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Multipath Propagation
In wireless telecommunications, multipath is the propagation phenomenon that results in radio signals reaching the receiving antenna by two or more paths. Causes of multipath include atmospheric ducting, ionospheric reflection and refraction, and reflection from water bodies and terrestrial objects such as mountains and buildings. Multipath causes multipath interference including constructive and destructive interference, and phase shifting of the signal. Destructive interference causes fading. Where the magnitudes of the signals arriving by the various paths have a distribution known as the Rayleigh distribution, this is known as Rayleigh fading
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Linear System
A linear system is a mathematical model of a system based on the use of a linear operator. Linear systems typically exhibit features and properties that are much simpler than the nonlinear case. As a mathematical abstraction or idealization, linear systems find important applications in automatic control theory, signal processing, and telecommunications. For example, the propagation medium for wireless communication systems can often be modeled by linear systems.Contents1 Definition 2 Time-varying impulse response 3 The convolution integral 4 Discrete time systems 5 See alsoDefinition[edit] A general deterministic system can be described by an operator, H displaystyle H , that maps an input, x ( t ) displaystyle x(t) , as a function of t displaystyle t to an output, y ( t ) displaystyle y(t) , a type of black box description
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Rice Distribution
1 − Q 1 ( ν σ , x σ ) displaystyle 1-Q_ 1 left( frac nu sigma , frac x sigma right) where Q1 is the Marcum Q-functionMean σ π / 2 L 1 / 2 ( − ν 2 / 2 σ 2 ) displaystyle sigma sqrt pi /2 ,,L_ 1/2 (-nu ^ 2 /2sigma ^ 2 ) Variance 2 σ 2 + ν 2 − π
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Impedance Matching
In electronics, impedance matching is the practice of designing the input impedance of an electrical load or the output impedance of its corresponding signal source to maximize the power transfer or minimize signal reflection from the load. In the case of a complex source impedance ZS and load impedance ZL, maximum power transfer is obtained when Z S = Z L ∗ displaystyle Z_ mathrm S =Z_ mathrm L ^ * , where the asterisk indicates the complex conjugate of the variable. Where ZS represents the characteristic impedance of a transmission line, minimum reflection is obtained when Z S = Z L displaystyle Z_ mathrm S =Z_ mathrm L , The concept of impedance matching found first applications in electrical engineering, but is relevant in other applications
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Signal Reflection
Signal reflection occurs when a signal is transmitted along a transmission medium, such as a copper cable or an optical fiber. Some of the signal power may be reflected back to its origin rather than being carried all the way along the cable to the far end. This happens because imperfections in the cable cause impedance mismatches and non-linear changes in the cable characteristics. These abrupt changes in characteristics cause some of the transmitted signal to be reflected. In radio frequency (RF) practice this is often measured in a dimensionless ratio known as voltage standing wave ratio (VSWR) with a VSWR bridge. The ratio of energy bounced back depends on the impedance mismatch. Mathematically, it is defined using the reflection coefficient. Because the principles are the same, this concept is perhaps easiest to understand when considering an optical fiber
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Wavelet
A wavelet is a wave-like oscillation with an amplitude that begins at zero, increases, and then decreases back to zero. It can typically be visualized as a "brief oscillation" like one recorded by a seismograph or heart monitor. Generally, wavelets are intentionally crafted to have specific properties that make them useful for signal processing. Using a "reverse, shift, multiply and integrate" technique called convolution, wavelets can be combined with known portions of a damaged signal to extract information from the unknown portions.Seismic waveletFor example, a wavelet could be created to have a frequency of Middle C and a short duration of roughly a 32nd note. If this wavelet were to be convolved with a signal created from the recording of a song, then the resulting signal would be useful for determining when the Middle C note was being played in the song
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Equalization (communications)
In telecommunication, equalization is the reversal of distortion incurred by a signal transmitted through a channel. Equalizers are used to render the frequency response—for instance of a telephone line—flat from end-to-end. When a channel has been equalized the frequency domain attributes of the signal at the input are faithfully reproduced at the output. Telephones, DSL
DSL
lines and television cables use equalizers to prepare data signals for transmission. Equalizers are critical to the successful operation of electronic systems such as analog broadcast television. In this application the actual waveform of the transmitted signal must be preserved, not just its frequency content
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ITU-T
The ITU
ITU
Telecommunication
Telecommunication
Standardization
Standardization
Sector (ITU-T) is one of the three sectors (divisions or units) of the International Telecommunication
Telecommunication
Union (ITU); it coordinates standards for telecommunications. The standardization efforts of ITU
ITU
commenced in 1865 with the formation of the International Telegraph Union (ITU). ITU
ITU
became a specialized agency of the United Nations in 1947
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GSM
GSM
GSM
(Global System for Mobile Communications, originally Groupe Spécial Mobile) is a standard developed by the European Telecommunications Standards Institute (ETSI) to describe the protocols for second-generation digital cellular networks used by mobile devices such as tablets, first deployed in Finland
Finland
in December 1991.[2] As of 2014[update], it has become the global standard for mobile communications – with over 90% market share, operating in over 193 countries and territories.[3] 2G networks developed as a replacement for first generation (1G) analog cellular networks, and the GSM
GSM
standard originally described as a digital, circuit-switched network optimized for full duplex voice telephony
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Receiver (radio)
In radio communications, a receiver (radio receiver or simply radio) is an electronic device that receives radio waves and converts the information carried by them to a usable form. It is used with an antenna. The antenna intercepts radio waves (electromagnetic waves) and converts them to tiny alternating currents which are applied to the receiver, and the receiver extracts the desired information
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Wireless
Wireless
Wireless
communication, or sometimes simply wireless, is the transfer of information or power between two or more points that are not connected by an electrical conductor. The most common wireless technologies use radio waves. With radio waves distances can be short, such as a few meters for Bluetooth
Bluetooth
or as far as millions of kilometers for deep-space radio communications. It encompasses various types of fixed, mobile, and portable applications, including two-way radios, cellular telephones, personal digital assistants (PDAs), and wireless networking
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G.hn
G.hn
G.hn
is a specification for home networking with data rates up to 2 Gbit/s and operation over four types of legacy wires: telephone wiring, coaxial cables, power lines and POF. A single G.hn semiconductor device is able to network over any of the supported home wire types
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Jitter
In electronics and telecommunications, jitter is the deviation from true periodicity of a presumably periodic signal, often in relation to a reference clock signal. In clock recovery applications it is called timing jitter.[1] Jitter
Jitter
is a significant, and usually undesired, factor in the design of almost all communications links. Jitter
Jitter
can be quantified in the same terms as all time-varying signals, e.g., root mean square (RMS), or peak-to-peak displacement. Also like other time-varying signals, jitter can be expressed in terms of spectral density. Jitter
Jitter
period is the interval between two times of maximum effect (or minimum effect) of a signal characteristic that varies regularly with time. Jitter
Jitter
frequency, the more commonly quoted figure, is its inverse
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Transmission (telecommunications)
In telecommunications, transmission (abbreviations: Tx, Xmit) is the process of sending and propagating an analogue or digital information signal over a physical point-to-point or point-to-multipoint transmission medium, either wired, optical fiber or wireless.[1][2] One example of transmission is the sending of a signal with limited duration, for example a block or packet of data, a phone call, or an email. Transmission technologies and schemes typically refer to physical layer protocol duties such as modulation, demodulation, line coding, equalization, error control, bit synchronization and multiplexing, but the term may also involve higher-layer protocol duties, for example, digitizing an analog message signal, and data compression. Transmission of a digital message, or of a digitized analog signal, is known as digital communication. See also[edit]Communication channelReferences[edit]^ " Telecommunications
Telecommunications
Technology Fundamentals"
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Television
Television
Television
(TV) is a telecommunication medium used for transmitting moving images in monochrome (black and white), or in colour, and in two or three dimensions and sound. The term can refer to a television set, a television program ("TV show"), or the medium of television transmission. Television
Television
is a mass medium for advertising, entertainment and news. Television
Television
became available in crude experimental forms in the late 1920s, but it would still be several years before the new technology would be marketed to consumers. After World War II, an improved form of black-and-white TV broadcasting became popular in the United States and Britain, and television sets became commonplace in homes, businesses, and institutions
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Fax
Fax
Fax
(short for facsimile), sometimes called telecopying or telefax (the latter short for telefacsimile), is the telephonic transmission of scanned printed material (both text and images), normally to a telephone number connected to a printer or other output device. The original document is scanned with a fax machine (or a telecopier), which processes the contents (text or images) as a single fixed graphic image, converting it into a bitmap, and then transmitting it through the telephone system in the form of audio-frequency tones. The receiving fax machine interprets the tones and reconstructs the image, printing a paper copy.[1] Early systems used direct conversions of image darkness to audio tone in a continuous or analog manner
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