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Direct-sequence Spread Spectrum
In telecommunications, direct-sequence spread spectrum (DSSS) is a spread-spectrum modulation technique primarily used to reduce overall signal interference. The direct-sequence modulation makes the transmitted signal wider in bandwidth than the information bandwidth. After the despreading or removal of the direct-sequence modulation in the receiver, the information bandwidth is restored, while the unintentional and intentional interference is substantially reduced. Swiss inventor, Gustav Guanella proposed a "means for and method of secret signals". With DSSS, the message symbols are modulated by a sequence of complex values known as ''spreading sequence''. Each element of the spreading sequence, a so-called ''chip'', has a shorter duration than the original message symbols. The modulation of the message symbols scrambles and spreads the signal in the spectrum, and thereby results in a bandwidth of the spreading sequence. The smaller the chip duration, the larger the bandw ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Telecommunications
Telecommunication, often used in its plural form or abbreviated as telecom, is the transmission of information over a distance using electronic means, typically through cables, radio waves, or other communication technologies. These means of transmission may be divided into communication channels for multiplexing, allowing for a single medium to transmit several concurrent Session (computer science), communication sessions. Long-distance technologies invented during the 20th and 21st centuries generally use electric power, and include the electrical telegraph, telegraph, telephone, television, and radio. Early telecommunication networks used metal wires as the medium for transmitting signals. These networks were used for telegraphy and telephony for many decades. In the first decade of the 20th century, a revolution in wireless communication began with breakthroughs including those made in radio communications by Guglielmo Marconi, who won the 1909 Nobel Prize in Physics. Othe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Galileo Positioning System
Galileo is a satellite navigation, global navigation satellite system (GNSS) created by the European Union through the European Space Agency (ESA) and operated by the European Union Agency for the Space Programme (EUSPA). It is headquartered in Prague, Czech Republic, Czechia, with two ground operations centres in Oberpfaffenhofen, Germany (mostly responsible for the control of the satellites), and in Fucine Lake, Fucino, Italy (mostly responsible for providing the navigation data). The €10 billion project began offering limited services in 2016. It is named after the Italian astronomer Galileo Galilei. One of the aims of Galileo is to provide an independent high-precision positioning system so European political and military authorities do not have to rely on the United States Global Positioning System, GPS or the Russian GLONASS systems, which could be disabled or degraded by their operators at any time. The use of basic (lower-precision) Galileo services is free and open ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radar
Radar is a system that uses radio waves to determine the distance ('' ranging''), direction ( azimuth and elevation angles), and radial velocity of objects relative to the site. It is a radiodetermination method used to detect and track aircraft, ships, spacecraft, guided missiles, motor vehicles, map weather formations, and terrain. The term ''RADAR'' was coined in 1940 by the United States Navy as an acronym for "radio detection and ranging". The term ''radar'' has since entered English and other languages as an anacronym, a common noun, losing all capitalization. A radar system consists of a transmitter producing electromagnetic waves in the radio or microwave domain, a transmitting antenna, a receiving antenna (often the same antenna is used for transmitting and receiving) and a receiver and processor to determine properties of the objects. Radio waves (pulsed or continuous) from the transmitter reflect off the objects and return to the receiver, giving ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radio-controlled Model
A radio-controlled model (or RC model) is a model that is steerable with the use of radio control (RC). All types of model vehicles have had RC systems installed in them, including ground vehicles, boats, planes, helicopters and even submarines and scale railway locomotives. History World War II saw increased development in radio control technology. The Luftwaffe used controllable winged bombs for targeting Allied ships. During the 1930s the Good brothers Bill and Walt pioneered vacuum tube based control units for RC hobby use. Their "Guff" radio controlled plane is on display at the National Aerospace museum. Ed Lorenze published a design in Model Airplane News that was built by many hobbyists. Later, after WW2, in the late 1940s to mid 1950 many other RC designs emerged and some were sold commercially, Berkeley's Super Aerotrol, was one such example. Originally simple 'on-off' systems, these evolved to use complex systems of relays to control a rubber powered escapement' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
WirelessHART
WirelessHART within telecommunications and computing, is a wireless sensor networking technology. It is based on the Highway Addressable Remote Transducer Protocol (HART). Developed as a multi-vendor, interoperable wireless standard, WirelessHART was defined for the requirements of process field device networks. Technical description The protocol utilizes a time synchronized, self-organizing, and self-healing mesh architecture. The protocol supports operation in the 2.4 GHz ISM band using IEEE 802.15.4 standard radios. The underlying wireless technology is based on the work of Dust Networks' TSMP technology. History The standard was initiated in early 2004 and developed by 37 HART Communications Foundation (HCF) companies that - amongst others - included ABB, Emerson, Endress+Hauser, Pepperl+Fuchs, Siemens, Freescale Semiconductor, Software Technologies Group (which developed the initial WirelessHART WiTECK stack), and AirSprite Technologies which went on to form WiTECK ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Zigbee
Zigbee is an IEEE 802.15.4-based specification for a suite of high-level communication protocols used to create personal area networks with small, low-power digital radios, such as for home automation, medical device data collection, and other low-power low-bandwidth needs, designed for small scale projects which need wireless connection. Hence, Zigbee is a low-power, low-data-rate, and close proximity (i.e., personal area) wireless ad hoc network. The technology defined by the Zigbee specification is intended to be simpler and less expensive than other wireless personal area networks (WPANs), such as Bluetooth or more general wireless networking such as Wi-Fi (or Li-Fi). Applications include wireless light switches, home energy monitors, traffic management systems, and other consumer and industrial equipment that requires short-range low-rate wireless data transfer. Its low power consumption limits transmission distances to line-of-sight, depending on power output and e ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Automatic Meter Reading
Automatic meter reading (AMR) is the technology of automatically collecting consumption, diagnostic, and status data from water meter or energy metering devices (gas, electric) and transferring that data to a central database for billing, troubleshooting, and analyzing. This technology mainly saves utility providers the expense of periodic trips to each physical location to read a meter. Another advantage is that billing can be based on near real-time consumption rather than on estimates based on past or predicted consumption. This timely information coupled with analysis can help both utility providers and customers better control the use and production of electric energy, gas usage, or water consumption. AMR technologies include handheld, mobile and network technologies based on telephony platforms (wired and wireless), radio frequency (RF), or powerline transmission. Technologies Touch technology With touch-based AMR, a meter reader carries a handheld computer or data colle ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Orthogonal Frequency-division Multiplexing
In telecommunications, orthogonal frequency-division multiplexing (OFDM) is a type of digital transmission used in digital modulation for encoding digital (binary) data on multiple carrier frequencies. OFDM has developed into a popular scheme for wideband digital communication, used in applications such as digital television and audio broadcasting, DSL internet access, wireless networks, power line networks, and 4G/ 5G mobile communications. OFDM is a frequency-division multiplexing (FDM) scheme that was introduced by Robert W. Chang of Bell Labs in 1966. In OFDM, the incoming bitstream representing the data to be sent is divided into multiple streams. Multiple closely spaced orthogonal subcarrier signals with overlapping spectra are transmitted, with each carrier modulated with bits from the incoming stream so multiple bits are being transmitted in parallel. [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Band (radio)
The radio spectrum is the part of the electromagnetic spectrum with frequencies from 3 Hz to 3,000 GHz (3 THz). Electromagnetic waves in this frequency range, called radio waves, are widely used in modern technology, particularly in telecommunication. To prevent interference between different users, the generation and transmission of radio waves is strictly regulated by national laws, coordinated by an international body, the International Telecommunication Union (ITU). Different parts of the radio spectrum are allocated by the ITU for different radio transmission technologies and applications; some 40 radiocommunication services are defined in the ITU's Radio Regulations (RR). In some cases, parts of the radio spectrum are sold or licensed to operators of private radio transmission services (for example, cellular telephone operators or broadcast television stations). Ranges of allocated frequencies are often referred to by their provisioned use (for example, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cordless Telephone
A cordless telephone or portable telephone has a portable telephone handset that connects by radio to a base station connected to the public telephone network. The operational range is limited, usually to the same building or within some short distance from the base station. A cordless telephone differs functionally from a mobile phone in its limited range and by depending on the base station on the subscriber premises. Current cordless telephone standards, such as Personal Handy-phone System, PHS and DECT, have blurred the once clear-cut line between cordless and mobile telephones by implementing cell handoff (handover); various advanced features, such as data-transfer; and even, on a limited scale, international roaming. In specialized models, a commercial mobile network operator may maintain base stations and users subscribe to the service. Unlike a corded telephone, a cordless telephone needs mains electricity (to power the base station). The cordless handset contains a re ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Multiple Access
Multiple may refer to: Economics *Multiple finance, a method used to analyze stock prices *Multiples of the price-to-earnings ratio *Chain stores, are also referred to as 'Multiples' *Box office multiple, the ratio of a film's total gross to that of its opening weekend Sociology *Multiples (sociology), a theory in sociology of science by Robert K. Merton, see Science *Multiple (mathematics), multiples of numbers *List of multiple discoveries, instances of scientists, working independently of each other, reaching similar findings *Multiple birth, because having twins is sometimes called having "multiples" *Multiple sclerosis, an inflammatory disease *Parlance for people with multiple identities, sometimes called "multiples"; often theorized as having dissociative identity disorder *Multiple myeloma (MM), a cancer that forms in a type of white blood cell (WBC) called plasma cells. Printing *Printmaking, where ''multiple'' is often used as a term for a print, especially in the US ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
CDMA
Code-division multiple access (CDMA) is a channel access method used by various radio communication technologies. CDMA is an example of multiple access, where several transmitters can send information simultaneously over a single communication channel. This allows several users to share a band of frequencies (see bandwidth). To permit this without undue interference between the users, CDMA employs spread spectrum technology and a special coding scheme (where each transmitter is assigned a code). CDMA optimizes the use of available bandwidth as it transmits over the entire frequency range and does not limit the user's frequency range. It is used as the access method in many mobile phone standards. IS-95, also called "cdmaOne", and its 3G evolution CDMA2000, are often simply referred to as "CDMA", but UMTS, the 3G standard used by GSM carriers, also uses "wideband CDMA", or W-CDMA, as well as TD-CDMA and TD-SCDMA, as its radio technologies. Many carriers (such as AT&T, U ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
