Cell site
Type | Cellular telephone site |
---|---|
First production | 20th century |
A cell site, cell phone tower, cell base tower, or cellular base station is a
Multiple cellular providers often save money by mounting their antennas on a common shared mast; since separate systems use different frequencies, antennas can be located close together without interfering with each other. Some provider companies operate multiple cellular networks and similarly use colocated base stations for two or more cellular networks, (CDMA2000 or GSM, for example).
Cell sites are sometimes required to be inconspicuous; they can be blended with the surrounding area[2] or mounted on buildings[3] or advertising towers.[citation needed] Preserved treescapes can often hide cell towers inside an artificial or preserved tree. These installations are generally referred to as concealed cell sites or stealth cell sites.
Overview
A cellular network is a network of handheld mobile phones (cell phones) in which each phone communicates with the telephone network by radio waves through a local antenna at a cellular base station (cell site). The coverage area in which service is provided is divided into a mosaic of small geographical areas called "cells", each served by a separate low power multichannel transceiver and antenna at a base station. All the cell phones within a cell communicate with the system through that cell's antenna, on separate frequency channels assigned by the base station from a common pool of frequencies used by the system.
The purpose of cellular organization is to conserve
Typically a cell tower is located at the edge of one or more cells and covers multiple cells using directional antennas. A common geometry is to locate the cell site at the intersection of three adjacent cells, with three antennas at 120° angles each covering one cell. The type of antenna used for cellular base stations (vertical white rectangles in pictures), called a sector antenna, usually consists of a vertical collinear array of dipoles. It has a flat fan-shaped radiation pattern, which is tilted slightly down to cover the cell area without radiating at higher angles into further off cells which reuse the same frequencies. The elevation angle of the antenna must be carefully adjusted, so the beam covers the entire cell without radiating too far. In modern sector antennas beam tilt can usually be adjusted electronically, to avoid the necessity of a lineman climbing the tower to mechanically tilt the antenna when adjustment is needed.
Operation
Range
The working range of a cell site (the range which mobile devices connects reliably to the cell site) is not a fixed figure. It will depend on a number of factors, including, but not limited to:
- Height of antenna over surrounding terrain (Line-of-sight propagation).
- The frequency of signal in use.
- The transmitter's rated power.
- The required uplink/downlink data rate of the subscriber's device[4]
- The directional characteristics of the site antenna array.
- Reflection and absorption of radio energy by buildings or vegetation.
- It may also be limited by local geographical or regulatory factors and weather conditions.
- In addition there are timing limitations in some technologies (e.g., even in free space, GSM would be limited to 150 km, with 180 km being possible with special equipment)
Generally, in areas where there are enough cell sites to cover a wide area, the range of each one will be set to:
- Ensure there is enough overlap for "handover" to/from other sites (moving the signal for a mobile device from one cell site to another, for those technologies that can handle it - e.g. making a GSM phone call while in a car or train).
- 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 high population density, with the most potential users. Cell phone traffic through a single site is limited by the base station's capacity; of -56 dBm signal there is a finite number of calls or data traffic that a base station can handle at once. This capacity limitation is commonly the factor that determines the spacing of cell mast sites. In suburban areas, masts are commonly spaced 2–3 km (1.2–1.9 mi) apart and in dense urban areas, masts may be as close as 400–800 m apart.[5]
The maximum range of a mast (where it is not limited by interference with other masts nearby) depends on the same considerations. In any case 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
Practical example of range
- 3G/4G/5G (FR1) Mobile base station tower: it is technically possible to cover up to 50–150 km. (Macrocell)[8]
- 5G (FR2) Mobile base station: the distances between the 5G base-station is about 250–300 m, due to the use of millimetre waves.[9]
Channel reuse
The concept of "maximum" range is misleading in a cellular network. Cellular networks are designed to support many conversations with a limited number of
Signal limiting factor
A cellphone may not work at times because it is too far from a mast, or because the phone is in a location where cell phone signals are
The
Geolocation
Cellular
An advanced forward link is where a device is within range of at least three cell sites and where the carrier has implemented timing system use.
Another method is using
In the United States, for emergency calling service using location data (locally called "Enhanced 911"), it was required that at least 95% of cellular phones in use on 31 December 2005 support such service. Many carriers missed this deadline and were fined by the Federal Communications Commission.[10]
Radio power and health
According to the U.S. Federal Communications Commission: "Measurement data obtained from various sources have consistently indicated that 'worst-case' ground-level power densities near typical cellular towers are on the order of 1 µW/cm² (or 10 mW/m²) or less (usually significantly less)."[11]
Cell phones, cell towers, wi-fi, smart meters, digital enhanced cordless telecommunications phones, cordless phones, baby monitors, and other wireless devices all emit non-ionizing radio frequencies, which the World Health Organization (WHO) has classified as a "potential" carcinogen,[12] According to the U.S. National Cancer Institute, "No mechanism by which ELF-EMFs or radiofrequency radiation could cause cancer has been identified."[13]
According to the U.S. Food and Drug Administration, "Scientific consensus shows that non-ionizing radiation is not a carcinogen and, at or below the radio frequency exposure limits set by the FCC, non-ionizing radiation has not been shown to cause any harm to people."[14]
Temporary sites
Although cell antennas are normally attached to permanent structures, carriers also maintain fleets of vehicles, called
COWs are also used at permanent cell sites—as temporary replacements for damaged equipment, during planned outages, and to augment capacity such as during conventions.
Employment
Cell site workers are called tower climbers or transmission tower workers. Transmission tower workers often work at heights of up to 460 m (1,500 ft), performing installation, maintenance and repair work for cellular phone and other wireless communications companies.
Spy agency setup
According to documents leaked to Der Spiegel, the NSA sells a $40,000 "active GSM base station" to be used as a tool to mimic a mobile phone tower and thus monitor cell phones.[15]
In November 2014, The Wall Street Journal reported that the Technical Operations Group of the U.S. Marshals utilizes spy devices, known as "dirtboxes", to mimic powerful cell tower signals. Such devices are designed to cause mobile phones to switch over to the tower, as it is the strongest signal within reach. The devices are placed on airplanes to effectively create a "dragnet", gathering data about phones as the planes travel above populated areas.[16][17]
Off-grid systems
This section needs additional citations for verification. (April 2012) |
An off-grid cell site is not connected to the public
- Solar power generator
- Wind generator
- Electro-chemical generator fuel cells
Electrical energy from intermittent sources is stored in
The renewable energy systems supply electrical power when available. The fuel cells are activated only when the natural sources are not enough to supply the energy the system needs. The emergency power supply (the fuel cells) is designed to last an average of ten days. In this way the structure is completely self-sufficient: this enables the maintenance team to pay only few visits to the site, since it is usually hard to get to.
Camouflage
There is often local opposition to new masts for reasons of
These concealed cell sites can distinguish themselves by foliage shape and bark type. The foliage of all these antennas is composed of leaves made of plastic material accurately designed, taking into consideration quantity, shape and array suitable to completely conceal the antennas and all accessory parts in a natural manner. The materials used guarantee absolute radio-electric transparency and resistance to UVA rays. Nicknames include "monopalm" for a monopole disguised as a palm tree or "Pseudopinus telephoneyensis" for a mast disguised as a pine tree.[21] In monopoles, the directional antennas are sometimes hidden in a plastic housing near the top of the pole so that the crossbars can be eliminated.
Rooftop structures such as concealment chimneys or panels, 6 to 12 meters high, may conceal one or more mobile telephone operators on the same station. Roofmask panels can be fixed to existing rooftop structures, restyling them quickly and cheaply.
-
An antenna colored to blend in with its host building, inSopot, Poland
-
Camouflaged monopole, called "monopalm", in Arizona, US
-
A site concealed in a tree in Yvelines, France
Miniature
Researchers at
Water tower cellular
Cellular companies sign leases with local governments to place cellular antennas on water towers.[23]
See also
- Cellular network
- Node B
- OpenBTS
- Mobile phone radiation and health
- Telecom infrastructure sharing
- Base transceiver station
- Remote radio head
- Radio masts and towers
- Mobile cell sites
- Distributed antenna system
- Telecommunications lease
- Title 47 of the Code of Federal Regulations
- In re Application of the United States for Historical Cell Site Data
- Tower climber
References
- ^ "Learn about what is on a cell tower". Without the Cat. Archived from the original on 24 June 2020. Retrieved 9 December 2010.
- ^ Rubenstein, Carin (11 July 2004). "The Girded, The Bland And the Prickly". The New York Times. Archived from the original on 25 June 2020. Retrieved 18 February 2017.
- ^ Buckley, Cara; Richtel, Matt (20 August 2010). "Good Cellphone Service Comes at a Price". The New York Times. Archived from the original on 4 December 2019. Retrieved 18 February 2017.
- ^ J. Andrews, A. Gohsh (2007). Fundamentals of WiMAX, p. 43
- ^ "Understanding Small-Cell Wireless Backhaul". Electronic Design. 3 April 2014. Archived from the original on 9 August 2020. Retrieved 4 December 2019.
- ^ Frequently Asked PCS Questions undated, URL retrieved 14 August 2007. Archived 9 May 2006 at the Wayback Machine
- ^ NTIA Seeks Input on Broadband Stimulus Money undated, URL retrieved 3 March 2009. Archived 22 November 2009 at the Wayback Machine
- ^ "Mobile Phone Base Stations, How do mobile base stations work, Mobile Base Stations in Australia, Cell Tower, Mobile Phone Tower". mobilenetworkguide.com.au. Archived from the original on 12 November 2020. Retrieved 4 December 2019.
- ^ "Full Page Reload". IEEE Spectrum: Technology, Engineering, and Science News. 27 January 2017. Archived from the original on 15 January 2021. Retrieved 4 June 2018.
- ^ "Sprint, Alltel, USC fined for missed e911 deadline". FierceWireless. 31 August 2007. Archived from the original on 29 November 2020. Retrieved 4 December 2019.
- ^ Questions and Answers about Biological Effects and Potential Hazards of Radiofrequency Electromagnetic Fields (PDF). OET Bulletin 56 (4th ed.). August 1999. p. 21. Archived (PDF) from the original on 20 October 2011. Retrieved 14 September 2022.
- PMID 28656257..
- ^ "Electromagnetic Fields and Cancer". National Cancer Institute. 7 January 2019. Archived from the original on 5 March 2020. Retrieved 26 February 2019.
- ^ "Radio Frequency Radiation and Cell Phones". U.S. Food and Drug Administration. 30 May 2022. Archived from the original on 30 September 2022. Retrieved 14 September 2022.
- ^ Appelbaum, Jacob; Horchert, Judith; Stöcker, Christian (29 December 2013). "Shopping for Spy Gear: Catalog Advertises NSA Toolbox". Der Spiegel. Archived from the original on 16 December 2020. Retrieved 4 December 2019 – via Spiegel Online.
- ^ Devlin Barrett (13 November 2014). "Americans' Cellphones Targeted in Secret U.S. Spy Program: Devices on Planes that Mimic Cellphone Towers Used to Target Criminals, but Also Sift Through Thousands of Other Phones". The Wall Street Journal. Archived from the original on 6 June 2018. Retrieved 14 November 2014.
- ^ Kate Knibbs (13 November 2014). "WSJ: A Secret U.S. Spy Program Is Using Planes to Target Cell Phones". Gizmodo. Archived from the original on 30 November 2020. Retrieved 14 November 2014.
- ^ Ballard fuel cells to power telecom backup power units for Motorola Archived 6 July 2011 at the Wayback Machine
- ^ "India telecoms to get fuel cell power". Archived from the original on 26 November 2010.
- ^ "Pembrokeshire: Wind and solar powered phone mast in UK first". BBC News. 15 June 2022. Archived from the original on 15 June 2022. Retrieved 15 June 2022.
- ^ BOWEN, Humphry (1 January 1999). "NEW CONIFER IN THE BRITISH ISLES?" (PDF). BSBI NEWS. No. January 1999. UK. p. 51. Archived from the original (PDF) on 26 July 2011. Retrieved 1 November 2023.
- ^ The tiny cube that could cut your cell phone bill Archived 12 November 2020 at the Wayback Machine, CNN Money, 21 March 2011, David Goldman
- ^ "Water tower-based cell antennas provide municipal revenues, better phone service". 26 July 2011.
External links
- Maps of All Towers Across the United Kingdom
- FCC: Universal Licensing Information Archived 28 March 2014 at the Wayback Machine
- FCC: Information On Human Exposure To Radio frequency Fields From Cellular and PCS Radio Transmitters
- Australian Radiation Protection and Nuclear Safety Agency (ARPANSA) Base Station Survey 2007- 2011