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Channel Noise Level
In telecommunications, the term channel noise level has the following meanings: #The ratio of the noise in the communication channel at any point in a transmission system to an arbitrary level chosen as a reference. #The noise power spectral density The power spectrum S_(f) of a time series x(t) describes the distribution of power into frequency components composing that signal. According to Fourier analysis, any physical signal can be decomposed into a number of discrete frequencies, ... in the frequency range of interest. #The average noise power in the frequency range of interest. See also * Ambient noise level Notes References *{{FS1037C MS188 Noise (electronics) ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Telecommunication
Telecommunication is the transmission of information by various types of technologies over wire, radio, optical, or other electromagnetic systems. It has its origin in the desire of humans for communication over a distance greater than that feasible with the human voice, but with a similar scale of expediency; thus, slow systems (such as postal mail) are excluded from the field. The transmission media in telecommunication have evolved through numerous stages of technology, from beacons and other visual signals (such as smoke signals, semaphore telegraphs, signal flags, and optical heliographs), to electrical cable and electromagnetic radiation, including light. Such transmission paths are often divided into communication channels, which afford the advantages of multiplexing multiple concurrent communication sessions. ''Telecommunication'' is often used in its plural form. Other examples of pre-modern long-distance communication included audio messages, such as coded drumb ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Noise (electronics)
In electronics, noise is an unwanted disturbance in an electrical signal. Noise generated by electronic devices varies greatly as it is produced by several different effects. In particular, noise is inherent in physics, and central to thermodynamics. Any conductor with electrical resistance will generate thermal noise inherently. The final elimination of thermal noise in electronics can only be achieved cryogenically, and even then quantum noise would remain inherent. Electronic noise is a common component of noise in signal processing. In communication systems, noise is an error or undesired random disturbance of a useful information signal in a communication channel. The noise is a summation of unwanted or disturbing energy from natural and sometimes man-made sources. Noise is, however, typically distinguished from interference, for example in the signal-to-noise ratio (SNR), signal-to-interference ratio (SIR) and signal-to-noise plus interference ratio (SNIR) measu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Communication Channel
A communication channel refers either to a physical transmission medium such as a wire, or to a logical connection over a multiplexed medium such as a radio channel in telecommunications and computer networking. A channel is used for information transfer of, for example, a digital bit stream, from one or several '' senders'' to one or several '' receivers''. A channel has a certain capacity for transmitting information, often measured by its bandwidth in Hz or its data rate in bits per second. Communicating an information signal across distance requires some form of pathway or medium. These pathways, called communication channels, use two types of media: Transmission line (e.g. twisted-pair, coaxial, and fiber-optic cable) and broadcast (e.g. microwave, satellite, radio, and infrared). In information theory, a channel refers to a theoretical ''channel model'' with certain error characteristics. In this more general view, a storage device is also a communication channel, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Transmission System
:''See Transmission (mechanics) for a car's transmission system'' In telecommunications, a transmission system is a system that transmits a signal from one place to another. The signal can be an Signal (electrical engineering), electrical, optical or Radio wave, radio signal. Some transmission systems contain multipliers, which amplify a signal prior to re-transmission, or Regenerator (telecommunication), regenerators, which attempt to reconstruct and re-shape the coded message before re-transmission. One of the most widely used transmission system technologies in the Internet and the PSTN is SONET. Also, transmission system is the medium through which data is transmitted from one point to another. Examples of common transmission systems people use everyday are: the internet, mobile network, cordless cables, etc. See also * Communications satellite * Submarine communications cable a cable on the sea bed. Notes Telecommunications systems In order to propel the vehicle, a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Decibel
The decibel (symbol: dB) is a relative unit of measurement equal to one tenth of a bel (B). It expresses the ratio of two values of a power or root-power quantity on a logarithmic scale. Two signals whose levels differ by one decibel have a power ratio of 101/10 (approximately ) or root-power ratio of 10 (approximately ). The unit expresses a relative change or an absolute value. In the latter case, the numeric value expresses the ratio of a value to a fixed reference value; when used in this way, the unit symbol is often suffixed with letter codes that indicate the reference value. For example, for the reference value of 1 volt, a common suffix is " V" (e.g., "20 dBV"). Two principal types of scaling of the decibel are in common use. When expressing a power ratio, it is defined as ten times the logarithm in base 10. That is, a change in ''power'' by a factor of 10 corresponds to a 10 dB change in level. When expressing root-power quantities, a change in ''ampl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Reference Noise
In telecommunication, reference noise is the magnitude of circuit noise chosen as a reference for measurement. Many different levels with a number of different weightings are in current use, and care must be taken to ensure that the proper parameters are stated. Specific ones include: dBa, dBa(F1A), dBa(HA1), dBa0, dBm, dBm(psoph), dBm0, dBrn, dBrnC The decibel (symbol: dB) is a relative unit of measurement equal to one tenth of a bel (B). It expresses the ratio of two values of a power or root-power quantity on a logarithmic scale. Two signals whose levels differ by one decibel have a p ..., dBrnC0, dBrn(f1-f2), dBrn(144-line), dBx. References * Noise (electronics) Communication circuits Telecommunications techniques {{telecomm-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
DBrn
The symbol dBrn or dB(rn) is an abbreviation for decibels above reference noise. Weighted noise power in dB is referred to 1.0 picowatt. Thus, 0 dBrn = -90 dBm. Use of 144 line, 144-receiver, or C-message weighting, or flat weighting, can be indicated in parentheses. With C-message weighting, a one-milliwatt, 1000 Hz tone will read +90 dBrn, but the same power as white noise, randomly distributed over a 3 kHz band will read approximately +88.5 dBrn, because of the frequency weighting. With 144 weightings, a one milliwatt, 1000 Hz white noise tone will also read +90 dBrn, but the same 3 kHz power will only read +82 dBrn, because of the different frequency weighting. Note: In telecommunications, ''dBrn adjusted'' also called dBa denotes "decibels adjusted", i.e. weighted absolute noise power. This is totally unrelated to and not a synonym for dB(A) A-weighting is the most commonly used of a family of curves defined in the International standard IEC 61672:2003 and various n ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
DBrnC
The decibel (symbol: dB) is a relative unit of measurement equal to one tenth of a bel (B). It expresses the ratio of two values of a power or root-power quantity on a logarithmic scale. Two signals whose levels differ by one decibel have a power ratio of 101/10 (approximately ) or root-power ratio of 10 (approximately ). The unit expresses a relative change or an absolute value. In the latter case, the numeric value expresses the ratio of a value to a fixed reference value; when used in this way, the unit symbol is often suffixed with letter codes that indicate the reference value. For example, for the reference value of 1 volt, a common suffix is " V" (e.g., "20 dBV"). Two principal types of scaling of the decibel are in common use. When expressing a power ratio, it is defined as ten times the logarithm in base 10. That is, a change in ''power'' by a factor of 10 corresponds to a 10 dB change in level. When expressing root-power quantities, a change in ''amp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
A-weighting
A-weighting is the most commonly used of a family of curves defined in the International standard IEC 61672:2003 and various national standards relating to the measurement of sound pressure level. A-weighting is applied to instrument-measured sound levels in an effort to account for the relative loudness perceived by the human ear, as the ear is less sensitive to low audio frequencies. It is employed by arithmetically adding a table of values, listed by octave or third-octave bands, to the measured sound pressure levels in dB. The resulting octave band measurements are usually added (logarithmic method) to provide a single A-weighted value describing the sound; the units are written as dB(A). Other weighting sets of values – B, C, D and now Z – are discussed below. The curves were originally defined for use at different average sound levels, but A-weighting, though originally intended only for the measurement of low-level sounds (around 40 phon), is now commonly used for ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Telecommunication Circuit
A telecommunication circuit is a path in a telecommunications network used to transmit information. Circuits have evolved over time from generally being built on physical connections between individual hardware cables, as in an analog phone switch, to virtual circuits established over packet switching networks. Definitions A telecommunication circuit may be defined as follows: * The complete path between two terminals over which one-way or two-way communications may be provided. * An electronic path between two or more points, capable of providing a single or multiple communication channels. * An electronic closed-loop path among two or more points used for signal transfer. In operational terms, a telecommunication circuit may be capable of transmitting information in only one direction (''simplex'' circuit), or it may be bi-directional (''duplex'' circuit). Bi-directional circuits may support half- duplex operation, when only one end of the channel transmits at any one time, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Interference (communication)
In telecommunications, an interference is that which modifies a signal in a disruptive manner, as it travels along a communication channel between its source and receiver. The term is often used to refer to the addition of unwanted signals to a useful signal. Common examples include: * Electromagnetic interference (EMI) * Co-channel interference (CCI), also known as crosstalk * Adjacent-channel interference (ACI) * Intersymbol interference (ISI) * Inter-carrier interference (ICI), caused by doppler shift in OFDM modulation (multitone modulation). * Common-mode interference (CMI) * Conducted interference Noise is a form of interference but not all interference is noise. Radio resource management aims at reducing and controlling the co-channel and adjacent-channel interference. Interference alignment A solution to interference problems in wireless communication networks is interference alignment, which was crystallized by Syed Ali Jafar at the University of California, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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