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Cellular Telecommunications Glossary [D - H]

- a glossary of terms used with cell phone or cellular telecommunications technology

Glossary pages: [ 0 - 9 ] , [ A - C ] , [ D - F ] , [ G - J ] , [ K - N ] , [ O - S ] and [ T - Z ]

Downlink –
The transmission from cell phone base station to mobile phone or terminal. This term is normally associated with GSM or UMTS networks.
DSSS - Direct Sequence Spread Spectrum.
A modulation technique where a pseudonoise sequence is multiplied with data to be transmitted and this sequence is used to phase modulate a carrier. The fact that the PN sequence has a higher data rate than the data means that the bandwidth of the transmission is increased while the spectral power density is lowered. The resulting RF signal has a noise-like spectrum, and in some applications it can be intentionally made to look like noise to unauthorised listeners. To regenerate the wanted data at the receiver the signal is “despread” by correlating it with a pseudorandom sequence. This is identical to the one used during transmission and it must also be in synchronization. Direct sequence spread spectrum is used as the basis of CDMA cellular phones where different users are allocated different spreading codes.
DTX - Discontinuous Transmission.
A scheme where a mobile only transmits when the user is talking. This has the advantages that it saves battery life and reduces interference levels, but it can clip the speech making it sound less natural. During the quiet periods background noise has to be added at the receiver to give it a more natural sound.
EDGE - Enhanced Data rates for GSM Evolution
(also referred to as Enhanced Data rates for Global Evolution). The system utilizes the basic GSM / GPRS network, but uses 8PSK modulation rather than GMSK to enable peak data rates of 384 kbps to be achieved.
EIR - Equipment Identity Register
The entity within a GSM system that stores information about the status of a mobile, for example if it has been stolen.
E-OTD - Enhanced Observed Time Difference.
A location technology in which the mobile measures the time difference of the arrival of signals from the base station. Using this information the network is able to calculate the position of the mobile.
Erlang –
This is a measure of traffic or load in a telecommunications system. 1 Erlang is equivalent to one telephone line being permanently used.
E-TACS - Extended TACS.
An extension to the basic TACS system where further channels were allocated to create further capacity.
ETSI - European Telecommunications Standards Institute.
The European Telecommunications Standards Institute that is responsible for telecommunications standards.
FDMA - Frequency division multiple access.
A technique that that enables multiple users to access a mobile phone network by allocating them different frequencies or channels.
FDD - Frequency Division Duplex.
A technique to allow simultaneous transmission to and from the handset where the uplink and downlink transmissions are separated by using different frequencies.
Forward link -
The transmission from the cell phone base station to the mobile phone or temrinal. This term is normally associated with cdmaOne (IS-95) or CDMA2000 (IS-2000) networks.

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