N-GEN Communications Web-based Seminars ©NGCS

Seminar - An Overview of Communications Technologies

Module 9 - Wireless Systems and Technologies                                                                                 Slide 80 of 80                                                                                                    ________________

Glossary

ADPCM - Adaptive Differential Pulse Code Modulation, a method of digitizing speech. PCM represents each instantaneous voltage sample as an 8-bit value specifying the amplitude. Differential PCM specifies the difference from the previous sample, which requires fewer bits. Adaptive differential PCM dynamically adjusts the step size, difference in amplitude represented by the bits, proving further reduction in the number of bits required to represent a signal. 

Bluetooth - A standard published by Bluetooth Special Interest Group, for 1 M bps data rate in the 2.4 G Hz band for short distances, typically within a home or a business.

CDPD - Cellular Digital Packet Data, overlays the conventional analog cellular system, using a channel-hopping technique to transmit data during idle times in cellular channels. It operates in full-duplex in the 800 M Hz and 900 M Hz frequency bands. It offers data rates up to 19.2 K bps. 

CDMA - Code Division Multiplexing Access, implemented for PCS cellular telephones, uses Direct Sequence Spread Spectrum to support more conversations in a given frequency bandwidth.

DAVIC - Digital Audio Video Council,  an international body, including major network operators, service providers and consumer electronics, telecommunications and computer industries, is involved in developing the LMDS standards.

DSSS - Direct Sequence Spread Spectrum, combines a data signal with a higher data-rate bit sequence to make it resistant to interference.

DVB - Digital Video Broadcasting, group set-up by the European Broadcasting Union developed the specification for digital TV broadcasting.

ETSI - The European Telecommunications Standard Institute is an independent, non-profit organization, whose mission is to produce telecommunications standards.

FDMA - Frequency Division Multiple Access, divides the available frequency spectrum into smaller frequency band segments. Each segment or channel is used to carry a call. 

HomeRF - A specification for wireless digital communications between PCs and consumer electronic devices within the home.

HyperLAN - Wireless data transmission standards (HyperLAN1 and HyperLAN2) developed by the European Telecommunications Standard Institute Broadband Radio Access Network organization.

IMT-2000 - Specifies international standards for the third-generation wireless services..

ITU - International Telecommunications Union, a standard-setting organization which is a specialized agency of the United Nations.  http://www.itu.ch

LMDS - Local Multipoint Distribution Service, a wireless metropolitan area network technology. An LMDS system consists of a series of cells connected to a central control point. LMDS systems are designed to operate at 24-40 G Hz band. 

MDS - Multipoint Distribution Service, precursor to MMDS. In Canada MDS is equivalent to MMDS

MMDS - Multichannel Multipoint Distribution Service, a wireless metropolitan area network technology. MMDS operates in 2.1 t0 2.7 G Hz radio frequencies with data rates up to 10 M bps with a 35 mile range. It was initially intended to provide TV services in remote locations.

OFDM - Orthogonal Frequency-Division Multiplexing, a modulation technique that divides a high-speed information signal into multiple lower-speed subsignals that the system transmits simultaneously at different frequencies in parallel.

PHS - Personal Handyphone System, a wireless system for the home, developed by the Nippon Telegraph and Telephone Corporation.

PSK - Phase-shift keying is a method of transmitting and receiving digital signals in which the phase of a transmitted signal is varied to convey information

QAM - Quadrature Amplitude Modulation) is a method of combining two amplitude-modulated signals into a single channel, thereby doubling the effective bandwidth. 

TDMA - Time Division Multiple Access is a technology used in digital cellular telephone communication that divides each cellular channel into time slots in order to increase the amount of data that can be carried..

Waveguide - A waveguide is an electromagnetic line used in microwave communications, broadcasting, and radar installations. A waveguide consists of a rectangular or cylindrical metal tube or pipe. The electromagnetic field propagates lengthwise. Waveguides are most often used with antennae.

WLL - Wireless Local Loops, connects subscribers 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. WLL includes cordless access systems, proprietary fixed radio access and fixed cellular systems. Synonymous with Fixed Radio Access and Radio in the Loop Systems.
 

                                                                                                   ________________