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Glossary
Aggregate Throughput: A measure
of the theoretical maximum amount of data
a network or other communications system
can carry in a given time frame. Basically
a total summation of all data rates of all
simultaneous transmissions possible at one
instance on the system. For example if a
system could support 5 simultaneous
transmissions of 2 Mbit/sec.
Amplitude Modulation (AM): A
technique whereby the voltage level or
amplitude of a carrier is varied in order
to transmit digital or analog
information.
ANSI: The American National
Standards Institute sets standards for the
US computer industry. ANSI participates in
defining network protocol standards.
Antenna: That part of a radio
communications system intended to radiate
and/or collect radio frequency energy.
Antenna Gain: A relative measure
of an antennas ability to direct or
concentrate radio frequency energy in a
particular direction or pattern. Typically
measured in dBi or dBd.
Anti-Jam: The ability of a
spread spectrum system to resist
interference or jamming signals.
Attenuation: The loss or
weakening of a signal through a
transmission line, transmission component,
or signal path. Usually refers to loss in
signal amplitude or signal power, and is
typically measured in decibels (dB).
Attenuator: A component that
reduces the magnitude of current, voltage,
or power of a signal in transmission
between points.
Bandpass Filter: A signal filter
designed to pass a continuous range of
frequencies, while attenuating frequencies
which are both above and below that
range.
Bandwidth: The width of the
operating or transmission channel of a
system. The difference expressed in Hertz
(between the highest and lowest
frequencies of a band).
Baud: The number of signal level
changes per second. Each signal level
contains one (or more) bits of
information.
Bias-T: An in-line device which
couples DC power onto a coax cable
enabling both DC power and RF signals to
travel through the same cable.
Bilateral Amplifier: A device
which amplifies an RF signal in both the
transmit and receive directions.
BPSK: Binary Phase Shift Keying
- Digital DSB suppressed carrier
modulation.
Bridge: Typically used to
describe a component of a communications
network which spans the network from one
physical medium to another, such as from a
wired Ethernet to Wireless.
Bulkhead Connector: A connector
type which is designed to be mounted
through a panel or wall.
Carrier Sense Multiple
Access/Collision Detection (CSMA/CD):
A technique of transmitting over a
local area network where only one
transmitter may use the line at one
time.
Cavity Filter: A popular type of
RF filter which employs a hollow resonant
cavity to resonate out unwanted
frequencies.
Cellular: A wireless
communications network architecture which
employs "cells" or modular coverage areas,
typically serviced by a “cell
site”, and usually provides hand-off
capability between cells for roaming
devices. (See also hand-off and
roaming)
Ceramic Filter: A type of radio
frequency filter which utilizes a
ceramic-dielectric material in its
construction.
Chip: In spread spectrum, the
time it takes to transmit a bit or single
symbol of a PN code (a single element of
the spreading code).
Circular Polarization: The
radiation of radio energy in a circular
pattern similar to sound wave propagation,
or the circular ripples in water caused by
a stone being dropped into it.
Coaxial Cable, Coax: A
concentric two-conductor cable in which
one conductor surrounds the other,
separated by an insulator.
Code: A digital bit stream with
noise-like characteristics. In Spread
spectrum the term code refers to the
pseudo-random code used to control the
modulation technique used to spread the
carrier.
Code Division Multiple Access
(CDMA): A technique used to increase
channel capacity which is associated with
spread-spectrum systems. Typically each
user is given a different pseudo-random
spreading code. To communicate with a
particular user, the sender must select
the code assigned to that user. This
technique can permit many users to operate
simultaneously on the same frequency.
Collisions: In network systems,
when two nodes transmit simultaneously,
causing destruction of a data
packet’s information.
Compression: In RF
amplification, an amplifier is said to be
“in compression” (distorting)
when the output is no longer a linear
representation of the input signal,
typically at the operational limits of the
amplifier.
Connectivity: The ability of a
device to communicate with other devices
through a data communications medium.
Corner Reflector: A type of
antenna which typically employs a bent
piece of sheet metal to serve as the
reflector element.
Correlator: The receiver
component that demodulates a Spread
Spectrum signal. Basically used to measure
the similarity of two signals. Sometimes
referred to as a "de-spreader" in direct
sequence systems.
CW: Continuous wave. An analog
signal which is always "on" (100% duty
cycle).
Data Encryption Standard (DES):
An encryption standard issued by the
National Bureau of Standards.
dBd: Decibels relative to a
dipole. (See also Decibel &
Dipole)
dBi: Decibels relative to an
isotrope. (See also Decibel &
Isotrope)
dBm: Decibels (dB) relative to
one milliwatt. (See also Decibel)
dBW: Decibels (dB) relative to
one Watt. (See also Decibel)
Decibel (dB): A logarithmic
representation of magnitude relationships
commonly used in radio and sound
measurement.
Demodulate: To convert a
modulated signal back to an unmodulated
"baseband" signal.
De-spreading: The process used
by a correlator to recover narrowband
information from a spread spectrum
signal.
Digital Signal: A signal that is
composed of two energy levels (on and
off). Digital signals are used by
computers to transmit data. The pattern of
the level changes represents individual
bits of information.
Digital Signal Processor (DSP):
A specialized microprocessor which
contains hardware features specifically
tailored to the processing of signals.
Diplexer: A device which
combines two transmitters onto one
transmission line.
Dipole Antenna: The most common
wire antenna. Length is equal to one-half
of the wavelength for the frequency of
operation. Fed by coaxial cable.
Direct Sequence (DS): A spread
spectrum modulation technique where a
pseudo-random code directly phase
modulates a carrier, increasing the
bandwidth of the transmission. The
resulting signal has a noise-like
spectrum. The signal is despread by
correlating with a pseudo-random code
identical to and in synchronization with
the code used to spread the carrier at the
transmitter.
Diversity: Used to describe a
receivers ability to select between two
receive antennas, typically cross polarize
(one horizontal and one vertical). This
feature is useful for operating in areas
susceptible to the affects of multi-path
interference.
DPSK: Differential Phase Shift
Keying - a simplified BPSK where only data
transitions are transmitted.
Driver: A low level software
module that controls an input/output port
or external device such as a keyboard or
monitor. Driver are used to control
wireless network interface cards, for
example.
Dummy Antenna/Dummy Load: A
device which serves as a transmitter's
antenna without radiating radio waves.
Generally used to test transmission
components. The device dissipates the
radio energy in the form of heat.
Duplexer: Simultaneous receive
and transmit on one transmission line. The
receiver filter passes the receive
frequency while rejecting the transmitters
frequency. The transmitter filter passes
its frequency while attenuating the
receive frequency.
Duty Cycle: A percentage of the
time "on" (transmitting) versus the time
"off" (not transmitting).
Effective Isotropic Radiated Power
(EIRP): A measure of a signal's
absolute power in a particular direction
(see ERP), but relative to an isotrope
rather than a dipole.
Effective Radiated Power (ERP):
The product of the transmitter peak
envelope power, expressed in Watts,
delivered to the antenna, and the relative
gain of the antenna over that of a half
wave dipole antenna.
EMI/RFI: Electro Magnetic
Interference/Radio Frequency Interference.
Broad spectrum noise or interfering
signals.
Encryption: Modification of a
bit stream so that it appears random.
Encryption is used for security purposes.
The sender and receiver must both employ
the same encryption method.
Ethernet: Ethernet is a type of
wired network that supports high speed
communications among devices over a
coaxial cable.
Ethernet Address: An Ethernet
address is a six-part hexadecimal number
in which a colon separates each part (for
example, 8:0:20:1:2f:0). This number
identifies the Ethernet board installed in
a PC and is used to identify the PC as a
member of the network.
ETSI: The pan-European
communications regulatory standards
board.
Fade Margin: The loss in signal
along a signal path, measured in dB,
caused by environmental factors such as
terrain, atmospheric conditions, etc.
Federal Communications Commission
(FCC): A board of commissioners,
appointed by the President, having the
power to regulate wire and radio
telecommunications in the United
States.
Feedhorn: That part of a
parabolic or grid reflector antenna which
contains the driven element.
Feedline Transmission Line: A
system of cable or other conductors that
connects an antenna to a radio.
File Server: A process running
on a computer that provides access to
files on that computer to programs running
on remote machines.
Filter: A device used to block
or reduce signals at certain frequencies
while allowing others to pass through.
Frequency: The number of cycles
of alternating current in one second,
measured in Hertz (Hz).
Frequency Hopping (FH): A spread
spectrum modulation technique where the
transmitter frequency hops from channel to
channel in a predetermined but
pseudo-random manner. The signal is
de-hopped at the receiver by a frequency
synthesizer controlled by a pseudo-random
sequence generator synchronized to the
transmitter's pseudo-random generator.
Frequency Modulation (FM): An
analog modulation technique whereby the
frequency of a carrier is varied to encode
information.
FTP: File Transfer Protocol, the
FTP application is used to provide file
transfer services across a wide variety of
network systems. Usually implemented as
application level programs, FTP uses
TELNET and TCP protocols. The server side
requires a client to supply a login
indentifier and password before it will
honor requests.
Full-duplex Transmission: A
channel that allows transmission in two
directions at the same time. For example,
cellular telephone service is typically
full duplex.
Gain: The relative increase in
power or magnitude of a signal typically
measured in decibels.
Gas Tube Arrestor: A type of
lightening arrestor which employs a gas
discharge tube, which is a component
containing a small amount of gas.
Grid Antenna: A type of antenna
which employs an open-frame grid as a
reflector, rather than a solid one. The
grid spacing is sufficiently small to
ensure that waves of the desired frequency
cannot pass through, and are hence
reflected back toward the driven
element.
Ground: A connection between a
device or circuit and the earth or some
device serving as the earth.
Half-duplex Transmission (HDX):
A channel that allows transmission in
only one direction at a time, switching
back and forth between transmit and
receive. Most spread spectrum wireless LAN
equipment is Half-Duplex.
Hand-Off: Typically used to
describe the ability of a wireless network
to pass the network connection of a
roaming device from one connection point
to another, without dropping the network
connection.
Hierarchical Network: A network
architecture in which one node retains
control of all traffic across the network
medium.
Hertz (Hz): One completed
alternating cycle per second. Named after
Heinrich R. Hertz, a German physicist.
Used as the international unit of
frequency. The number of cycles per
second.
High-Pass Filter: A signal
filter which passes all frequencies above
a certain frequency, and attenuates all
lower frequencies.
Impedance: Nominal impedance of
the device. The variation of this
impedance with frequency is measured as
VSWR.
In-Line: Power or signal passage
through a device which is in series with
the line.
Insertion Loss: The loss in
signal strength due to the insertion of a
device in series with a signal path.
Typically measured over the intended
operating frequency range of the
device.
Intermodulation (Intermod): The
distortion product of an amplifier, caused
by the interaction of different signal
products within the amplifier.
IP: Internet Protocol. The
TCP/IP standard protocol that defines the
IP as a unit of information passed across
an Internet and provides the basis for
packet delivery service. The protocol
suite is often referred to as TCP/IP
because TCP and IP are the two most
fundamental protocols.
IP Address: Internet Protocol
Address. This is a 32-bit address assigned
to host on a TCP/IP Internet. The IP
address has a host component and a network
component.
Isotropic: A theoretical
"isotrope" is a single point in free space
which radiates energy equally in every
direction.
Jamming: The typically
intentional or malicious interference with
another radio signal.
Lightning Arrester: A device
whose purpose is to eliminate transients
on a conductor which are induced by nearby
lightning activity.
Linear Amplifier: A device that
accurately reproduces a radio wave in
magnified form.
Low-Pass Filter: A signal filter
which passes all frequencies below a
certain frequency, and attenuates all
higher frequencies.
Low-Noise Amplifier (LNA):
Typically a small-signal amplifier for
receive applications.
Maximum Surge: The maximum
single surge current and specified wave
form that can be handled by the device
without failure.
Metal Oxide Varistor (MOV): A
type of lightning arrester which offers
high resistance to low voltages, and low
resistance to high voltages. Placing a MOV
from a conductor to ground causes high
voltage spikes to short-circuit to
ground.
Metropolitan Area Network (MAN):
Similar to a LAN but typically over a
larger area like a city.
Microwave: Usually referring to
all radio frequencies above 2 GHz or
so.
Modulate: To vary the amplitude,
frequency or phase of a radio frequency
wave in accordance with the information to
be conveyed.
Multipath Interference: Signal
reflections and delayed signal images
which are typically associated with indoor
wireless LAN applications, and interfere
with the desired signal.
Multiple Access: A method for
accommodating more users in the same
frequency band.
Multipoint: A communications
circuit interconnecting several nodes
(usually more than two).
Multi-Strike Capability: The
ability for a device to survive and work
again after a lightning strike.
Narrowband: A signal where the
transmission bandwidth is on the order of
its information bandwidth.
NDIS: Network Device Interface
Specification. The NDIS specification is
used for all communication with network
adapters. The specification was developed
by Microsoft and 3Com to provide a common
programming interface for MAC drivers and
transport drivers. NDIS works primarily
with LAN manager and allows multiple
protocol stacks to share a single network
interface card.
Network Address: A unique number
associated with a host that identifies it
to other hosts during network
transactions.
NetBIOS: Network basic
Input/Output system. It provides a Session
Layer interface between network
applications running on a PC and the
underlying protocol software of the
Transport and Network Layers.
Netware: A popular netware
operating system developed by Novell.
Network Interface Card (NIC):
Usually refers to a network adapter card
which installs in a computer.
Noise-Like: Having properties
that cause the appearance of random
noise.
Omni-Directional Antenna: An
antenna which radiates RF energy in a 360
degree pattern about an axis.
Oscillator: A device which
produces a "vibration" or variation in
level at a given frequency.
Parabolic Dish Antenna: An
antenna which utilizes a dish-like
reflector to focus radio energy of a
specific range of frequencies on a tuned
element.
Parabolic Grid Antenna: An
antenna which employs an open-frame grid
rather than a solid dish reflector. (See
also Grid Antenna)
Part 15 Rules (FCC): That part
of the FCC regulations which regulates
unlicenced use of the ISM bands for
wireless networking and other uses.
Patch Antenna: Typically a flat
rectangular or round antenna having a
hemispherical pattern.
Path Budget: A mathematical
model of a wireless communications link
which accounts for a wide variety of
factors which affect operating range and
performance. Sometimes called a "link"
budget.
Path Loss: The weakening of a
signal over its path of travel due to
various factors like terrain, obstructions
and environmental conditions.
PCS: Personal Communication
System - usually associated with cordless
telephone-like devices, and personal data
assistant devices. Service is typically
digital.
Peer-To-Peer Network: All nodes
on the network have equal access to and
control of the network medium.
PING: The Packet Internet Groper
is a program that is useful for testing
and debugging networks. It sends an Echo
to the specified host, and waits for a
response. It reports success or failure
statistics about its operation.
PN: Pseudo Noise - a digital
signal with noise-like properties.
Polling: A process in which a
device polls the terminals connected to
it, asking whether or not they have data
to be sent to the host.
Point-to-Point: A communications
channel that runs from one point to
another.
Point-to-Multipoint: A
communications channel that runs from one
point to several other points.
Power Meter: A device used to
measure radio energy.
Powder Coat: An "environmentally
sound" type of durable plastic coating
used on various types of outdoor
equipment, which is applied electro
Propagation: The travel of a
signal through a medium such as air or
free space.
Radiation: Electromagnetic
energy, such as radio waves, traveling
forth into space from a transmitter.
Radio Frequency (RF): Typically
a frequency from 20 kHz to 3 GHZ. RF is
usually referred to whenever a signal is
radiated through the air. Literally, any
and all frequencies that can be radiated
as an electromagnetic wave.
Radio Wave: A combination of
electric and magnetic fields varying at a
radio frequency and traveling through
space at the speed of light.
Raw Data Rate: Typically refers
to the number of bits per second which can
be transmitted, not accounting for
overhead associated with error correction,
packetizing, and other protocol-related
factors.
Receive Gain: A measure of
receive signal boost contributed by an
amplifier or antenna system, and typically
measured in dB.
Receiver Sensitivity: The
ability of a receiver to differentiate a
signal from the background noise.
Remote-Powered: Typically used
to describe a device which is powered
through the antenna feed cable by way of a
"bias-T" or DC injector.
Repeater: Any device which
regenerates a signal to continue its
propagation, usually increasing total
distance or coverage area.
RF Sensing: A circuit which is
able to detect the transmitted energy of a
transmitter.
Roaming: Typically used to
describe a portable communications device
moving its network connection from one
fixed access point to another.
Router: A router has two or more
network interfaces to different networks.
The primary function of a router is to
direct packets between these networks,
delivering them to their final destination
or to another router. When used with
TCP/IP, the term refers to an IP gateway
that routes data using IP destination
addresses.
RS-232: A popular connection
standard for wired serial data
communications.
Safety Ground: The local earth
ground. The earth ground which grounds the
neutral return A system may be earth
grounded as many times as needed.
Saturation: In amplification, a
term which describes the point at which
the amplifier is producing the most output
power it is capable of, basically in an
over-driven situation. Typically a device
driven to saturation is no longer
performing in a linear fashion or
distortion-free manner. (See also
compression)
Server: A computer or network
node that provides services to the network
or other nodes.
Short Circuit: An unintended low
resistance connection across a low voltage
source resulting in high current and
possible damage.
Signal-To-Noise Ratio (SNR): A
measure of the magnitude of a desired
signal relative to the magnitude of an
undesired signal or noise.
Spectrum: A series of radiated
energies arranged in order of wavelength.
The radio spectrum extends from 20
kilohertz upward.
Spectrum Analyzer: An instrument
which can be used to view signals across a
wide range of frequencies.
Splitter/Combiner: A
transmission component which divides or
sums power between two or more ports.
Spread Spectrum (SS): A wideband
modulation which imparts noise-like
characteristics to an RF signal. This
communications technique spreads a signal
over a wide range of frequencies for
transmission and then de-spreads it to the
original data bandwidth at the
receiver.
Spurious Emissions: Unwanted
radio frequency signals emitted from a
transmitter that sometimes causes
interference.
Throughput: A measure of the
volume of data which can be transmitted
(typically per second) through a given
communications system.
Time Division Multiple Access
(TDMA): A digital multiplexing
technique whereby each signal is sent and
received at a fixed time slots in a series
of time slots. The transmitter and
receiver must be time-synchronized. Public
telephone networks typically use TDMA.
Transceiver: A combination radio
transmitter and receiver.
Ultra High Frequency (UHF):
Ultra high frequency radio waves that
are in the range of 300 to 3,000 MHz.
Very High Frequency (VHF): Very
high frequency waves that are in the range
of 30 to 300 MHz.
Voltage Standing Wave Ratio (VSWR):
The amount of reflected signal due to
impedance mis-match.
Wide Area Network (WAN): Large
network formed by bridging smaller LANs or
using dial-up lines. WANs can span the
globe.
Wavelength: The distance that an
electromagnetic wave travels in one
complete cycle.
Wind Loading: A characteristic
of an antenna or other structure which is
a measure of the forces applied to the
structure due to wind.
Wireless: A new all-encompassing
"buzzword" which describes what used to be
called "radio", but which typically also
implies some of the newer cellular or
digital radio technologies as well.
Wireless "Ethernet": A misnomer
in actuality since "Ethernet" is a wired
system by definition, but appropriate
nevertheless to describe CSMA/CA wireless
LAN’s&emdash;since their operation
has a great deal in common and they are
typically integrated easily.
Wireless Local Area Network
(WLAN): A short range computer to
computer wireless data communications
network.
Yagi Antenna: A directional
antenna named for one of its inventors,
which consists of a boom supporting a
series of elements which are typically
aluminum rods. Often called a
“beam” antenna.
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