Data Communication and Networking
Transmisssion Control Protocol (TCP)
2.) Unguided Media: WIRELESS
Unguided media transport electromagnetic waves without using a physical conductor.
This type of communication is often referred to as wireless communication. Signals are normally broadcast through free space and thus are available to anyone who has a device capable of receiving them. Figure below shows the part of the electromagnetic spectrum, ranging from 3 kHz to 900 THz, used for wireless communication.
Unguided signals can travel from the source to destination in several ways: ground propagation, sky propagation, and line-of-sight propagation. We can divide wireless transmission into three broad groups: radio waves, microwaves, and infrared waves.
- Radio waves are used for multicast communications, such as radio and television, and paging systems. They can penetrate through walls.
- Highly regulated.
- Use omni directional antennas
The omnidirectional characteristics of radio waves make them useful for multicasting, in which there is one sender but many receivers. AM and FM radio, television, maritime radio, cordless phones, and paging are examples of multicasting.
- Microwaves are used for unicast communication such as cellular telephones, satellite networks, and wireless LANs.
- Higher frequency ranges cannot penetrate walls.
- Use directional antennas – point to point line of sight communications.
Microwaves, due to their unidirectional properties, are very useful when unicast
(one-to-one) communication is needed between the sender and the receiver. They are
used in cellular phones , satellite networks ,and wireless LANs.
- Infrared signals can be used for short-range communication in a closed area using line-of-sight propagation.
- Transceivers must be within line of sight of each other (directly or via reflection ).
- Infrared does not penetrate walls.
Posted by Vissicomp Technology