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Transcript
CSC 242
Introduction to
Telecommunications Systems
Lecture # 1
Dr. Ehsan Munir
Department of Computer Science
COMSATS Institute of Information Technology
What is Communication


When we communicate we share
information
Local Communication


Face to face
Remote Communication

Over distance
2
DATA COMMUNICATIONS
Data communications are the exchange of data between
two devices via some form of transmission medium such
as a wire cable. The word data refers to information
presented in whatever form is agreed upon by the parties
creating and using the data.
3
Data Communication System

For data communication to occur,
communicating devices must be a part
of a system made up of some specific
kind of hardware and software. This
system is known as “DC System”
4
DC System Components





Message
Sender
Receiver
Transmission Medium
Protocol
5
Figure Five components of data communication
6
Factors Effecting DC System

Delivery


Accuracy


Deliver data accurately
Timeliness


Deliver data to correct destination
Deliver data in a timely manner
Jitter

Variation in packet arrival time
7
Figure Data flow (simplex, half-duplex, and full-duplex)
8
Data Flow

Simplex


Half duplex


Transmission in one direction. Example Television
Either direction, but only one way at a time.
Example Walkie-talkies
Full duplex

Both directions at the same time. Example
Phones.
9
What is Telecommunication




Tele is Greek word, meaning “far off”
Webster calls it communications at a
distance
The IEEE Standard Dictionary defines
telecommunications as the transmission
of signals over long distance,
Science of communicating over distance
10
Networks




A network is a set of devices (nodes)
connected by communication links.
A node can be a computer, printer, or any
other device capable of sending and/or
receiving data generated by other nodes on
the network.
A link is a communication pathway that
transfers data from one device to another
Topology: Arrangement of nodes in a network
specify topology.
11
Figure Types of connections: point-to-point and multipoint
12
Network Criteria

Performance



Reliability


Throughput: Number of bits transmitted in one
second
Delay: How long it takes a bit of data to travel in
network
Robustness : ability of the network to perform its
function in the face of attack (node failure)
Security


Unauthorized access
viruses
13
Categories of topology
14
Figure A bus topology connecting three stations
15
Bus Topology




Single cable connect all computers
Each computer has connector to shared cable
Cable must end with a terminator
Advantages




Ease of installation
Inexpensive
Works well for small networks
Disadvantages


Cable break, whole network down
Limited number of devices can be attached
16
Figure A star topology connecting four stations
17
Star Topology



All computers attach to central point
The devices are not directly linked to one
another
Advantages




Ease of installation
Inexpensive (less than mesh)
Robustness
Disadvantages


Hub fails, whole network down
Costly than bus
18
Figure A fully connected mesh topology (five devices)
19
Mesh Topology


Each device connected to every other device
Advantages



Robustness
Can carry more data
Disadvantages



Expensive
Difficult to install
Difficult to manage
20
Figure A ring topology connecting six stations
21
Ring Topology



Each device connected to two devices
(immediate neighbors)
The signal is passed along the ring in one
direction
Advantages



Easy to install and reconfigure
Inexpensive (less than mesh)
Disadvantages


Break in a ring disables the whole network
Unidirectional
22
Figure A hybrid topology: a star backbone with three bus networks
23
Types of Networks

Local Area Network (LAN)


Wide Area Network (WAN)


Links the nodes in a single office, building or
campus
Links the nodes in states, countries or in the
whole world
Metropolitan Area Network (MAN)


Between LAN and WAN
Links the nodes in a town or city
24
Protocols

Protocol defines:




What is communicated
How, it is communicated
When, it is communicated
Elements of a protocol



Syntax
Semantics
Timing
25
Standards


A standard provides a model for
development that makes it possible for
a product to work regardless of the
individual manufacturer
Standards are essential in:


Creating/Maintaining open and competitive
market
Guaranteeing National/International
Interoperability
26