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Wireless Glossary and Dictionary [C-D]

C/I: Carrier-to-Interference ratio
Carrier-to-Interference ratio (C/I) is the ratio of power in an RF carrier to the interference power in the channel.

C/N: Carrier-to-Noise ratio
Carrier-to-Noise ratio (C/N) is the ratio of power in an RF carrier to the noise power in the channel. Carrier-to-Noise ratio indicates the difference in amplitude between the desired radio frequency (RF) carrier and the noise in a portion of the spectrum.

CAI: Common Air Interface
Common Air Interface (CAI) is a set of open standards describing the physical and logical characteristics of a link between a base station and a mobile station. These standards are used by infrastructure and handset manufactures to design and build equipment that is capable of interoperating with each other's systems.

Call Diversion
Call Diversion is the feature used to divert incoming calls on a mobile phone to any other telephone or to a Mailbox/Combox on a GSM system.

CAMEL: Customized Application for Mobile Network Enhanced Logic
Customized Application for Mobile Network Enhanced Logic (CAMEL) refers to a set of 3rd Generation APIs based on ETSI recommendation TS 129 078 (V3.3.0). CAMEL finds widespread applicability in developing applications for next generation networks converging Phase 2+ GSM/UMTS. CAMEL allows roaming subscribers access to their full portfolio of IN services. CAMEL GSM phase 2+ connects the home and visited mobile networks to various Intelligent Network (IN) platforms used throughout national networks to provide features such as Pre-Paid Calling, personal Numbering and more complex location dependent services. As a result, CAMEL is a relatively inexpensive method of allowing telecom operators to add new services to the existing network infrastructure.

CAP CODE is a pager's unique electronic identification number.

Carrier means the continuous frequency capable of being modulated or impressed with a second signal.

Carrier frequency
Carrier Frequency refers to the nominal frequency of a carrier wave, the frequency of the unmodulated electrical wave at the output of an amplitude modulated, the center frequency of a frequency modulation signal, frequency modulated, or phase modulated transmitter of the output of a transmitter when the modulation is zero.

Carrier recovery
Carrier recovery is a technique for extracting the RF carrier from a modulated signal so that it can be reinserted and used to recover the modulating signal.

CBC: Cell Broadcast Center
Cell Broadcast Center (CBC) is the functional entity within the mobile network that is responsible for the generation of cell broadcast information.

CBCH: Cell Broadcast Channel
Cell Broadcast Channel (CBCH) is a downlink point-to-multipoint logical channel in a GSM system used to broadcast user information from a service center to mobile stations listening in a given cell area.

Chase Combining
Chase Combining (CC), also known as Convolution Code, is one of the two fundamental forms of Hybrid ARQ (HARQ). The other one is an incremental redundancy (IR). In Chase combining, each retransmission repeats the first transmission or part of it. While Chase combining is sufficient to make AMC robust, IR offers the potential for better performance with high initial code rates and FER operating points at the cost of additional memory and decoding complexity.

CCDF: Complementary Cumulative Distribution Function
Complementary Cumulative Distribution Function (CCDF) is a method used to characterize the peak power statistics of a digitally modulated signal. The CCDF curve can be used to determine design parameters for CDMA systems (such as the amount of back-off to run in a power amplifier).

CCH: Control Channel
Control Channel (CCH) refers the channels that transmit signaling and control information between the network and the mobile stations.

CCI: Co-Channel Interference
Co-channel interference (CCI) refers to interference from 2 different radio stations on the same frequency. CCI is one of the major limitations in cellular and PCS wireless telephone networks. In the case of TDMA networks, such as GSM/GPRS or NADC (otherwise known as "IS-136"), the co-channel interference is mainly caused by the spectrum allocated for the system being reused multiple times ("frequency reuse"). Co-channel interference, when not minimized, decreases the ratio of carrier to interference powers (C/I) at the periphery of cells, causing diminished system capacity, more frequent handoffs, and dropped calls.

CCITT: International Telegraph and Telephone Consultative Committee
CCITT is the abreviation of the International Telegraph and Telephone Consultative Committee in France. CCITT is standards body based in Geneva that publishes "recommendations" on standards used throughout the world communication industry.

CCM: Counter mode with Cipher-block chaining Message authentication code
Counter mode with Cipher-block chaining Message authentication code (CCM) is an encryption protocol in the 802.11i standard. The CCM protocol (CCMP) is based upon the CCM mode of the AES encryption algorithm and utilizes 128-bit keys, with a 48-bit initialization vector (IV) for replay detection.

CCMP: Counter mode with Cipher-block chaining Message authentication code
Protocol Counter mode with Cipher-block chaining Message authentication code Protocol(CCMP) is an encryption protocol in the 802.11i standard. The CCMP is based upon the CCM mode of the AES encryption algorithm and utilizes 128-bit keys, with a 48-bit initialization vector (IV) for replay detection.

CCSA: China Communications Standards Association
China Communications Standards Association (CCSA) is a P. R. China gorvenment sponsored organization to establish a nationally unified standards in the communication technologies. With the approval of the Ministry of Information Industries (MII) and Standardization Administration of China and the Civil Affairs Ministry, China Communications Standards Associatio (CCSA) was founded in December 18, 2002.

CCTrCH: Coded Composite Transport Channel
Coded Composite Transport Channel (CCTrCH), a technology in the UMTS physical layer, is the connection between Transport Channel and Physical Channel which results in a data stream from encoding and multiplexing of one or several transport channels.

CDF: Cumulative Distribution Function
Cumulative Distribution Function (CDF) describes the probability distribution of a real-valued random variable, X. The Kolmogorov-Smirnov test is based on cumulative distribution functions and can be used to test to see whether two empirical distributions are different or whether an empirical distribution is different from an ideal distribution.

CDG: CDMA Development Group
CDMA Development Group (CDG) is an international consortium of companies who have joined together to lead the adoption and evolution of 3G CDMA wireless systems around the world. The CDG is comprised of CDMA service providers and manufacturers, application developers and content providers. By working together, the members help to ensure interoperability among systems, while expediting the availability of 3G CDMA technology to consumers.

CDM: Code Division Multiplexing
Code Division Multiplexing or Code Division Multiplex (CDM) is a technique in which each channel transmits its bits as a coded channel-specific sequence of pulses. This coded transmission typically is accomplished by transmitting a unique time-dependent series of short pulses, which are placed within chip times within the larger bit time. All channels, each with a different code, can be transmitted on the same fiber and asynchronously demultiplxed. Other widely used multiple access techniques are Time Division Multiple Access (TDMA) and Frequency Division Multiple Access (FDMA).

CDMA: Code Division Multiple Access
Code Division Multiple Access (CDMA) is a second generation (2G) cellular technology defined by Qualcomm in IS-95 and IS-2000. Other widely used multiple access techniques for cellular are Time Division Multiple Access (TDMA) and Frequency Division Multiple Access (FDMA). CDMA technologies are evolving into CDMA2000 to meet the challenges. CDMA2000 is the 3rd Generation solution based on IS-95.

Code Division Multiple Access 2000 (CDMA2000 or CDMA-2000) is the 3rd Generation solution based on CDMA IS-95, which supports 3G services as defined by the ITU 3G standards IMT-2000. CDMA2000 defines both an air interface and a core network. CDMA2000 has already been implemented as an evolutionary step from cdmaOne as CDMA2000 provides full backward compatibility with IS-95B.

cdmaOne is the commercial name for a CDMA (Code Division Multiple Access) system defined by the consortium including Qualcomm, AT&T Wireless and Motorola. The IS-95 standard is part of cdmaOne as the air interface.

CDP: Code Domain Power
Code Domain Power (CDP) is a measurement of the power contained in each Walsh coded channel in CDMA signals. The CDP measurement is beneficial in troubleshooting CDMA transmitter designs.

CDPD: Cellular Digital Packet Data
Cellular Digital Packet Data (CDPD) technology is used by telecommunications carriers to transfer data to users via unused analog cellular networks. If one part of the network -- a specific geographic area or "cell" -- is overused, CDPD can automatically reallocate network resources to handle extra traffic.

CDVCC: Coded Digital Verification Color Code
Coded Digital Verification Color Code (CDVCC) is a unique 12-bit code word used to identify the base station. It is added at the base station to the downlink or forward channel and the mobile then detects and returns the code. The CDVCC is used to determine channel continuity, and only one CDVCC is usually assigned to a base station or sector.

In wireless communication, Cell is the geographic area encompassing the signal range from one base station (a site containing a radio transmitter/receiver and network communication equipment). Wireless transmission networks are comprised of many hexagonal, overlapping cell sites to efficiently use radio spectrum for wireless transmissions. Also, cellis the basis for the term "cellular phone".

Cell Broadcast
Cell Broadcast (CB), also known as Short Message Service - Cell Broadcast (SMS-CB), is a one-to-many geographically focused messaging service, whereas the Short Message Service - Point to Point (SMS-PP) is a one-to-one and one-to-a-few service. Cell Broadcast is designed for simultaneous delivery of messages to multiple users in a specified area. CB is a mobile technology feature defined by the ETSI's GSM committee and is part of the GSM standard. Cell Broadcast messaging is also supported by UMTS, as defined by 3GPP.

Cell Site
Cell Site, also called Base Station, is the local cellular tower and radio antenna (including the radios, controller, switch interconnect, etc.) that handles communication with subscribers in a particular area or cell. A cellular network is made up of many cell sites, all connected back to the switch via landline or microwave.

Cell splitting
Cell splitting is the process of splitting a mobile cell into several smaller cells. This is usually done to make more voice channels available to accommodate traffic growth in the area covered by the original cell.

In wireless communications, cellular refers most basically to the structure of the wireless transmission networks which are comprised of cells or transmission sites. Cellular is also the name of the wireless telephone system originally developed by Bell Laboratories that used low-powered analog radio equipment to transmit within cells. The terms "cellular phone" or "cell phone" are used interchangeably to refer to wireless phones. Within the wireless industry, cellular is also used to refer to non-PCS products and services.

Cellular Handoff
Cellular Handoff refers to the process that a telephone call is switched by computers from one transmitter to the next without disconnecting the signal, as a vehicle moves from cell to cell. The mobile remains on a specific channel until signal strength diminishes, and then is automatically told to go to another channel and pick up the transferred transmissions there.

Cellular Radio
Cellular Radio is the technology that uses radio transmissions to access telephone-company networks. Service is provided in a particular area by a low-power transmitter.

Center Frequency
Center Frequency refers to the middle frequency of the bandwidth of a channel.

CELP: Code-Book Excited Linear Predictive
Code-Book Excited Linear Predictive(CELP) is a powerful low-rate coding technique where a short excitation frame, typically 5ms, is modeled by a Gaussian vector chosen from a large stochastic codebook. The vector is chosen such that the error between the original and synthesized speech is minimized.

CEPT: Committee of European Posts & Telephones
Committee of European Posts & Telephones (CEPT) is a European regulatory body responsible for coordinating telecommunications within Europe.

CGSA: Cellular Geographic Service Area
Cellular Geographic Service Area (CGSA) describes the physical area over which a cellular carrier is licensed to provide service.

Channel refers to a one-way telecommunications link or transmission medium through which information or signal is transmitted from a sender (or transmitter) to a receiver. They may be either physical or logical depending on the application. A Radio Frequency (RF) channel is a physical channel, whereas control and traffic channels within the RF channel would be considered logical channels.

Channel coding
Channel coding is the application of forward error correction codes to an RF channel to improve performance and throughput.

Channel equalization
Channel equalization is the process of reducing amplitude, frequency and phase distortion in a radio channel with the intent of improving transmission performance.

cHTML: Compact HTML
Compact HTML (cHTML) is a subset of HTML for small information devices, such as smart phones and PDAs. cHTML does not support JPEG images, tables, image maps, multiple fonts and styles of fonts, background colors and images, frames, style sheets and more than two colors, typically black and white.

CINR: Carrier to Interference + Noise Ratio
Carrier to Interference-plus-Noise Ratio (CINR), expressed in decibels (dBs), is a measurement of signal effectiveness. The carrier is the desired signal, and the interference can either be noise or co-channel interference or both. In order for the signal receiver to be able to decode the signal, the signal must fall into an acceptable CINR range, which differs with the technology used (i.e., CDMA, GSM, etc.).

CIR: Carrier to Interference Ratio
Carrier to Interference Ratio (CIR), expressed in decibels (dBs), is a measurment of signaling effectiveness. CIR is the ratio of C (carrier signal) to the (I) Interference expressed. The carrier is the desired signal, and the interference can either be adjacent and co-channel interference, along with noise and background effects all detract from the potential quality of the received signal.

Client Association
Client Association is the process by which a wireless client -- like a laptop computer -- connects to an access point.

Clock recovery
Clock recovery is the process of extracting the timing signals from a digitally modulated carrier wave. The recovered clock signal is then used to decode and further process the data.

CMRS: Commercial Mobile Radio Services
Commercial Mobile Radio Services (CMRS) is an FCC designation for any carrier or licensee whose wireless network is connected to the public switched telephone network and/or is operated for profit.

Co-channel interference
Co-channel interference is the unwanted interference within a radio channel from another transmitter using the same channel at a different location. Co-channel interference is very common in a frequency reuse system and must be carefully controlled to prevent problems.

Codebook is an ordered collection of all possible values that can be assigned to a scalar or a vector variable. Each vector is called a codeword.

Codewrod means a contiguous set of bits that together form a piece of information. The codewords used in digital paging codes include redundant bits that allow a receiver to reconstruct the information if some of the bits were received incorrectly.

Coding gain
Coding gain is the effective gain, measured in dB, that coding provides over an uncoded signal. Coding gain is usually measured as the dB difference in C/N ratios between a coded and uncoded signal producing the same BER.

Coherent detection
Coherent detection, also referred to as coherent demodulation, is a technique of phase locking to the carrier wave to improve detection. Knowledge of the carrier phase improves demodulator performance.

COLT: Cell Site on Light Truck
Cell Site on Light Truck (CPLT) is a mobile site on a vehicle placed at a location to fill in or increase coverage.

Communication satellite
Communication Satellite refers to a space vehicle launched into orbit to relay audio, data or video signals as part of a telecommunications network. Signals are transmitted to the satellite from earth station antennas, amplified and sent back to earth for reception by other earth station antennas. Satellites are capable of linking two points, one point with many others, or multiple locations with other multiple locations.

Concatenated coding
Concatenated coding is the use of two codes, an inner and outer code, to further improve transmission performance. Using this technique, a data stream is encoded with the outer code, and then the coded data is further encoded with the outer code. This technique is particularly effective in bursty environments. The use of concatenated codes is most common in space communications and usually involves a convolutional inner code and Reed-Solomon outer code.

Constellation is a graphical representation of signal states for a digital system.

Convolutional code
Convolutional code is a type of forward error correction code using a shift register containing a number of stages to shift the input bits one at a time to produce a coded output. With the convolutional code, (a) each m-bit information symbol (each m-bit string) to be encoded is transformed into an n-bit symbol, where m/n is the code rate (n >= m) and (b) the transformation is a function of the last k information symbols, where k is the constraint length of the code.

Core Network
Core Network, in a 3G mobile network, refers to the switching part of the UMTS or WCDMA network. It provides call control and performs mobility and high-level security functions such as location updating and authentication. Core network includes a radio access network, terminals and applications.

COST-231 is ETSI propagation model for 2 GHz applications. The COST-231 Model is the most sophisticated empirical model. All walls in the vertical plane between transmitter and receiver are considered, and for each wall, individual materaial properties are taken into account.

Coverage in wireless communicatons refers to the region within which a paging receiver can receive reliably the transmission of the paging signals.

Coverage area
Coverage area is the geographical reach of a mobile communications network or system.

Coverage hole
Coverage hole is an area within the radio coverage footprint of a wireless system in which the RF signal level is below the design threshold. Coverage holes are usually caused by physical obstructions such as buildings, foliage, hills, tunnels and indoor parking garages.

Covered SMR
Covered SMR is a subset of specialized mobile radio operators subject to a particular set of regulations. It is a definition developed during the implementation of E911 regulations encompasses operators whose networks use intelligent switching capabilities and offer seamless hand-off to customers.

COW: Cell site On Wheels
Cell site On Wheels (COW) is a mobile site placed at a location to fill in or increase coverage.

CP: Cyclic Prefix
The cyclic prefix is actually a copy of the last portion of the data symbol appended to the front of the symbol during the guard interval. By adding a cyclic prefix, the channel can be made to behave as if the transmitted waveforms were from time minus infinite, and thus ensure orthogonality, which essentially prevents one subcarrier from interfering with another (called intercarrier interference, or ICI). This is accomplished because the amount of time dispersion from the channel is smaller than the duration of the cyclic prefix. After discovering the process for OFDM, a cyclic prefix has been proposed for other modulations to improve the robustness to multipath.

CPM: Continuous Phase Modulation
Continuous Phase Modulation (CPM) is a phase modulation technique employing smooth transitions between signal states. This reduces sidelobe spectral energy and improves co-channel performance.

CPNI: Customer Proprietary Network Information
Customer Proprietary Network Information (CPNI) refers to the carrier's data about a specific customer's service and usage. The FCC restricts CPNI use in marketing, banning win-back efforts specifically aimed at high-usage customers who have quit a network.

CPP: Calling Party Pays
Calling Party Pays (CPP) is the arrangement in which the mobile subscriber does not pay for incoming calls. Instead, the calling party pays for those calls. CPP is offered in many places, but has not been regulated in the United States where Mobile Party Pays (MPP) is still predominant.

CQI: Channel Quality Indicator
Channel Quality Indicator (CQI) is a measurement of the communication quality of wireless channels. CQI can be a value (or values) representing a measure of channel quality for a given channel. Typically, a high value CQI is indicative of a channel with high quality and vice versa. A CQI for a channel can be computed by making use of performance metric, such as a signal-to-noise ratio (SNR), signal-to-interference plus noise ratio (SINR), signal-to-noise plus distortion ratio (SNDR), and so forth of the channel. These values and others can be measured for a given channel and then used to compute a CQI for the channel. The CQI for a given channel can be dependent upon the transmission (modulation) scheme used by the communications system. For example, a communications system using code-division multiple access (CDMA) can make use of a different CQI than a communications system that makes use of orthogonal frequency division multiplexing (OFDM). In more complex communications systems, such as those making use of multiple-input multiple output (MIMO) and space-time coded systems, the CQI used can also be dependent on receiver type. Other factors that may be taken into account in CQI are performance impairments, such as Doppler shift, channel estimation error, interference, and so forth.

CRNC: Controlling Radio Network Controller
The Controlling Radio Network Controller (CRNC or Controlling RNC) is the RNC (Radio Network Controller) responsible for the configuration of a Node B. A UE (User Equipment) accessing the system will send an access to a Node B, which in turn will forward this message onto its CRNC.

CRC: Cyclic Redundancy Code
Cyclic Redundancy Code (CRC) is the use of the syndrome of a cyclic block code to detect errors.

Cross correlation
Cross correlation is the complex inner product of a first sequence with a shifted version of a second sequence. Sequences are considered to have good cross correlation properties when there is very little correlation between the sequences as they are shifted against each other.

Cross talk
Cross Talk refers to the interfering energy transferred from one circuit to another, or the unwanted information from one channel to "spill over" into an adjacent channel.

CSCF: Call Session Control Function
Call Session Control Function (CSCF) is a functional entity within IP Based Multimedia Subsystem (IMS) and part of 3GPP UMTS Reference Architecture. CSCF performs signalling operations for call session control. It manages SIP sessions and coordinates with other network entities for session control, service control and resource allocation. To fulfil such functionalities, the CSCF can act as Proxy CSCF (P-CSCF), Serving CSCF (S-CSCF) or Interrogating CSCF (I-CSCF).

CSN: Connectivity Service Network
Connectivity Service Network (CSN), a concept in the mobile WiMAX network, is at the core of the WiMAX network architecture providing control and management for the Access Service Network (ASN) and subscribers with services such as DHCP server, AAA, FTP, inter-operator and inter-technology roaming, services and other applications. The CSN also includes the Internet Protocol Multimedia Subsystem (IMS) services support capable of offering Internet access, location-based services, Internet Multimedia and Multimedia Broadcast/Multicast MBS services and voice services.

CSTD: Cyclic Shift Transmit Diversity
Cyclic Shift Transmit Diversity (CSTD) is an adaptation of the idea of delay diversity to OFDM systems. With CSTD, each antenna element in transmit array sends a circularly shifted version of the same OFDM time domain symbol. Note that each antenna adds a cyclic prefix after circularly shifting the OFDM symbol, and thus the delay-spread protection offered by the cyclic prefix is unaffected by the CSTD.

CT-2: Cordless Telephone 2
Cordless Telephone 2 is a second generation cordless telephone system that allows users to roam away from their home base stations and receive service in public places. Away from the home base station, the service was one way outbound from the phone to a telepoint within range.

CTC: Convolutional Turbo Code
Convolutional Turbo Code (CTC) is a type of turbo codes with some of the convolutional schemes used. For its high-performance error correction nature, CTC is the iterative decoding scheme of choice as evidenced by their wide adoption in standards bodies including 3GPP (W-CDMA), 3GPP2 (CDMA2000) and DVB-RCS.

CTIA: Cellular Telecommunications & Internet Association
The Cellular Telecommunications & Internet Association (CTIA) is the international organization that aims to represent all elements of wireless communication -- cellular, personal communications services, enhanced specialized mobile radio and mobile satellite services -- and serve the interests of service providers, manufacturers and others.

CWTS: China Wireless Telecommunications Standards group
China Wireless Telecommunication Standards Group (CWTS) is a non-profit organization, which has the responsibility to define, produce and maintain Chinese wireless telecommunication standards in China. CWTS was established under the Chinese Standardization Law, with the approval of the Ministry of Information Industry (MII) of China. CWTS is set up with the purpose of promoting and accelerating the wireless telecommunications standardization process in China.

Cyclic codes
Cyclic codes are a subclass of linear block codes with an algebraic structure that enables encoding to be implemented with a linear shift register and decoding to be implemented without a lookup table.

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.

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.

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 antenna
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.

dBi: deciBels referenced to an isotropic antenna
deciBels referenced to an isotropic antenna (dBi) is a technique for expressing a power gain measurement in logarithmic form using a theoretical isotropic 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.

DCA: Dynamic Channel Allocation
Dynamic 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.

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.

DCMA: Dynamic Channel Multicarrier Architecture
Dynamic Channel Multicarrier Architecture (DCMA), a technology developed by ComSpace Corp., is used for specialized mobile radio networks that can configure the number and bandwidth of voice and data channels based on a carrier's requirements.

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 Telecommunications
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 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 slightlyDispersive channelDispersive 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 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 is the transmission path from the base station down to the mobile station.

DPCCH: Dedicated Physical Control CHannel
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 Shift Keying
Differential Quadrature Phase Shift Keying (DQPSK) modulation uses differential encoding of the digital information stream.

Drift RNC: Drift Radio Network Controller
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: 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.

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 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 stands for Digital Video Broadcasting - Handheld. 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, 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 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 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 OFDMmodulation with concatenated channel coding (i.e. COFDM). The adopted source coding methods are MPEG-2 and, more recently, H.264.

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