3 Wireless communication technologies using radio waves

a. Bluetooth 

Bluetooth technology uses radio waves in the frequency range of 2.402 GHz to 2.480 GHz. This technology is used for short range communication (approx. 10 m) in a variety of devices for wireless communication. Cell phones, laptops, mouse, keyboard, tablets, head sets, cameras etc.

Characteristics of Bluetooth transmission 

• Line of sight between communicating devices is not required. 

• Bluetooth can connect upto eight devices simultaneously. 

• Slow data transfer rate (upto 1 Mbps).

b. Wi-Fi 

Wi-Fi network makes use of radio waves to transmit information across a network like cell phones, televisions and radios. The radio waves used in Wi-Fi ranges from a frequency of 2.4 GHz to 5 GHz. Communication across a wireless network is two-way radio communication. The wireless adapter in a computer translates data into radio signal and transmits it using an antenna. A wireless router receives the signal and decodes it. Once decoded, the data will be sent to the Internet or network through a wired Ethernet /wireless connection.

Characteristics of Wi-Fi transmission 

• Line of sight between communicating devices is not required 

• Data transmission speed is up to 54 Mbps 

• Wi-Fi can connect more number of devices simultaneously 

• Used for communication upto 375 ft (114 m

c. Wi-MAX

 Worldwide Interoperability for Microwave Access (Wi-MAX) combines the benefits of broadband and wireless. Wi-MAX has a the frequency range of 2 GHz to 11 GHz.  

Characteristics of Wi-MAX transmission 

• Hundreds of users can connect to a single station. 

• Provides higher speed connection upto 70 Mbps over an area of 45 Kilometres. 

• Line of sight between communicating devices is not required. 

• Weather conditions like rain, storm etc. could interrupt the signal.

• Very high power consumption. 

• High costs of installation and operation

d. Satellite 

link Long distance wireless communication systems use satellite links for transmitting signals. Usually, a signal travels in a straight line and is not able to bend around the globe to reach a destination far away. Signals can be sent to geostationary satellites in space and then redirected to another satellite or directly to a far away destination. A geostationary satellite orbits the earth in the same direction and amount of time it takes to revolve the earth once is equal to the time taken for earth’s one rotation. From the earth, therefore, the satellite appears to be stationary, always above the same area of the earth. These satellites carry electronic devices called transponders for receiving, amplifying, and rebroadcasting signals to the earth. Transmission of signals from the earth to a satellite is called uplink and from a satellite to the earth is called downlink. There are multiple micro wave frequency bands which are used for satellites links. Frequency used for uplink varies from 1.6 GHz to 30.0 GHz and that for downlink varies from 1.5 GHz to 20.0 GHz. Downlink frequency is always lower than the uplink frequency.

The satellite system is very expensive, but its coverage area is very large. Communication satellites are normally owned by governments or by government approved organisations of various countries. 

Characteristics of transmission using satellite link 

• Satellites cover a large area of the earth.

 • This system is expensive. 

• Requires legal permission and authorization

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