Communication channels refer to the medium used for sending and receiving information in a computer network. Some of the important and commonly used communication channels are twisted pair cable, Co-axial cable, Fiber optic cable, Wireless links.
TWISTED PAIR CABLE
Set of four pairs of insulated copper wires twisted around one another. These are of two types – Shielded Twisted Pair (STP) cables and Unshielded Twisted Pair (UTP) cables. Shielding twisted pair (STP) cable has a protective shielding whereas unshielded twisted pair (UTP) cable doesn’t have any shielding. Twists reduce the electromagnetic interference from adjacent pairs and other electrical devices.
Shielded twisted pair cables are heavier than UTPs because of the extra shielding and are used in ring topology networks. As compared to UTP, STP (Shielded Twisted Pair) has less electromagnetic interference. Twisted cables are used in Local Area Network and may cause errors due to electromagnetic interference.
Consists of two conductors with a thick conducting core at the center an insulator surrounds the core followed by a conducting wire mesh over the insulator. The wired mesh is finally surrounded by a protective jacket.
These types of cables are heavier than a twisted pair cable and are used in bus topology in LANs. The performance of a Co-axial cable is better than a Twisted Pair cable as its conducting quality and shielding are better. They are immune to electromagnetic interference.
FIBER OPTIC CABLE
In Fiber optic, the fiber core of plastic or glass at the center is covered by a cladding of lower refractive index. There is a total internal reflection between glasses and cladding so the minimum loss of data is the key feature. Hence, fiber optic cables are the best option for reliable and quick communication across large distances. Some very bib service providers like MTNL use fiber optic cables in their network. Fiber optic cables can carry huge amounts of data as they support a transfer rate of 1000 megabits/second.
Wireless links use air as a communication medium for data transfer. The laying of cables can sometimes be very difficult, especially across mountains and rivers. Wireless links are used very effectively at such locations. satellite communications Wireless links include cellular communications, microwave.
Wireless communication is also used in office LENs. cost-effective Wireless links typically cover large geographic areas. Frequencies below 1000 MHz are known as Radio wave frequencies whereas frequencies more than 1000 MHz are called Microwave frequencies. Satellite transmission uses the frequency range of 4-12 GHz.
There are a number of satellites that move in stationary orbit at about 22,300 miles above the earth’s surface. The function of a satellite is to receive the signal from one earth station and transfer it to another earth station, located at a distance. Satellite communication gives maximum geographical coverage around the globe.