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Base station (or base radio station, BS) is – according to the International Telecommunication Union's (ITU) Radio Regulations (RR)ITU Radio Regulations, Section IV. Radio Stations and Systems – Article 1.71, definition: "base station / base radio station" – a "land station in the land mobile service."
A base station is called node B in 3G, EnodeB in LTE (4G), and GNodeB in 5G.
The term is used in the context of mobile telephony, wireless computer networking and other wireless communications and in land surveying. In surveying, it is a GPS receiver at a known position, while in wireless communications it is a transceiver connecting a number of other devices to one another and/or to a wider area. In mobile telephony, it provides the connection between and the wider telephone network. In a computer network, it is a transceiver acting as a switch for in the network, possibly connecting them to a/another local area network and/or the Internet. In traditional wireless communications, it can refer to the hub of a dispatch fleet such as a taxi or delivery fleet, the base of a TETRA network as used by government and emergency services or a CB radio shack.
Base stations use RF power amplifiers (radio-frequency power amplifiers) to transmit and receive signals. The most common RF power amplifiers are metal–oxide–semiconductor field-effect transistors (MOSFETs), particularly LDMOS (power MOSFET) RF amplifiers. RF LDMOS amplifiers replaced RF bipolar transistor amplifiers in most base stations during the 1990s, leading to the wireless revolution.
options such as CTCSS are optional.]]Professional base station radios are often one channel. In lightly used base stations, a multi-channel unit may be employed.Block diagram is from: "Figure 2: Two Channel VHF Base Station," Planning Emergency Medical Communications: Volume 2, Local/Regional Level Planning Guide, (Washington, D.C.: National Highway Traffic Safety Administration, US Department of Transportation, 1995) pp. 42. In heavily used systems, the capability for additional channels, where needed, is accomplished by installing an additional base station for each channel. Each base station appears as a single channel on the dispatch center control console. In a properly designed dispatch center with several staff members, this allows each dispatcher to communicate simultaneously, independently of one another, on a different channel as necessary. For example, a taxi company dispatch center may have one base station on a high-rise building in Boston and another on a different channel in Providence. Each taxi dispatcher could communicate with taxis in either Boston or Providence by selecting the respective base station on his or her console.Base stations in land mobile systems are often located at remote sites such as hilltops or water towers. Some are controlled from two or more locations. For example, a base station used to communicate with taxis may be connected to remote control consoles at both a taxi company office and an answering service for after-hours calls. The taxi company and answering service may be miles apart. Single channel base stations reduce confusion by eliminating the possibility that the wrong channel may be selected.
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, and busy indicator lights. A typical console has two speakers identified as select and unselect. Audio from a primary selected channel is routed to the select speaker and to a headset. Each channel has a busy light which flashes when someone talks on the associated channel.To read more about multi-channel consoles, look at the service manual for a relatively simple console: 8-Channel Remote Console, 120, 220, 240 V AC or 12 V DC T16167 AM or BM, 68-81021E80, (Schaumburg, Illinois: Motorola, Inc. 1980.) This is a relatively simple analog console compared to large, enterprise-level Centracom-series units.
Base stations can be local 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, (sometimes called RTO circuits), a DS-1, or radio links.The term RTO circuit is legacy jargon and comes from Bell System billing terminology. RTO circuits refer to analog radio remote control and radio broadcast leased telephone circuits. The consoles multiplex transmit commands onto remote control circuits. Some system configurations require duplex, or four wire, audio paths from the base station to the console. Others require only a two-wire or half duplex link.For a brief discussion of remote controlled base stations, see: "Evaluating Regional Alternatives: Systems Design Considerations," Planning Emergency Medical Communications: Volume 2, Local/Regional Level Planning Guide, (Washington, D.C.: National Highway Traffic Safety Administration, US Department of Transportation, 1995) pp. 39–41. Tone remote controls are described in this section.
used to reduce the base station receiver's exposure to unwanted signals. It also reduces the transmission of undesired signals. The Circulator is a one-way device which reduces the ease of signals from nearby transmitters going up the antenna line and into the base station transmitter. This prevents the unwanted mixing of signals inside the base station transmitter which can generate interference.]] Interference could be defined as receiving any signal other than from a radio in your own system. To avoid interference from users on the same channel, or interference from nearby strong signals on another channel, professional base stations use a combination of:Block diagram is from: "Figure 8: Bandpass Cavity/Isolator Location," Planning Emergency Medical Communications: Volume 2, Local/Regional Level Planning Guide, (Washington, D.C.: National Highway Traffic Safety Administration, US Department of Transportation, 1995) pp. 57.Bulleted items condensed from, "EMS Communications," "System Coordination," and "Site Engineering," in Planning Emergency Medical Communications: Volume 2, Local/Regional Level Planning Guide, (Washington, D.C.: National Highway Traffic Safety Administration, US Department of Transportation, 1995) pp. 10–19, 55–58.
Base stations are sometimes called control or fixed stations in US Federal Communications Commission licensing. These terms are defined in regulations inside Part 90 of the commissions regulations. In US licensing jargon, types of base stations include:
An UHF CB base station is another example of part of a system used for hobby or family communications.
A wireless telephone base station communicates with a mobile or hand-held phone. For example, in a wireless telephone system, the signals from one or more mobile telephones in an area are received at a nearby base station, which then connects the call to the land-line network. Other equipment is involved depending on the system architecture. Mobile telephone provider networks, such as European GSM networks, may involve multiplexing, microwave radio, and switching facilities to connect the call. In the case of a portable phone such as a US cordless phone, the connection is directly connected to a wired land line.
Because mobile phones and their base stations are two-way radios, they produce radio-frequency (Radio frequency) radiation in order to communicate, exposing people near them to RF radiation giving concerns about mobile phone radiation and health. Hand-held mobile telephones are relatively low power so the RF radiation exposures from them are generally low.
The World Health Organization has concluded that "there is no convincing scientific evidence that the weak RF signals from base stations and wireless networks cause adverse health effects.".
The consensus of the scientific community is that the power from these mobile phone base station antennas is too low to produce health hazards as long as people are kept away from direct access to the antennas. However, current international exposure guidelines (ICNIRP) are based largely on the thermal effects of base station emissions, NOT considering the non-thermal effects harmless.
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