Editing Microwave (section)

=== Communication ===
{{main|Point-to-point (telecommunications)|Microwave transmission|Satellite communications}}
[[File:SuperDISH121.jpg|thumb|A [[satellite dish]] on a residence, which receives [[satellite television]] over a [[Ku band|K<sub>u</sub> band]] 12–14&nbsp;GHz microwave beam from a direct broadcast [[communications satellite]] in a [[geostationary orbit]] 35,700 kilometres (22,000 miles) above the Earth]]

Before the advent of [[fiber-optic]] transmission, most [[long-distance call|long-distance]] [[telephone call]]s were carried via networks of [[microwave radio relay]] links run by carriers such as [[AT&T Long Lines]].  Starting in the early 1950s, [[frequency-division multiplexing]] was used to send up to 5,400 telephone channels on each microwave radio channel, with as many as ten radio channels combined into one antenna for the ''hop'' to the next site, up to 70&nbsp;km away.

[[Wireless LAN]] [[Protocol (computing)|protocol]]s, such as [[Bluetooth]] and the [[IEEE Standards Association|IEEE]] [[802.11]] specifications used for Wi-Fi, also use microwaves in the 2.4&nbsp;GHz [[ISM band]], although [[802.11a]] uses [[ISM band]] and [[U-NII]] frequencies in the 5&nbsp;GHz range.  Licensed long-range (up to about 25&nbsp;km) Wireless Internet Access services have been used for almost a decade in many countries in the 3.5–4.0&nbsp;GHz range.  The FCC recently{{when |date=August 2011}} carved out spectrum for carriers that wish to offer services in this range in the U.S. — with emphasis on 3.65&nbsp;GHz.  Dozens of service providers across the country are securing or have already received licenses from the FCC to operate in this band. The WIMAX service offerings that can be carried on the 3.65&nbsp;GHz band will give business customers another option for connectivity.

[[Metropolitan area network]] (MAN) protocols, such as [[WiMAX]] (Worldwide Interoperability for Microwave Access) are based on standards such as [[IEEE 802.16]], designed to operate between 2 and 11&nbsp;GHz. Commercial implementations are in the 2.3&nbsp;GHz, 2.5&nbsp;GHz, 3.5&nbsp;GHz and 5.8&nbsp;GHz ranges.

[[Mobile Broadband]] Wireless Access (MBWA) protocols based on standards specifications such as [[IEEE 802.20]] or ATIS/ANSI [[HC-SDMA]] (such as [[iBurst]]) operate between 1.6 and 2.3&nbsp;GHz to give mobility and in-building penetration characteristics similar to mobile phones but with vastly greater spectral efficiency.<ref>{{cite web |title= IEEE 802.20: Mobile Broadband Wireless Access (MBWA) |work= Official web site |url= https://grouper.ieee.org/groups/802/20/ |access-date= August 20, 2011 }}</ref>

Some [[mobile phone]] networks, like [[GSM frequency bands|GSM]], use the low-microwave/high-UHF frequencies around 1.8 and 1.9&nbsp;GHz in the Americas and elsewhere, respectively.  [[DVB-SH]] and [[S-DMB]] use 1.452 to 1.492&nbsp;GHz, while proprietary/incompatible [[satellite radio]] in the U.S. uses around 2.3&nbsp;GHz for [[Digital Audio Radio Service|DARS]].

Microwave radio is used in [[point-to-point (telecommunications)|point-to-point]] [[telecommunications]] transmissions because, due to their short wavelength, highly [[directional antenna]]s are smaller and therefore more practical than they would be at longer wavelengths (lower frequencies).  There is also more [[bandwidth (signal processing)|bandwidth]] in the microwave spectrum than in the rest of the radio spectrum; the usable bandwidth below 300&nbsp;MHz is less than 300&nbsp;MHz while many GHz can be used above 300&nbsp;MHz. Typically, microwaves are used in [[remote broadcasting]] of news or sports events as the [[backhaul (broadcasting)|backhaul]] link to transmit a signal from a remote location to a television station from a specially equipped van.  See [[broadcast auxiliary service]] (BAS), [[remote pickup unit]] (RPU), and [[studio/transmitter link]] (STL).

Most [[satellite communications]] systems operate in the C, X, K<sub>a</sub>, or K<sub>u</sub> bands of the microwave spectrum. These frequencies allow large bandwidth while avoiding the crowded UHF frequencies and staying below the atmospheric absorption of EHF frequencies.  [[Satellite TV]] either operates in the C band for the traditional [[TVRO|large dish]] [[fixed satellite service]] or K<sub>u</sub> band for [[direct-broadcast satellite]].  Military communications run primarily over X or K<sub>u</sub>-band links, with K<sub>a</sub> band being used for [[Milstar]].