Terrestrial microwave radio system with two antenna arrays configured for space-diversity In telecommunications, a diversity scheme refers to a method for improving the reliability of a message signal by utilizing two or more communication channels with different characteristics. Diversity plays an important role in combating fading and co-channel interference and avoiding error bursts. It is based on the fact that individual channels experience different levels of fading and interference. Multiple versions of the same signal may be transmitted and/or received and combined in the receiver. Alternatively, a redundant forward error correction code may be added and different parts of the message transmitted over different channels. Diversity techniques may exploit the multipath propagation, resulting in a diversity gain, often measured in decibels. Image File history File links Download high-resolution version (392x1280, 339 KB) Please credit the photographer, David Jordan, when using this image. ...
Image File history File links Download high-resolution version (392x1280, 339 KB) Please credit the photographer, David Jordan, when using this image. ...
This article is about the type of Electromagnetic radiation. ...
Telecommunication involves the transmission of signals over a distance for the purpose of communication. ...
Fading (or fading channels) are mathematical models for the distortion that a carrier-modulated telecommunication signal experiences over certain propagation media. ...
In telecommunication, an error burst is a contiguous sequence of symbols, received over a data transmission channel, such that the first and last symbols are in error and there exists no contiguous subsequence of m correctly received symbols within the error burst. ...
In telecommunication, forward error correction (FEC) is a system of error control for data transmission, whereby the sender adds redundant data to its messages, which allows the receiver to detect and correct errors (within some bound) without the need to ask the sender for additional data. ...
In wireless communications, diversity gain is the increase in signal-to-interference ratio due to some diversity scheme, or how much the transmission power can be reduced when a diversity scheme is introduced, without a performance loss. ...
The decibel is a dimensionless unit (like percent) that is a measure of ratios on a logarithmic scale. ...
The following classes of diversity schemes can be identified:
- Time diversity: Multiple versions of the same signal are transmitted at different time instants. Alternatively, a redundant forward error correction code is added and the message is spread in time by means of bit-interleaving before it is transmitted. Thus, error bursts are avoided, which simplifies the error correction.
- Frequency diversity: The signal is transferred using several frequency channels or spread over a wide spectrum that is affected by frequency-selective fading. Examples are:
- Space diversity: The signal is transferred over several different propagation paths. In the case of wired transmission, this can be achieved by transmitting via multiple wires. In the case of wireless transmission, it can be achieved by antenna diversity using multiple transmitter antennas (transmit diversity) and/or multiple receiving antennas (diversity reception). In the latter case, a diversity combining technique is applied before further signal processing takes place. If the antennas are at far distance, for example at different cellular base station sites or WLAN access points, this is called macrodiversity). If the antennas are at a distance in the order of one wavelength, this is called microdiversity. A special case is phased antenna arrays, which also can be utilized for beamforming, MIMO channels and Space–time coding (STC).
- Polarisation diversity: Multiple versions of a signal are transmitted and received via antennas with different polarization. A diversity combining technique is applied on the receiver side.
- Multiuser diversity: Multiuser diversity is obtained by opportunistic user scheduling at either the transmitter or the receiver. Opportunistic user scheduling is as follows that the transmit selects the best user among candidate receivers according to qualities of each channel between the transmit and each receiver. In FDD systems, a receiver must feed back the channel quality information to the transmitter with the limited level of resolution.
- Cooperative diversity: enables to achieve the Antenna diversity gain by the use of the cooperation of distributed antennas belonging to each node.
Time Diversity is used in digital communication systems to combat that the transmissions channel may suffer from error bursts due to time-varying channel conditions. ...
In telecommunication, forward error correction (FEC) is a system of error control for data transmission, whereby the sender adds redundant data to its messages, which allows the receiver to detect and correct errors (within some bound) without the need to ask the sender for additional data. ...
Interleaver redirects here. ...
In telecommunication, an error burst is a contiguous sequence of symbols, received over a data transmission channel, such that the first and last symbols are in error and there exists no contiguous subsequence of m correctly received symbols within the error burst. ...
Fading (or fading channels) are mathematical models for the distortion that a carrier-modulated telecommunication signal experiences over certain propagation media. ...
Fading (or fading channels) are mathematical models for the distortion that a carrier-modulated telecommunication signal experiences over certain propagation media. ...
Orthogonal frequency division modulation (OFDM, also called orthogonal frequency division multiplexing) is a technique for the modulation of digital information onto an analog carrier electromagnetic (e. ...
“Interleaver†redirects here. ...
In telecommunication, forward error correction (FEC) is a system of error control for data transmission, whereby the sender adds redundant data to its messages, which allows the receiver to detect and correct errors (within some bound) without the need to ask the sender for additional data. ...
Spread-spectrum telecommunications is a technique in which a signal is transmitted in a bandwidth considerably greater than the frequency content of the original information. ...
Frequency-hopping spread spectrum (FHSS) is a spread-spectrum method of transmitting signals by rapidly switching a carrier among many frequency channels, using a pseudorandom sequence known to both transmitter and receiver. ...
Direct-Sequence Code Division Multiple Access (DS-CDMA) is a multiple access scheme based on direct-sequence spread spectrum, by spreading the signals from/to different users with different codes. ...
In telecommunications, a diversity scheme refers to a method for improving the reliability of a message signal by utilizing two or more communication channels with different characteristics. ...
Antenna Diversity is a transmission technique in which the information-carrying signal is transmitted along different propagation paths. ...
This method is used to improve the signal quality at receiver and also reduces the interference to the signal . ...
Diversity Combining is the technique applied to combine the multiple received signals of a diversity reception device into a single improved signal. ...
In wireless communication, Macrodiversity means a situation where several receiver antennas and/or transmitter antennas are used for transferring the same signal. ...
For other uses, see Wavelength (disambiguation). ...
A giant phased-array radar in Alaska In telecommunication, a phased array is a group of antennas in which the relative phases of the respective signals feeding the antennas are varied in such a way that the effective radiation pattern of the array is reinforced in a desired direction and...
Beamforming is a signal processing technique used with arrays of transmitting or receiving transducers that control the directionality of, or sensitivity to, a radiation pattern. ...
See also systems analysis. ...
A space–time code (STC) is a method employed to improve the reliability of data transmission in wireless communication systems using multiple transmit antennas. ...
This article treats polarization in electrodynamics. ...
Diversity Combining is the technique applied to combine the multiple received signals of a diversity reception device into a single improved signal. ...
Antenna Diversity is a transmission technique in which the information-carrying signal is transmitted along different propagation paths. ...
Cooperative diversity is a communication technique that achieves a diversity gain exploiting both the relayed signal and the direct signal. ...
See also
A space–time code (STC) is a method employed to improve the reliability of data transmission in wireless communication systems using multiple transmit antennas. ...
Antenna Diversity is a transmission technique in which the information-carrying signal is transmitted along different propagation paths. ...
In wireless communication, Macrodiversity means a situation where several receiver antennas and/or transmitter antennas are used for transferring the same signal. ...
Diversity Combining is the technique applied to combine the multiple received signals of a diversity reception device into a single improved signal. ...
Aperture synthesis is a type of interferometry that mixes signals from a collection instruments to produce measurements having the same angular resolution as an instrument the size of the entire collection. ...
Cooperative diversity is a communication technique that achieves a diversity gain exploiting both the relayed signal and the direct signal. ...
In communications, a channel access method is used to share a communications channel or physical communications medium between multiple users. ...
Fresnel zone. ...
Tropospheric scatter (or troposcatter) is the scattering of distant TV and FM radio stations by the troposphere so that they travel farther than the line of sight. ...
External links - Diversity reception - Background information of the development of Diversity reception devices.
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