H- Glossary

Half-rate - A variant on GSM; doubles capacity by more efficient coding using speech compression.
Handoff (inter-cell) - The process by which subscribers traveling throughout the system coverage area are switched from cell-to-cell (and different channels) with better coverage for that particular area when poor quality conversation is detected.
Handoff (intra-cell) - The process by which subscribers traveling throughout the system coverage area are switched from cell sector-to-sector (and different channels) with better coverage for that particular area when poor quality conversation is detected.
Hands-free: - A feature that's included with most of today's car phones. It permits the driver to use his cellular car phone without lifting or holding the handset to his ear. An important safety feature.
HO Tone - Handoff Tone. 50ms of signaling tone sent by the mobile on the REVC to indicate leaving the source cell site during handoff.
Hand Off Measurement Request. (HOMR) - A digital message sent from the MTSO to a possible target cell site requesting the scanning receiver at that cell scan and report the RSSI of a particular mobile.
Handshaking - A set of signals that coordinate the transfer of data from one device to another.
Hard-Handoff - A hand off that occurs when the subscriber is already using the TPC (three-party-conference) card, and the TPC card cannot be used to aid in a smooth handoff.
Harmonic Filter - Used in the base-station and subscriber transmitter circuits to remove unwanted harmonics from being transmitted and radiated by the antenna.
High Side Injection - A superhet receiver design in which the oscillator frequency is above the carrier frequency.
HIPERLAN - An ETSI approved wireless WLAN, operating at 5.2 GHz with data rates up to 20 Mbps per channel (5 channels).
Hybrid - A circuit used in telephony to convert 2-wire to 4-wire operation and vice-versa. Every telephone contains a hybrid to separate ear piece and mouthpiece audio and couple both into a 2-wire circuit that connects to the Central Office. If the hybrid is not balanced properly, echo or 'loop-back' can result in the circuit when the transmitted signal is reflected back into the receive path.

G- Glossary

GaAs - Gallium Arsenide.
GEO - Geosynchronous Earth Orbit satellite. Geosynchronous systems include Inmarsat and OmniTRACS. The Inmarsat system uses allocations in the 6 GHz band from the ground station to the satellite, 1.5 GHz for the satellite-to-terminal downlink, 1.6 GHz for the terminal-to-satellite uplink, and 1 GHz from the satellite to the ground station.
Glare Hold and Glare Release - A method of glare resolution. Glare occurs when both the local and distant end of a trunk are seized at the same instant; this usually results in deadlock of the trunk. To prevent this, one end of the trunk is assigned a glare hold status and the other a glare release status. In the event of glare, the glare hold end holds the trunk and the glare release end releases the trunk and attempts to seize another. Used between MTSO and connecting cell sites.
GLONASS - The Russian Global Navigation Satellite System is similar in operation and may prove complimentary to the NAVSTAR system. Launched in 1996, is a 24 satellite constellation 19,100 Km above the earth in three orbital planes.
GMSK - Gaussian Minimum Shift Keying. A form of frequency shift keying which shapes pulses to minimize spectral leakage. Used in GSM.
GNSS - Global Navigation Satellite Systems. Extended GPS systems, providing users with sufficient accuracy and integrity information to be useable for critical navigation applications.
GPS - Global Positioning Satellite. Satellite-based radio positioning systems that provide 24 hour three-dimensional position, velocity and time information to suitably equipped users anywhere on or near the surface of the Earth (and sometimes off the earth). GPS is a 24 satellite constellation, 20,000 Km above the earth in six orbital planes. The NAVSTAR system, operated by the U.S. Department of Defense, was the first GPS system widely available to civilian users.
Grade-of-Service - A measure of what percentage of calls placed through an exchange fail to be completed due to congestion of that exchange. In cellular, a 2% GOS is considered acceptable.
GSM - Global System for Mobiles. The most mature digital wireless standard is GSM, usually referred to as the 'European' digital standard. GSM is a TDMA standard, with 8 users per channel. The speech is taken in 20 ms windows, which are sampled (13-bit resolution at 8 ksps), processed and compressed. The vocoder rate of 13 kbits/s is used. A channel is 200 KHz wide, and contains data from eight users. Each user has a time slot of 0.577 mS, during which a burst of 156 bits is transmitted at a modulation frequency of approximately 270 KHz. GSM is transmitted on a 900 MHz carrier.

F- Glossary

Fade - A drop in the received signal strength as a result of the RF transmission's interactions with the transmission environment.
FCC - Federal Communications Commission. The government agency responsible for regulating telecommunications in the United States, located in Washington, D.C. Their responsibilities for public radio communications, such as cellular, include allocation of frequencies, the development of regulations that govern their use and monitoring to ensure that regulations are followed.
FDMA - Frequency Division Multiple Access. FDMA systems transmit one voice circuit per channel. Each conversation gets its own, unique, radio channel. The channels are relatively narrow, usually 30 KHz or less and are defined as either transmit or receive channels. A full duplex conversation requires a transmit & receive channel pair. For example, if a FDMA system had 200 channels, the system could handle 100 simultaneously full duplex conversations. (100 channels for transmitting and 100 channels for receiving)
Example:FDMA channel

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30KHz   | Single voice circuit - one way conversation only  |

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FEC - Forward Error Correction (coding / decoding technique). 

FER - Frame Error Rate.
FH - Frequency Hopping.
FHMA - Frequency Hopping Multiple Access.
Flash- Hook - 400ms of signaling tone sent on the reverse voice channel (by the mobile) to request a hook flash.
FM - Frequency Moduation; modulation of the RF carrier frequency.
Follow-Me Roaming - The ability for the cellular system to automatically forward calls to a roaming mobile that has left it's primary service area. Without this feature, the calling party must know the location of the roamer and place a call to that areas MTSO first (calling a 'port'), then calling the mobile.
Forced Disconnect - A call processing function that forces termination of a call, usually not at the mobile subscriber's request.
Forward Control Channel (FOCC) - A Control Channel used from the base station-to-subscriber direction, also known as the control channel downlink.
Forward Voice Channel (FVC) - A voice channel used in the base station-to-subscriber direction, also known as the voice channel downlink.
Four-Wire Line - A two-way transmission circuit using two pairs of conductors, to allow full duplex (simultaneous) conversation without multiplexing.
Free space loss - This is simply the power loss of the signal as a result of the signal spreading out as it travels through space. As a wave travels, it spreads out its power over space, I.E. as the wave front spreads, so does its power.
Frequency hopping - The transmitter hops to one of many channels, The receiver knows the sequence of the frequency hopper and follows each hop.
Frequency Reuse - The ability to use the same frequencies repeatedly within a single system, made possible by the basic design approach for cellular. Since each cell is designed to use radio frequencies only within its boundaries, the same frequencies can be reused in other cells not far away with little potential for interference. The reuse of frequencies is what allows a cellular system to handle a huge number of calls with a limited number of channels.
Frequency Shift Keying (FSK) - The form of frequency modulation that used two separate audio frequencies to transmit binary ones and zeros.
Front-End - The first stage of filtering in a receiver. The first circuit stage following the antenna input to the receiver.
FSK - Frequency Shift Keying; a digital binary modulation of the RF carrier frequency.
Full Duplex - Refers to a communications system that uses two separate transmit and receive paths to allow simultaneous conversation in two directions.

E- Glossary

EIA/TIA-553 - The ANSI version of the analog cellular standard. Generally one step behind IS-91, and without support for NAMPS.
Electronic Serial Number (ESN) - A 32 bit code that is unique to each mobile unit. Used to validate mobile. Not alterable by both cellular operator and end user. Each cellular phone is assigned an ESN, which is automatically transmitted to the base station every time a cellular call is placed. The Mobile Telephone Switching Office checks the ESN to make sure it is valid, that the phone has not been reported stolen, that the user's monthly bill has been paid, etc., before permitting the call to go through.
Erlang - A dimensionless quantity used in the traffic statistical measurements in the cellular system. One erlang is equivalent to the average number of simultaneous calls. One erlang equals 3600 call-seconds per hour or 36 CCS (call century seconds) per hour.
ESMR - Enhanced Specialized Mobile Radio. Digital mobile telephone services offered to the public over channels previously used only for analog two-way dispatch.
ETACS - Extended TDMA. This system uses the same 30 KHz channels as TDMA, but has six users per channel. The vocoder rate is cut to 4 Kbits/sec, and the channels are dynamically assigned based on voice activity detection.
ETSI - European Telecommunications Standards Institute. The mission of ETSI is "to produce the technical standards which are necessary to achieve a large unified European telecommunications market". This includes the specification of the GSM cellular and PCS standard.
Execute source - An order sent to the mobile on the Forward Voice Channel telling mobile to change channels. Order contains new channel number and new power level.
Execute target - An order sent to the cell a mobile is being handed off to, informing the cell of the pending arrival of a mobile.

D- Glossary

DAR - Digital Audio Radio.
DAS Tape - The magnetic tape that is used at the MTSO to record traffic statistics and call billing information. This tape is sent to a third-party 'billing-house' where the actual billing of the subscribers is done.
dB (decibel) - A unit stating the logarithmic ratio between two amounts of power. Typically used in receiver and transmitter measurements.
dBi - Decibel, Isotropic; decibel referenced to the gain of a theoretical isotropic radiator.
dBm - Decibel, Milliwatt; decibel referenced to one milliwatt into 50 ohms.
DBS - Direct Broadcast Satellite.
DCS - Digital Cellular System
DCS-1800 - Low power variant of GSM, with 1.8 GHz carrier, used in Europe (e.g., Mercury One-2-One)
DCS-1900 - Proposed use of GSM with 1.9 GHz carrier for PCS applications.
DCTU - Digital Cordless Telephone U.S. - a version of DECT proposed for the U.S. PCS market
DDS - Direct Digital Synthesis.
DECT - Digital European Cordless Telephone. A digital cordless telephone standard that incorporates some of the features of the cellular telephone systems. DECT telephones use picocells, and calls can be handed off from one cell to the next.
Detector (Demodulator) - The circuit in a receiver which is used to recover the intelligence (audio) from a signal.
De-Spreading - The process used by a correlator to recover narrowband information from a spread spectrum signal.
Destructive interference - Interference that occurs when waves occupying the same space combine to form a single weaker wave. This type of interference occurs when waves out of phase combine to form a composite wave which is weaker than any of it's component waves. For example if you transmitted two waves that were exactly 180 degrees out of phase, each with an amplitude of 10, they would completely cancel each other out.
DGPS - Differential GPS.
Digital modulation - A method of encoding information for transmission that will eventually replace analog transmission. Digital modulation reduces voice to binary code -- the zeros and ones of computer language. At the receiving end, the information is reconverted. Digital transmission offers stronger reception, less static, greater call handling capacity, fewer dropped calls, improved call privacy, and the potential for additional voice and data service such as fax and computer data transmission.
Direct Sequence - A pseudorandom (PN) code is added to the data signal which increases the modulation rate and signal bandwidth. This spreading of the energy over a wide bandwidth looks like a low level signal to other users in the band. The receiver must know the PN code transmitted and be synchronized to the code to assemble each data bit.
Diversity - Sharing a signal characteristic to allow more users in the same frequency band.
Diversity Receive - A method commonly employed by cellular manufactures to improve the signal strength of received signals. Uses two independent antennas that receive signals which differ in phase and amplitude resulting from the slight difference in antennas position. These two signals are either summed or the strongest is accepted by voting. The most popular methods include dual-antenna phase switching, dual-receiver audio switching and "ratio diversity" audio combining. The most effective method is ratio diversity combining.
Discontinuous Transmission (DTX) - A subscriber unit feature that allows the mobile to disable it's RF PA during conversation when the subscriber is not talking. Save on battery life to increase talk time. The cellular system must support this feature if the subscriber wants to use DTX.
DMR - Digital Mobile Radio.
DPSK - Differential Phase Shift Keying -- a simplified BPSK where only data transitions are transmitted.
Drop Out - A momentary loss of the carrier and sound, or a buildup of background noise when the transmitter is in a certain location in the room. Moving the transmitter (even a few inches) usually restores the sound to normal.
DSP - Digital Signal Processing.
DSRR - Digital Short Range Radio. The Commission of the European Community has designated 880 to 890 MHz and 933 to 935 MHz for unlicensed, business citizens band radio in Europe. For point-to-point communications over distances up to 6 km maximum, depending on antenna height.
DTMF - Dual Tone Multi Frequency. Commonly known as 'touch-tones', this in-band signaling is made up of two tones (out of a group of 8) and is used to translate dialed digits.

C- Glossary PAGE 3

Constructive interference - Interference that occurs when waves occupying the same space combine to form a single stronger wave. The strength of the composite wave depends on the how close in phase the two component waves are. For example if you transmitted two waves of the same phase, each with an amplitude of 10, they would combine into a composite wave of amplitude 20, but two waves slightly out of phase would combine into a composite wave of amplitude less than 20.

Control Channel - A unique RF channel used by each base station dedicated for the transmission of digital control information from the base station to the mobile unit. Used to assign voice channels, control mobile power, authorize handoffs, etc.

Correlator - The receiver component that demodulates a spread spectrum signal; a device that measures the similarity of of an incoming signal and a stored reference code.

COTS - Commercial Off The Shelf.

Cross-correlation - A measure of the similarity of two different signals.

CT2 - Cordless Telephone 2.

CTIA - Cellular Telecommunications Industry Association.

C- Glossary PAGE 2

CDPD - Cellular Digital Packet Data - sending digital data over the existing AMPS system, by transmitting dense packets on vacant analog channels
CDPD Forum - Cellular Digital Packet Data Forum. A trade association to promote the development of the cellular data industry and, in particular, to the standardization and effective use of cellular digital packet data (CDPD technology). This group maintains the CDPD protocol specification that allows the transmission of packet data over analog cellular channels.
Cell - The RF coverage area in the cellular system resulting from operation of a single multiple-channel set of base station frequencies. Cell can also refer to the base site equipment servicing this area. A city or county is divided into smaller "cells", each of which is equipped with a low-powered radio transmitter/receiver. The cells can vary in size depending upon terrain, capacity demands, etc. By controlling the transmission power, the radio frequencies assigned to one cell can be limited to the boundaries of that cell.
Cell splitting - A means of increasing the capacity of a cellular system by subdividing or splitting cells into two or more smaller cells.
CELP - Code Excited Linear Predictive compression algorithm.
Central Office (CO) - The switching office that connects the MTSO (Mobile Telephone Switching Office) to the PSTN (Public Switched Telephone Network). The CO is also known as a Class 5, or 'end' office.
CGSA - Cellular Geographic Service Area. The actual area in which a cellular company provides cellular service.
Channel - A unique RF frequency that is used for communication between subscriber unit and cell site base station. Must be assigned by the FCC (Federal Communications Commission).
Chip - The time it takes to transmit a bit or single symbol of a PN code.
Click Tone - A particular progress tone injected onto the forward voice channel (mobile unit receive, base station transmit) to indicate to the subscriber that the call has not been abandoned by the system.
Cochannel interference - Cochannel interference refers to the interference caused between two cells transmitting on the same frequency within a network. Since cochannel interference is caused by another cell transmitting the same frequency, you can't simply filter out the interference. You can only minimize the cochannel interference through proper cellular network design. A cellular network must be designed to maximize the C/I ratio. The C/I ratio is the carrier-to-cochannel interference ratio. One of the ways to maximize the C/I ratio is to increase the frequency re-use distance, I.E. increase the distance between cells using the same set of transmission frequencies. The C/I ratio in part determines the frequency re-use distance of a cellular network.
Compandor - A combination of a compressor at the transmitter to reduce the dynamic range of the transmitted signal and an expander at the receiver to recover this signal to the original dynamic range. The transmitter encodes (compresses) the dynamics of the audio signal and the receiver decodes (expands) the dynamics of the audio signal. Used in communications systems to improve signal-to-noise as a result of reduced transmitted dynamic range. In analog cellular, 2:1 syllabic compression is used to limit the maximum peak voice deviation to +/- 2.9 KHz.

C- Glossary

Call Forwarding - A feature allowing the subscriber to forward a call to another telephone number.
Call Processing - The complete process of routing, originating, terminating cellular telephone calls, along with the necessary billing and statistical collection processes.
Call Record - A record stored on DAS tape containing mobile number, dialed digits, time stamp information, and other data needed to bill or 'ticket' a cellular telephone call.
Call Setup - The call processing events that occur during the time a call is being established, but not yet connected.
Call Waiting - A feature allowing the subscriber to be alerted of another call during a current conversation. User can answer the call waiting, but cannot connect all parties (connecting all parties is considered a conference call).
Carrier - The operating frequency of a wireless system. A fixed frequency radio signal which is shifted up and down (modulated) in either frequency (FM) or level (AM) by the audio signal.
CDMA - Code Division Multiple Access. In a CDMA system, each voice circuit is labeled with a unique code and transmitted on a single channel simultaneously along with many other coded voice circuits. The receiver uses the same code to recover the signal from the noise. The only distinctions between the multiple voice circuits are the assigned codes. The channel is typically very wide with each voice circuit occupying the entire channel bandwidth. This system used 1.23 MHz wide channel sets. The full vocoder rate is 8.55 Kbits/sec, but voice activity detection and variable rate coding can cut the data rate to 1200 bits/sec. A very robust and secure channel can be established, even for an extremely low-power signal-theoretically, the signal can be weaker than the noise floor.
Example:CDMA channel
           -----------------------------------

1.25MHz     |   64 different voice circuits   |

            -----------------------------------

64 different voice circuits can be simultaneously transmitted on the same channel. More impressively, by using different codes, a number of different channels can simultaneously share the same spectrum, without interfering with each other. The voice circuits are identified by their assigned codes.

B- Glossary

Bandit Mobile - A mobile subscriber that is revealed in the toll-ticketing records as having an invalid ESN, invalid telephone number, or other problem that warrants denial of service to that mobile.
Bandwidth - The amount of frequency allocated for an RF transmission. For example, a cellular channel typically has a bandwidth of 30 KHz, I.E. a cellular system requires 30 KHz of frequency per channel to transmit it's signal.
Base station - The base station is a multicircuit transceiver located at the center of a cell whose primary purpose is to handle all incoming & outgoing calls within the cell. The base station relays the mobile's signal to the MTSO via wireline.
BER - Bit Error Rate.
Broadband - A communications channel that has a bandwidth greater than 64 kilobits per second and that can provide higher speed data communications than a standard telephone circuit (also called wide band).
BT - Bandwidth data rate product, filter bandwidth times bit period, for various modulations including GMSK. Also referred as modulation depth. For example, GSM uses GMSK with BT=0.3.

A - Glossary

ADC - Analog to Digital Converter.
Adjacent channel interference - Refers to interference caused by the energy from a transmitting channel spilling over into an adjacent channel. This interference can be minimized by applying filters to the transmitting and receiving ends or by simply using non-adjacent frequency channels within a cell. Cellular systems typically transmit on non-adjacent frequencies within a cell in order to prevent adjacent channel interference.
Airtime - Actual time spent talking on the cellular telephone. Most carriers bill customers based on how many minutes of airtime they use each month.
AJ - Anti-Jam. A communication signal that is designed to resist interference or jamming.
Alert - Constant 10 KHz signaling tone sent on the reverse voice channel (by the mobile), in an analog conversation, while the mobile phone is ringing.
Alphanumeric - A message or other type of readout containing both letters ("alphas") and numbers ("numerics"). In cellular, "alphanumeric memory dial" is a special type of dial-from- memory option that displays both the name of the individual and that individual's phone number on the cellular phone handset.
AM - Amplitude Modulation. The simplest carrier modulation technique where the RF carrier's amplitude envelope is modulated.
AMPS - Advanced Mobile Phone System. The current analog cellular FM system in North America. It uses 30 KHz channels and signaling is done superaudio.
Analog - The traditional method of modulating radio signals so that they can carry information. AM (amplitude modulation) and FM (frequency modulation) are the two most common methods of analog modulation. Analog modulation techniques have been around for more than 50 years and offer a proven, known method of using analog, but the switch to digital is already underway.
ANSI - American National Standards Institute. The ultimate accolade for any standard is ANSI certification. This does not mean that ANSI has reviewed the standard, but that it has been circulated widely throughout the industry and that it conforms to their document design and publication guidelines.
ARDIS - A wireless two-way data network jointly owned and operated by Motorola and IBM.
Attenuation - Weakening of the RF signal due to being partially blocked or absorbed. Attenuation is heavily dependent on the frequency of the RF transmission and on the physical characteristics of the material that the transmission interacts with. For example, high frequency microwave transmissions are severely attenuated by rain, but lower frequency cellular transmissions are not.
Auto-correlation - A measure of the similarity between a signal and a time-shifted replica of itself; a special case of cross-correlation. The auto-correlation function is the theoretical basis of direct sequence spread spectrum.