Wireless+Media

=**Wireless** Media (radiated media) = =A network in which there are no physical connections between computers; instead, the computers communicate using radio-frequency signals. =
 * Radio
 * Infrared
 * Microwave
 * Satellite



**Radio**

**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.


 * Wireless transmission of electrical waves through air
 * Each device has a radio transceiver with a specific frequency
 * Often attached to portables (Laptops, PDAs, cell phones)

=Infrared =



**Infared** is just below the visible range of light between 100Ghz and 1000Thz. A light emitting diode (LED) or laser is used to transmit the signal. The signal cannot travel through objects. Light may interfere with the signal. The types of infared are:

>
 * Point to point - Transmission frequencies are 100GHz-1,000THz . Transmission is between two points and is limited to line of sight range. It is difficult to eavesdrop on the transmission. The speed is 100Kbps to 16Mbps
 * Broadcast - The signal is dispersed so several units may receive the signal. The unit used to disperse the signal may be reflective material or a transmitter that amplifies and retransmits the signal. Normally the speed is limited to 1Mbps. The transmission frequency is normally 100GHz-1,000THz with transmission distance in 10's of meters. Installation is easy and cost is relatively inexpensive for wireless.


 * Microwave Radio **



<span style="font-family: 'Times New Roman',Times,serif; font-size: 16px;">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.


 * <span style="font-family: 'Times New Roman',Times,serif; font-size: 16px;">Extremely short (//micro//) wavelength (1 cm to 1 m)
 * <span style="font-family: 'Times New Roman',Times,serif; font-size: 16px;">Performs same functions as cables

<span style="font-family: 'Times New Roman',Times,serif; font-size: 28px;">**Satellite Communications**



<span style="font-family: 'Times New Roman',Times,serif; font-size: 16px;">A **satellite** orbits at 22,300 miles above the earth, which is an altitude that will cause it stay in a fixed position relative to the rotation of the earth. A station on the ground will send and receive signals from the satellite. The signal can have propagation delays between 0.5 to 5 seconds due to the distances involved. The transmission frequency is normally 11-14GHz with a transmission speed in the range of 1-10Mbps.

> <span style="font-family: 'Times New Roman',Times,serif; font-size: 16px;">Home
 * <span style="font-family: 'Times New Roman',Times,serif; font-size: 16px;">Special form of microwave communications

<span style="font-family: 'Times New Roman',Times,serif; font-size: 16px; line-height: 24px;">Advantages and Disadvantages of Wireless Media

<span style="font-family: 'Times New Roman',Times,serif; font-size: 16px; line-height: 24px;">Sources