Wireless communication

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This article is about wireless communication. For the more general article about wireless technology see wireless.

For the article on wireless networking see Wireless networking.

Wireless communication is the transfer of information over a distance without the use of electrical conductors or "wires".^[1] The distances involved may be short (a few meters as in television remote control) or very long (thousands or even millions of kilometers for radio communications). When the context is clear the term is often simply shortened to "wireless". Wireless communications is generally considered to be a branch of telecommunications.

1 Wireless communication
- 1.1 Categories of wireless implementations, devices and standards
2 See also
3 References
4 External links
- 4.1 Patents
- 4.2 General

[edit] Wireless communication

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Wireless is a term used to describe telecommunications in which electromagnetic waves (rather than some form of wire) carry the signal over part or the entire communication path. Common examples of wireless equipment in use today include:

· Cellular phones and pagers: provide connectivity for portable and mobile applications, both personal and business.

· Global Positioning System (GPS): allows drivers of cars and trucks, captains of boats and ships, and pilots of aircraft to ascertain their location anywhere on earth.

· Cordless computer peripherals: the cordless mouse is a common example; keyboards and printers can also be linked to a computer via wireless.

· Cordless telephone sets: these are limited-range devices, not to be confused with cell phones.

· Satellite television: allows viewers in almost any location to select from hundreds of channels.

Wireless networking is used to meet a variety of needs. Perhaps the most common use is to connect laptop users who travel from location to location. Another common use is for mobile networks that connect via satellite. A wireless transmission method is a logical choice to network a LAN segment that must frequently change locations. The following situations justify the use of wireless technology:

· To span a distance beyond the capabilities of typical cabling.

· To avoid obstacles such as physical structures, EMI, or RFI.

· To provide a backup communications link in case of normal network failure.

· To link portable or temporary workstations.

· To overcome situations where normal cabling is difficult or financially impractical.

· To remotely connect mobile users or networks.

In this lesson we examine the basics of wireless communication starting with the electromagnetic spectrum, identifying the frequencies used in wireless communication. Then we will look at the actual signal and how data is placed on the frequency. At that point, we will look at the various limitations or challenges that may occur in a wireless network. Finally we will look at the various types of antennas that are being used and how proper placement can reduce the adverse affect on the environment.

Wireless communication involves

radio frequency communication.
microwave communication, for example long-range line-of-sight via highly directional antennas, or short-range communication.
infrared (IR) short-range communication, for example from remote controls or via IRDA.

Applications may involve point-to-point communication, point-to-multipoint communication, broadcasting , cellular networks and other wireless networks.

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[edit] Categories of wireless implementations, devices and standards

Broadcasting
Amateur radio
Communication radio
Cordless telephony
- DECT (Digital Enhanced Cordless Telecommunications)
Cellular systems
- 0G
- 1G
- 2G
- 3G
- 4G
Short-range point-to-point communication
Wireless sensor networks
- ZigBee
Personal area networks
- Bluetooth
- Ultra-wideband (UWB from WiMedia Alliance).
Wireless computer networks
- Wireless Local Area Networks (WLAN)
  - IEEE 802.11 branded as WiFi
  - HIPERLAN
- Wireless Metropolitan Area Networks (WMAN) and Broadband Fixed Access (BWA)
  - LMDS
  - WiMAX
  - HIPERMAN

The Electromagnetic Spectrum

We are all affected by the Electromagnetic Spectrum in our daily lives. Light, colors, AM and FM radio, broadcast TV, microwaves, portable phones, cell phones, satellite TV and, yes, even your wireless laptop, all work on the Electromagnetic Spectrum.

In the US the frequencies that are available for use for communication are treated as a public resource and are regulated by the Federal Communications Commission (FCC). This is a very important role because it determines which frequency ranges can be used for what purpose and by whom. This may sound very controlled, but just imagine the chaos if, for example, airlines didn't have specific frequencies to work under and some ham radio buff was interfering with the pilots ability to land an airplane.

Wireless communication spans the spectrum from 9 KHz to 300 GHz. It must be remembered that the airwaves are a spectrum. This means frequencies close to each other can interfere with each other if not regulated properly. Medical equipment and cell phones are not a very good mix and that is why cell phone use is banned in hospitals and doctors offices.