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Modern Telecommunication Networks

Syed A. Rizvi

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Introduction

� Most modern telecommunication systems transfer information in digital format.

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Introduction (Continued)

� The information may consist of voice, video, computer data, etc.

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Essential Components

� Essential components of a modern communication system include:

1. Computers (for information processing)2. Input/output devices to send or receive data

� Input devices: keyboard, microphone, video camera, computer storage devices, etc.

� Output devices: display, printer, speakers, storage media

3. Communication channels: � telephone lines, coaxial cable, fiber optic cable, wireless

links etc.

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Essential Comp….(Continued)

4. Supporting hardware to connect heterogeneous subnetworks:� Modems, multiplexers, routers, etc.

5. Communications software

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Communication Channels

1. Twisted wires:� The oldest transmission medium� Low cost� Relatively slow for data transmission

2. Coaxial Cable:� Consists of thickly insulated copper wire� Can transmit larger amount of data� Faster than twisted wire

3. Fiber Optics Cables:1. Consists of thousands of strands of clear glass

fiber

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Communication Channels (Continued)

2. Thickness of the glass fiber is as small as the thickness of a human hair

3. Data is transmitted into pulses of light4. More suitable for providing high-speed backbone

network� Advantages:

1. Lighter and more durable that coaxial cable and twisted wire

2. Can handle a very large volume of data

� Disadvantages:1. Difficult to work with2. Relatively expensive

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Communication Channels (Continued)

1. Wireless links:� Data (information) is transmitted through

atmosphere via electro-magnetic waves

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Network Topologies

� Star Topology:

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Network Topologies: Star

� All computers in a star network are connected to each other through a host computer

� Host computer directs the incoming messages to the correct destination computer

� If the host computer goes down it affects the operation of whole star network

� Individual computer can be brought down for maintenance or removed without affecting the rest of the star network

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Network Topologies (Continued)

� Bus network:

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Network Topologies: Bus

� All computers are connected through a common line (could be a twisted wire, coaxial cable, fiber optics cable etc.)

� Each message is broadcasted in both directions to the entire network

� If a computer goes down, it does not affect the rest of the network

� Bus network handles one message at a time� If two or more computers send messages

simultaneously a collision occurs, the messages must be re-sent

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Network Topologies (Continued)

� Token Ring Network:

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Network Topologies: Token Ring

� In a ring network, computers are connected via a closed loop wired connection

� Data is transmitted in one direction � A token is passed through the ring and any

computer in need of transmitting the data holds the token and starts transmitting the message

� The computer with the delivery address receives the data

� When the message arrives at the source computer it signals the completion of the transmission

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Network Topologies: Token Ring

� The computer holding the token then passes the token to the next computer

� If the next computer needs to send the data it will hold the token and start transmitting the message; otherwise, it will pass the token to the next computer

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Local Area Network (LAN)

� Local area network covers a limited area such as a building or a few buildings in a close proximity

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LAN (Continued)

� LAN generally use Bus or Ring topology� Usually connects computer and related equipment

with in 2000 feet radius� Often used to connect PCs/workstation to shared

printers and file-servers etc.� A special computer known as network gateway

connects the LAN to other networks� Both wired and wireless LAN technologies are

available � Wide area networks (WAN) span a large

geographical area and contain thousands of LANs and other heterogeneous networks in an entire continents

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Enterprise Networking

� An enterprise network connects PCs, workstations, NCs, LANs, and other organization-wide computing resources together as well as to Internet