Wireless communication (unbounded media)Wireless (unbounded) media is a type of media that is used to transmit data from one point to another without using physical connections. In this case, a transmitting antenna & a receiver aerial are used to facilitate the communication. Examples of wireless communication media include:
Microwave transmissionMicrowave frequencies have a small wavelength, and can easily release their energy in water as heat. This is why they are used in making domestic kitchen appliances, e.g., microwave ovens. In networking, microwaves are suitable for point-to-point transmissions, whereby a signal is directed through a focused beam from the transmitter to the receiver station. Satellite communicationA Satellite is a microwave relay station. The microwave earth stations have parabolic dishes with an antenna fixed on them in order to focus a narrow beam towards the satellite in space. A satellite transmission system has 3 main components:
A communication satellite is usually launched into space about 36,000 km above the earth in such a manner that its speed is almost equal to the rotation speed of the earth. This makes the satellite appear as if it is stationary in space. Such types of satellites are called geostationary satellites.
Advantages of using satellites
Very Small Aperture Terminal (VSAT)A VSAT is a very small satellite dish used both in data, radio, and TV communication. It can be set up at home or in a small business. It enables direct access to satellite communication instead of having to go through state-owned or licensed satellite gateways. The dish has an antenna that receives the satellite signals. The signals are decoded using a decoder which is plugged directly to a television set or a computer. Radio communicationRadio waves are used in radio and television broadcasts. Radio waves travel just like surface water waves, i.e., they start from a central point and spread outwards in all directions. As they travel outwards, their energy spreads outwards over the covered area. The waves are radiated into the atmosphere by a radio frequency antenna at constant velocity. The figure below shows a typical radio waves link between two separate geographical locations.
Radio waves can be of:
High frequency (HF) radio wavesThe High frequency radio wave signal is transmitted by directing it to the ionosphere of the earth. The ionosphere reflects it back to the earth’s surface, and the receiver then picks the signal. Disadvantage of HF communication
They are transmitted along the earth’s surface. However, since the earth is somehow curved, the signal tends to attenuate at the horizons of mountains and buildings. This means that, repeater stations have to be built on raised areas in order to receive, amplify, and propagate the signal from one area to another. Note. The range of VHF is limited, however, it is preferred to HF because; it is possible to make a VHF wave follow a narrower & more direct path to the receiver. Ultra-High frequency (UHF) radio wavesThe UHF radiowaves use the line of sight principle used by the VHF waves. This means that, there should be no barrier between the sending & the receiving aerial. However, they require smaller aerials. For example;The Television aerial for VHF is bigger than the one for UHF radio waves. This is because; UHF radio waves can be made to follow a narrower & a more direct path to the receiver than VHF radio waves. The Bluetooth technologyThis is a worldwide and short range radio transmission technology that allows all personal, hand-held devices to be able to communicate with each other through wireless technology. It enables people to use hand-held communication devices such as mobile phones & Personal Digital Assistants (PDA’s) to access the Internet. The main component in Bluetooth is a small low power two-way radio transceiver, which can be inserted in small devices. Bluetooth enabled devices use a network called the Wireless personal area network (WPAN) or piconet. Infrared transmissionCommunication through infrared waves (signals) is achieved by having infrared transmitters & receivers (transceivers) within a line of sight in the same room. This is because; infrared signals cannot penetrate obstacles like walls and ceilings. However, the signal can be reflected off these surfaces until they reach their destination. For example;Most mobile phones have an infrared transceiver. Once activated, two people in the same room can send messages to each other on their mobile phones without going through the mobile service provider; hence avoid being charged. In computer networking environment, infrared technology can be used to connect devices in the same room to each other without the need for cables, e.g., a computer and a printer. However, the computer’s infrared transceiver must maintain a line of sight with the one for the printer. Advantages of wireless communication.
Disadvantages of wireless communication.
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