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There are 45 names in this directory beginning with the letter D.
D-AMPS: Digital AMPS
Digital AMPS (D-AMPS), based on the IS-54 and IS-136 standards, is the second-generation (2G) mobile phone systems. It is used throughout the Americas, particularly in the United States and Canada. D-AMPS is considered end-of-life, and existing networks are in the process of being replaced by GSM/GPRS and CDMA2000 technologies.

DAC: Digital to Analog Converter
Digital to Analog Converter (DAC) is a device that takes a digital representation of a signal and transforms it into a facsimile of its original form.

Db: DeciBel
Decibel (dB) is an unit for measuring relative power ratios in terms of gain or loss. The units of dB are expressed in terms of the logarithm to base 10 of a ratio and typically are expressed in watts. For example, a -3dB loss indicates a 50% loss in power; a +3dB reading is a doubling of power; 10 dB indicates an increase (or a loss) by a factor of 10; 20 dB indicates an increase (or a loss) of a factor of 100; 30 dB indicates an increase (or a loss) by a factor of 1000.

dBc: deciBels referenced to the carrier
deciBels referenced to the carrier (dBc) is a technique for expressing a power measurement in logarithmic form using the carrier power as a reference.

dBd: deciBels referenced to a dipole ant
deciBels referenced to a dipole antenna (dBd) is a technique for expressing a power gain measurement in logarithmic form using a standard dipole antenna as a reference.

dBm: deciBels referenced to a milli-Watt
deciBels referenced to a milli-Watt (dBm) is a technique for expressing a power measurement in logarithmic form using 1 mW as a reference.

DCCH: Dedicated Control Channel
Dedicated Control Channel (DCCH) is a dedicated channel used to carry signalling information in active GSM and cdma2000 traffic channels.

DCD: Downlink Channel Descriptor
Downlink Channel Descriptor (DCD) is a concept in IEEE 802.16 (WiMAX) networks to describe a MAC (Medium Access Control) message that describes the physical layer characteristics of a downlink channel.

DCS 1800: digital cellular system
Digital Cellular System 1800 (DCS 1800) is a global Digital Cellular System for mobile communications-based PCS networks used outside of the U.S.

DCT: Digital Cordless Telephone
Digital Cordless Telephone (DCT) is a telephone with a wireless handset which communicates with a base station connected to a fixed telephone landline (POTS) via radio waves and can only be operated close to (typically less than 100 metres of) its base station, such as in and around the house.

Dead Spot
Dead Spot is an area within the coverage area of a wireless network in which there is no coverage or transmission falling off. Dead spots are often caused by electronic interference or physical barriers such as hills, tunnels and indoor parking garages. See also coverage area.

DECT: Digital Enhanced Cordless Telecomm
Digital Enhanced Cordless Telecommunications (DECT) is a digital wireless technology for cordless telephones, wireless offices and even wireless telephone lines to the home. DECT has been designed and specified to interwork with many other types of network, such as the PSTN (conventional telephone networks), ISDN (new digital and data phone networks), GSM (mobile phone networks) and more.

Delay spread
Delay spread is a type of distortion due to multipath resulting in the spreading out or "smearing" of the received signal. It occurs when identical signals arrive via different paths and have different time delays.

Demodulation
Demodulation is the process of recovering the original modulating signal from a modulated carrier. The original modulating signal is usually the information being transmitted, typically voice or data.

DEMS: digital electronic message service
Digital Electronic Message Service (DEMS) is the service in the range at the band 18 GHz originally then move to 24 GHz.

Differential detection
Differential detection is an encoding and detection technique that uses phase changes in the carrier to signal binary "ones" and "zeros". The signal is sampled every T seconds, and a phase change of 180 degrees could be set to be a "zero" and no phase change would then be a "one".

Digital paging
Digital Paging, also called Numeric Paging, is the most widely used type of paging. The caller simply calls your pager phone number and enters the number where you can reach them.

Digital Signal
A digital signal is composed only of electrical pulses representing either zero or one. Because digital signals are made up only of binary streams, less information is needed to transmit a message. Digital encoding therefore increases the capacity of a given radio frequency. Furthermore, only digitized information can be transported through a noisy channel without degradation. Even if corruption occurs, as long as the one-zero pattern is recognizable, the original information content can be perfectly replicated at the receiving end.

Dipola Antenna
Dipola Antenna is a type of antenna that offers omnidirectional coverage, but not much gain. Access points usually have one or two dipole antennas to increase their gain slightly

Dispersive channel
Dispersive channel is a radio channel that not only introduces AWGN, but also the effects of multipath and frequency selective fading.

Distributed antenna system
Distributed antenna system is a type of antenna system that is distributed or remotely located away from the transmitter. Such an antenna or series of antennas can be connected via coaxial cable, leaky feeder or optical fiber link.

Diversity
Diversity is a technique to reduce the effects of fading by using multiple spatially separated antennas to take independent samples of the same signal at the same time. The theory is that the fading in these signals is uncorrelated and that the probability of all samples being below a threshold at a given instant is low.

Diversity Reception
Diversity Reception refers to a method for improving reception of a radio signal, typically achieved by the use of dual receivers whose antennas are located in physically distinct locations (which can be less than a meter apart). An electronic circuit or software combines or selects from the receive antenna to receive an improved quality signal.

Doppler Shift
Doppler Shift is the magnitude of the change in the observed frequency of a wave due to the relative velocity of a transmitter with respect to a receiver.

Downlink
Downlink is the transmission path from the base station down to the mobile station.

DPCCH: Dedicated Physical Control CHanne
Dedicated Physical Control Channel(DPCCH), a term from UMTS, is the physical channel from layer 2 on which the signalling is transmitted on the uplink by the UE (user equipment) to the Node-B (the base transceiver station).

DPM: Digital Phase Modulation
Digital Phase Modulation is a form of CPM in which the shaped symbol pulses are directly applied to the phase modulator. This technique provides the advantages of CPM techniques and is easily implemented in VLSI. It is also easier to demodulate than other types of CPM.

DQPSK: Differential Quadrature Phase Shi
Differential Quadrature Phase Shift Keying (DQPSK) modulation uses differential encoding of the digital information stream.

Drift RNC: Drift Radio Network Controlle
Drift Radio Network Controller (DRNC or Drift RNC) is a type of Radio Network Controller (RNC) in a 3G mobile wireless network. Drift RNC is the place where the mobiles physical layer communications terminate. One or more Drift RNCs communicate with the Serving RNC via the IUr interface. Where no soft handover activity is in progress, a Drift RNC may also be the Serving RNC.

DS: Direct Sequence
Direct Sequence (DS) is a process of spectrum spreading where the digital information stream is multiplied, using an exclusive OR technique, by a high speed pseudorandom code (spreading sequence) to generate a spread spectrum signal.

DSFN: Dynamic Single Frequency Network
Dynamic Single Frequency Networks (DSFN) is a transmitter macrodiversity technique for, for example, OFDM-based cellular networks. DSFN is based on the idea of single frequency networks (SFN), which is a group of radio transmitters that send the same signal simultaneously over the same frequency. The concept of DSFN implies that the SFN grouping is changed dynamically over time, from timeslot to timeslot. The aim is to achieve efficient spectrum utilization for downlink unicast or multicast communication services in centrally controlled cellular systems based on, for example, the OFDM modulation scheme.

DSSS: Direct-Sequence Spread Spectrum
Direct-Sequence Spread Spectrum (DSSS) is used in WLAN 802.11 and 802.11b physical layer. Its transmissions multiply a "noise" signal to the data being transmitted. This noise signal is a pseudorandom sequence of 1 and -1 values, at a frequency much higher than that of the original signal, thereby spreading the energy of the original signal into a much wider band.

DTE: Data Terminal Equipment
Data Terminal Equipment(DTE) refers to an end instrument that converts user information into signals for transmission, or reconverts the received signals into user information. A DTE is the functional unit of a data station that serves as a data source or a data sink and provides for the data communication control function to be performed in accordance with link protocol.

DTMF: Dual Tone Multi Frequency
Dual Tone Multi Frequency (DTMF) is the sounds made by a phone's keypad when a button is pressed. Each button emits a sound that is actually the combination of two specific sounds in order to minimize the possibility of an incorrect signal being received by the equipment listening to the press of the buttons.

DTX: Discontinuous Transmission
Discontinuous Transmission (DT) is a feature in mobile systems where transmitters mute when there is no information to send, such as during periods of silence. This feature prolongs battery life in portable phones and reduces interference in wireless systems.

Dual Band
Dual Band refers to mobile phones that could work on networks operating on different frequency bands. This is useful for mobile phone users who move between areas covered by different networks. For example, GSM 900 and GSM 1800, or the 800 MHz digital band and the 1900 MHz digital PCS band.

Dual Mode
Dual Mode refers to a feature of a wireless device that can operate on either an analog or digital transmission network. However, multiple digital transmission systems exist, so dual-mode phone users must ensure that their dual-mode phone will operate on the digital transmission system used by their selected service provider.

DVB Project
The Digital Video Broadcasting (DVB) Project is an industry-led consortium of over 270 broadcasters, manufacturers, network operators, software developers, regulatory bodies and others in over 35 countries committed to designing global standards for the global delivery of digital television and data services. Services using DVB standards are available on every continent with more than 120 million DVB receivers deployed.

DVB-C
DVB-C stands for Digital Video Broadcasting - Cable, and it is the DVB European consortium standard for the broadcast transmission of digital television over cable. This system transmits an MPEG-2 family digital audio/video stream, using a QAM modulation with channel coding.

DVB-H DVB-H stands for Digital Video B
DVB-H is a technical specification for bringing broadcast services to handheld receivers and was formally adopted as ETSI standard EN 302 304 in November, 2004. The DVB-H specification (EN 302 304) can be downloaded from the DVB-H Online website ([1]). The major competitor of this technology is DMB.

DVB-S
DVB-S, standing for Digital Video Broadcasting-Satelite, is the original Digital Video Broadcasting (DVB) forward error coding and modulation standard for satellite television and dates from 1995. It is used via satellites serving every continent of the world. DVB-S is used in both MCPC and SCPC modes for broadcast network feeds, as well as for direct broadcast satellite services like Sky TV (UK) via Astra in Europe, Dish Network in the U.S., and Bell ExpressVu in Canada. The transport stream delivered by DVB-S is mandated as MPEG-2.

DVB-S2
DVB-S2 is an improved and updated specification to replace the DVB-S (Digital Video Broadcasting-Satelite) standard, ratified by ETSI in March, 2005. The main use for this standard is the distribution of HDTV, while the original standard DBV-S was mainly applied to SDTV services. The development of DVB-S2 coincided with the introduction of HDTV and H.264 (MPEG-4) video codecs.

DVB-T
DVB-T stands for Digital Video Broadcasting - Terrestrial, and it is the DVB European consortium standard for the broadcast transmission of digital terrestrial television. This system transmits a compressed digital audio/video stream, using OFDM modulation with concatenated channel coding (i.e. COFDM). The adopted source coding methods are MPEG-2 and, more recently, H.264.

DVB: Digital Video Broadcasting
Digital Video Broadcasting (DVB) is a suite of internationally accepted, open standards for digital television maintained by the DVB Project and published by the Joint Technical Committee (JTC) of European Telecommunications Standards Institute (ETSI), European Committee for Electrotechnical Standardization (CENELEC) and European Broadcasting Union (EBU). DVB standards define the physical layer and data link layer of a distribution system. Devices interact with the physical layer via a synchronous parallel interface (SPI), synchronous serial interface (SSI), or asynchronous serial interface (ASI). All data is transmitted in MPEG-2 transport streams with some additional constraints (DVB-MPEG). A standard for temporally compressed distribution to mobile devices (DVB-H) has been published in November, 2004.

Dynamic
DCA: Dynamic Channel Allocation Channel Allocation (DCA) is an automatic process for assigning traffic channels in a frequency reuse wireless system. The base station continuously monitors the interference in all idle channels and makes an assignment using an algorithm that determines the channel that will produce the least amount of additional interference.


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