Base station (orbase radio station, BS) is – according to theInternational Telecommunication Union's (ITU)Radio Regulations (RR)[1] – a "land station in theland mobile service."
A base station is callednode B in3G,eNB inLTE (4G), andgNB in5G.
The term is used in the context ofmobile telephony,wireless computer networking and otherwireless communications and inland surveying. In surveying, it is aGPS receiver at a known position, while in wireless communications it is atransceiver connecting a number of other devices to one another and/or to a wider area.In mobile telephony, it provides the connection betweenmobile phones and the widertelephone network. In acomputer network, it is a transceiver acting as aswitch forcomputers in the network, possibly connecting them to a/anotherlocal area network and/or theInternet. In traditional wireless communications, it can refer to the hub of adispatch fleet such as ataxi ordelivery fleet, the base of aTETRA network as used bygovernment andemergency services or aCBshack.
In the context of external land surveying, a base station is aGPS receiver at an accurately-known fixed location which is used to derive correction information for nearby portable GPS receivers. This correction data allowspropagation and other effects to be corrected out of the position data obtained by the mobile stations, which gives greatly increased location precision and accuracy over the results obtained by uncorrected GPS receivers.
In the area of wireless computer networking, a base station is a radio receiver/transmitter that serves as the hub of the local wireless network, and may also be the gateway between a wired network and the wireless network. It typically consists of a low-power transmitter andwireless router.
Inradio communications, a base station is awireless communications station installed at a fixed location and used to communicate as part of one of the following:
Base stations useRF power amplifiers (radio-frequency power amplifiers) to transmit and receive signals. The most common RF power amplifiers aremetal–oxide–semiconductor field-effect transistors (MOSFETs), particularlyLDMOS (power MOSFET) RF amplifiers.[2][3][4] RF LDMOS amplifiers replaced RFbipolar transistor amplifiers in most base stations during the 1990s,[2] leading to thewireless revolution.[5]
In professional two-way radio systems, a base station is used to maintain contact with adispatch fleet ofhand-held ormobile radios, and/or to activate one-way paging receivers. The base station is one end of a communications link. The other end is a movable vehicle-mounted radio or walkie-talkie.[6] Examples of base station uses in two-way radio include the dispatch oftow trucks andtaxicabs.
Professional base station radios are often one channel. In lightly used base stations, a multi-channel unit may be employed.[7] 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 inBoston and another on a different channel inProvidence. Each taxi dispatcher could communicate with taxis in either Boston or Providence by selecting the respective base station on his or her console.[8]
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 asselect andunselect. 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.[9]
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- orDC-remote circuits. The dispatch point console and remote base station are connected by leased private line telephone circuits, (sometimes calledRTO circuits), aDS-1, or radio links.[10] 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.[11]
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:[12][13]
Base stations are sometimes calledcontrol orfixed stations in USFederal 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:
Inamateur radio, a base station also communicates withmobile rigs but for hobby or family communications. Amateur systems sometimes serve as dispatch radio systems during disasters, search and rescue mobilizations, or other emergencies.
AnAustralianUHF CB base station is another example of part of a system used for hobby or family communications.
Wireless telephone differ from two-way radios in that:
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 involvecarrier,microwave radio, andswitching 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.
While low levels of radio-frequency power are usually considered to have negligible effects on health, national and local regulations restrict the design of base stations to limit exposure toelectromagnetic fields. Technical measures to limit exposure include restricting the radio frequency power emitted by the station, elevating the antenna above ground level, changes to theantenna pattern, and barriers to foot or road traffic. For typical base stations, significant electromagnetic energy is only emitted at the antenna, not along the length of the antenna tower.[18]
Because mobile phones and their base stations are two-way radios, they produce radio-frequency (RF) radiation in order to communicate, exposing people near them toRF radiation giving concerns aboutmobile phone radiation and health. Hand-held mobile telephones are relatively low power so the RF radiation exposures from them are generally low.
TheWorld 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."[19]
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 thethermal effects of base station emissions, NOT considering thenon-thermal effects harmless.
Fuel cellbackup power systems are added to critical base stations orcell sites to provide emergency power.[20][21]
