating cable (see radiating cable).
lens antenna
The lens antenna is placed in front of a horn antenna to focus the radio
frequency (RF) energy.
license
An interest in property for a limited time and purpose.
light amplification by stimulated emission of radiation (laser)
A device that
produces coherent, highly directional light with a narrow range of wavelengths used
in a transmitter to convert information from electric to optical form.
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Glossary
light-emitting diode (LED)
A semiconductor diode that spontaneously emits incoherent
light from the p-n junction when forward current is applied. It converts information from
electrical to optical form. An LED typically has a large spectral width. LEDs give
moderate performance at lower prices than laser diodes. LEDs are commonly used with
multimode optical fiber in data enterprise and industrial applications.
lightweight access point protocol (LWAPP)
Not a current Institute of Electrical and
®
®
Electronics Engineers, Inc. (IEEE ) standard, although the intention is for LWAPP to
standardize how switches/routers communicate with access providers.
line of sight (LoS)
The line that connects the observer’s eye with the object the
observer is looking at. See Fresnel zone.
linearity
A signal output voltage directly proportional to the signal input voltage.
link margin
The amount of available signal level (in decibels [dB]) between the normal
receive level and the point at which the signal is too weak to be received.
link reliability
A calculation of how much of the time a system is expected to be
functional (expressed in percent or time).
load balancing
A mechanism for distributing incoming requests among a collection of
devices or circuits to reduce response times. In a network, load balancing is used to
distribute network traffic/requests across multiple devices to maximize use of otherwise
idle resources.
local area network (LAN)
A data communications system that covers an area generally
associated with some or all of the space within a building (e.g., single department or all
locations within a building) and consisting of a group of interconnected network clients
sharing applications, data, and peripheral devices.
local area network (LAN) address
Any network client’s (e.g., personal computer (PC),
laptop, server) address within the LAN. Networking addresses are protocol dependant.
local exchange carrier (LEC)
A telecommunications company that provides public
switched network access service. (TIA). Can be referred to as incumbent local exchange
carrier (iLec) and competitive local exchange carrier (cLec).
local multipoint distribution services (LMDS)
A fixed wireless technology that
operates in the 27.5 gigahertz (GHz) to 29.5 GHz band and offers line of sight (LoS)
coverage over distances up to 4.8 kilometers (km) to 8 km (3 miles [mi] to 5 mi). It
can deliver data and telephony services to 80,000 customers from a single node.
log-periodic dipole array (LPDA)
Consists of a system of driven elements, but not
all elements in the system are active on a single frequency of operation.
loss
Attenuation of a signal, usually expressed in decibels (dB).
low frequency (LF)
Frequencies in the range of 30 kilohertz (kHz) to 300 kHz.
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Glossary
M
MAC address
See medium access control (MAC) address and device address.
main cross-connect (MC) [campus distributor (CD)]
The cross-connect normally
located in the (main) equipment room (ER) for cross-connection and interconnection of
entrance cables, first-level backbone cables, and equipment cables. Campus distributor
is the international equivalent term for main cross-connect.
management
See network management.
man in the middle
An attack on weak or nonexistent authentication mechanisms
between two endpoints. The attacker inserts himself between these endpoints, where
he can view information passing back and forth, which allows him the ability to modify
or inject data going into such a connection.
medium
1. The transport media through which network devices communicate with each
other. 2. A material (e.g., magnetic disk) on which data may be stored.
medium access control (MAC)
The set of procedures that enables a device to access
a network (e.g., carrier sense multiple access with collision detection [CSMA/CD] or
token passing for local area networks [LANs]).
medium access control (MAC) address
An address used to uniquely identify each
device on a local area network (LAN) and typically coded onto the network interface
card (NIC). The MAC layer defines the access protocol to a shared media, the frame
format and size, and more protocols to maintain the functioning of the media. See
application address and network address.
medium frequency (MF)
megabit per second (Mb/s)
Frequencies in the range of 300 kilohertz (kHz) to 3000 kHz.
A transmission rate equal to one million bits per second.
mega chips per second (Mc/s)
A measure of the number of bits (chips) per second
in the spreading sequence of direct sequence spreading code.
megahertz (MHz)
A unit of frequency equal to one million cycles per second (hertz).
mesh topology
A topology where each device or network is connected to all other
devices or networks by multiple paths.
metric
metrics
1. In routing, a value assigned to a path. 2. A standard of measurement.
Specifications.
metropolitan area network (MAN)
A data communications network that covers an
area larger than a campus area and smaller than a wide area network (WAN). Typically
interconnects two or more local area networks (LANs) and usually covers an entire
metropolitan area (a large city and its suburbs).
micro cell
A base station (BS) with a very small coverage area designed to provide
service in areas having a very high density of mobile subscribers. Microcells are
traditionally used in convention centers, airports, and similar areas.
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Glossary
microwave
An electromagnetic wave having a wavelength from 300 millimeters (mm)
to 1 mm (1 gigahertz [GHz] to 300 GHz). Wireless communication systems employing
microwave signals generally require line of sight (LoS) between transmitting and receiving
antennas.
microwave flange connector
pieces together.
mid-span powering
A style of connector that uses screws to hold two mating
See power over Ethernet (PoE).
Mie scattering
A phenomenon related to free space optics (FSO) that describes light
particle being scattered due to fog.
millimeter wave
An electromagnetic wave having a wavelength from 1 millimeter (mm)
to 0.1 mm (300 gigahertz [GHz] to 3000 GHz). Millimeter waves exhibit many of the
properties usually associated with waves in the optical regime.
mobile access
A form of resource access where connection to a local area network
(LAN) is made from a remote station using a temporary telecommunications link.
mobile application part (MAP)
A protocol using the lower level layers of the Signaling
System 7 (SS7) protocol stack (e.g., transaction capabilities application part, signaling
connection control part, message transfer part) for communication between the various
registers and other mobile switching centers (MSCs).
mobile assisted handoff (MAHO)
A handoff technique involving feedback from the
mobile station as part of the handoff process. The feedback is usually in the form of
signal level and quality measurements on the downlink and signal level measurements
from neighbor cells.
mobile identification number (MIN)
a cellular user.
Usually the mobile station number assigned to
mobile Internet protocol (IP)
An IP designed to support the mobility of a user (host).
Host mobility is becoming important because of the recent proliferation of laptop
computers and the increased need for continuous network connectivity at any location.
mobile station (MS)
network.
The term used to describe the customer terminal in a wireless
modem
A device that converts digital signals to analog for transmission over analog
telephone lines and then reconverts analog signals to digital for processing by computers.
moderate frequency base motion
(expressed in seconds).
A period of movement due to strong winds
modulation
Any of several techniques (e.g., amplitude modulation [AM], frequency
modulation [FM]) used to modulate a carrier signal with an information bearing signal.
The process of coding and decoding information for transmission. For example, a voice
conversation is coded into binary bits (digital information), transmitted and then decoded
at the receiving end.
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Glossary
modulator
An electronic device that modulates baseband video, audio, and data signals
to specific carrier frequencies for insertion into the broadband radio frequency (RF)
distribution system (DS).
monopole
A resonant antenna that can be thought of as being one arm of a dipole
antenna, with the other arm having been removed. The optimal length of a monopole
antenna is one quarter of the wavelength of the signal being received or transmitted by
the antenna. A monopole antenna is a narrowband antenna, operating efficiently in only
a narrow band of frequencies. See dipole.
multi-carrier code division multiple access (MC-CDMA)
A combination of three
interim standard (IS)-95 carriers to form one wideband carrier. It is an evolution of IS-95
for third generation (3G) systems. Also called cdma2000. The current nomenclature is
temporary, with a formal name for this technology to be determined under the Third
Generation Partnership Project (3GPP).
multicast
A technique for sending data, audio, or voice to a selected group of devices
on a network using a single point of transmission. See broadcast and unicast.
multimode telephone
technologies.
A cellular telephone compatible with a number of air interface
multipath
The propagation phenomenon that results in radio signals reaching the
receiving antenna by two or more paths.
multipath fading
On a wireless network, signal fading caused by the arrival of signals
from different directions, each with a different path length.
multipath propagation
On a wireless network, the arrival of signals from different
directions, each with a different path length.
multiple access
1. In satellite communications, the capability of a communications
satellite having simultaneous access to one communications satellite from a number of
ground stations. 2. A scheme that allows users to share the same channel instead of being
assigned a unique frequency.
multiple-aperture
Separate transmit and receive antennas within a free space optics
(FSO) transceiver.
multiplexer (mux)
A device that combines two or more signals over a single
communications channel (e.g., time division multiplexing [TDM], wavelength division
multiplexing [WDM]).
multiplexing (muxing)
1. The combining of two or more communications channels into
a common, high-capacity channel from which the original signals may be individually
recovered. 2. In data transmission, a function that permits two or more data sources to
share a common transmission medium such that each data source has its own channel.
multiple zone wireless local area network (WLAN)
A WLAN with two or more
overlapping zones, each equipped with an access point (AP).
multipoint microwave distribution system (MMDS)
A wireless broadband
technology for Internet access, also known as multichannel multipoint distribution system
(MMDS) and wireless cable.
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Glossary
N
N type or N connector
A medium-size threaded connector for use with direct current
(dc) through 11 gigahertz (GHz). It features a characteristic 50 ohm impedance structure.
nanometer (nm)
A unit of length equal to one billionth of a meter. The most common unit
of measurement for optical fiber operating wavelengths.
narrowband
Any analog signal or analog representation of a digital signal whose essential
spectral content is limited to that which can be contained within a voice channel of
nominal 4 kilohertz (kHz) bandwidth. Narrowband radio uses a voice channel with a
nominal 3 kHz bandwidth.
National Electrical Code® (NEC®)
A safety code written and administered by the
National Fire Protection Association.
National Electrical Manufacturing Association (NEMA)
The association that wrote
a standard code for equipment enclosure types used to fire/weather protect radio
frequency (RF) equipment.
National Fire Protection Association (NFPA)
The association that writes and
administers the National Electrical Code® (NEC®).
network
A group of two or more nodes that can communicate with each other, either
directly, through cabling, or indirectly, through repeaters to separated cabling. See data
network.
network access device
Equipment used to interconnect stations, servers, and shared
peripheral devices on a local area network (LAN) or internetwork.
network address
An address used to uniquely identify each local area network (LAN)
connected to an internetwork. See device address.
network administration
A set of tasks performed to provide secure and reliable access
to appropriate network resources.
network interface card (NIC)
Circuitry in a device that provides the means to connect
to the network. Wireless network interface cards are equipped with a built-in antenna.
Network layer
Open Systems Interconnection (OSI) Reference Model layer responsible
for transferring data in the form of datagrams from one network device to another on an
internetwork. Also called Layer 3.
network management
The combination of planning, procedures, hardware, software,
and personnel needed to maintain network operations at maximum efficiency at all times.
network management center (NMC)
An operations center used to manage network
resources such as mobile switching centers (MSCs), location registers, and base stations
(BSs).
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Glossary
node
Addressable point on the network with processing abilities (e.g., personal computer
(PC), terminal, printer).
nonrepudiation service
Network processes that provide proof that a message was sent
from a specific source, thereby preventing that source from denying having sent the
message.
null
Area where signal strength has zero magnitude.
O
Occupational Safety and Health Administration (OSHA)
United States (U.S.)
agency that develops and enforces safety and health standards that apply to the work
conditions, practices, means, methods, operations, installations, and processes performed
in U.S. workplaces, including telecommunications locations and at telecommunications
field installations.
octet
A measurement of eight bits. See byte.
off-axis
1. Not in a straight line. 2. A state of an optical system in which the optical axis
of the aperture does not coincide with the mechanical center of the aperture.
Office of Engineering and Technology (OET)
A Federal Communications Commission
body that certifies all mobile phones intended for use in the United States, insuring
compliance with spectrum allocations, technical standards, and safe specific absorption
rate (radiation) levels.
Office of Strategic Planning and Policy Analysis (OSP)
A Federal Communications
Commission (FCC) body responsible for working with the chairman, commissioners,
bureaus, and offices to develop a strategic plan identifying short- and long-term policy
objectives for the agency. OSP is responsible for monitoring the state of the
communications industry to identify trends, issues, and overall industry health and
producing staff working papers. OSP acts as an expert consultant to the FCC in areas of
economic, business, and market analysis and other subjects that cut across traditional lines
such as the Internet. OSP reviews other legal trends and developments not necessarily
related to current FCC proceedings, such as intellectual property law, Internet, and
e-commerce issues.
offset
A degree to which the cable or conduit changes direction.
offset (frequency)
frequencies.
The difference between the frequency of source and reference
ohm
A unit of measure of electrical resistance; one ohm is defined as the resistance that
allows one ampere, the unit of electric current, to flow when one volt is applied.
omnidirectional
Radiating in all directions for the source signal.
omnidirectional antenna
An antenna characterized by a broad coverage zone that
radiates signals in all directions equally. See directional antenna and unidirectional antenna.
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\Glossary
Open Systems Interconnection (OSI) Reference Model
A seven-layer architecture
developed by the International Organization for Standardization (ISO) that has served as a
foundation for the development of many standards for network systems communications.
The seven layers are physical, data link, network, transport, session, presentation, and
application.
operating system (OS)
Software that controls the execution of all programs and the
utilization of resources on a device such as a personal computer (PC).
optical fiber
Transmission medium using glass or plastic to transmit pulse light signals.
Its bandwidth is higher than copper and not subject to electromagnetic interference. The
optical fiber consists of a central core (glass or plastic) and an outer cladding.
optical field of view
The area visible through the lens of an optical instrument.
order of magnitude
lower value.
An expression where the upper value is 10 times larger than the
organizational network
An interconnected system of computers, peripheral devices,
and software designed to enable the transfer of data between users and devices.
orthogonal frequency division multiplexing (OFDM)
A technique whereby a wide
frequency band is split into a number of narrow frequency bands. Data is inverse
multiplexed across the subchannels. OFDM is used in the Institute of Electrical and
Electronics Engineers, Inc.® (IEEE®) 802.11a and IEEE 802.11g networks.
overfill
The energy around a receive antenna that is lost due to its being outside the
surface where it can be captured.
P
packet
A group of bits, including data and control elements, that are switched and
transmitted together. See datagram.
packet binary convolutional coding (PBCC)
An encoding method proposed for
Institute of Electrical and Electronics Engineers, Inc.® (IEEE®) 802.11g. Because of
the peak transfer rate of 33 megabits per second (Mb/s), it was rejected in favor of
orthogonal frequency division multiplexing (OFDM). It is still included in IEEE 802.11g
as an option.
packet switching
A data communications switching and transmission system in which an
input data stream is broken down into uniform data packets. Each packet is transmitted
independently between devices through the network without first establishing a dedicated
communications path between the devices. At the receiving end, the packets are checked
for errors, resequenced as necessary, and combined into an output data stream.
pairing
Creates keys for use on encrypted links in Bluetooth®.
panel antenna
A style of radio frequency (RF) antenna constructed in a flat panel shape.
A flat panel antenna is highly directional and usually a phased array antenna.
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Glossary
parabolic antenna
A concave reflector used to produce a parallel beam when the source
is placed at its focus or to focus an incoming parallel beam.
parked state
Refers to a Slave device in Bluetooth®. A parked slave is not active on the
channel, but will remain synchronized to the clock of the master.
passive distribution equipment
Equipment that does not require electric power.
patch antenna
Comprises a patch of conductive material fixed above a conductive plane
and separated from the plane by a thin dielectric substrate.
path loss
In a communications system, the attenuation undergone by an electromagnetic
wave in transit between a transmitter and a receiver. It may be caused by many effects
such as free-space loss, refraction, reflection, aperture-medium coupling loss, and
absorption.
peak output power
Maximum allowable output power of a transmission source.
peer-to-peer local area network (LAN)
A network environment where any station
can contribute to or access network resources. All network devices function as equals.
perigee
The point at which a satellite is closest to the earth.
personal area network (PAN)
A data communications system that covers an area
generally associated with an individual workspace (e.g., office, cubicle).
phase modulation (PM)
An angle modulation in which the phase angle of a carrier is
caused to depart from its reference value by an amount proportional to the instantaneous
value of the modulating signal.
phased array antenna
An antenna that can transmit/receive electromagnetic fields
at/from any direction without any mechanical movement. Such antennas usually support
broad bandwidth and carry more information. They have low visibility and are difficult
to detect due to the absence of moving parts.
phase-shift keying (PSK)
In digital transmission, angle modulation in which the phase
of the carrier is discretely varied in relation either to a reference phase or to the phase
of the immediately preceding signal element, in accordance with data being transmitted.
Physical layer
An Open Systems Interconnection (OSI) Reference Model layer
responsible for the transfer of bit streams over various mediums. Also called Layer 1.
piconet
A single Bluetooth® wireless personal area network (WPAN) that can contain
a maximum of eight active devices. Each master device and the slave device, or devices
associated with it, form a piconet. It provides a base level of connectivity to even the
simplest of sensing and computing objects. See scatternet.
point of presence (POP)
In wireline, the physical demarcation or access point (AP) of
control and billing at an interexchange carrier, local exchange carrier (LEC), competitive
LEC, customer premises equipment (CLE), or service provider (SP).
point of sale (POS)
A location where credit card transactions are performed with the
cardholder present, such as a retail establishment. The card is read magnetically, and the
cardholder’s signature is obtained as insurance against the transaction. This is the most
secure form of credit card commerce.
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Glossary
point-to-multipoint
A wireless connection from one point to several other points.
point-to-point (PTP)
A direct connection established between two specific locations,
such as between two buildings or devices.
polarization
The orientation with respect to a given position, force, voltage, direction,
etc. As with antennas, this is the direction of the radiated electric field in relation to the
surface of the Earth. This is generally vertical in mobile radio systems.
portal
An access point (AP) that connects a wireless local area network (WLAN) to
another Institute of Electrical and Electronics Engineers, Inc.® (IEEE®) 802 network
(e.g., Ethernet or token ring).
positive intrinsic negative (PIN) diode
signals in a receiver.
Used to convert optical signals to electrical
Post Office Code Standardization Advisory Group (POCSAG)
pattern used in global paging markets.
A basic signaling
power over Ethernet (PoE)
A feature associated with access points (APs) that allows
the AP to be connected to a wired network using a single cable. Two pairs of a 4-pair
balanced twisted-pair cable are used for Ethernet signaling and the other two pairs are
used to provide direct current (dc) voltage to the AP. Mid-span requires that the
equipment will be powered over the unused pairs of the balanced twisted-pair cable.
End-span will run the power over the same wire pairs that are used for data transmission.
power splitter
A passive device that accepts an input signal and delivers multiple output
signals with specific phase and amplitude characteristics.
Presentation layer
responsible for various forms of message conversion, including compression and
encryption. Also called Layer 6.
private branch exchange (PBX)
A device allowing private local voice (and other
voice-related services) switching over a network.
privity
The doctrine of privity of contract stipulates that only parties to the contract can
sue or be sued in respect of it.
propagation
The motion of waves through or along a medium.
protected and diversity
A wireless system that provides redundancy through the use
of two transmitters each connected to a separate antenna. See protected system and
unprotected system.
protected system
A wireless system that provides redundancy by using a transmitter
combiner to connect two transceivers to an antenna for redundancy. See protected and
diversity and unprotected system.
protocol
A set of rules and procedures governing the formatting of messages and the
timing of their exchange between devices on a network covering addressing, transmitting,
receiving, and verifying.
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Glossary
protocol data unit (PDU)
Information that is exchanged between peer entities on a
network. It contains control information and may optionally contain data.
protocol stack/suite
A comprehensive set of specifications governing how devices
exchange information over a network.
Q
quadrature amplitude modulation (QAM)
A means of encoding digital information
over radio, wireline, or optical fiber transmission links. It is a modulation technique that
uses variations in signal amplitude and phase, allowing data encoded symbols to be
represented as a multitude of 2N states where N ≥ 4 (e.g., 16, 32, 64, 128, 256). The levels
most commonly used are QAM-4, QAM-16, QAM-64, and QAM-256.
quadrature phase-shift keying (QPSK)
Phase-shift keying in which four different
phase angles are used. In QPSK, the four angles are usually out of phase by 90 degrees.
quality-of-service (QoS)
1. A commitment to performance, based on predefined service
parameters. 2. A measure of the level of service provided on a network.
quarter-wave antenna
the design frequency.
A radio antenna that is one fourth the size of the wavelength of
R
radian
An International System of Units (SI) of plane angular measure. There are 2 π
(pi) or approximately 6.28318 radians in a complete circle. Thus, one radian is about
57.296 angular degrees.
radiating cable/leaky coaxial
Comprises solid copper helical outer coaxial cable with
solid copper inner and foam dielectric. The helical outer conductor has slots that allow
ingress and egress of signals within a limited range of the cable. Coverage is
omnidirectional perpendicular to the cable run for a cable suspended in space, but some
modification of the radiation pattern results from the structure to which the cable is
attached. The main applications of this cable are indoor and underground coverage in
large buildings, tunnels and underground mines and facilities.
radiation pattern envelope (RPE)
A graphical representation of radiation properties of
an antenna as a function of space coordinates. RPE is the guaranteed maximum directive
gain (relative to boresight gain) that should be encountered due to side lobes on a dish
antenna.
radio frequency (RF)
Any electromagnetic frequency that is above the range of hearing.
RF is measured in cycles per second or hertz (Hz).
radio frequency (RF) dispersion
A term used to describe any process by which
RF signal propagating in the air is degraded because the various wave components
(i.e., frequencies) of the signal have different propagation velocities.
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Glossary
radio frequency identification (RFID)
A generic term for technologies that use radio
waves to automatically identify people or objects.
radio frequency interference (RFI)
A disturbance in the reception of radio and other
electromagnetic signals due to conflict with undesired signals. See electromagnetic
compatibility and electromagnetic interference.
radio repeater
A combination of a radio receiver and a radio transmitter that receives a
weak or low-level signal and retransmits it at a higher power so that the signal can cover
longer distances without degradation.
radome cover
An antenna cover that safeguards the antenna against environmental
concerns, such as wind, blowing sand, snow, ice, rain, ultraviolet sunlight, temperature,
fungus, and corrosion.
radome loss
The sum of the ordinary insertion loss of the antenna signal passing through
the radome wall plus the scattering loss off the radome panel framework blocking
(shadowing) the antenna aperture.
rake receiver
Used in a multipath environment to counter multipath effects, combines
signals using estimated delay and weighting factors for each channel.
Rayleigh scattering
1. The scattering of electromagnetic radiation (e.g., light) by
particles much smaller than the wavelength of the radiation. 2. In optical fiber, the
scattering of light that results from small inhomogeneities of material density or
composition. Such scattering results in signal attenuation.
receiver
An electronic device that detects and demodulates and amplifies transmitted
signals.
receiver, optical
An optoelectronic circuit that converts an optical signal to an electrical
serial logic signal. It contains a photo detector, amplifier, discriminator, and pulse-shaping
electronics.
receive sensitivity
The minimum value of average received power to achieve a
1 × 10–10 bit error ratio (BER).
reciprocity
A principle by which an antenna behaves in the same manner as a linear
network, whether receiving or transmitting. It can capture a field to produce power
of the same magnitude at its terminals as the power required to create such a field
if it were transmitting.
reflection
Reflection is the abrupt change in direction of a wave front at the interface
between two dissimilar media so that the incident wave front returns into the medium
from which it originated. For example, radio frequency (RF) waves can be strongly
reflected off the surface of a lake, off the side of a large building, or off walls inside
a building. See Fresnel reflection.
reflector
In a radio frequency (RF) antenna, one or more conducting elements or
surfaces that reflect incident radiant energy. A reflector may consist of a large surface,
as in a dish antenna, or a linear element, as in a Yagi antenna.
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Glossary
refraction
The angular change in direction of a beam of light at an interface between two
dissimilar media or a medium whose refractive index is a continuous function of position
(graded-index medium).
remote authentication dial-in user service (RADIUS)
A distributed client and server
system that secures networks against unauthorized access. (Cisco Systems, Inc.)
repeater
A device that regenerates a digital signal. A repeater receives a signal from one
source, reads it, generates a completely new signal identical to the original, and transmits
it to the next destination. Repeaters can be separate devices to boost long-haul
transmissions or can be incorporated into other devices such as switches and routers.
request to send (RTS)
A frame type used to request permission to transmit. The
response is a clear to send (CTS) signal if the wireless medium is available for
transmission.
retina
The back of the eye.
ring laser gyroscope
a gyro wheel.
A gyroscope consisting of a body rotating around an axle called
roaming
1. In cellular technology (mobile telephony technology), the use of a wireless
telephone outside a specified tariffed geographic area defined by the service provider
(SP), which usually is called the “home” area; outside of the home area, additional
charges usually apply. 2. In wireless local area network (WLAN) technology, this refers
to the ability to move seamlessly between the wireless cells from adjacent access points
(APs) while remaining connected to the network.
S
S-band
The frequency spectrum used for land-based microwave and some mobile
satellite communications.
scalability
The ability of a network to grow without degradation of quality. Examples of
scalability include the ability to expand the number of users or to increase the capabilities
of a computing solution for the current users without making major changes to the system
or software.
scattering
The deflection of light by small particles or inhomogeneities whose size is
similar to or smaller than the wavelength of the incident radiation. See Rayleigh scattering.
scatternet
Consists of two or more piconets in a common area, where each piconet
contains at least one Bluetooth® device that is part of two or more piconets.
scintillation
In free space optics (FSO), describes the temporal and special variations in
light intensities caused by differences of refractive index along the propagation path due
to slight temperature variations among different air pockets.
second generation (2G)
See 2G.
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Glossary
security (network)
Protection against unauthorized activities, generally requiring a
combination of access controls, data integrity, and transaction confidentiality.
sensitivity
1. In optical fiber receivers, the minimum power required to achieve a
specified bit error rate (BER). See bit error rate (BER). 2. In an electronic device
(e.g., communications system receiver, detection device, positive intrinsic negative [PIN]
diode), the minimum input signal required to produce a specified output signal having a
specified signal-to-noise ratio (SNR) or other specified criteria. The signal input may be
expressed as power in decibel milliwatt (dBm) or as field strength in microvolts per meter
(µV/m), with input network impedance stipulated.
serial port profile (SPP)
Defines the steps required to make an emulated serial port
®
connection in a Bluetooth connection.
server
A network device that combines hardware and software to provide and manage
shared services and resources on the network.
service discovery profile (SDP)
Discovers from other Bluetooth® devices such as
printers or fax machines, Bluetooth services such as cordless telephony, file transfer
profile, or headset profile.
service set identifier (SSID)
A character string used for identification of a service set.
Service sets must have identical SSIDs to establish radio contact. See basic service set
(BSS) and independent basic service set (IBSS).
servo
A transducer that converts coded electrical signals into precise angular or linear
motion.
Session layer
responsible for providing services used to organize, synchronize, and manage a given
message exchange between network devices. Also called Layer 5.
short message service (SMS)
Similar to e-mail store and forward, SMS is a service
for sending short text messages (up to 160 characters) to mobile phones via SMS centers.
shrouded dish
Used where interference to/from other systems on the same frequency
and in the same area must be avoided.
signal encoding
medium.
The conversion of data into a form suitable for transmission over a
signaling
The central information or supervisory information provided by a network to
facilitate circuit setup and disconnection. One example of signaling is the process used
to transfer a sequence of bits over a communications medium.
signal splitters
radio.
Signal splitters are used to connect more than one antenna to a single
signal strength
In a communications system, the signal power or intensity at a specified
point and with respect to a specified reference level.
Signaling System 7 (SS7)
A separate packet network using out-of-band signaling
channels to connect the cellular network and carry information for advanced calling
features.
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Glossary
simplex
A process during which signals are transmitted in only one direction; one station
is the transmitter and the other is the receiver.
simplex signaling
A signaling method in which data transfer can occur in only one
direction with no capabilities to change directions. See dual-duplex signaling, full-duplex
signaling, and half-duplex signaling.
single sideband modulation
A variation of the amplitude modulation (AM) technique
where the carrier and one half of the sideband is suppressed. This effectively halves
the bandwidth and power requirements of a radio frequency (RF) transmission.
site survey
A process used to identify the characteristics of an environment. It is
required for the design of a wireless network.
sky wave
A radio wave that travels upward from the antenna. A sky wave may be
reflected to Earth by the ionosphere, troposphere, or stratosphere.
slave
A Bluetooth® wireless device that communicates with a master to form a piconet.
slow frequency hopping
A frequency-hopping spread spectrum (FHSS) technique in
which the frequency is changed once every 4.615 ms.
smart antenna
Combines multiple antenna elements with an active electronics signal
processing capability to optimize and adapt the antenna pattern dynamically in response
to the signal environment.
soft handoff A cellular signal that is controlled by multiple cells before disconnecting and
being handed off from the previous controlling cell (make-before-break).
solar interference
Intense levels of direct sunlight that interfere with signal reception
in free space optical systems.
space diversity
Two vertically spaced antennas that enable the received signal to be
absorbed by at least one of the two antennas, reducing the effect of signal fading.
spectral mask
A radio transmitter’s radiated power confined to a band of frequencies
through the use of a bandpass filter.
spreading ratio
message bit.
The number of bits used in the chipping sequence to represent a
spread spectrum
A radio transmission technology that distributes the transmitted signal
over multiple frequencies within the assigned frequency band and thereby increases the
overall immunity of the signal to noise and prevents message interception.
spurious emissions
Emission on a frequency or frequencies that are outside the
necessary bandwidth and the level of that may be reduced without affecting the
corresponding transmission of information. Spurious emissions include harmonic emissions,
parasitic emissions, intermodulation products, and frequency conversion products, but
exclude out-of-band emissions.
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Glossary
spurious rejection
The ability of a receiver to reject emission on a frequency or
frequencies which are outside the necessary bandwidth and the level of which may
be reduced without affecting the corresponding transmission of information.
standard
A collection of requirements that encompass properties of components and
systems that are intended to ensure an accepted degree of functionality and longevity.
Standards are intended to reflect accepted norms as typically determined through a
balloting process conducted by a nationally or internationally accredited organization.
standing wave ratio
The ratio of the amplitude of a standing wave at an antinode to
the amplitude at a node.
star topology
A topology in which telecommunications cables are distributed from a
central point. (TIA)
static dissipaters
This device is an array that dissipates static charges by providing a
low resistance route for static ground charge to reach the atmosphere, thus preventing
a buildup of the ground charge to the value necessary to trigger a strike.
steerable/polar mount
Antenna support structure that steers the reflector.
storage area network (SAN)
storage devices.
A specialized high-speed network used to interconnect
subnet
A portion of a network that contains a common address component. On
transmission control protocol/Internet protocol (TCP/IP) networks, subnets are defined
as all devices whose IP addresses have the same prefix. (Webopedia)
subnetting
The process of dividing a single broadcast domain into two or more smaller
broadcast domains by modifying network layer address assignments. See subnetwork.
subnetwork
A single broadcast domain in a network that is made up of multiple
broadcast domains.
subscriber identity module (SIM) card
A smart card inserted into the Global System
for Mobile Communications (GSM) mobile station containing customer information.
superhigh frequency (SHF)
Frequencies in the range of 3 gigahertz (GHz) to 30 GHz.
synchronization profile
Commonly used in a personal area network (PAN) to update
calendar and scheduling information between laptop, personal digital assistant (PDA),
and mobile phone. Once the PDA device comes within range, the synchronization can
automatically occur.
synchronous connection oriented (SCO) link
A point-to-point (PTP) link between
the master device and one slave device, used primarily for synchronous voice traffic.
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Glossary
T
T1(DS1)
The digital transmission link consisting of 24 channels to support rates of
1.54 megabits per second (Mb/s).
T3 (DS3)
The digital transmission link consisting of 672 channels to support rates of
44.7 megabits per second (Mb/s), each channel supporting 64 kilobits per second (kb/s).
tapped trunk
A cable connection system where a coaxial cable is tapped by means
of a splitter or vampire tap.
Telecommunications Industry Association (TIA)
A standards association that
publishes telecommunications standards and other documents. Many TIA definitions
are contained in this glossary.
third generation (3G)
throughput
of time.
The amount of data transferred between two points in a given amount
through-window
through glass.
thruster
See 3G.
Refers to transmitting and receiving free space optics (FSO) signal
A motor used to propel a satellite in a specific direction.
time division duplex (TDD)
Is a radio frequency (RF) communication scheme that
transmits and receives alternately with sequential time slots using a single frequency.
time division multiplexing (TDM)
A transmission technique whereby several
low-speed channels are multiplexed into a high-speed channel for transmission.
Each low-speed channel is allocated a specific time position in the bit stream.
time division synchronous code division multiple access (TD-SCDMA)
A third
generation (3G) mobile telephony standard being developed by the China Academy of
Telecommunications Technology in collaboration with Datang and Siemens.
topology
The physical or communications path layout of a network or internetwork.
See logical topology and physical topology.
transceiver
1. A radio transmitter and receiver combined into a single unit. 2. A device
that acts as an interface between the network and the connected device.
transfer impedance
A measure of shielding performance determined by the ratio of the
voltage on the conductors enclosed by a shield to the surface currents on the outside of
the shield. (TIA)
transmission
The movement of information as electrical or optical signals from one
point to another via a medium (e.g., air, water, copper wire, optical fiber).
transmission line
A medium used to transport a desired signal between two points
(e.g., coaxial cable, waveguide, optical fiber).
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Glossary
transmission media
The physical carriers of electromagnetic energy (e.g., copper,
optical fiber, air) radiation.
transmission medium
See medium.
transmit opportunity (TXOP)
Provides a channel access function controlled with a
defined starting time and a maximum duration. Access may be obtained by contention
or through polling.
transmitter (TX)
Signaling source.
transmitter (optical)
optical signal.
An electronic package that converts an electrical signal to an
transmitter combiners
A device that allows several transmitters operating in the same
frequency range to use a single transmission line and antenna.
transponder
repeater.
A combination uplink receiver and downlink transmitter acting like a
Transport layer
responsible for providing a level of quality to the data transfer process. Also called
Layer 4.
troposphere
The lower layers of atmosphere in which the change of temperature with
height is relatively large. It is the region where clouds form, convection is active, and
mixing is continuous and more or less complete.
tunnel
A virtual private network connection through the Internet.
turbulence
An atmospheric condition of dissimilar temperatures among air cells and air
pockets over a given path and surface area.
U
ultrahigh frequency (UHF)
3000 MHz.
Frequencies in the range of 300 megahertz (MHz) to
ultraviolet (UV) light
The portion of the electromagnetic spectrum in which the
longest wavelength is just below the visible spectrum, extending from approximately
10 nanometers (nm) to approximately 400 nm.
Um
A global system for mobile telephony air interface component or radio link.
unbounded medium
A term sometimes used to describe wireless communication.
unequal splitter
A device that asymmetrically splits a radio frequency (RF) signal
between two outputs while maintaining direct current (dc) continuity between all ports.
unicast
A technique for sending data to a single attached network device. A one-to-one
mode of communication. See broadcast and multicast.
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Glossary
unidirectional antenna
An antenna characterized by a very narrow focus and an
extended reach. See directional antenna and omnidirectional antenna.
unidirectional signaling
Signaling that occurs in one direction.
unintentional radiators
A device that intentionally generates radio frequency (RF)
energy for use within the device or that sends RF signals by conduction to associated
equipment via connecting wiring, but which is not intended to emit RF energy by radiation
or induction (e.g., microwave oven).
Universal Mobile Telecommunications Service (UMTS)
A third generation (3G)
broadband, packet-based transmission of text, digitized voice, video, and multimedia at
data rates up to 2 megabits per second (Mb/s), similar to wideband code division multiple
access (WCDMA).
unlicensed frequency band
Radio frequencies (RFs) that require no license. The
unlicensed frequency requirements vary by country.
unlicensed multipoint
A radio system linking three or more nodes that does not require
formal government license to install and operate (i.e., spread spectrum radio).
unlicensed national information infrastructure (U-NII)
Designated to provide shortrange, high-speed wireless networking communication at low cost. Consists of three
frequency bands in the 5 gigahertz (GHz) band of 100 megahertz (MHz) each: 5.15 to
5.25 GHz, 5.25 to 5.35 GHz and 5.725 to 5.825 GHz.
unprotected system
antenna.
A non-redundant wireless system that uses a single transceiver and
uplink
1. Signals transmitted from ground stations to satellites. 2. In demand priority
access method, the communications channel between a connected end node and a
repeater or between a repeater and a higher-level repeater.
V
vertical spiral
An omnidirectional vertical log-periodic antenna may be formed using a
continuous spiral with the radius and spacing of each turn varying in the same manner as
the dipole array relationship. Such an antenna must be operated over a ground plane and
fed unbalanced.
very high frequency (VHF)
very low frequency (VLF)
Frequencies from 30 megahertz (MHz) to 300 MHz.
Frequencies from 3 kilohertz (kHz) to 30 kHz.
vibration resistance
The ability of an antenna to mechanically survive the flexing and
vibration caused by wind blowing across it and its supporting structure.
Vigants formula
1. An equation that models performance factors used when providing
space diversity to an unprotected system. 2. An equation that models rain outages of radio
frequency (RF) systems.
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Glossary
virtual circuit
A temporary communications link through an internetwork that appears to
be a dedicated circuit between two network devices.
virtual LAN (VLAN)
A technique, made possible by switching technologies, that permits
the logical grouping of any number of network devices into one or more subnetworks to
improve traffic management and/or security.
virtual private network (VPN)
A combination of hardware and software technologies
designed to enable secure passage of organizational network traffic over the Internet.
See tunnel.
voice band
An analog voice circuit that transmits signals in a frequency band of 300 hertz
(Hz) to 3400 Hz.
voice frequency (VF)
Pertaining to those frequencies within the part of the audio range
that is used for the transmission of speech.
voice over Internet protocol (VoIP)
A system in which voice signals are converted
to packets and transmitted over a network using transmission control protocol/Internet
protocol (TCP/IP).
voltage standing wave ratio (VSWR)
The ratio of the maximum to the minimum
voltage in the standing wave pattern that appears along a transmission line.
voltage standing wave ratio (VSWR) protection
A device that measures the level of
undesirable reverse power caused by impedance mismatches between a radio frequency
(RF) transmitter, its transmission line, and the antenna. The measuring and limiting reverse
RF power will prevent damage of these components.
W
Walsh code
A common orthogonal code used for direct sequence spread spectrum
(DSSS) in a code division multiple access (CDMA) network.
war driving
A process of traveling and looking for wireless access point (AP) signals that
can be used to acquire network access. This is typically accomplished by using a wireless
personal computer (PC) card, laptop, or handheld computer running a software program
that scans the Institute of Electrical and Electronics Engineers, Inc.® (IEEE®) 802.11
networks and a high-gain directional antenna.
waveguide
A device used to direct radio frequency (RF) transmissions or light waves.
Waveguide in radio systems normally consists of a hollow metallic conductor, usually
rectangular, elliptical, of circular in cross section. In light wave applications waveguide
is normally small prisms or optical fibers.
wavelength
The distance between two points in the same phase in consecutive cycles
measured in the direction of propagation.
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Glossary
wavelength division multiplexing (WDM)
Developed to increase the informationcarrying capacity of optical fiber transmission systems. This technique modulates a series
of data streams using a different wavelength of light for each stream and simultaneously
transporting the multiple wavelengths over a single optical fiber.
wayside
A channel on a microwave carrier that can accommodate small amounts of
traffic without requiring multiplexers at each site.
Web
Used as a noun, it is shorthand for the World Wide Web (www) services found
on the Internet.
Web site
An Internet host location developed to provide information, electronic
commerce, etc.
whip antenna
A long, thinly-shaped antenna.
wide area network (WAN)
An Internet network that uses telecommunications links
to connect geographically distant networks.
wideband
The property of a circuit that has a bandwidth wider than normal for the type
of circuit, frequency of operation, or type of modulation.
wideband code division multiple access (WCDMA)
A channel that is four times
wider than the current channels typically used in second generation (2G) networks in
North America.
Wi-Fi Alliance
An organization made up of a consortium of leading wireless equipment
and software providers for the purpose of certifying all Institute of Electrical and
Electronics Engineers, Inc.® (IEEE®) 802.11-based products for interoperability. Formally
known as the Wireless Ethernet Compatibility Association.
wind load
The total force exerted by the wind on a structure or part of a structure. The
total design wind load includes the sum of the horizontal forces applied to the structure in
the direction of the wind and the design wind load on tower guys and discrete
appurtenances.
window attenuation
In free space optics (FSO) systems, clear glass windows introduce
approximately four percent attenuation for each pane of glass traversed by a beam. Tinted
or coated windows, however, can cause much greater attenuation of the optical beam.
wired equivalent privacy (WEP)
WEP data encryption is defined by the Institute of
Electrical and Electronics Engineers, Inc.® (IEEE®) 802.11 standard to prevent (a) access
to the network by intruders using similar wireless local area network (WLAN) equipment
and (b) capture of WLAN traffic through eavesdropping. Access is denied by anyone
who does not have an assigned key.
wireless fidelity (WiFi)
Often used when referring to Institute of Electrical and
Electronics Engineers, Inc.® (IEEE®) 802.11b equipment, a trade term promulgated by
the Wi-Fi Alliance. WiFi is used in place of IEEE 802.11b in the same way that Ethernet
is used in place of IEEE 802.3.
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Glossary
wireless local area network (WLAN)
Using radio frequency (RF) technology, such
networks transmit and receive data over the air, minimizing the need for wired
connections. Thus WLANs combine data connectivity with user mobility. WLANs are
essentially networks that allow the transmission of data and the ability to share resources,
such as printers, without the need to physically connect each node, or computer.
wireless local area network (WLAN) gateway
A device that provides functions similar
to a WLAN switch but with additional administrative features.
wireless local area network (WLAN) switch
A network access device designed to
centrally manage all connected access points (APs) in a WLAN environment.
X
xDSL
A family of digital technologies designed to provide high data rates over existing
(legacy) telecommunications circuits. See digital subscriber line (DSL).
Y
Yagi array antenna
A tree-shaped antenna named for its designer, Hidetsugu Yagi.
The Yagi antenna uses one or more director elements to focus the radiated signal in
one direction or plane.
Z
zone
In wireless networking, a zone consists of one access point (AP) and the group
of devices associated with that AP. Also called a cell.
NOTE:
Definitions followed by TIA in parentheses are reprinted with permission of the
Telecommunications Industry Association. Complete copies of all TIA standards
can be purchased through BICSI at 800-242-7405 or 813-979-1991, or at
www.bicsi.org.
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WDRM, 2nd edition - Falcon Electronics

Transcription

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