Networking Guide : Physical Media - Wireless

Radio frequency (RF) refers to frequencies of radio waves. RF is part of electromagnetic spectrum that ranges from 3 Hz - 300 GHz. Radio wave is radiated by an antenna and produced by alternating currents fed to the antenna. RF is used in many standard as well as proprietary wireless communication systems. RF has long been used for radio and TV broadcasting, wireless local loop, mobile communications, and amateur radio.


Picture: Radio waves radiated by a Base Station's antenna

Microwave is the upper part of RF spectrum, i.e. those frequencies above 1 GHz. Because of the availability of larger bandwidth in microwave spectrum, microwave is used in many applications such as wireless PAN (Bluetooth), wireless LAN (Wi-Fi), broadband wireless access or wireless MAN (WiMAX), wireless WAN (2G/3G cellular networks), satellite communications and radar. But it became a household name because of its use in microwave oven.


Picture: Microwave is used in satellite communication.

Infrared light is part of electromagnetic spectrum that is shorter than radio waves but longer than visible light. Its frequency range is between 300 GHz and 400 THz, that corresponds to wavelength from 1mm to 750 nm. Infrared has long been used in night vision equipment and TV remote control. Infrared is also one of the physical media in the original wireless LAN standard, that's IEEE 802.11. Infrared use in communication and networking was defined by the IrDA (Infrared Data Association). Using IrDA specifications, infrared can be used in a wide range of applications, e.g. file transfer, synchronization, dial-up networking, and payment. However, IrDA is limited in range (up to about 1 meter). It also requires the communicating devices to be in LOS and within its 30-degree beam-cone.


Picture: TV remote control uses infrared.

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