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Packet Switching
A core network transmission technique that involves splitting information into "packets" of data that are then re-routed independently through the network over different routes to the final destination. This technique is attractive for mobile access because the radio spectrum is used only when data is actually being transmitted. The alternative is circuit switching. GPRS is a packet-based technology designed for digital mobile networks.

Parasitic Element
A radiating element, not connected to the feed lines of an antenna, which affects the radiation pattern and/or impedance of an antenna

Personal Communication Network. PCNs are usually short range (100's of feet to 1 mile or so) and involve cellular radio type architecture. Services include digital voice, FAX, mobile data and national/international data communications. Also -- A network of pocket-size radio telephones served by clusters of receiver transmitter cells.

Personal Communications Service. A generic term for a mass-market mobile personal communications service, independent of the technology used to provide it. Also, a type of digital wireless network in North America that operates in the 1,900 MHz frequency band. Example: Sprint PCS, which uses CDMA technology.

Personal Digital Cellular. The digital wireless standard used in Japan. Uses TDMA air interface.

Phase Modulation; modulation of the phase of an RF carrier.

Phased Array
An antenna comprised of multiple identical radiating elements in a regular arrangement and fed to obtain a prescribed radiation pattern.

Plane Earth Reflection Loss
the loss between two antennas above ground due to reflection from the ground between them.

Pseudo Noise -- a digital signal with noise-like properties. Also -- a wideband modulation which imparts noise-like characteristics to an RF signal.

In an antenna, the direction in which the electric field vector is aligned during the passage of at least one full cycle.

Stands for "Plain Old Telephone Service." This describes basic telephone service needed in developing countries.

Principal Planes
In an antenna, the azimuth and elevation plane radiation pattern cuts usually taken through the peak of the beam.

Processing Gain
N, the ratio of the bandwidth of a spread spectrum signal to the data rate of the information.

Programmable Logic Device
This is a catch-all term for an integrated circuit that can be programmed to perform complex functions. A PLD consists of arrays of AND and OR gates. A system designer implements a logic design with a device programmer that blows fuses on the PLD to control gate operation. System designers can use development software that converts basic code into instructions a device programmer needs to implement a design. PLDs types can classified as -- (1) PROMs (Programmable Read Only Memory), which offer high speed and low cost for relatively small designs; (2) PLAs (Programmable Logic Array), which offer flexible features for more complex designs; or (3) PAL/GALs (Programmable Array Logic/Generic Array Logic), which offer good flexibility and are faster and less expensive than PLAs.

Programmable Read Only Memory.

Phase Shift Keying; a digital modulation of the phase of a signal's RF carrier.

Stands for Public Switched Telephone Network, the traditional, wired telephone network.


Quadrature Phase Shift Keying; 4 phase digital modulation.


A European R&D initiative that started in the 1980s. It was the starting point for some of the radio developments that are being employed today in mobile third generation systems.

Radiation Pattern
A graphical representation in either polar or rectangular coordinates of the spatial energy distributions of an antenna.

Radio access network
The portion of a mobile network that handles subscriber access, including radio base stations and control and concentration nodes.

Radio cell
Also see Cell. The area served by a radio base station in a cellular or cordless communication system. This is where the term "cellular" came from. Cell size ranges from a few tens of metres to several kilometres.

Telecommunications using radio waves.

Real-time communications
A communication service (usually two-way) in which the information sent is received instantly by the other party in a continuous stream. As an example, telephone calls and videoconferencing are real-time, while database access and e-mails are not.

Radio Frequency (RF)
Generally, a frequency from approximately 50 kHz to 3 GHz. RF is usually referred to whenever a signal is radiated through the air.

Radio in the Loop (RITL)
A telephone system where subscribers are connected to the Public Switched Telephone Network using radio signals rather than copper wire for part or all of the connection between the subscriber and the switch. Includes cordless access systems, proprietary fixed radio access and fixed cellular systems. Synonymous with Fixed Radio Access and Wireless Local Loop Systems.

In an antenna, the redirection of an impinging RF wave from a conducting surface.

Reflector Element
In an antenna, a parasitic element located in a direction other than forward of the driven element intended to increase the direcctivity of the antenna in the forward direction.

The bending of an RF wave while passing through a non-uniform transmission medium.

Return Loss
Expressed in decibels, Return Loss is a measure of VSWR.

Ability of a cordless or mobile phone user to travel from one cell to another, with complete communications continuity. Supported by a cellular network of radio base stations. Roaming is also the term given for inter-network operability, i.e. moving from one network provider to another (internationally).

Read Only Memory.

Radio Transmission Technology.


SCADA, or Supervisory Control and Data Acquisition System
An industrial measurement and control system consisting of a central host or master (usually called a master station, master terminal unit or MTU); one or more field data gathering and control units or remotes (usually called remote stations, remote terminal units, or RTU's); and a collection of standard and/or custom software used to monitor and control remotely located field data elements. Contemporary SCADA systems exhibit predominantly open-loop control characteristics and utilize predominantly long distance communications, although some elements of closed-loop control and/or short distance communications may also be present. Similar to Distributed Control Systems, but usually the field elements are more geographically dispersed.

The random redirection of RF energy from irregular conducting surfaces.

Second Generation
Refers to the second generation of mobile telephones using digital technology to transmit voice and data, which came into use in the 1990s.

Side Lobe
In an antenna, a radiation lobe in any direction other than that of the major lobe.

Simplex Operation
Operating method in which transmission is made possible alternatively in one direction of a telecommunications channel, for example, by means of manual control.

Spread Spectrum (SS)
A communication technique that spreads a signal bandwidth over a wide range of frequencies for transmission and then de-spreads it to the original data bandwidth at the receiver.

Super High Frequency (SHF)
A signal in the frequency range of from 3 to 30 GHz.

A joint venture originally set up by Ericsson, Nokia and Psion to develop an industry-standard operating system for mobile multimedia terminals (EPOC).

Symmetrical Communications
Two-way communications in which equal volumes of information flow in each direction. For example, a videoconference call is symmetrical, Video-on-Demand is not. Also see asymmetric communications.


Trellis Coded Modulation.

The data protocols used for the Internet.

TDMA, or Time Division Multiple Access
A digital multiplexing (channel sharing) technique whereby each signal is sent at a repeating time slot in a frequency channel. Because the data from each user always appears in the same time slot, the receiver can separate the signals. A technique used in Second Generation wireless phone systems, such as GSM, D-AMPS (IS-136) and PDC air interfaces. D-AMPS in North America is often called just TDMA -- see TDMA (ANSI-136) below.

"TDMA" has been adopted as the new name for the "Digital AMPS" (D-AMPS) mobile standard, now called ANSI-136, used in the Americas, Asian Pacific and other areas. TDMA services can be delivered in the 800 MHz and 1900 MHz frequency bands.

TDOA, or Time Difference of Arrival
A location identification technology that uses the time delay between arrival of signals received by at least three different antennas, and knowing the transmit and receive time, can determine position.

Third Generation
Revamped broadband digital networks expected in the early 2000s, that will be able to handle broadband data communications, with transmission rates much higher than the current average of 10 Kbs per second.

Telecommunications Industry Association. A US telecom industry standards body, that handles the evolution of D-AMPS and IS-95.


Ultra High Frequency (UHF)
A signal in the frequency range of from 300 to 3000 MHz.

Universal Mobile Telecommunications System. The European third-generation system developed under the auspices of ETSI - A third generation and highly advanced system optimized for GSM operators.

A radio link from a site on the earth or from an aircraft to a satellite.

EMTS Terrestrial Radio Access. The ETSI term for WCDMA.

Universal Wireless Communications consortium. The industry body that represents the interests of vendors, operators and users of AMPS and TDMA (ANSI-136) mobile networks


Vertical Polarization
In an antenna, a linearly polarized electric field vector whose direction is vertical relative to ground or some arbitrary coordinate system.

Very High Frequency (VHF)
A signal in the frequency range of from 30 to 300 Mhz.

Very Small Aperture Terminal; a small (under 2 meter diameter dish) antenna and satellite receiver.

Voltage Standing Wave Ratio.


Wireless Application Protocol (WAP)
An open, global specification that empowers mobile users with wireless devices to easily access and interact instantly with information and services.

A classification of the information capacity (or bandwidth) of a communication channel. Wideband is generally taken to mean a bandwidth between 64 kbps and 2 Mbps.

Wideband Code Division Multiple Access (W-CDMA)
A refinement of CDMA technology that could raise data transmission rates up to two megabits per second. W-CDMA spreads the chips of the wireless signal over a much wider band of frequencies than CDMA does. This is the air interface technology selected by the major Japanese mobile communications operators, and in January 1998 by ETSI, for wideband wireless access to support third-generation services. This technology will permit very high-speed multimedia services such as full-motion video, Internet access and video-conferencing.

Wireless Local Loops (WLL)
A telephone system where subscribers are connected to the Public Switched Telephone Network using radio signals rather than copper wire for part or all of the connection between the subscriber and the switch. Includes cordless access systems, proprietary fixed radio access and fixed cellular systems. Synonymous with Fixed Radio Access and Radio in the Loop Systems.

"Wireless" Local Area Network (Wireless LAN) or (WLAN)
A nominal 1000 foot (or less) short range computer-to-computer data communications network.

"Wireless" Universe Area Network (WUAN)
A collection of wireless MANs or WANs that link together an entire nation or the world. UANs typically use very small aperture (VSAT) earth station gateway technology.

World Wide Web (WWW)
Name of the total space for highly graphical and multimedia applications on the Internet.



Yagi Antenna
A multiple element parasitic antenna; originated by Yagi-Uda, in Japan; a common VHF and UHF means of achieving high antenna gain in a compact physical size. It is a linear end-fire array consisting of a driven element, a reflector element, and one or more director elements.


Low power, Low Rate Wireless Personal Area Networking (LR-WPAN) technology designed for wireless automation and other lower data tasks, such as smart home automation and remote monitoring. Advantages: Low power consumption, reliable, relative cheap equipment costs. Disadvantages: Low bandwidth (usually under 250 Kbps) may limit the number of applications.

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