| 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.
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| 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.
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| 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.
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| 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.
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| 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.
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| 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.
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| DCCH: Dedicated Control Channel |
Dedicated Control Channel (DCCH) is a dedicated channel used to carry signalling information in active GSM and cdma2000 traffic channels.
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| 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.
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| 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.
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| 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.
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| 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.
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| 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.
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| 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.
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| 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.
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| 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.
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| 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".
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| 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.
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| 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.
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| 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
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| Dispersive channel |
Dispersive channel is a radio channel that not only introduces AWGN, but also the effects of multipath and frequency selective fading.
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| 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.
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| 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.
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| 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.
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| 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.
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| Downlink |
Downlink is the transmission path from the base station down to the mobile station.
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