Unguided/Wireless communication media:

Unguided communication media transmits the information through the air in much the same way as radio stations broadcast their programming. They are also called unbound or wireless transmission media because they do not use any physical wire or a closed circuit for data communication. Following are the example of unguided communication media are: Satellite, Microwave, Wireless media.

Microwave:

• Parabolic antennas are mounted on towers to send beams.
• It is cheaper than digging trenches for laying cables, and maintaining repeaters of cables if cables get broken by a variety of causes.
• Transmitter and receiver must be in line of sight- 30 miles apart because of earth curvature.
• Possible interference from environment.
• Lack of security.
• High initial equipment cost.
• Relatively high speed data rates upto 250 Mbps.
• Usage: Voice communication (Cellular services)

Satellite:

• Line of sight required between satellite and earth stations.
• 12 to 24 transponders per satellite. These transponders receive, amplify, change frequency and transmit.
• Geosynchronous orbit (22,300 miles)
• Low security. Anyone with satellite dish and right frequency can tune in.
• Easy of adding stations.
• Data rates of upto 50 Mbps.
• It provides high bandwidth for large amount of audio, data and video transmission.
• Usage: Television transmission with multiple channels.

Wireless media:

Some common types of wireless media are infrared light and radio. Infrared transmission is usually limited to a small area, e.g. one room, with transmitter pointed toward the receiver. The hardware is inexpensive and does not require an antenna. A network that uses electromagnetic radio waves operates at Radio Frequency and its transmissions are called RF transmissions. Each host on the network attaches to an antenna, which can both send and receive RF.

Bluetooth

It is a low cost, low power, wireless radio  frequency technology that allows various devices to communicate with each other. One of the advantage of Bluetooth over infrared is that close proximity between the communication devices is not required distance of up to 10 meters or 32 feet are allowed.

Wi-Fi (wireless fidelity)

The full form of Wi-Fi wireless fidelity, WI-FI is the popular wireless networking technology that used radio wave to provides wireless high speed internet and network connection. The WI-FI alliance organization that owns the WI-FI, it is specifically define WI-FI as any wireless local area networks (WLAN) products that are based on the IEEE.WI-FI works with no physical wired connected between sender and receiver by using RF (radio frequency), a frequency within the electromagnetic spectrum associated with radio wave propagation. When an RF current is supply in an antenna an electromagnetic field is created that then is able to propagate through space.