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Mobile Computing Glossary

[Index] [A - D] [E - H] [I - L] [M - P] [Q - T] [U - X] [Y - Z] [#'s & symbols]

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EMF (Electromagnetic Field)

The minute magnetic energy fields which surround all things in nature and are suspected of causing health problems in significant strengths.

EMI (Electromagnetic Interference)

Interference by electromagnetic signals that can cause reduced data integrity and increased error rates on transmission channels. Signal noise pollution from radio, radar, fluorescent lights, or electronic instruments.

EMS (Enhanced Message Service)

An upgrade of SMS (Short Message Service) - a two-way text-based message service on primarily GSM network in Europe.  EMS allows graphics, images, ring tones, etc.  EMS provides an important evolutionary step between SMS and full Multimedia Messaging Service (MMS) of future.

Electromagnetic Radiation

All forms of visible light, invisible light, radio signal, and other energy used for the wireless transmission of data communications


The processing of data under a secret key in such a way that the original data can only be determined by a recipient in possession of a secret key.

End-to-End Delivery

Delivery of data between a source and destination endpoint. In CDPD at least one endpoint must be an MES. The other may be an MES or an FES. In the application sense, it implies client and server applications in a client/server design.

ETC (Enhance Throughput Cellular)

AT&T Paradyne protocol for data transmission over analog cellular connections consisting of enhancements to V.42 and V.32bis for compression, error detection, and error correction.

ECC (Enhanced Control Cellular)

Proprietary protocol from Motorola for cellular modems.


1 hour, 300 seconds, and 36 CCs. If a channel is occupied (used) constantly for 1 hour, that circuit has carried 1 Erlang of traffic. Also known as a carried load.

ESMR --Extended Specialized Mobile Radio


The combination of out-of-phase multiple signals that results in a weaker or self-canceling data signal.

FCC -- Federal Communications Commission.

FDDI (Fiber Data Distributed Interchange)

FDDI provides 125 Mbps signal rate with 4 bits encoded into 5-bit format for a 100-Mbit/s transmission rate. It functions on single- or dual-ring and star network with a maximum circumference of 250 km.

FDMA (Frequency Division Multiple Access)

The analog communications technique that uses a common channel for communication among multiple users allocating unique time slots to different users.

FES (Fixed End System)

The non-mobile communication system (and software) that handles OSI transport and higher layers of CDPD transmission.


A device, mechanism, bridge, Router, or gateway which prevents unauthorized access by hackers, crackers, vandals, and employees from private network services and data.

Frequency Hopping

A radio frequency transmission method. Typically this uses the ISM band from 2.4000 to 2.4835 GHz with 85 one-megahertz channels or "hops." Also, CDPD uses frequency hopping on analog cellular systems to unoccupied voice channels. Transmissions hop from one channel to the other, staying only 1/10 of a second on any given channel. The channels are visited in a predefined order specified by a hopping sequence.

FHSS (Frequency Hopping Spread Spectrum)

IEEE 802.11 Wireless LAN Standards Committee approval for Lannair Ltd.’s concept for at least 2 Mbps transmission rate with dynamic data rate switching.

Geosynchronous Orbit

Orbit taken by satellites where the satellite’s orbit velocity matches the rotation of the earth, causing the satellite to remain stationary relative to a position on the earth’s surface. Geosynchronous orbit demands a position about 23,000 miles above the earth’s surface over the equator.

GIS (Geographic Information System) - Generally refers to a database of geographical data. In some circles, it refers to Graphics database .

GLS (Global Locationing System) - A triangulation system used to locate a vehicle and convey that information to a central management facility.

GPS (Global Positioning System) - A satellite-based triangulation system used to ascertain current location.

GSM (Global System For Mobile Communications) - European digital cellular system standard now implemented in North America and Asia as wel..

Handoff - The transfer of responsibility for a call from one cell site to the next. The process by which the MTSO, sensing by signal strength that cellular mobile is reaching the outer range of one cell, transfer or "hands off" the call to an adjacent cell with a stronger signal. See also Cell Site.

HomeRF - Home Radio Frequency standard - See Bluetooth

Hz (Hertz) -Signal frequency use for voice, data, TV, and other forms of electronic communications represented by the number of cycles per second.

HLR (Home Location Register) -- Database of information about each cellular subscriber.

Hopping Sequence -The pre-set order in which frequency-hopping RF transmissions are distributed over the 82 channels of the assigned ISM band.

Host - Any computer, although typically a mainframe, mid-sized computer, mini-computer, or LAN server, servicing users and their processing at the centrally-based processor but distributing the results to terminal based or client connections.

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