1.
Computer network
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A computer network or data network is a telecommunications network which allows nodes to share resources. In computer networks, networked computing devices exchange data with other using a data link. The connections between nodes are established using either cable media or wireless media, the best-known computer network is the Internet. Network computer devices that originate, route and terminate the data are called network nodes, nodes can include hosts such as personal computers, phones, servers as well as networking hardware. Two such devices can be said to be networked together when one device is able to exchange information with the other device, Computer networks differ in the transmission medium used to carry their signals, communications protocols to organize network traffic, the networks size, topology and organizational intent. In most cases, application-specific communications protocols are layered over other more general communications protocols and this formidable collection of information technology requires skilled network management to keep it all running reliably. The chronology of significant computer-network developments includes, In the late 1950s, in 1960, the commercial airline reservation system semi-automatic business research environment went online with two connected mainframes. Licklider developed a group he called the Intergalactic Computer Network. In 1964, researchers at Dartmouth College developed the Dartmouth Time Sharing System for distributed users of computer systems. The same year, at Massachusetts Institute of Technology, a group supported by General Electric and Bell Labs used a computer to route. Throughout the 1960s, Leonard Kleinrock, Paul Baran, and Donald Davies independently developed network systems that used packets to transfer information between computers over a network, in 1965, Thomas Marill and Lawrence G. Roberts created the first wide area network. This was an precursor to the ARPANET, of which Roberts became program manager. Also in 1965, Western Electric introduced the first widely used telephone switch that implemented true computer control, in 1972, commercial services using X.25 were deployed, and later used as an underlying infrastructure for expanding TCP/IP networks. In July 1976, Robert Metcalfe and David Boggs published their paper Ethernet, Distributed Packet Switching for Local Computer Networks, in 1979, Robert Metcalfe pursued making Ethernet an open standard. In 1976, John Murphy of Datapoint Corporation created ARCNET, a network first used to share storage devices. In 1995, the transmission speed capacity for Ethernet increased from 10 Mbit/s to 100 Mbit/s, by 1998, Ethernet supported transmission speeds of a Gigabit. Subsequently, higher speeds of up to 100 Gbit/s were added, the ability of Ethernet to scale easily is a contributing factor to its continued use. Providing access to information on shared storage devices is an important feature of many networks, a network allows sharing of files, data, and other types of information giving authorized users the ability to access information stored on other computers on the network
2.
Telecommunications network
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A telecommunications network is a collection of terminal nodes, links are connected so as to enable telecommunication between the terminals. The transmission links connect the nodes together, the nodes use circuit switching, message switching or packet switching to pass the signal through the correct links and nodes to reach the correct destination terminal. Each terminal in the network usually has an address so messages or connections can be routed to the correct recipients. The collection of addresses in the network is called the address space, for example, businesses need a greater telecommunications network if they plan to expand their company. With Internet, computer, and telephone networks, businesses can allocate their resources efficiently and these core types of networks will be discussed below, Computer network, a computer network consists of computers and devices connected to one another. Information can be transferred from one device to the next, for example, an office filled with computers can share files together on each separate device. Computer networks can range from a local area to a wide area network. The difference between the types of networks is the size and these types of computer networks work at certain speeds, also known as broadband. The Internet network connects computers worldwide, Internet network, access to the network allows users to use many resources. Over time the Internet network will replace books and this will enable users to discover information almost instantly and apply concepts to different situations. The Internet can be used for recreational, governmental, educational, businesses in particular use the Internet network for research or to service customers and clients. Telephone network, the network connects people to one another. This network can be used in a variety of ways, many businesses use the telephone network to route calls and/or service their customers. Some businesses use a network on a greater scale through a private branch exchange. It is a system where a specific business focuses on routing and servicing calls for another business, majority of the time, the telephone network is used around the world for recreational purposes. In general, every telecommunications network conceptually consists of three parts, or planes, The data plane carries the networks users traffic, the actual payload, the control plane carries control information. The management plane carries the operations and administration traffic required for network management, the management plane is sometimes considered a part of the control plane. The data network is used throughout the world to connect individuals
3.
Wireless
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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 television or as far as thousands or even millions of kilometers for deep-space radio communications. It encompasses various types of fixed, mobile, and portable applications, including radios, cellular telephones, personal digital assistants. Somewhat less common methods of achieving wireless communications include the use of other wireless technologies, such as light, magnetic. The term wireless has been used twice in history, with slightly different meaning. It was initially used from about 1890 for the first radio transmitting and receiving technology, as in wireless telegraphy and this became its primary usage in the 2000s, due to the advent of technologies such as LTE, LTE-Advanced, Wi-Fi and Bluetooth. Wireless operations permit services, such as communications, that are impossible or impractical to implement with the use of wires. The term is used in the telecommunications industry to refer to telecommunications systems which use some form of energy to transfer information without the use of wires. Information is transferred in this manner over both short and long distances, similar to free-space optical communication, the photophone also required a clear line of sight between its transmitter and its receiver. It would be decades before the photophones principles found their first practical applications in military communications. Marconi soon developed a system that was transmitting signals way beyond distances anyone could have predicted, guglielmo Marconi and Karl Ferdinand Braun were awarded the 1909 Nobel Prize for Physics for their contribution to this form of wireless telegraphy. Free space means the light travel through the open air or outer space. This contrasts with other technologies that use light beams traveling through transmission lines such as optical fiber or dielectric light pipes. The technology is useful where physical connections are due to high costs or other considerations. Sonic, especially ultrasonic short range communication involves the transmission and reception of sound, electromagnetic induction has short range communication and power. This has been used in situations such as pacemakers, as well as for short-range Rfid tags. Common examples of wireless equipment include, Infrared and ultrasonic remote control devices Professional LMR and SMR typically used by business, industrial, consumer Two-way radio including FRS Family Radio Service, GMRS and Citizens band radios. Consumer and professional Marine VHF radios, airband and radio navigation equipment used by aviators and air traffic control Cellular telephones and pagers, provide connectivity for portable and mobile applications, both personal and business
4.
Radio
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When radio waves strike an electrical conductor, the oscillating fields induce an alternating current in the conductor. The information in the waves can be extracted and transformed back into its original form, Radio systems need a transmitter to modulate some property of the energy produced to impress a signal on it, for example using amplitude modulation or angle modulation. Radio systems also need an antenna to convert electric currents into radio waves, an antenna can be used for both transmitting and receiving. The electrical resonance of tuned circuits in radios allow individual stations to be selected, the electromagnetic wave is intercepted by a tuned receiving antenna. Radio frequencies occupy the range from a 3 kHz to 300 GHz, a radio communication system sends signals by radio. The term radio is derived from the Latin word radius, meaning spoke of a wheel, beam of light, however, this invention would not be widely adopted. The switch to radio in place of wireless took place slowly and unevenly in the English-speaking world, the United States Navy would also play a role. Although its translation of the 1906 Berlin Convention used the terms wireless telegraph and wireless telegram, the term started to become preferred by the general public in the 1920s with the introduction of broadcasting. Radio systems used for communication have the following elements, with more than 100 years of development, each process is implemented by a wide range of methods, specialised for different communications purposes. Each system contains a transmitter, This consists of a source of electrical energy, the transmitter contains a system to modulate some property of the energy produced to impress a signal on it. This modulation might be as simple as turning the energy on and off, or altering more subtle such as amplitude, frequency, phase. Amplitude modulation of a carrier wave works by varying the strength of the signal in proportion to the information being sent. For example, changes in the strength can be used to reflect the sounds to be reproduced by a speaker. It was the used for the first audio radio transmissions. Frequency modulation varies the frequency of the carrier, the instantaneous frequency of the carrier is directly proportional to the instantaneous value of the input signal. FM has the capture effect whereby a receiver only receives the strongest signal, Digital data can be sent by shifting the carriers frequency among a set of discrete values, a technique known as frequency-shift keying. FM is commonly used at Very high frequency radio frequencies for high-fidelity broadcasts of music, analog TV sound is also broadcast using FM. Angle modulation alters the phase of the carrier wave to transmit a signal
5.
OSI model
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Its goal is the interoperability of diverse communication systems with standard protocols. The model partitions a communication system into abstraction layers, the original version of the model defined seven layers. A layer serves the layer above it and is served by the layer below it, two instances at the same layer are visualized as connected by a horizontal connection in that layer. The model is a product of the Open Systems Interconnection project at the International Organization for Standardization and these two international standards bodies each developed a document that defined similar networking models. In 1983, these two documents were merged to form a standard called The Basic Reference Model for Open Systems Interconnection, the standard is usually referred to as the Open Systems Interconnection Reference Model, the OSI Reference Model, or simply the OSI model. It was published in 1984 by both the ISO, as standard ISO7498, and the renamed CCITT as standard X.200. OSI had two components, an abstract model of networking, called the Basic Reference Model or seven-layer model. The concept of a model was provided by the work of Charles Bachman at Honeywell Information Services. Various aspects of OSI design evolved from experiences with the ARPANET, NPLNET, EIN, CYCLADES network, the new design was documented in ISO7498 and its various addenda. In this model, a system was divided into layers. Within each layer, one or more entities implement its functionality, each entity interacted directly only with the layer immediately beneath it, and provided facilities for use by the layer above it. Protocols enable an entity in one host to interact with an entity at the same layer in another host. Service definitions abstractly described the functionality provided to an -layer by an layer, the OSI standards documents are available from the ITU-T as the X. 200-series of recommendations. Some of the specifications were also available as part of the ITU-T X series. The equivalent ISO and ISO/IEC standards for the OSI model were available from ISO, the recommendation X.200 describes seven layers, labeled 1 to 7. Layer 1 is the lowest layer in this model, at each level N, two entities at the communicating devices exchange protocol data units by means of a layer N protocol. Each PDU contains a payload, called the service data unit, data processing by two communicating OSI-compatible devices is done as such, The data to be transmitted is composed at the topmost layer of the transmitting device into a protocol data unit. The PDU is passed to layer N-1, where it is known as the service data unit, at layer N-1 the SDU is concatenated with a header, a footer, or both, producing a layer N-1 PDU
6.
Cell phone network
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A cellular network or mobile network is a communication network where the last link is wireless. The network is distributed over land areas called cells, each served by at least one fixed-location transceiver and this base station provides the cell with the network coverage which can be used for transmission of voice, data and others. A cell might use a different set of frequencies from neighboring cells, to avoid interference, when joined together these cells provide radio coverage over a wide geographic area. This allows mobile phones and mobile computing devices to be connected to the switched telephone network. Private cellular networks can be used for research or for large organizations and fleets, each of these cells is assigned with multiple frequencies which have corresponding radio base stations. The group of frequencies can be reused in other cells, provided that the frequencies are not reused in adjacent neighboring cells as that would cause co-channel interference. If there is a single transmitter, only one transmission can be used on any given frequency. Unfortunately, there is some level of interference from the signal from the other cells which use the same frequency. This means that, in a standard FDMA system, there must be at least a one cell gap between cells which reuse the same frequency, in the simple case of the taxi company, each radio had a manually operated channel selector knob to tune to different frequencies. As the drivers moved around, they would change from channel to channel, the drivers knew which frequency covered approximately what area. When they did not receive a signal from the transmitter, they would try other channels until they found one that worked, the taxi drivers would only speak one at a time, when invited by the base station operator. With TDMA, the transmitting and receiving time slots used by different users in each cell are different from each other, with FDMA, the transmitting and receiving frequencies used by different users in each cell are different from each other. In a simple system, the taxi driver manually tuned to a frequency of a chosen cell to obtain a strong signal. The principle of CDMA is more complex, but achieves the same result, time division multiple access is used in combination with either FDMA or CDMA in a number of systems to give multiple channels within the coverage area of a single cell. The key characteristic of a network is the ability to re-use frequencies to increase both coverage and capacity. The elements that determine frequency reuse are the distance and the reuse factor. The reuse distance, D is calculated as D = R3 N, cells may vary in radius from 1 to 30 kilometres. The boundaries of the cells can also overlap between adjacent cells and large cells can be divided into smaller cells, the frequency reuse factor is the rate at which the same frequency can be used in the network
7.
Wireless LAN
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This gives users the ability to move around within a local coverage area and yet still be connected to the network. A WLAN can also provide a connection to the wider Internet, most modern WLANs are based on IEEE802.11 standards and are marketed under the Wi-Fi brand name. Wireless LANs have become popular for use in the home, due to their ease of installation and they are also popular in commercial complexes that offer wireless access to their customers. Norman Abramson, a professor at the University of Hawaii, developed the worlds first wireless communication network, ALOHAnet. The system included seven computers deployed over four islands to communicate with the computer on the Oahu Island without using phone lines. Wireless LAN hardware initially cost so much that it was used as an alternative to cabled LAN in places where cabling was difficult or impossible. Early development included industry-specific solutions and proprietary protocols, but at the end of the 1990s these were replaced by standards, beginning in 1991, a European alternative known as HiperLAN/1 was pursued by the European Telecommunications Standards Institute with a first version approved in 1996. This was followed by a HiperLAN/2 functional specification with ATM influences accomplished February 2000, in 2009802. 11n was added to 802.11. It operates in both the 2.4 GHz and 5 GHz bands at a data transfer rate of 600 Mbit/s. Most newer routers are able to utilise both wireless bands, known as dualband and this allows data communications to avoid the crowded 2.4 GHz band, which is also shared with Bluetooth devices and microwave ovens. The 5 GHz band is wider than the 2.4 GHz band, with more channels. Not all channels are available in all regions, a HomeRF group formed in 1997 to promote a technology aimed for residential use, but it disbanded at the end of 2002. All components that can connect into a medium in a network are referred to as stations. All stations are equipped with wireless network interface controllers, Wireless stations fall into two categories, wireless access points, and clients. Access points, normally wireless routers, are base stations for the wireless network and they transmit and receive radio frequencies for wireless enabled devices to communicate with. The basic service set is a set of all stations that can communicate with other at PHY layer. Every BSS has an identification called the BSSID, which is the MAC address of the access point servicing the BSS, there are two types of BSS, Independent BSS, and infrastructure BSS. An independent BSS is an ad hoc network that contains no access points, an extended service set is a set of connected BSSs
8.
Sensor
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A sensor is always used with other electronics, whether as simple as a light or as complex as a computer. Moreover, analog sensors such as potentiometers and force-sensing resistors are still widely used, applications include manufacturing and machinery, airplanes and aerospace, cars, medicine, robotics and many other aspects of our day-to-day life. A sensors sensitivity indicates how much the output changes when the input quantity being measured changes. For instance, if the mercury in a thermometer moves 1 cm when the changes by 1 °C. Some sensors can also affect what they measure, for instance, Sensors are usually designed to have a small effect on what is measured, making the sensor smaller often improves this and may introduce other advantages. Technological progress allows more and more sensors to be manufactured on a scale as microsensors using MEMS technology. In most cases, a microsensor reaches a higher speed. Most sensors have a transfer function. The sensitivity is defined as the ratio between the output signal and measured property. For example, if a sensor measures temperature and has a voltage output, the sensitivity is the slope of the transfer function. Converting the sensors electrical output to the measured units requires dividing the output by the slope. In addition, an offset is added or subtracted. For example -40 must be added to the output if 0 V output corresponds to -40 C input, for an analog sensor signal to be processed, or used in digital equipment, it needs to be converted to a digital signal, using an analog-to-digital converter. The full scale range defines the maximum and minimum values of the measured property, the sensitivity may in practice differ from the value specified. This is called a sensitivity error and this is an error in the slope of a linear transfer function. If the output differs from the correct value by a constant. This is an error in the y-intercept of a transfer function. Nonlinearity is deviation of a transfer function from a straight line transfer function
9.
Satellite
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In the context of spaceflight, a satellite is an artificial object which has been intentionally placed into orbit. Such objects are called artificial satellites to distinguish them from natural satellites such as Earths Moon. In 1957 the Soviet Union launched the worlds first artificial satellite, since then, about 6,600 satellites from more than 40 countries have been launched. According to a 2013 estimate,3,600 remained in orbit, of those, about 1,000 were operational, the rest have lived out their useful lives and become space debris. Approximately 500 operational satellites are in orbit,50 are in medium-Earth orbit. A few large satellites have been launched in parts and assembled in orbit. Over a dozen space probes have been placed into orbit around other bodies and become artificial satellites to the Moon, Mercury, Venus, Mars, Jupiter, Saturn, a few asteroids, Satellites are used for many purposes. Common types include military and civilian Earth observation satellites, communications satellites, navigation satellites, weather satellites, Space stations and human spacecraft in orbit are also satellites. Satellite orbits vary greatly, depending on the purpose of the satellite, well-known classes include low Earth orbit, polar orbit, and geostationary orbit. A launch vehicle is a rocket that throws a satellite into orbit, usually it lifts off from a launch pad on land. Some are launched at sea from a submarine or a mobile maritime platform, Satellites are usually semi-independent computer-controlled systems. Satellite subsystems attend many tasks, such as power generation, thermal control, telemetry, attitude control, the first fictional depiction of a satellite being launched into orbit was a short story by Edward Everett Hale, The Brick Moon. The idea surfaced again in Jules Vernes The Begums Fortune, in 1903, Konstantin Tsiolkovsky published Exploring Space Using Jet Propulsion Devices, which is the first academic treatise on the use of rocketry to launch spacecraft. He calculated the speed required for a minimal orbit. In 1928, Herman Potočnik published his book, The Problem of Space Travel — The Rocket Motor. He described the use of orbiting spacecraft for observation of the ground, in a 1945 Wireless World article, the English science fiction writer Arthur C. Clarke described in detail the possible use of communications satellites for mass communications. He suggested that three geostationary satellites would provide coverage over the entire planet, the first artificial satellite was Sputnik 1, launched by the Soviet Union on October 4,1957, and initiating the Soviet Sputnik program, with Sergei Korolev as chief designer. This in turn triggered the Space Race between the Soviet Union and the United States, Sputnik 1 helped to identify the density of high atmospheric layers through measurement of its orbital change and provided data on radio-signal distribution in the ionosphere
10.
Microwave
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Microwaves are a form of electromagnetic radiation with wavelengths ranging from one meter to one millimeter, with frequencies between 300 MHz and 300 GHz. Different sources define different frequency ranges as microwaves, the broad definition includes both UHF and EHF bands. A more common definition in radio engineering is the range between 1 and 100 GHz, in all cases, microwaves include the entire SHF band at minimum. Frequencies in the range are often referred to by their IEEE radar band designations, S, C, X, Ku, K, or Ka band. The prefix micro- in microwave is not meant to suggest a wavelength in the micrometer range and it indicates that microwaves are small, compared to waves used in typical radio broadcasting, in that they have shorter wavelengths. The boundaries between far infrared, terahertz radiation, microwaves, and ultra-high-frequency radio waves are fairly arbitrary and are used variously between different fields of study. At the high end of the band they are absorbed by gases in the atmosphere, microwaves are extremely widely used in modern technology. Although at the low end of the band they can pass through building walls enough for useful reception, therefore on the surface of the Earth microwave communication links are limited by the visual horizon to about 30 -40 miles. Microwaves are absorbed by moisture in the atmosphere, and the attenuation increases with frequency, beginning at about 40 GHz, atmospheric gases also begin to absorb microwaves, so above this frequency microwave transmission is limited to a few kilometers. A spectral band structure causes absorption peaks at specific frequencies, in a microwave beam directed at an angle into the sky, a small amount of the power will be randomly scattered as the beam passes through the troposphere. A sensitive receiver beyond the horizon with a high gain antenna focused on that area of the troposphere can pick up the signal. This technique has been used at frequencies between 0.45 and 5 GHz in tropospheric scatter communication systems to communicate beyond the horizon and their short wavelength allows narrow beams of microwaves to be produced by conveniently small high gain antennas from a half meter to 5 meters in diameter. Therefore beams of microwaves are used for point-to-point communication links, an advantage of narrow beams is that they allow frequency reuse by nearby transmitters. Parabolic antennas are the most widely used directive antennas at microwave frequencies, flat microstrip antennas are being increasingly used in consumer devices. Where omnidirectional antennas are required, for example in wireless devices and Wifi routers for wireless LANs, small monopoles, dipole, or patch antennas are used. Due to the high cost and maintenance requirements of waveguide runs, the term microwave also has a more technical meaning in electromagnetics and circuit theory. As a consequence, practical microwave circuits tend to away from the discrete resistors, capacitors. Open-wire and coaxial transmission lines used at lower frequencies are replaced by waveguides and stripline, high-power microwave sources use specialized vacuum tubes to generate microwaves
11.
ALOHAnet
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ALOHAnet, also known as the ALOHA System, or simply ALOHA, was a pioneering computer networking system developed at the University of Hawaii. ALOHAnet became operational in June,1971, providing the first public demonstration of a wireless data network. ALOHA originally stood for Additive Links On-line Hawaii Area, but even before such frequencies were assigned there were two other media available for the application of an ALOHA channel – cables and satellites. In the 1970s ALOHA random access was employed in the nascent Ethernet cable based network, in the early 1980s frequencies for mobile networks became available, and in 1985 frequencies suitable for what became known as Wi-Fi were allocated in the US. These regulatory developments made it possible to use the ALOHA random-access techniques in both Wi-Fi and in telephone networks. ALOHA channels were used in a way in the 1980s in 1G mobile phones for signaling. In addition SMS message texting was implemented in 2G mobile phones, the goal was to use low-cost commercial radio equipment to connect users on Oahu and the other Hawaiian islands with a central time-sharing computer on the main Oahu campus. The first packet broadcasting unit went into operation in June 1971, terminals were connected to a special purpose terminal connection unit using RS-232 at 9600 bit/s. This acknowledgment mechanism was used to detect and correct for collisions created when two client machines both attempted to send a packet at the same time, aLOHAnets primary importance was its use of a shared medium for client transmissions. Unlike the ARPANET where each node could only directly to a node at the other end of a wire or satellite circuit. This meant that some sort of mechanism was needed to control who could talk at what time, the ALOHAnet solution was to allow each client to send its data without controlling when it was sent, with an acknowledgment/retransmission scheme used to deal with collisions. This approach radically reduced the complexity of the protocol and the networking hardware and this solution became known as a pure ALOHA, or random-access channel, and was the basis for subsequent Ethernet development and later Wi-Fi networks. Various versions of the ALOHA protocol also appeared later in communications, and were used in wireless data networks such as ARDIS, Mobitex, CDPD. Two frequencies were used so that a device could both receive acknowledgments regardless of transmissions, All transmitting stations will need to try resending later. Note that the first step implies that Pure ALOHA does not check whether the channel is busy before transmitting, since collisions can occur and data may have to be sent again, ALOHA cannot use 100% of the capacity of the communications channel. How long a station waits until it transmits, and the likelihood a collision occurs are interrelated, to assess Pure ALOHA, there is a need to predict its throughput, the rate of transmission of frames. First, lets make a few simplifying assumptions, All frames have the same length, stations cannot generate a frame while transmitting or trying to transmit. The population of stations attempts to transmit according to a Poisson distribution, let T refer to the time needed to transmit one frame on the channel, and lets define frame-time as a unit of time equal to T
12.
WaveLAN
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WaveLAN was a brand name for a family of wireless networking technology sold by NCR, AT&T, and Lucent, as well as being sold by other companies under OEM agreements. The WaveLAN name debuted on the market in 1988 and was in use into the mid-1990s, WaveLAN has been used on two different families of wireless technology, Pre-IEEE802.11 WaveLAN, also called Classic WaveLAN IEEE802. The next year NCR contributed the WaveLAN design to the IEEE802 LAN/MAN Standards Committee and this led to the founding of the 802.11 Wireless LAN Working Committee which produced the original IEEE802.11 standard, which eventually became known popularly as Wi-Fi. The technology was sold as WaveLAN under an OEM agreement by Epson, Hitachi, and NEC. It competed directly with Aironets non-802.11 ARLAN lineup, which offered similar speeds, frequency ranges, during this time frame, networking professionals also realized that since NetWare 3. x and 4. Many NetWare classes and textbooks of the time included a NetWare OS CD with a 2-person license, when the 802.11 procotol was ratified, Lucent began producing chipsets to support this new standard under the name of WaveLAN IEEE, which it later renamed to ORiNOCO. Shortly thereafter, Lucent spun off the division that produced these chipsets as Agere Systems, Proxim later renamed its entire 802.11 wireless networking lineup to ORiNOCO, including products based on Atheros chipsets. Classic WaveLAN operates in the 900 MHz or 2.4 GHz ISM bands, being a proprietary pre-802.11 protocol, it is completely incompatible with the 802.11 standard. The PCMCIA cards used the Intel 82593 PHY controller, the radio modem section was hidden from the OS, thus making the WaveLAN card appear to be a typical Ethernet card, with the radio-specific features taken care of behind the scenes. DES encryption was an option in some of the ISA and MCA cards, even if DES encryption is used, as of 2009, 56-bit DES is widely considered to be obsolete and is subject to brute force attacks well within the capabilities of consumer-grade computer equipment. Windows 3.11,95, and NT3. 5/4.0 Windows 3.11, Windows 95, Windows NT3.51 did not natively support the WaveLAN cards, but additional drivers from Microsofts Windows NT Driver Library were available. OS/2 NDIS and NetWare Requester LAN Manager/IBM LAN Server Artisoft Lantastic PC-TCP for DOS NetWare Lite,2,3, netware 4.11 through 5. x supported the ISA and MCA cards natively but did not provide any configuration or link diagnostics utilities. The DOS drivers came with configuration and link diagnostics utilities, status of support for MCA Classic Wavelan cards is unknown. FreeBSD version 2.2. 1-up and the Mach4 kernel have had support for the ISA Classic WaveLAN cards for several years. OpenBSD and NetBSD do not natively support any of the Classic WaveLAN cards, several open-source projects, such as NdisWrapper and Project Evil, currently exist that allow the use of NDIS drivers via a wrapper. This allows non-Windows OS to utilize the near-universal nature of written for the Windows platform to the benefit of other operating systems, such as Linux, FreeBSD. Full-length MCA card F connector NCR 008-0127216 HOLI chip NCR 008-0126999 Icarus chip NCR 8-127000A socketed DES encryption chip Intel N82586 PHY controller chip MCA id number 6A14, PC card Large EAM Intel i82593 PHY controller chip AT&T part number 3399-K080 Compaq/DEC Roamabout part number, DEINA-AA. PC card -2.4 GHz, selectable frequency, large EAM, Intel N82593 PHY controller chip AT&T part number, AT&T 3399-K624
13.
NCR Corporation
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They also provide IT maintenance support services. NCR had been based in Dayton, Ohio, starting in 1884, NCR was founded in 1884 and acquired by AT&T in 1991. A restructuring of AT&T in 1996 led to NCRs re-establishment January 1,1997 as a separate company, NCR is the only AT&T spin-off company that has retained its original name—all the others have either been purchased or renamed following subsequent mergers. The company began as the National Manufacturing Company of Dayton, Ohio, was established to manufacture, in 1884, the company and patents were bought by John Henry Patterson and his brother Frank Jefferson Patterson, and the firm was renamed the National Cash Register Company. Patterson formed NCR into one of the first modern American companies by introducing new, aggressive sales methods and he established the first sales training school in 1893 and introduced a comprehensive social welfare program for his factory workers. Other significant figures in the history of the company were Charles F. Kettering, Thomas J. Watson, Sr. Deeds and Kettering went on to found Dayton Engineering Laboratories Company which later became Delco Products Division of General Motors, Watson eventually worked his way up to general sales manager. At an uninspiring sales meeting, Watson interrupted, saying The trouble with one of us is that we dont think enough. We dont get paid for working with our feet — we get paid for working with our heads, Watson then wrote THINK on the easel. Signs with this motto were erected in factory buildings, sales offices, THINK later became a widely known symbol of IBM. Kettering designed the first cash register powered by a motor in 1906. Within a few years he developed the Class 1000 register which was in production for 40 years, telephone Credit Authorization system for verifying credit in department stores. When John H. Patterson and his brother took over the company, cash registers were expensive, there was little demand for the expensive device, but Patterson believed the product would sell once shopkeepers understood it would drastically decrease theft by salesclerks. He created a team known as the American Selling Force which worked on commissions and followed a standard sales script. The philosophy was to sell a business rather than just a piece of machinery. Sales demonstrations were set up in hotels depicting a store interior complete with real merchandise, the sale prospect was described as the P. P. or Probable Purchaser. Once initial objections were swept aside and the P. P. admitted to internal theft losses, the deal was sealed with a 25 cent cigar. NCR expanded quickly and became multi-national in 1888, between 1893 and 1906 it acquired a number of smaller cash register companies
14.
IEEE 802.11
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They are created and maintained by the Institute of Electrical and Electronics Engineers LAN/MAN Standards Committee. The base version of the standard was released in 1997, and has had subsequent amendments, the standard and amendments provide the basis for wireless network products using the Wi-Fi brand. As a result, in the marketplace, each tends to become its own standard. The 802.11 family consists of a series of half-duplex over-the-air modulation techniques that use the basic protocol. 802. 11-1997 was the first wireless networking standard in the family, but 802. 11b was the first widely accepted one, followed by 802. 11a,802. 11g,802. 11n, and 802. 11ac. Other standards in the family are service amendments that are used to extend the current scope of the existing standard, which may also include corrections to a previous specification. 802. 11b and 802. 11g use the 2.4 GHz ISM band, operating in the United States under Part 15 of the U. S. Federal Communications Commission Rules and Regulations. Because of this choice of band,802. 11b and g equipment may occasionally suffer interference from microwave ovens, cordless telephones. Better or worse performance with higher or lower frequencies may be realized,802. 11n can use either the 2.4 GHz or the 5 GHz band,802. 11ac uses only the 5 GHz band. The segment of the frequency spectrum used by 802.11 varies between countries. In the US,802. 11a and 802. 11g devices may be operated without a license, as allowed in Part 15 of the FCC Rules and Regulations. Frequencies used by one through six of 802. 11b and 802. 11g fall within the 2.4 GHz amateur radio band. Licensed amateur radio operators may operate 802. 11b/g devices under Part 97 of the FCC Rules and Regulations, allowing increased power output but not commercial content or encryption. 802.11 technology has its origins in a 1985 ruling by the U. S. Federal Communications Commission that released the ISM band for unlicensed use, in 1991 NCR Corporation/AT&T invented a precursor to 802.11 in Nieuwegein, the Netherlands. The inventors initially intended to use the technology for cashier systems, the first wireless products were brought to the market under the name WaveLAN with raw data rates of 1 Mbit/s and 2 Mbit/s. Vic Hayes, who held the chair of IEEE802.11 for 10 years, in 1999, the Wi-Fi Alliance was formed as a trade association to hold the Wi-Fi trademark under which most products are sold. The original version of the standard IEEE802.11 was released in 1997 and clarified in 1999 and it specified two net bit rates of 1 or 2 megabits per second, plus forward error correction code. The latter two radio technologies used microwave transmission over the Industrial Scientific Medical frequency band at 2.4 GHz, some earlier WLAN technologies used lower frequencies, such as the U. S.900 MHz ISM band
15.
Wi-Fi
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Wi-Fi or WiFi is a technology for wireless local area networking with devices based on the IEEE802.11 standards. Wi-Fi is a trademark of the Wi-Fi Alliance, which restricts the use of the term Wi-Fi Certified to products that successfully complete interoperability certification testing. Devices that can use Wi-Fi technology include personal computers, video-game consoles, smartphones, digital cameras, tablet computers, digital audio players, Wi-Fi compatible devices can connect to the Internet via a WLAN network and a wireless access point. Such an access point has a range of about 20 meters indoors, hotspot coverage can be as small as a single room with walls that block radio waves, or as large as many square kilometres achieved by using multiple overlapping access points. Wi-Fi most commonly uses the 2.4 gigahertz UHF and 5 gigahertz SHF ISM radio bands, having no physical connections, it is more vulnerable to attack than wired connections, such as Ethernet. In 1971, ALOHAnet connected the Hawaiian Islands with a UHF wireless packet network, ALOHAnet and the ALOHA protocol were early forerunners to Ethernet, and later the IEEE802.11 protocols, respectively. A1985 ruling by the U. S. Federal Communications Commission released the ISM band for unlicensed use and these frequency bands are the same ones used by equipment such as microwave ovens and are subject to interference. In 1991, NCR Corporation with AT&T Corporation invented the precursor to 802.11, the first wireless products were under the name WaveLAN. They are the credited with inventing Wi-Fi. In 1992 and 1996, CSIRO obtained patents for a method used in Wi-Fi to unsmear the signal. The first version of the 802.11 protocol was released in 1997 and this was updated in 1999 with 802. 11b to permit 11 Mbit/s link speeds, and this proved to be popular. In 1999, the Wi-Fi Alliance formed as an association to hold the Wi-Fi trademark under which most products are sold. Wi-Fi uses a number of patents held by many different organizations. In April 2009,14 technology companies agreed to pay CSIRO $1 billion for infringements on CSIRO patents and this led to Australia labeling Wi-Fi as an Australian invention, though this has been the subject of some controversy. In 2016, the local area network Test Bed was chosen as Australias contribution to the exhibition A History of the World in 100 Objects held in the National Museum of Australia. The name Wi-Fi, commercially used at least as early as August 1999, was coined by the brand-consulting firm Interbrand, the Wi-Fi Alliance had hired Interbrand to create a name that was a little catchier than IEEE802. 11b Direct Sequence. Phil Belanger, a member of the Wi-Fi Alliance who presided over the selection of the name Wi-Fi, has stated that Interbrand invented Wi-Fi as a pun upon the word hi-fi. Interbrand also created the Wi-Fi logo, the yin-yang Wi-Fi logo indicates the certification of a product for interoperability
16.
Moon
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The Moon is an astronomical body that orbits planet Earth, being Earths only permanent natural satellite. It is the fifth-largest natural satellite in the Solar System, following Jupiters satellite Io, the Moon is second-densest satellite among those whose densities are known. The average distance of the Moon from the Earth is 384,400 km, the Moon is thought to have formed about 4.51 billion years ago, not long after Earth. It is the second-brightest regularly visible celestial object in Earths sky, after the Sun and its surface is actually dark, although compared to the night sky it appears very bright, with a reflectance just slightly higher than that of worn asphalt. Its prominence in the sky and its cycle of phases have made the Moon an important cultural influence since ancient times on language, calendars, art. The Moons gravitational influence produces the ocean tides, body tides, and this matching of apparent visual size will not continue in the far future. The Moons linear distance from Earth is currently increasing at a rate of 3.82 ±0.07 centimetres per year, since the Apollo 17 mission in 1972, the Moon has been visited only by uncrewed spacecraft. The usual English proper name for Earths natural satellite is the Moon, the noun moon is derived from moone, which developed from mone, which is derived from Old English mōna, which ultimately stems from Proto-Germanic *mǣnōn, like all Germanic language cognates. Occasionally, the name Luna is used, in literature, especially science fiction, Luna is used to distinguish it from other moons, while in poetry, the name has been used to denote personification of our moon. The principal modern English adjective pertaining to the Moon is lunar, a less common adjective is selenic, derived from the Ancient Greek Selene, from which is derived the prefix seleno-. Both the Greek Selene and the Roman goddess Diana were alternatively called Cynthia, the names Luna, Cynthia, and Selene are reflected in terminology for lunar orbits in words such as apolune, pericynthion, and selenocentric. The name Diana is connected to dies meaning day, several mechanisms have been proposed for the Moons formation 4.51 billion years ago, and some 60 million years after the origin of the Solar System. These hypotheses also cannot account for the angular momentum of the Earth–Moon system. This hypothesis, although not perfect, perhaps best explains the evidence, eighteen months prior to an October 1984 conference on lunar origins, Bill Hartmann, Roger Phillips, and Jeff Taylor challenged fellow lunar scientists, You have eighteen months. Go back to your Apollo data, go back to computer, do whatever you have to. Dont come to our conference unless you have something to say about the Moons birth, at the 1984 conference at Kona, Hawaii, the giant impact hypothesis emerged as the most popular. Afterward there were only two groups, the giant impact camp and the agnostics. Giant impacts are thought to have been common in the early Solar System, computer simulations of a giant impact have produced results that are consistent with the mass of the lunar core and the present angular momentum of the Earth–Moon system
17.
Atmosphere
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An atmosphere is a layer of gases surrounding a planet or other material body, that is held in place by the gravity of that body. An atmosphere is likely to be retained if the gravity it is subject to is high. The atmosphere of Earth is mostly composed of nitrogen, oxygen, argon with carbon dioxide, the atmosphere helps protect living organisms from genetic damage by solar ultraviolet radiation, solar wind and cosmic rays. Its current composition is the product of billions of years of modification of the paleoatmosphere by living organisms. The term stellar atmosphere describes the region of a star. Stars with sufficiently low temperatures may form compound molecules in their outer atmosphere, Atmospheric pressure is the force per unit area that is applied perpendicularly to a surface by the surrounding gas. It is determined by a gravitational force in combination with the total mass of a column of gas above a location. On Earth, units of air pressure are based on the recognized standard atmosphere. It is measured with a barometer, the pressure of an atmospheric gas decreases with altitude due to the diminishing mass of gas above. The height at which the pressure from an atmosphere declines by a factor of e is called the height and is denoted by H. For such an atmosphere, the pressure declines exponentially with increasing altitude. However, atmospheres are not uniform in temperature, so the determination of the atmospheric pressure at any particular altitude is more complex. Surface gravity, the force that holds down an atmosphere, differs significantly among the planets, for example, the large gravitational force of the giant planet Jupiter is able to retain light gases such as hydrogen and helium that escape from objects with lower gravity. Thus, the distant and cold Titan, Triton, and Pluto are able to retain their atmospheres despite their relatively low gravities, rogue planets, theoretically, may also retain thick atmospheres. Since a collection of gas molecules may be moving at a range of velocities. Lighter molecules move faster than ones with the same thermal kinetic energy. It is thought that Venus and Mars may have lost much of their water when, after being photo dissociated into hydrogen and oxygen by solar ultraviolet, Earths magnetic field helps to prevent this, as, normally, the solar wind would greatly enhance the escape of hydrogen. However, over the past 3 billion years Earth may have lost gases through the polar regions due to auroral activity
18.
Geosynchronous orbit
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A geosynchronous orbit is an orbit about the Earth of a satellite with an orbital period that matches the rotation of the Earth on its axis of approximately 23 hours 56 minutes and 4 seconds. Over the course of a day, the position in the sky traces out a path, typically in a figure-8 form, whose precise characteristics depend on the orbits inclination. Satellites are typically launched in an eastward direction, a special case of geosynchronous orbit is the geostationary orbit, which is a circular geosynchronous orbit at zero inclination. A satellite in a geostationary orbit appears stationary, always at the point in the sky. Popularly or loosely, the term geosynchronous may be used to mean geostationary, specifically, geosynchronous Earth orbit may be a synonym for geosynchronous equatorial orbit, or geostationary Earth orbit. A semi-synchronous orbit has a period of ½ sidereal day. Relative to the Earths surface it has twice this period, examples include the Molniya orbit and the orbits of the satellites in the Global Positioning System. Circular Earth geosynchronous orbits have a radius of 42,164 km, all Earth geosynchronous orbits, whether circular or elliptical, have the same semi-major axis.4418 km3/s2. In the special case of an orbit, the ground track of a satellite is a single point on the equator. A geostationary equatorial orbit is a geosynchronous orbit in the plane of the Earths equator with a radius of approximately 42,164 km. A satellite in such an orbit is at an altitude of approximately 35,786 km above sea level. It maintains the position relative to the Earths surface. The theoretical basis for this phenomenon of the sky goes back to Newtons theory of motion. In that theory, the existence of a satellite is made possible because the Earth rotates. Such orbits are useful for telecommunications satellites, a perfectly stable geostationary orbit is an ideal that can only be approximated. Elliptical geosynchronous orbits can be and are designed for satellites in order to keep the satellite within view of its assigned ground stations or receivers. A satellite in a geosynchronous orbit appears to oscillate in the sky from the viewpoint of a ground station. Satellites in highly elliptical orbits must be tracked by ground stations
19.
Spread spectrum
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This is a technique in which a telecommunication signal is transmitted on a bandwidth considerably larger than the frequency content of the original information. Frequency hopping is a modulation technique used in spread spectrum signal transmission. This technique decreases the potential interference to other receivers while achieving privacy, spread spectrum generally makes use of a sequential noise-like signal structure to spread the normally narrowband information signal over a relatively wideband band of frequencies. The receiver correlates the received signals to retrieve the information signal. Frequency-hopping spread spectrum, direct-sequence spread spectrum, time-hopping spread spectrum, chirp spread spectrum, ultra-wideband is another modulation technique that accomplishes the same purpose, based on transmitting short duration pulses. Wireless standard IEEE802.11 uses either FHSS or DSSS in its radio interface, techniques known since the 1940s and used in military communication systems since the 1950s spread a radio signal over a wide frequency range several magnitudes higher than minimum requirement. DS is good at resisting continuous-time narrowband jamming, while FH is better at resisting pulse jamming, by contrast, in narrowband systems where the signal bandwidth is low, the received signal quality will be severely lowered if the jamming power happens to be concentrated on the signal bandwidth. Multiple access capability, known as code-division multiple access or code-division multiplexing and their approach was unique in that frequency coordination was done with paper player piano rolls - a novel approach which was never put into practice. A synchronous digital system is one that is driven by a signal and. In fact, a clock signal would have all its energy concentrated at a single frequency. It has become a technique to gain regulatory approval because it requires only simple equipment modification. It is even more popular in portable electronics devices because of faster clock speeds, since these devices are designed to be lightweight and inexpensive, traditional passive, electronic measures to reduce EMI, such as capacitors or metal shielding, are not viable. Active EMI reduction techniques such as spread-spectrum clocking are needed in these cases, however, spread-spectrum clocking, like other kinds of dynamic frequency change, can also create challenges for designers. Principal among these is clock/data misalignment, or clock skew, note that this method does not reduce total radiated energy, and therefore systems are not necessarily less likely to cause interference. Spreading energy over a larger bandwidth effectively reduces electrical and magnetic readings within narrow bandwidths, typical measuring receivers used by EMC testing laboratories divide the electromagnetic spectrum into frequency bands approximately 120 kHz wide. If the system under test were to all its energy in a narrow bandwidth. Distributing this same energy into a larger bandwidth prevents systems from putting enough energy into any one narrowband to exceed the statutory limits, FCC certification testing is often completed with the spread-spectrum function enabled in order to reduce the measured emissions to within acceptable legal limits. However, the spread-spectrum functionality may be disabled by the user in some cases and this might be considered a loophole, but is generally overlooked as long as spread-spectrum is enabled by default
20.
Free-space optical communication
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Free-space optical communication is an optical communication technology that uses light propagating in free space to wirelessly transmit data for telecommunications or computer networking. Free space means air, outer space, vacuum, or something similar and this contrasts with using solids such as optical fiber cable or an optical transmission line. The technology is useful where the connections are impractical due to high costs or other considerations. Optical communications, in forms, have been used for thousands of years. The Ancient Greeks used an alphabetic system of signalling with torches developed by Cleoxenus, Democleitus and Polybius. In the modern era, semaphores and wireless solar telegraphs called heliographs were developed, in 1880, Alexander Graham Bell and his assistant Charles Sumner Tainter created the photophone, at Bells newly established Volta Laboratory in Washington, DC. Bell considered it his most important invention, the device allowed for the transmission of sound on a beam of light. On June 3,1880, Bell conducted the worlds first wireless transmission between two buildings, some 213 meters apart. Its first practical use came in military communication systems many decades later, German colonial troops used heliograph telegraphy transmitters during the Herero and Namaqua genocide starting in 1904, in German South-West Africa as did British, French, US or Ottoman signals. Optical telephone communications were tested at the end of the war, in addition, special blinkgeräts were used for communication with airplanes, balloons, and tanks, with varying success. A major technological step was to replace the Morse code by modulating optical waves in speech transmission, carl Zeiss, Jena developed the Lichtsprechgerät 80/80 that the German army used in their World War II anti-aircraft defense units, or in bunkers at the Atlantic Wall. The invention of lasers in the 1960s, revolutionized free space optics, military organizations were particularly interested and boosted their development. However the technology lost market momentum when the installation of fiber networks for civilian uses was at its peak. Many simple and inexpensive consumer remote controls use low-speed communication using infrared light and this is known as consumer IR technologies. Free-space point-to-point optical links can be implemented using infrared laser light, infrared Data Association technology is a very simple form of free-space optical communications. On the communications side the FSO technology is considered as a part of the Optical Wireless Communications applications, free-space optics can be used for communications between spacecraft. The demand for a high-speed and long range FSO system is apparent in the market place, in 2008, MRV Communications introduced a free-space optics -based system with a data rate of 10 Gbit/s initially claiming a distance of 2 km at high availability. This equipment is no longer available, before end-of-life, the products useful distance was changed down to 350 m, in April 2014, the company with Scientific and Technological Centre Fiord demonstrated the transmission speed 30 Gbit/s under laboratory conditions
21.
Line-of-sight propagation
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Line-of-sight propagation is a characteristic of electromagnetic radiation or acoustic wave propagation which means waves which travel in a direct path from the source to the receiver. Electromagnetic transmission includes light emissions traveling in a straight line, the rays or waves may be diffracted, refracted, reflected, or absorbed by atmosphere and obstructions with material and generally cannot travel over the horizon or behind obstacles. In contrast to line-of-sight propagation, at low frequency due to radio waves can travel as ground waves. This enables AM broadcast radio stations to transmit beyond the horizon, however, at frequencies above 30 MHz and in lower levels of the atmosphere, neither of these effects are significant. Thus, any obstruction between the antenna and the receiving antenna will block the signal, just like the light that the eye may sense. The farthest possible point of propagation is referred to as the radio horizon, in practice, the propagation characteristics of these radio waves vary substantially depending on the exact frequency and the strength of the transmitted signal. Broadcast FM radio, at low frequencies of around 100 MHz, are less affected by the presence of buildings. Low-powered microwave transmitters can be foiled by tree branches, or even heavy rain or snow, if a direct visual fix cannot be taken, it is important to take into account the curvature of the Earth when calculating line-of-sight from maps. Designs for microwave used to use 4/3 earth radius to compute clearances along the path, the presence of objects not in the direct visual line of sight can interfere with radio transmission. This is caused by diffraction effects, for the best propagation, reflected radiation from the ground plane also acts to cancel out the direct signal. This effect, combined with the free-space r−2 propagation loss to a r−4 propagation loss and this effect can be reduced by raising either or both antennas further from the ground, the reduction in loss achieved is known as height gain. Although the frequencies used by mobile phones are in the line-of-sight range, for mobile phone services, these problems are tackled using, rooftop or hilltop positioning of base stations many base stations. A phone can typically see at least three, and usually as many as six at any given time, sectorized antennas at the base stations. Instead of one antenna with omnidirectional coverage, the station may use as few as 3 or as many as 32 separate antennas and this allows the base station to use a directional antenna that is pointing at the user, which improves the signal to noise ratio. If the user moves from one sector to another, the base station automatically selects the proper antenna. Electromagnetic radiation is blocked where the wavelength is longer than any gaps and this means that windowless metal enclosures will completely block cell signs, such as elevator cabins, and parts of trains, cars, and ships. The same problem can affect signals in buildings with steel reinforcement. The radio horizon is the locus of points at which direct rays from an antenna are tangential to the surface of the Earth, if the Earth was a perfect sphere and there was no atmosphere, the radio horizon would be a circle
22.
Bluetooth
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Bluetooth is a wireless technology standard for exchanging data over short distances from fixed and mobile devices, and building personal area networks. Invented by telecom vendor Ericsson in 1994, it was conceived as a wireless alternative to RS-232 data cables. It can connect up to seven devices, overcoming problems that older technologies had when attempting to connect to each other. Bluetooth is managed by the Bluetooth Special Interest Group, which has more than 30,000 member companies in the areas of telecommunication, computing, networking, the IEEE standardized Bluetooth as IEEE802.15.1, but no longer maintains the standard. The Bluetooth SIG oversees development of the specification, manages the qualification program, a manufacturer must meet Bluetooth SIG standards to market it as a Bluetooth device. A network of patents apply to the technology, which are licensed to individual qualifying devices, the development of the short-link radio technology, later named Bluetooth, was initiated in 1989 by Nils Rydbeck, CTO at Ericsson Mobile in Lund, Sweden, and by Johan Ullman. The purpose was to develop wireless headsets, according to two inventions by Johan Ullman, SE 8902098-6, issued 1989-06-12 and SE9202239, issued 1992-07-24, Nils Rydbeck tasked Tord Wingren with specifying and Jaap Haartsen and Sven Mattisson with developing. Both were working for Ericsson in Lund, the specification is based on frequency-hopping spread spectrum technology. The idea of this name was proposed in 1997 by Jim Kardach who developed a system that would allow mobile phones to communicate with computers, at the time of this proposal he was reading Frans G. Bengtssons historical novel The Long Ships about Vikings and King Harald Bluetooth. The implication is that Bluetooth does the same with communications protocols, the Bluetooth logo is a bind rune merging the Younger Futhark runes and, Haralds initials. Bluetooth operates at frequencies between 2402 and 2480 MHz, or 2400 and 2483.5 MHz including guard bands 2 MHz wide at the end and 3.5 MHz wide at the top. This is in the globally unlicensed Industrial, Scientific and Medical 2.4 GHz short-range radio frequency band, Bluetooth uses a radio technology called frequency-hopping spread spectrum. Bluetooth divides transmitted data into packets, and transmits each packet on one of 79 designated Bluetooth channels, each channel has a bandwidth of 1 MHz. It usually performs 800 hops per second, with Adaptive Frequency-Hopping enabled, Bluetooth low energy uses 2 MHz spacing, which accommodates 40 channels. Originally, Gaussian frequency-shift keying modulation was the modulation scheme available. Since the introduction of Bluetooth 2. 0+EDR, π/4-DQPSK and 8DPSK modulation may also be used between compatible devices, devices functioning with GFSK are said to be operating in basic rate mode where an instantaneous data rate of 1 Mbit/s is possible. The term Enhanced Data Rate is used to describe π/4-DPSK and 8DPSK schemes, the combination of these modes in Bluetooth radio technology is classified as a BR/EDR radio. Bluetooth is a protocol with a master-slave structure
23.
Infrared
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It extends from the nominal red edge of the visible spectrum at 700 nanometers, to 1000000 nm. Most of the radiation emitted by objects near room temperature is infrared. Like all EMR, IR carries radiant energy, and behaves both like a wave and like its quantum particle, the photon, slightly more than half of the total energy from the Sun was eventually found to arrive on Earth in the form of infrared. The balance between absorbed and emitted infrared radiation has an effect on Earths climate. Infrared radiation is emitted or absorbed by molecules when they change their rotational-vibrational movements and it excites vibrational modes in a molecule through a change in the dipole moment, making it a useful frequency range for study of these energy states for molecules of the proper symmetry. Infrared spectroscopy examines absorption and transmission of photons in the infrared range, Infrared radiation is used in industrial, scientific, and medical applications. Night-vision devices using active near-infrared illumination allow people or animals to be observed without the observer being detected, Infrared thermal-imaging cameras are used to detect heat loss in insulated systems, to observe changing blood flow in the skin, and to detect overheating of electrical apparatuses. Thermal-infrared imaging is used extensively for military and civilian purposes, military applications include target acquisition, surveillance, night vision, homing, and tracking. Humans at normal body temperature radiate chiefly at wavelengths around 10 μm, Infrared radiation extends from the nominal red edge of the visible spectrum at 700 nanometers to 1 mm. This range of wavelengths corresponds to a range of approximately 430 THz down to 300 GHz. Below infrared is the portion of the electromagnetic spectrum. Sunlight, at a temperature of 5,780 kelvins, is composed of near thermal-spectrum radiation that is slightly more than half infrared. At zenith, sunlight provides an irradiance of just over 1 kilowatt per square meter at sea level, of this energy,527 watts is infrared radiation,445 watts is visible light, and 32 watts is ultraviolet radiation. Nearly all the radiation in sunlight is near infrared, shorter than 4 micrometers. On the surface of Earth, at far lower temperatures than the surface of the Sun, almost all thermal radiation consists of infrared in mid-infrared region, much longer than in sunlight. Of these natural thermal radiation processes only lightning and natural fires are hot enough to produce much visible energy, thermal infrared radiation also has a maximum emission wavelength, which is inversely proportional to the absolute temperature of object, in accordance with Wiens displacement law. Therefore, the band is often subdivided into smaller sections. Due to the nature of the blackbody radiation curves, typical hot objects, such as exhaust pipes, the three regions are used for observation of different temperature ranges, and hence different environments in space
24.
Zigbee
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The technology defined by the ZigBee specification is intended to be simpler and less expensive than other wireless personal area networks, such as Bluetooth or Wi-Fi. Its low power consumption limits transmission distances to 10–100 meters line-of-sight, depending on power output, ZigBee devices can transmit data over long distances by passing data through a mesh network of intermediate devices to reach more distant ones. ZigBee was conceived in 1998, standardized in 2003, and revised in 2006, the name refers to the waggle dance of honey bees after their return to the beehive. ZigBee is a low-cost, low-power, wireless mesh network standard targeted at the development of long battery life devices in wireless control. Zigbee devices have low latency, which further reduces average current, ZigBee chips are typically integrated with radios and with microcontrollers that have between 60-256 KB of flash memory. ZigBee operates in the industrial, scientific and medical radio bands,2.4 GHz in most jurisdictions worldwide,784 MHz in China,868 MHz in Europe and 915 MHz in the USA, data rates vary from 20 kbit/s to 250 kbit/s. The ZigBee network layer natively supports both star and tree networks, and generic mesh networking, every network must have one coordinator device, tasked with its creation, the control of its parameters and basic maintenance. Within star networks, the coordinator must be the central node, both trees and meshes allow the use of ZigBee routers to extend communication at the network level. ZigBee builds on the layer and media access control defined in IEEE standard 802.15.4 for low-rate WPANs. ZDOs are responsible for tasks, including keeping track of device roles, managing requests to join a network, as well as device discovery. ZigBee is one of the standards of communication protocol formulated by the significant task force under the IEEE802.15 working group. The fourth in the series, WPAN Low Rate/ZigBee is the newest and provides specifications for devices that have low data rates, other standards like Bluetooth and IrDA address high data rate applications such as voice, video and LAN communications. ZigBee-style self-organizing ad-hoc digital radio networks were conceived in the 1990s, the IEEE802.15. 4-2003 ZigBee specification was ratified on December 14,2004. The ZigBee Alliance announced availability of Specification 1.0 on June 13,2005, in September 2006, the ZigBee 2006 Specification was announced, obsoleting the 2004 stack. The library is a set of standardised commands, organised under groups known as clusters with names such as Smart Energy, Home Automation, ZigBee PRO is fully backward-compatible with ZigBee 2006 devices. A ZigBee 2007 device may join and operate on a ZigBee 2006 network, due to differences in routing options, ZigBee PRO devices must become non-routing ZigBee End-Devices on a ZigBee 2006 network, and ZigBee 2006 devices must become ZEDs on a ZigBee PRO network. The applications running on those devices work the same, regardless of the stack profile beneath them, the first ZigBee Application Profile, Home Automation, was announced November 2,2007. ZigBee protocols are intended for embedded applications requiring low power consumption, the resulting network will use very small amounts of power — individual devices must have a battery life of at least two years to pass ZigBee certification
25.
Intel
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Intel Corporation is an American multinational corporation and technology company headquartered in Santa Clara, California that was founded by Gordon Moore and Robert Noyce. It is the worlds largest and highest valued semiconductor chip makers based on revenue, and is the inventor of the x86 series of microprocessors, Intel supplies processors for computer system manufacturers such as Apple, Lenovo, HP, and Dell. Intel Corporation was founded on July 18,1968, by semiconductor pioneers Robert Noyce and Gordon Moore, the companys name was conceived as portmanteau of the words integrated and electronics. The fact that intel is the term for intelligence information made the name appropriate. Intel was a developer of SRAM and DRAM memory chips. Although Intel created the worlds first commercial microprocessor chip in 1971, during the 1990s, Intel invested heavily in new microprocessor designs fostering the rapid growth of the computer industry. The Open Source Technology Center at Intel hosts PowerTOP and LatencyTOP, and supports other projects such as Wayland, Intel Array Building Blocks, and Threading Building Blocks. Client Computing Group – 55% of 2016 revenues – produces hardware components used in desktop, data Center Group – 29% of 2016 revenues – produces hardware components used in server, network, and storage platforms. Internet of Things Group – 5% of 2016 revenues – offers platforms designed for retail, transportation, industrial, buildings, non-Volatile Memory Solutions Group – 4% of 2016 revenues – manufactures NAND flash memory products primarily used in solid-state drives. Intel Security Group – 4% of 2016 revenues – produces software, particularly security, programmable Solutions Group – 3% of 2016 revenues – manufactures programmable semiconductors. In 2016, Dell accounted for 15% of Intels total revenues, Lenovo accounted for 13% of total revenues, in the 1980s, Intel was among the top ten sellers of semiconductors in the world. In 1991, Intel became the biggest chip maker by revenue and has held the position ever since, other top semiconductor companies include TSMC, Advanced Micro Devices, Samsung, Texas Instruments, Toshiba and STMicroelectronics. Competitors in PC chip sets include Advanced Micro Devices, VIA Technologies, Silicon Integrated Systems, however, the cross-licensing agreement is canceled in the event of an AMD bankruptcy or takeover. Some smaller competitors such as VIA Technologies produce low-power x86 processors for small factor computers, however, the advent of such mobile computing devices, in particular, smartphones, has in recent years led to a decline in PC sales. Since over 95% of the worlds smartphones currently use processors designed by ARM Holdings, ARM is also planning to make inroads into the PC and server market. Intel has been involved in disputes regarding violation of antitrust laws. Intel was founded in Mountain View, California in 1968 by Gordon E. Moore, a chemist, and Robert Noyce, arthur Rock helped them find investors, while Max Palevsky was on the board from an early stage. Moore and Noyce had left Fairchild Semiconductor to found Intel, Rock was not an employee, but he was an investor and was chairman of the board
26.
Windows 7
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Windows 7 is a personal computer operating system developed by Microsoft. It is a part of the Windows NT family of operating systems, Windows 7 was released to manufacturing on July 22,2009, and became generally available on October 22,2009, less than three years after the release of its predecessor, Windows Vista. Windows 7s server counterpart, Windows Server 2008 R2, was released at the same time, Windows 7 continued improvements on Windows Aero with the addition of a redesigned taskbar that allows applications to be pinned to it, and new window management features. Other new features were added to the system, including libraries, the new file sharing system HomeGroup. A new Action Center interface was added to provide an overview of system security and maintenance information. Windows 7 also shipped with updated versions of several applications, including Internet Explorer 8, Windows Media Player. Windows 7 was a success for Microsoft, even prior to its official release. Originally, a version of Windows codenamed Blackcomb was planned as the successor to Windows XP, major features were planned for Blackcomb, including an emphasis on searching and querying data and an advanced storage system named WinFS to enable such scenarios. However, an interim, minor release, codenamed Longhorn, was announced for 2003, by the middle of 2003, however, Longhorn had acquired some of the features originally intended for Blackcomb. Development of Longhorn was also restarted, and thus delayed, in August 2004, a number of features were cut from Longhorn. Blackcomb was renamed Vienna in early 2006, as such, adoption of Vista in comparison to XP remained somewhat low. In July 2007, six months following the release of Vista, it was reported that the next version of Windows would then be codenamed Windows 7. Bill Gates, in an interview with Newsweek, suggested that Windows 7 would be more user-centric, Gates later said that Windows 7 would also focus on performance improvements. Senior Vice President Bill Veghte stated that Windows Vista users migrating to Windows 7 would not find the kind of device compatibility issues they encountered migrating from Windows XP, an estimated 1,000 developers worked on Windows 7. These were broadly divided into core operating system and Windows client experience, in October 2008, it was announced that Windows 7 would also be the official name of the operating system. The first external release to select Microsoft partners came in January 2008 with Milestone 1, at PDC2008, Microsoft demonstrated Windows 7 with its reworked taskbar. On December 27,2008, the Windows 7 Beta was leaked onto the Internet via BitTorrent. According to a performance test by ZDNet, Windows 7 Beta beat both Windows XP and Vista in several key areas, including boot and shutdown time and working with files, such as loading documents
27.
Virtual reality
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VR also simulates a users physical presence in this environment. A person using virtual reality equipment is able to look around the world, and with high quality VR move about in it. Virtual reality is displayed with a virtual reality headset, VR headsets are head-mounted goggles with a screen in front of the eyes. Programs may include audio and sounds through speakers or headphones, advanced haptic systems may include tactile information, generally known as force feedback in medical, video gaming and military training applications. Some VR systems used in games can transmit vibrations and other sensations to the user through the game controller. Virtual reality also refers to remote communication environments which provide a presence of users with through telepresence and telexistence or the use of a virtual artifact. The immersive environment can be similar to the world in order to create a life-like experience grounded in reality or sci-fi. In 1938, Antonin Artaud described the nature of characters and objects in the theatre as la réalité virtuelle in a collection of essays. The English translation of book, published in 1958 as The Theater. The term artificial reality, coined by Myron Krueger, has been in use since the 1970s, the term virtual reality was used in The Judas Mandala, a 1982 science fiction novel by Damien Broderick. Virtual has had the meaning being something in essence or effect, the term virtual has been used in the computer sense of not physically existing but made to appear by software since 1959. A dictionary definition for cyberspace states that word is a synonym for virtual reality. Virtual reality shares some elements with augmented reality, AR is a type of virtual reality technology that blends what the user sees in their real surroundings with digital content generated by computer software. The additional software-generated images with the virtual scene typically enhance way the real look in some way. Some AR systems use a camera to capture the surroundings or some type of display screen which the user looks at. The Virtual Reality Modelling Language, first introduced in 1994, was intended for the development of worlds without dependency on headsets. The Web3D consortium was founded in 1997 for the development of industry standards for web-based 3D graphics. The consortium subsequently developed X3D from the VRML framework as an archival and these components led to relative affordability for independent VR developers, and lead to the 2012 Oculus Rift kickstarter offering the first independently developed VR headset
28.
Orthogonal frequency-division multiplexing
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Orthogonal frequency-division multiplexing is a method of encoding digital data on multiple carrier frequencies. OFDM is a frequency-division multiplexing scheme used as a digital modulation method. A large number of closely spaced orthogonal sub-carrier signals are used to carry data on several parallel data streams or channels, each sub-carrier is modulated with a conventional modulation scheme at a low symbol rate, maintaining total data rates similar to conventional single-carrier modulation schemes in the same bandwidth. The primary advantage of OFDM over single-carrier schemes is its ability to cope with severe conditions without complex equalization filters. Channel equalization is simplified because OFDM may be viewed as using many slowly modulated narrowband signals rather than one rapidly modulated wideband signal. e, the following list is a summary of existing OFDM-based standards and products. For further details, see the Usage section at the end of the article, High spectral efficiency as compared to other double sideband modulation schemes, spread spectrum, etc. Can easily adapt to severe conditions without complex time-domain equalization. This greatly simplifies the design of both the transmitter and the receiver, unlike conventional FDM, a filter for each sub-channel is not required. The orthogonality requires that the spacing is Δ f = k T U Hertz, where TU seconds is the useful symbol duration. Therefore, with N sub-carriers, the passband bandwidth will be B ≈ N·Δf. The orthogonality also allows high spectral efficiency, with a symbol rate near the Nyquist rate for the equivalent baseband signal. Almost the whole available frequency band can be utilized, OFDM generally has a nearly white spectrum, giving it benign electromagnetic interference properties with respect to other co-channel users. A simple example, A useful symbol duration TU =1 ms would require a sub-carrier spacing of Δ f =11 m s =1 k H z for orthogonality, N =1,000 sub-carriers would result in a total passband bandwidth of NΔf =1 MHz. For this symbol time, the bandwidth in theory according to Nyquist is B W =1 / =0.5 M H z. If a guard interval is applied, Nyquist bandwidth requirement would be even lower, the FFT would result in N =1,000 samples per symbol. If no guard interval was applied, this would result in a base band complex valued signal with a rate of 1 MHz. However, the passband RF signal is produced by multiplying the signal with a carrier waveform resulting in a passband bandwidth of 1 MHz. A single-side band or vestigial sideband modulation scheme would achieve almost half that bandwidth for the symbol rate
29.
Fixed wireless
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Fixed wireless is the operation of wireless devices or systems used to connect two fixed locations with a radio or other wireless link, such as laser bridge. Usually, fixed wireless is part of a wireless LAN infrastructure, the purpose of a fixed wireless link is to enable data communications between the two sites or buildings. Fixed wireless data links are often an alternative to leasing fiber or installing cables between the buildings. Fixed wireless devices usually derives their electrical power from the utility mains. Fixed wireless services typically use a radio antenna on each end of the signal. These antennas are generally larger than those seen in Wi-Fi setups and are designed for outdoor use, several types of radio antennas are available that accommodate various weather conditions, signal distances and bandwidths. They are usually selected to make the beam as narrow as possible and thus focus transmit power to their destination, increasing reliability, the links are usually arranged as a point-to-point setup to permit the use of these antennas. This also permits the link to have speed and or better reach for the same amount of power. With the growing infrastructure of the GSM wireless networks, fixed wireless has also become a solution for broadband access. Using the 3G speed and reliability, businesses and homes can use fixed-wireless antenna technology to access broadband Internet, in rural areas where wired infrastructure is not yet available, fixed-wireless broadband has become a viable option for Internet access. Internet access Mobile wireless communication Mobile broadband Ethernet bridge
30.
Point-to-point (telecommunications)
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In telecommunications, a point-to-point connection refers to a communications connection between two nodes or endpoints. An example is a call, in which one telephone is connected with one other. This is contrasted with a point-to-multipoint or broadcast connection, in which many nodes can receive information transmitted by one node, other examples of point-to-point communications links are leased lines, microwave relay links, and two way radio. Point-to-point is sometimes abbreviated as P2P and this usage of P2P is distinct from P2P referring to peer-to-peer for file sharing networks. A traditional point-to-point data link is a medium with exactly two endpoints and no data or packet formatting. The host computers at either end had to take responsibility for formatting the data transmitted between them. The connection between the computer and the medium was generally implemented through an RS-232 or similar interface. Computers in close proximity may be connected by wires directly between their interface cards, when connected at a distance, each endpoint would be fitted with a modem to convert analog telecommunications signals into a digital data stream. When the connection used a telecommunications provider, the connections were called a dedicated, leased, the ARPANET used leased lines to provide point-to-point data links between its packet-switching nodes, which were called Interface Message Processors. In, the term point-to-point telecommunications relates to fixed wireless communications for Internet or voice over IP via radio frequencies in the multi-gigahertz range. The Telecommunications Industry Associations engineering committees develop U. S. standards for point-to-point communications, online tools help users find if they have such line of sight. The telecommunications signal is typically bi-directional, either time division multiple access or channelized, in hubs and switches, a hub provides a point-to-multipoint circuit which divides the total bandwidth supplied by the hub among each connected client node. Within many switched telecommunications systems, it is possible to establish a permanent circuit, one example might be a telephone in the lobby of a public building, which is programmed to ring only the number of a telephone dispatcher. Nailing down a switched connection saves the cost of running a circuit between the two points. The resources in such a connection can be released when no longer needed, for example, a television circuit from a parade route back to the studio
31.
Laser
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A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The term laser originated as an acronym for light amplification by stimulated emission of radiation, the first laser was built in 1960 by Theodore H. Maiman at Hughes Research Laboratories, based on theoretical work by Charles Hard Townes and Arthur Leonard Schawlow. A laser differs from other sources of light in that it emits light coherently, spatial coherence allows a laser to be focused to a tight spot, enabling applications such as laser cutting and lithography. Spatial coherence also allows a laser beam to stay narrow over great distances, Lasers can also have high temporal coherence, which allows them to emit light with a very narrow spectrum, i. e. they can emit a single color of light. Temporal coherence can be used to produce pulses of light as short as a femtosecond, Lasers are distinguished from other light sources by their coherence. Spatial coherence is typically expressed through the output being a narrow beam, Laser beams can be focused to very tiny spots, achieving a very high irradiance, or they can have very low divergence in order to concentrate their power at a great distance. Temporal coherence implies a polarized wave at a single frequency whose phase is correlated over a great distance along the beam. A beam produced by a thermal or other incoherent light source has an amplitude and phase that vary randomly with respect to time and position. Lasers are characterized according to their wavelength in a vacuum, most single wavelength lasers actually produce radiation in several modes having slightly differing frequencies, often not in a single polarization. Although temporal coherence implies monochromaticity, there are lasers that emit a broad spectrum of light or emit different wavelengths of light simultaneously, there are some lasers that are not single spatial mode and consequently have light beams that diverge more than is required by the diffraction limit. However, all devices are classified as lasers based on their method of producing light. Lasers are employed in applications where light of the spatial or temporal coherence could not be produced using simpler technologies. The word laser started as an acronym for light amplification by stimulated emission of radiation, in the early technical literature, especially at Bell Telephone Laboratories, the laser was called an optical maser, this term is now obsolete. A laser that produces light by itself is technically an optical rather than an optical amplifier as suggested by the acronym. It has been noted that the acronym LOSER, for light oscillation by stimulated emission of radiation. With the widespread use of the acronym as a common noun, optical amplifiers have come to be referred to as laser amplifiers. The back-formed verb to lase is frequently used in the field, meaning to produce light, especially in reference to the gain medium of a laser. Further use of the laser and maser in an extended sense, not referring to laser technology or devices, can be seen in usages such as astrophysical maser
32.
Wireless mesh network
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A wireless mesh network is a communications network made up of radio nodes organized in a mesh topology. It is also a form of ad hoc network. Wireless mesh networks often consist of mesh clients, mesh routers, the mesh clients are often laptops, cell phones and other wireless devices while the mesh routers forward traffic to and from the gateways which may, but need not, be connected to the Internet. The coverage area of the radio working as a single network is sometimes called a mesh cloud. Access to this mesh cloud is dependent on the radio working in harmony with each other to create a radio network. A mesh network is reliable and offers redundancy, when one node can no longer operate, the rest of the nodes can still communicate with each other, directly or through one or more intermediate nodes. Wireless mesh networks can form and self heal. Wireless mesh networks can be implemented with various technologies including 802.11,802.15,802.16, cellular technologies. Wireless mesh architecture is a first step towards providing cost effective, Wireless mesh infrastructure is, in effect, a network of routers minus the cabling between nodes. Its built of peer radio devices that dont have to be cabled to a wired port like traditional WLAN access points do, Mesh infrastructure carries data over large distances by splitting the distance into a series of short hops. Intermediate nodes not only boost the signal, but cooperatively pass data from point A to point B by making forwarding decisions based on their knowledge of the network, i. e. perform routing. Such an architecture may, with design, provide high bandwidth, spectral efficiency. Wireless mesh networks have a stable topology except for the occasional failure of nodes or addition of new nodes. The path of traffic, being aggregated from a number of end users. This type of infrastructure can be decentralized or centrally managed, both are relatively inexpensive, and can be very reliable and resilient, as each node needs only transmit as far as the next node. Nodes act as routers to transmit data from nearby nodes to peers that are too far away to reach in a single hop, the topology of a mesh network is also reliable, as each node is connected to several other nodes. If one node drops out of the network, due to failure or any other reason. Mesh networks may involve either fixed or mobile devices, an important possible application for wireless mesh networks is VoIP
33.
WiMAX
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WiMAX is a family of wireless communication standards based on the IEEE802.16 set of standards, which provide multiple physical layer and Media Access Control options. The forum describes WiMAX as a standards-based technology enabling the delivery of last mile broadband access as an alternative to cable. IEEE802. 16m or WirelessMAN-Advanced was a candidate for the 4G, WiMAX was initially designed to provide 30 to 40 megabit-per-second data rates, with the 2011 update providing up to 1 Gbit/s for fixed stations. WiMAX refers to implementations of the IEEE802.16 family of wireless-networks standards ratified by the WiMAX Forum. The original IEEE802.16 standard was published in 2001, WiMAX adopted some of its technology from WiBro, a service marketed in Korea. Mobile WiMAX is the revision that was deployed in many countries, WiMAX is sometimes referred to as Wi-Fi on steroids and can be used for a number of applications including broadband connections, cellular backhaul, hotspots, etc. It is similar to Long-range Wi-Fi, but it can enable usage at much greater distances, the bandwidth and range of WiMAX make it suitable for the following potential applications, Providing portable mobile broadband connectivity across cities and countries through various devices. Providing a wireless alternative to cable and digital subscriber line for last mile broadband access, Providing data, telecommunications and IPTV services. Providing Internet connectivity as part of a continuity plan. Smart grids and metering WiMAX can provide at-home or mobile Internet access across whole cities or countries, in many cases this has resulted in competition in markets which typically only had access through an existing incumbent DSL operator. Additionally, given the low costs associated with the deployment of a WiMAX network. Mobile WiMAX was a replacement candidate for cellular phone technologies such as GSM and CDMA, fixed WiMAX is also considered as a wireless backhaul technology for 2G, 3G, and 4G networks in both developed and developing nations. In North America, backhaul for urban operations is provided via one or more copper wire line connections. In other regions, urban and rural backhaul is usually provided by microwave links, WiMAX has more substantial backhaul bandwidth requirements than legacy cellular applications. Consequently, the use of wireless microwave backhaul is on the rise in North America, capacities of between 34 Mbit/s and 1 Gbit/s are routinely being deployed with latencies in the order of 1 ms. In many cases, operators are aggregating sites using wireless technology, WiMAX in this application competes with microwave radio, E-line and simple extension of the fiber network itself. WiMAX directly supports the technologies that make triple-play service offerings possible and these are inherent to the WiMAX standard rather than being added on as Carrier Ethernet is to Ethernet. The new company hopes to benefit from combined services offerings and network resources as a springboard past its competitors, the cable companies will provide media services to other partners while gaining access to the wireless network as a Mobile virtual network operator to provide triple-play services
34.
IEEE 802.16
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IEEE802.16 is a series of wireless broadband standards written by the Institute of Electrical and Electronics Engineers. The IEEE Standards Board established a group in 1999 to develop standards for broadband for wireless metropolitan area networks. The Workgroup is a unit of the IEEE802 local area network, although the 802.16 family of standards is officially called WirelessMAN in IEEE, it has been commercialized under the name WiMAX by the WiMAX Forum industry alliance. The Forum promotes and certifies compatibility and interoperability of products based on the IEEE802.16 standards, the 802. 16e-2005 amendment version was announced as being deployed around the world in 2009. The version IEEE802. 16-2009 was amended by IEEE802. 16j-2009, projects publish draft and proposed standards with the letter P prefixed. Once a standard is ratified and published, that P gets dropped and replaced by a trailing dash, the 802.16 standard essentially standardizes two aspects of the air interface – the physical layer and the media access control layer. This section provides an overview of the employed in these two layers in the mobile 802. 16e specification. 802. 16e uses scalable OFDMA to carry data, supporting channel bandwidths of between 1.25 MHz and 20 MHz, with up to 2048 subcarriers, in intermediate conditions,16 QAM and QPSK can also be employed. Although the standards allow operation in any band from 2 to 66 GHz, mobile operation is best in the bands which are also the most crowded. Further features of the MAC layer include power saving mechanisms and handover mechanisms, a key feature of 802.16 is that it is a connection-oriented technology. The subscriber station cannot transmit data until it has allocated a channel by the base station. This allows 802. 16e to provide support for quality of service. Quality of service in 802. 16e is supported by allocating each connection between the SS and the BS to a specific QoS class. In 802. 16e, there are 5 QoS classes, The BS, because the IEEE only sets specifications but does not test equipment for compliance with them, the WiMAX Forum runs a certification program wherein members pay for certification. WiMAX certification by this group is intended to guarantee compliance with the standard, the mission of the Forum is to promote and certify compatibility and interoperability of broadband wireless products. WiBro WiMAX WiBAS WiMAX MIMO Wireless mesh network 4G LTE The IEEE802.16 Working Group on Broadband Wireless Access Standards, get IEEE802 official standards download
35.
Microwave transmission
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Microwave transmission is the transmission of information or energy by electromagnetic waves whose wavelengths are measured in small numbers of centimetre, these are called microwaves. This part of the spectrum ranges across frequencies of roughly 1.0 gigahertz to 300 GHz. These correspond to wavelengths from 30 centimeters down to 0.1 cm, communication satellites which transferred data between ground stations by microwaves took over much long distance traffic in the 1960s. This allows nearby microwave equipment to use the same frequencies without interfering with each other, a disadvantage is that microwaves are limited to line of sight propagation, they cannot pass around hills or mountains as lower frequency radio waves can. Microwave radio transmission is used in point-to-point communication systems on the surface of the Earth, in satellite communications. Other parts of the radio band are used for radars, radio navigation systems, sensor systems. Radio waves in this band are usually strongly attenuated by the Earthly atmosphere and particles contained in it, also, in wide band of frequencies around 60 GHz, the radio waves are strongly attenuated by molecular oxygen in the atmosphere. Wireless transmission of power Proposed systems e. g, in microwave radio relay, microwaves are transmitted between the two locations with directional antennas, forming a fixed radio connection between the two points. The requirement of a line of sight limits the distance between stations to 30 or 40 miles. Beginning in the 1950s, networks of microwave links, such as the AT&T Long Lines system in the U. S. carried long distance telephone calls. The first system, dubbed TD-2 and built by AT&T, connected New York and these included long daisy-chained series of such links that traversed mountain ranges and spanned continents. Much of the traffic is now carried by cheaper optical fibers and communication satellites. Antennas must be highly directional, these antennas are installed in elevated locations such as radio towers in order to be able to transmit across long distances. Typical types of antenna used in radio relay link installations are parabolic antennas, dielectric lens, and horn-reflector antennas, highly directive antennas permit an economical use of the available frequency spectrum, despite long transmission distances. Because of the frequencies used, a line-of-sight path between the stations is required. Additionally, in order to avoid attenuation of the beam an area around the beam called the first Fresnel zone must be free from obstacles, obstacles in the signal field cause unwanted attenuation. In the planning process, it is essential that path profiles are produced, multipath fades are usually deep only in a small spot and a narrow frequency band, so space and/or frequency diversity schemes can be applied to mitigate these effects. Rare events of temperature, humidity and pressure profile versus height, may produce large deviations and distortion of the propagation and affect transmission quality
36.
Parabolic reflector
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A parabolic reflector is a reflective surface used to collect or project energy such as light, sound, or radio waves. Its shape is part of a paraboloid, that is. The parabolic reflector transforms an incoming plane wave traveling along the axis into a spherical wave converging toward the focus, conversely, a spherical wave generated by a point source placed in the focus is reflected into a plane wave propagating as a collimated beam along the axis. Parabolic reflectors are used to collect energy from a distant source, since the principles of reflection are reversible, parabolic reflectors can also be used to focus radiation from an isotropic source into a narrow beam. In optics, parabolic mirrors are used to light in reflecting telescopes and solar furnaces, and project a beam of light in flashlights, searchlights, stage spotlights. In acoustics, parabolic microphones are used to record faraway sounds such as calls, in sports reporting. Strictly, the shape of the reflector is called a paraboloid. A parabola is the two-dimensional figure, however, in informal language, the word parabola and its associated adjective parabolic are often used in place of paraboloid and paraboloidal. Correspondingly, the dimensions of a symmetrical paraboloidal dish are related by the equation,4 F D = R2, where F is the length, D is the depth of the dish. All units must be the same, if two of these three quantities are known, this equation can be used to calculate the third. A more complex calculation is needed to find the diameter of the dish measured along its surface. This is sometimes called the diameter, and equals the diameter of a flat, circular sheet of material, usually metal. Two intermediate results are useful in the calculation, P =2 F and Q = P2 + R2, where F, D, and R are defined as above. The diameter of the dish, measured along the surface, is given by, R Q P + P ln . The volume of the dish, the amount of liquid it could hold if the rim were horizontal and the vertex at the bottom, is given by 12 π R2 D, where the symbols are defined as above. This can be compared with the formulae for the volumes of a cylinder, a hemisphere (23 π R2 D, {\displaystyle \scriptstyle, and a cone. π R2 is the area of the dish, the area enclosed by the rim. The area of the surface of the dish can be found using the area formula for a surface of revolution which gives A = π R6 D2
37.
Omnidirectional antenna
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This radiation pattern is often described as doughnut shaped. Note that this is different from an antenna, which radiates equal power in all directions and has a spherical radiation pattern. Higher-gain omnidirectional antennas can also be built, higher gain in this case means that the antenna radiates less energy at higher and lower elevation angles and more in the horizontal directions. High-gain omnidirectional antennas are generally realized using collinear dipole arrays and these consist of multiple half-wave dipoles mounted collinearly, fed in phase. The coaxial collinear antenna uses transposed coaxial sections to produce in-phase half-wavelength radiators, a Franklin Array uses short U-shaped half-wavelength sections whose radiation cancels in the far-field to bring each half-wavelength dipole section into equal phase. Another type is the Omnidirectional Microstrip Antenna, Omnidirectional radiation patterns are produced by the simplest practical antennas, monopole and dipole antennas, consisting of one or two straight rod conductors on a common axis. Antenna gain is defined as antenna efficiency multiplied by antenna directivity which is expressed mathematically as, G = e D. A useful relationship between omnidirectional radiation pattern directivity in decibels and half-power beamwidth based on the assumption of a sin b θ / b θ pattern shape is, D =10 log 10 d B
38.
Cellular network
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A cellular network or mobile network is a communication network where the last link is wireless. The network is distributed over land areas called cells, each served by at least one fixed-location transceiver and this base station provides the cell with the network coverage which can be used for transmission of voice, data and others. A cell might use a different set of frequencies from neighboring cells, to avoid interference, when joined together these cells provide radio coverage over a wide geographic area. This allows mobile phones and mobile computing devices to be connected to the switched telephone network. Private cellular networks can be used for research or for large organizations and fleets, each of these cells is assigned with multiple frequencies which have corresponding radio base stations. The group of frequencies can be reused in other cells, provided that the frequencies are not reused in adjacent neighboring cells as that would cause co-channel interference. If there is a single transmitter, only one transmission can be used on any given frequency. Unfortunately, there is some level of interference from the signal from the other cells which use the same frequency. This means that, in a standard FDMA system, there must be at least a one cell gap between cells which reuse the same frequency, in the simple case of the taxi company, each radio had a manually operated channel selector knob to tune to different frequencies. As the drivers moved around, they would change from channel to channel, the drivers knew which frequency covered approximately what area. When they did not receive a signal from the transmitter, they would try other channels until they found one that worked, the taxi drivers would only speak one at a time, when invited by the base station operator. With TDMA, the transmitting and receiving time slots used by different users in each cell are different from each other, with FDMA, the transmitting and receiving frequencies used by different users in each cell are different from each other. In a simple system, the taxi driver manually tuned to a frequency of a chosen cell to obtain a strong signal. The principle of CDMA is more complex, but achieves the same result, time division multiple access is used in combination with either FDMA or CDMA in a number of systems to give multiple channels within the coverage area of a single cell. The key characteristic of a network is the ability to re-use frequencies to increase both coverage and capacity. The elements that determine frequency reuse are the distance and the reuse factor. The reuse distance, D is calculated as D = R3 N, cells may vary in radius from 1 to 30 kilometres. The boundaries of the cells can also overlap between adjacent cells and large cells can be divided into smaller cells, the frequency reuse factor is the rate at which the same frequency can be used in the network
39.
Transceiver
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A transceiver is a device comprising both a transmitter and a receiver that are combined and share common circuitry or a single housing. When no circuitry is common between transmit and receive functions, the device is a transmitter-receiver, the term originated in the early 1920s. Similar devices include transponders, transverters, and repeaters, in radio terminology, a transceiver means a unit which contains both a receiver and a transmitter. From the beginning days of radio the receiver and transmitter were separate units, amateur radio or ham radio operators can build their own equipment and it is now easier to design and build a simple unit containing both of the functions, transmitting and receiving. Almost all modern radio equipment is now a transceiver but there is an active market for pure radio receivers. An example of a transceiver would be a walkie-talkie or a CB radio, on a wired telephone, the handset contains the transmitter and receiver for the audio and in the 20th century was usually wired to the base unit by tinsel wire. The whole unit is referred to as a receiver. On a mobile telephone or other radiotelephone, the unit is a transceiver. A cordless telephone uses an audio and radio transceiver for the handset, if a speakerphone is included in a wired telephone base or in a cordless base station, the base also becomes an audio transceiver in addition to the handset. A modem is similar to a transceiver, in that it sends and receives a signal and it modulates a signal being transmitted and demodulates a signal being received. Transceivers are called Medium Attachment Units in IEEE802.3 documents and were used in 10BASE2. Fiber-optic gigabit,10 Gigabit Ethernet,40 Gigabit Ethernet, and 100 Gigabit Ethernet utilize transceivers known as GBIC, SFP, SFP+, QSFP, XFP, XAUI, CXP, and CFP. 4P4C, de facto standard connector for telephone handsets Duplex, two-Way communications capability Transponder#Optical communications U. S, patent 0,716,136, John Stone Stone, Apparatus for simultaneously transmitting and receiving space telegraph signals 7 MHz SSB transceiver Homebrew HF transceivers
40.
Cell site
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In Global System for Mobile Communications networks, the correct term is Base Transceiver Station, and colloquial synonyms are mobile phone mast or base station. The term base station site might better reflect the increasing co-location of multiple mobile operators, depending on an operators technology, even a site hosting just a single mobile operator may house multiple base stations, each to serve a different air interface technology. Some cities require that sites be inconspicuous, they can be blended with the surrounding area or mounted on buildings or advertising towers. Preserved treescapes can often hide cell towers inside a tree or preserved tree. These installations are generally referred to as concealed cell sites or stealth cell sites, the working range of a cell site is not a fixed figure. It will depend on a number of factors, including, but not limited to, the frequency of signal in use. Timing limitations in some technologies The transmitters rated power, the required uplink/downlink data rate of the subscribers device The directional characteristics of the site antenna array. Reflection and absorption of energy by buildings or vegetation. It may also be limited by geographical or regulatory factors. Generally, in areas where there are enough cell sites to cover a wide area, Ensure that the overlap area is not too large, to minimize interference problems with other sites. In practice, cell sites are grouped in areas of population density. Cell phone traffic through a site is limited by the base stations capacity. This limitation is another factor affecting the spacing of cell mast sites, in suburban areas, masts are commonly spaced 1–2 miles apart and in dense urban areas, masts may be as close as ¼-½ mile apart. The maximum range of a mast depends on the same circumstances, some technologies, such as GSM, normally have a fixed maximum range of 35 kilometres, which is imposed by technical limitations. CDMA and IDEN have no limit, but the limiting factor is the ability of a low-powered personal cell phone to transmit back to the mast. As a rough guide, based on a tall mast and flat terrain, when the terrain is hilly, the maximum distance can vary from as little as 5 kilometres to 8 kilometres due to encroachment of intermediate objects into the wide center fresnel zone of the signal. Depending on terrain and other circumstances, a GSM Tower can replace between 2 and 50 miles of cabling for fixed wireless networks, the concept of maximum range is misleading, however, in a cellular network. Cellular networks are designed to support many conversations with a number of radio channels that are licensed to an operator of a cellular service
41.
Base station
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Base station is – according to article 1.71 of the International Telecommunication Union´s ITU Radio Regulations – defined as A land station in the land mobile service. In mobile telephony it provides the connection between mobile phones and the telephone network. In a computer network it is a transceiver acting as a router for computers in the network, in the context of external land surveying, a base station is a GPS receiver at an accurately-known fixed location which is used to derive correction information for nearby portable GPS receivers. It typically consists of a transmitter and wireless router. The base station is one end of a communications link, the other end is a movable vehicle-mounted radio or walkie-talkie. Examples of base station uses in two-way radio include the dispatch of tow trucks, professional base station radios are often one channel. In lightly used stations, a multi-channel unit may be employed. In heavily used systems, the capability for additional channels, where needed, is accomplished by installing an additional station for each channel. Each base station appears as a channel on the dispatch center control console. In a properly designed dispatch center with several members, this allows each dispatcher to communicate simultaneously, independently of one another. For example, a taxi company dispatch center may have one station on a high-rise building in Boston. Each taxi dispatcher could communicate with taxis in either Boston or Providence by selecting the respective base station on his or her console, in dispatching centers it is common for eight or more radio base stations to be connected to a single dispatching console. Dispatching personnel can tell which channel a message is being received on by a combination of local protocol, unit identifiers, volume settings, a typical console has two speakers identified as select and unselect. Audio from a selected channel is routed to the select speaker. Each channel has a light which flashes when someone talks on the associated channel. Base stations can be controlled or remote controlled. Local controlled base stations are operated by front panel controls on the base station cabinet, remote control base stations can be operated over tone- or DC-remote circuits. The dispatch point console and remote base station are connected by leased private line telephone circuits, the consoles multiplex transmit commands onto remote control circuits
42.
Pager
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A pager is a wireless telecommunications device that receives and displays alphanumeric messages and/or receives and announces voice messages. One-way pagers can only receive messages, while response pagers and two-way pagers can also acknowledge, reply to, Pagers operate as part of a paging system which includes one or more fixed transmitters, as well as a number of pagers carried by mobile users. These systems can range from a restaurant system with a single low-power transmitter, in the 2000s, the widespread availability of cellphones and smartphones has greatly diminished the pager industry. This resilience has led public safety agencies to adopt pagers over cellular, the first telephone pager system was patented in 1949 by Alfred J. Gross. One of the first practical paging services was launched in 1950 for physicians in the New York City area, physicians paid $12 per month for the service and carried a 200-gram pager that would receive phone messages within 40 kilometres of a single transmitter tower. The system was manufactured by the Reevesound Company and operated by Telanswerphone, in 1962 the Bell System—the U. S. telephone monopoly colloquially known as Ma Bell—presented its Bellboy radio paging system at the Seattle Worlds Fair. Bellboy was the first commercial system for personal paging and it also marked one of the first consumer applications of the transistor, for which three Bell Labs inventors received a Nobel Prize in Physics in 1956. Solid-state circuitry enabled the Bellboy pager, about the size of a small TV remote device, to fit into a pocket or purse. The Bellboy was a terminal that notified the user when someone was trying to call them, when the person received an audible signal on the pager, he found a telephone and called the service centre, which informed him of the callers message. The ReFLEX protocol was developed in the mid 1990s, another is a facility handling classified information, where various radio transmitter or data storage devices are excluded to ensure security. First responders in rural areas with inadequate cellular coverage are often issued pagers, volunteer firefighters, EMS paramedics, and rescue squad members usually carry pagers to alert them of emergency call outs for their department. These pagers receive a tone from a fire department radio frequency. Restaurant pagers are in use in the 2000s. Customers are given a portable receiver that usually vibrates, flashes, Pagers have been popular with birdwatchers in Britain and Ireland since 1991, with companies Rare Bird Alert and Birdnet Information offering news of rare birds sent to pagers that they sell. The U. S. paging industry generated $2.1 billion in revenue in 2008, in Canada,161,500 Canadians paid $18.5 million for pager service in 2013. Telus, one of the three major carriers, announced the end to its Canadian pager service as of March 31,2015. Many paging network operators now allow numeric and textual pages to be submitted to the paging networks via email and this can result in pager messages being delayed or lost. Older forms of message submission using the Telelocator Alphanumeric Protocol involve modem connections directly to a paging network, for this reason, older forms of message submission retain their usefulness for disseminating highly-important alerts to users such as emergency services personnel
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Smartphone
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A smartphone is a mobile phone with an advanced mobile operating system that combines features of a personal computer operating system with other features useful for mobile or handheld use. Smartphones can access the Internet and can run a variety of third-party software components and they typically have a color display with a graphical user interface that covers more than 76% of the front surface. In 1999, the Japanese firm NTT DoCoMo released the first smartphones to achieve mass adoption within a country, smartphones became widespread in the late 2000s. Most of those produced from 2012 onward have high-speed mobile broadband 4G LTE, motion sensors, in the third quarter of 2012, one billion smartphones were in use worldwide. Global smartphone sales surpassed the sales figures for regular cell phones in early 2013, devices that combined telephony and computing were first conceptualized by Nikola Tesla in 1909 and Theodore Paraskevakos in 1971 and patented in 1974, and were offered for sale beginning in 1993. Paraskevakos was the first to introduce the concepts of intelligence, data processing and they were installed at Peoples Telephone Company in Leesburg, Alabama and were demonstrated to several telephone companies. The original and historic working models are still in the possession of Paraskevakos, the first mobile phone to incorporate PDA features was a prototype developed by Frank Canova in 1992 while at IBM and demonstrated that year at the COMDEX computer industry trade show. It included PDA features and other mobile applications such as maps, stock reports. A refined version was marketed to consumers in 1994 by BellSouth under the name Simon Personal Communicator, the Simon was the first commercially available device that could be properly referred to as a smartphone, although it was not called that in 1994. The term smart phone appeared in print as early as 1995, in the mid-late 1990s, many mobile phone users carried a separate dedicated PDA device, running early versions of operating systems such as Palm OS, BlackBerry OS or Windows CE/Pocket PC. These operating systems would later evolve into mobile operating systems, in March 1996, Hewlett-Packard released the OmniGo 700LX, a modified HP 200LX palmtop PC that supported a Nokia 2110 phone with ROM-based software to support it. It had a 640×200 resolution CGA compatible four-shade gray-scale LCD screen and could be used to place and receive calls and it was also 100% DOS5.0 compatible, allowing it to run thousands of existing software titles, including early versions of Windows. In August 1996, Nokia released the Nokia 9000 Communicator, a cellular phone based on the Nokia 2110 with an integrated PDA based on the PEN/GEOS3.0 operating system from Geoworks. The two components were attached by a hinge in what known as a clamshell design, with the display above. The PDA provided e-mail, calendar, address book, calculator and notebook applications, text-based Web browsing, when closed, the device could be used as a digital cellular phone. In June 1999 Qualcomm released the pdQ Smartphone, a CDMA digital PCS Smartphone with an integrated Palm PDA, subsequent landmark devices included, The Ericsson R380 by Ericsson Mobile Communications. The first device marketed as a smartphone, it combined the functions of a phone and PDA. The Kyocera 6035 introduced by Palm, Inc, combining a PDA with a mobile phone, it operated on the Verizon network, and supported limited Web browsing
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