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Adaptive Communications
Adaptive communications can mean any communications system, or portion thereof, that automatically uses feedback information obtained from the system itself or from the signals carried by the system to modify dynamically one or more of the system operational parameters to improve system performance or to resist degradation. The modification of a system parameter may be discrete, as in hard-switched diversity reception, or may be continuous, as in a predetection combining algorithm. See also *Automatic Link Establishment *Channel use *CALM M5 CALM M5 is the ISO 21215 standard that incorporates WAVE (WAVE PHY/MAC is IEEE 802.11p standard) and adds the following features: * Global (European) 5 GHz spectrum * Regulatory domain (border) management * Directivity and EMC control * Regiona ... Telecommunications techniques {{telecomm-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Communications System
A communications system or communication system is a collection of individual telecommunications networks, transmission systems, relay stations, tributary stations, and terminal equipment usually capable of interconnection and interoperation to form an integrated whole. The components of a communications system serve a common purpose, are technically compatible, use common procedures, respond to controls, and operate in union. Telecommunications is a method of communication (e.g., for sports broadcasting, mass media, journalism, etc.). Communication is the act of conveying intended meanings from one entity or group to another through the use of mutually understood signs and semiotic rules. Types By media An optical communication system is any form of telecommunication that uses light as the transmission medium. Equipment consists of a transmitter, which encodes a ''message'' into an optical ''signal'', a ''communication channel'', which carries the signal to its dest ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Feedback
Feedback occurs when outputs of a system are routed back as inputs as part of a chain of cause-and-effect that forms a circuit or loop. The system can then be said to ''feed back'' into itself. The notion of cause-and-effect has to be handled carefully when applied to feedback systems: History Self-regulating mechanisms have existed since antiquity, and the idea of feedback had started to enter economic theory in Britain by the 18th century, but it was not at that time recognized as a universal abstraction and so did not have a name. The first ever known artificial feedback device was a float valve, for maintaining water at a constant level, invented in 270 BC in Alexandria, Egypt. This device illustrated the principle of feedback: a low water level opens the valve, the rising water then provides feedback into the system, closing the valve when the required level is reached. This then reoccurs in a circular fashion as the water level fluctuates. Centrifugal governors were ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Information
Information is an abstract concept that refers to that which has the power to inform. At the most fundamental level information pertains to the interpretation of that which may be sensed. Any natural process that is not completely random, and any observable pattern in any medium can be said to convey some amount of information. Whereas digital signals and other data use discrete signs to convey information, other phenomena and artifacts such as analog signals, poems, pictures, music or other sounds, and currents convey information in a more continuous form. Information is not knowledge itself, but the meaning that may be derived from a representation through interpretation. Information is often processed iteratively: Data available at one step are processed into information to be interpreted and processed at the next step. For example, in written text each symbol or letter conveys information relevant to the word it is part of, each word conveys information rele ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Degradation (telecommunications)
In telecommunication, degradation is the loss of quality of an electronic signal, which may be categorized as either "'' graceful''" or "''catastrophic''", and has the following meanings: #The deterioration in quality, level, or standard of performance of a functional unit. #In communications, a condition in which one or more of the required performance parameters fall outside predetermined limits, resulting in a lower quality of service. There are several forms and causes of degradation in electric signals, both in the time domain and in the physical domain, including runt pulse, voltage spike, jitter, wander, swim, drift, glitch, ringing, crosstalk, antenna effect (not the same antenna effect as in IC manufacturing), and phase noise. Degradation usually refers to reduction in quality of an analog or digital signal. When a signal is being transmitted or received, it undergoes changes which are undesirable. These changes are called degradation. Degradation is usually caused by: ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Diversity Reception
In telecommunications, a diversity scheme refers to a method for improving the reliability of a message signal by using two or more Channel (communications), communication channels with different characteristics. Diversity is mainly used in radio communication and is a common technique for combatting 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. Diversity techniques The following classes of diversity schemes can be identified: * Time diversity: Multiple versions of the same signal are transmitted at dif ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Automatic Link Establishment
Automatic Link Establishment, commonly known as ALE, is the worldwide de facto standard for digitally initiating and sustaining HF radio communications. ALE is a feature in an HF communications radio transceiver system that enables the radio station to make contact, or initiate a circuit, between itself and another HF radio station or network of stations. The purpose is to provide a reliable rapid method of calling and connecting during constantly changing HF ionospheric propagation, reception interference, and shared spectrum use of busy or congested HF channels. Mechanism A standalone ALE radio combines an HF SSB radio transceiver with an internal microprocessor and MFSK modem. It is programmed with a unique ALE address, similar to a phone number (or on newer generations, a username). When not actively in contact with another station, the HF SSB transceiver constantly scans through a list of HF frequencies called ''channels'', listening for any ALE signals transmitted by oth ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Channel Use
Channel use is a quantity used in signal processing or telecommunication related to symbol rate and channel capacity. Capacity is measured in bits per input symbol into the channel (bits per channel use). If a symbol enters the channel every ''T''s seconds (for every symbol period a symbol is transmitted) the channel capacity in bits per second is ''C/T''s. The phrase "1 bit per channel use" denotes the transmission of 1 symbol (of duration ''T''s) containing 1 data bit. See also * Adaptive communications *End instrument *Spectral efficiency Spectral efficiency, spectrum efficiency or bandwidth efficiency refers to the information rate that can be transmitted over a given bandwidth in a specific communication system. It is a measure of how efficiently a limited frequency spectrum is ut ... and modulation efficiency in (bit/s)/Hz Data transmission Information theory {{Telecomm-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
CALM M5
CALM M5 is the ISO 21215 standard that incorporates WAVE (WAVE PHY/MAC is IEEE 802.11p standard) and adds the following features: * Global (European) 5 GHz spectrum * Regulatory domain (border) management * Directivity and EMC control * Regional DSRC cooperation * Multiple radios/interfaces/antenna management through network connection * GPRS/UMTS/+++ network interconnectivity See also * Common technical regulation *IEEE 802.11p IEEE 802.11p is an approved amendment to the IEEE 802.11 standardization, standard to add wireless access in vehicular environments (WAVE), a vehicular communication systems, vehicular communication system. It defines enhancements to 802.11 (the bas ... References Status of Project IEEE 802.11p* Bob Williams, ''Intelligent Transport Systems Standards'', p. 221, Artech House, 2008 . * Piyushimita (Vonu) Thakuriah, D. Glenn Geers, ''Transportation and Information: Trends in Technology and Policy'', p. 24, Springer, 2013 . IEEE 802.11 { ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
