On any network, the various entities must communicate through some form of media.
Just as human scan communicate through telephone wires or sound waves in the air, computers can communicate through cables, light, and radio waves.
Transmission media enables computers to send and receive messages but do not guarantee that the messages will be understood.
Communication is possible only if information is encoded in a signal, and the signal is carried on a transmission ,the characteristics of the signal and of the medium both determine the quality of the communication medium. There are two main groups of transmission media, namely the guided medium and the wireless medium. 3 ILLUMINATI
For the guided medium, there is a physical path (such as a cable) for electromagnetic wave propagation. For the wireless medium, however, the electromagnetic wave is transmitted through air, water, or vacuum. A wireless medium is also called an unguided medium. 4 ILLUMINATI
CHARACTERISTICS A good transmission medium should provide communication with good quality at long distance. For voice communication, quality of communication is determined by the voice quality. For data communication, however, the quality of communication is mainly determined by the effective data rate of communication. 5 ILLUMINATI
FACTORS AFFECTING DATA COMMUNICATION DISTANCE OF A MEDIUM Communication bandwidth of the medium Interference The transmission impairments 6 ILLUMINATI
The bandwidth of a medium determines the signal frequencies that can be carried in the medium. A wide bandwidth, or broadband, usually allows communication at a higher data rate. 7 ILLUMINATI
Attenuation Distortion during signal propagation Noises. REASONS FOR TRANSMISSION IMPAIRENCE 8 ILLUMINATI
TYPES ofTRANSMISSION MEDIA 9 ILLUMINATI
Guided Media Guided media includes everything that ‘guides’ the transmission. That usually takes the form of some sort of a wire. Usually copper, but can also be optical fibre. 11 ILLUMINATI
Twisted Pair Cable
A transmission medium consisting of pairs of twisted copper wires.
We can transmit 1 Mbps over short distances (less than 100m).
They are mainly used to transmit analog signals, but they can be used for digital signals.
Twisted Pair Cable 13 ILLUMINATI
In its simplest form, coaxial consists of a core made of solid copper surrounded by insulation, a braided metal shielding, and an outer cover.
A transmission medium consisting of thickly insulated copper wire, which can transmit a large volume of data than twisted wire.
Coaxial Cable 15 ILLUMINATI
Optical fiber consists of a glass core, surrounded by a glass cladding with slightly lower refractive index.
In most networks fiber-optic cable is used as the high-speed backbone, and twisted wire and coaxial cable are used to connect the backbone to individual devices.
Optical Fiber 17 ILLUMINATI
Unguided Media Unguided media is still ‘media’ (stuff that signal travels though). The trick is that the media is usually not directional, like air, space, etc. Because the effect is usually much wider than with guided media, there have been a lot of regulation, licensing, and standardization of transmissions via unguided media. 18 ILLUMINATI
Wireless transmission that sends signals through air or space without any physical wire.
Common uses of wireless data transmission include pagers, cellular telephones, microwave transmissions, communication satellites, mobile data networks, personal digital assistants, television remote controls.
SOME BASIC DIFFERENCES
It is inexpensive and already is in use. Twisted wires are slow, high-speed transmission causes interference (crosstalk). Limiting factors: skin effect & radiation effect. Twisted Wire 21 ILLUMINATI
It is often used in place of twisted wire for important links in a network because it is a faster. More interference-free transmission medium (speed: 200 megabits per second). Coaxial cable is thick, is hard to wire in many buildings. It does not support analog conversations. Coaxial Cable 22 ILLUMINATI
Optical fibers are faster, lighter, and suitable for transferring large amount of data. Fiber-optic cable is more difficult to work with, more expensive. Its difficult to install them. Optical Fiber 23 ILLUMINATI
Optical fiber cable differs from both these transmission media in that it carries the transmitted information in the form of a fluctuating beam of light in a glass fiber.
Light transmission has much wider bandwidth, thus enabling the transmission rate of hundreds of megabits per second.
Comparison 24 ILLUMINATI
Optical transmission is immune to electromagnetic interference and crosstalk. While others are immune to interference.
Optical fibers have less loss of signal strength than copper, after every 30 miles we need to use a repeater, whereas in copper, we should insert repeaters at an interval of 2.8 miles .
Optical fiber is more secure, no easy tapping on the cable, like in copper.
But optical fibers are more expensive than other two cables.
Bandwidth: The difference between the lowest and highest frequency signals that can be transmitted across a transmission line or communication system. Interference: The distortion on the signal in transmission due to unwanted signals from outside sources. KEY Terms 26 ILLUMINATI
Transmission Impairments: Attenuation, distortion, or noises that will degrade the signal quality during transmission. Attenuation: The loss of a signal’s energy when the signal is transmitted across a medium. Signal Distortion: Any change in a signal during signal transmission. 27 ILLUMINATI
Noises: Random signals that can be picked up during signal transmission and result in degradation or distortion of data. Trunk Circuits: The communication circuits between two switching offices. 28 ILLUMINATI
In summary, transmission media are essential for communication systems. Signals that carry information can be transmitted on a transmission medium for communication purposes. The transmission characteristics of the medium in use are important because they directly affect the communication quality. Since different types of transmission media have different transmission characteristics and costs, they are used in different (and the most suited) applications. Conclusion 29 ILLUMINATI