CSCD 218 : DATA COMMUNICATIONS AND NETWORKING 1 LECTURE 4 INTRODUCTION AND BASIC CONCEPTS TRANSMISSION MEDIA AND TRANSMISSION TECHNOLOGIES LECTURER : FERDINAND KATSRIKU (PhD)

TRANSMISSSION MEDIA  Refers to the physical pathways that connect computers, other devices, and people on a network—the highways and byways that comprise the information superhighway.

CLASSIFICATION OF TRANSMISSSION MEDIA  Guided Media (Wired) –Twisted-Pair Cable –Coaxial Cable –Fiber-Optic Cable  Unguided Media (Wireless) –Radio Waves –Microwaves –Infrared

CLASSIFICATION OF TRANSMISSSION MEDIA

TRANSMISSION MEDIA CHARACTERISTICS  Cost  Installation requirements  Bandwidth  Band Usage – Baseband : Devotes the entire capacity of the medium to one communication channel. Mostly used in LANs – Broadband : Enables two or more communicating channels to share the bandwidth of the medium. Eg;TV  Attenuation  Immunity from electromagnetic interference

Cable Media – Primary cable types  Three main types : Coaxial cableTwisted-Pair cable Fibre-Optic cable Coaxial cable, Twisted-Pair cable and Fibre-Optic cable The Coaxial Cable

Cable Media – Primary cable types The Coaxial Cable

Types of Coaxial Cable Types of Coaxial Cable  Two main types : The thinnet and the thicknet The Thinnet A light and flexible cabling medium that is inexpensive and very easy to install. It can reliably transmit a signal for 185metres(about 610 feet). The Thicknet Thicker than thinnet. It is harder to work with compared to the thinnet. It can transmit a signal approximately 500metres (1,650 feet) Connectors for Coaxial Cables Coaxial cables are used on bus topologies and the most common connector used for coaxial cables is the British Naval Connector (BNC).A BNC T-connector connects the network board in the PC to the network.

BNC Connectors

 BNC = Bayone-Neill- Concelman  BNC Connector is used to connect the end of the cable to a device  BNC T is used in networks to branch out a cable for connection to a computer or other device  BNC Terminator is used at the end of the cable to prevent the reflection of signal.

Twisted – Pair Cable

One of the wires carries signal, the other is used only as a ground reference. The receiver uses the difference b/w the two levels. Twisting increases the probability that both wires are effected by the noise in the same manner, thus the difference at the receiver remains same. Therefore, number of twists per unit length determines the quality of the cable.

Twisted Pair - Transmission Characteristics analog – needs amplifiers every 5km to 6km digital – can use either analog or digital signals – needs a repeater every 2-3km limited distance limited bandwidth (1MHz) limited data rate (100MHz) susceptible to interference and noise

Unshielded vrs Shielded Twisted pair cable UTP and STP cables

Unshielded Twisted Pair (UTP) Ordinary telephone wire Cheapest Easiest to install Suffers from external EM interference

Shielded Twisted Pair (UTP) Metal braid or sheathing that reduces More expensive Harder to handle (thick, heavy)

Grades or Categories of UTP

Categories of UTP

Connectors of UTP Applications (UTP):  Telephone lines connecting subscribers to the central office  DSL lines  LAN – 10Base-T and 100Base-T Applications (STP): Most common medium Telephone network Within buildings For local area networks (LAN)

Fibre – Optic Cable