File:CB Base Station.jpg (CB) base station]] The term base station can be used in the context of land surveying and wireless communications

Land surveying

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. This correction data allows radio propagation 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.

Computer networking

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 and wireless router

Wireless communications

In radio communications, a base station is a wireless communications station installed at a fixed location and used to communicate as part of either: * a Push to talk two-way radio system, or; * a Radiotelephone system such as Mobile phone CDMA or GSM cell site * Terrestrial Trunked Radio

Two-way radio

Professional

In professional two-way radio systems, a base station is used to maintain contact with a Dispatch (logistics) fleet of Walkie talkie or Mobile radio 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."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. 39-43. Examples of base station uses in two-way radio include the dispatch of tow truck and taxicab . File:Base station 2 channel block diagram.png 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, Massachusetts and another on a different channel in Providence, Rhode Island 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 selectand 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 4-20_mA#Two-way_radio_use circuits. The dispatch point console and remote base station are connected by leased private line telephone circuits, (sometimes called RTO circuit), a Digital Signal 1 or radio links.The term RTO circuitis 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. File:base station antenna network.png used to reduce the base station Receiver (radio) 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. * minimum receiver specifications and filtering.For an example of receiver specifications, see, "Table 9-3," 800 MHz Trunked Radio Request for Proposals: Public Safety Projects Office,(Oklahoma City, Oklahoma: Oklahoma City Municipal Facilities Authority, 2000, pp. 181. A list of types of filtering used to prevent interference between equipment at the same site is included in "6.2.4 Electromagnetic Compatibility Studies," 800 MHz Trunked Radio Request for Proposals: Public Safety Projects Office,(Oklahoma City, Oklahoma: Oklahoma City Municipal Facilities Authority, 2000, pp. 119. More detail of interference reduction equipment is provided in, "9.1.2 Base Station/Mobile Relay, 800 MHz," 800 MHz Trunked Radio Request for Proposals: Public Safety Projects Office,(Oklahoma City, Oklahoma: Oklahoma City Municipal Facilities Authority, 2000, pp. 165-168. * analysis of other frequencies in use nearby. * in the US, coordination of shared frequencies by coordinating agencies.For example, US federal government systems are coordinated and licensed by the National Telecommunications and Information Administration Business band licenses are coordinated by the Personal Communications Industry Association (PCIA) and licensed by the Federal Communications Commission. * locating equipment so that terrain blocks interfering signals. * use of directional antennas to reduce unwanted signals. Base stations are sometimes called controlor fixedstations 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: * A fixed station is a base station used in a system intended only to communicate with other base stations. A fixedstation can also be radio link used to operate a distant base station by remote control. (No mobile or hand-held radios are involved in the system.) * A control station is a base station used in a system with a repeater where the base station is used to communicate through the repeater. * A temporary base is a base station used in one location for less than a year. * A [[Radio repeater|repeater]] is a type of base station that extends the range of hand-held and mobile radios.

Amateur and hobbyist use

In amateur radio a base station also communicates with mobile rig but for hobby or family communications. Amateur systems sometimes serve as dispatch radio systems during disasters, search and rescue mobilizations, or other emergencies. An Australia UHF CB base station is another example of part of a system used for hobby or family communications.

Wireless telephone

Radiotelephone differ from two-way radios in that: * wireless telephones are circuit switched: the communications paths are set up by dialing at the start of a call and the path remains in place until one of the callers hangs up. * wireless telephones communicate with other telephones usually over the public switched telephone network 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 Telephone exchange 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.

Emissions issues

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 to electromagnetic field . Technical measures to limit exposure include restricting the radio frequency power emitted by the station, elevating the antenna above ground level, changes to the antenna (radio) 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. 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 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 thermaleffects of base station emissions. Some scientists have questioned whether there are non thermaleffects from being exposed to low level RF such as are transmitted from mobile phone base stations. Such non-thermal effects include how the actual frequencies interfere with the human brain and all other cells in the human body.

Emergency power

Fuel cell backup power systems are added to critical base stations or cell site to provide emergency power http://fr.chfca.ca/itoolkit.asp?pgBALLARD_07132009 Ballard fuel cells to power telecom backup power units for motorola]http://cleantech.com/news/3674/india-telecom-get-fuel-cells India telecoms to get fuel cell power].

Media

Image:GaffneySC-CellTower.jpg|A cell tower near Thicketty, South Carolina Image:BaseStationsBlorg.jpg|Two GSM mobile phone base station towers disguised as trees in Dublin Ireland Image:PalmCellTower.jpg|A base station disguised as a palm tree in Tucson Arizona Image:base station mexico-city.JPG|Close-up of a base station antenna in Mexico City Mexico There are three antennas: each serves a 120-degree segment of the horizon. The microwave dish links the site with the telephone network. Image:iden.JPG|A professional rack-mount Integrated Digital Enhanced Network Base Radio at a Cell Site. Image:Trunked 5ch central control.svg|Trunked radio system have groups of base stations configured as Radio repeater The center blocks with frequencies in this trunked block diagram each represent a base station. File:136 to 174 MHz base station antennas.jpg|136-174 MHz US professional base station antenna examples. File:WiMAX equipment.jpg|WiMAX base station equipment with a sector antenna and wireless modem on top

See also

* Base Transceiver Station * Mobile Switching Center * Macrocell * Microcell * Picocell * Femtocell * Access point base station * Cell site * Cellular repeater * Mobile phone * Mobile phone radiation and health * Portable phone * Signal strength * Audio level compression * OpenBTS

Notes

References

External links

* http://www.osha.gov/SLTC/radiofrequencyradiation/ Occupational Safety and Health Admin. Non-Ionizing Radiation Exposure Guidelines.] Category:Surveying Category:Wireless networking Category:Telecommunications infrastructure da:Trådløs basisstation de:Basisstation he:תחנת בסיס ja:基地局 no:Basestasjon fi:Tukiasema sv:Basstation zh:基地台 ru:Базовая станция