the wireless revolution, and communication systems

1. 1
Lecture 1: Introduction
SEN 713 Comp Comm. &
Network
Dr. Ibrahim A. S.

2. Learning objectives
 learning about computer network organization
and implementation, obtaining a theoretical
understanding of data communication and
computer networks.
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Dr. Ibrahim A. S.

3. Course Outline
 Discuss connectivity, the wireless revolution,
and communication systems
 Describe physical and wireless communications
channels
 Discuss connection devices, and services
including dial-up, DSL, cable, satellite and
cellular.
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Dr. Ibrahim A. S.

4. 4
1.0 Technology Revolution
• 18th Century Mechanical systems
• 19th Century Steam Engine
• 20th Century Information
- gathering
- distribution
- processing
- creating
Dr. Ibrahim A. S.

5. 5
Communications
The process of sharing data, programs, and
information between two or more computers
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6. 6
Communications Today
Numerous applications depend on communication
systems—E-mail, Instant messaging (IM), Internet
telephone, and Electronic commerce
Connectivity uses computer networks to link people
and resources
Going wireless has been the most dramatic change
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7. 7
Communication Systems
Four basic elements
 Message
 Sending and receiving devices
 Communication channel
 Connection devices (medium)
 Data transmission specifications (protocol)
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8. Fundamental Characteristics
 The effectiveness of a data communication
system depend on four fundamental
characteristics:
 Delivery
 Accuracy
 Timelines
 Jitter

9. 9
Communication Channels/
o Communication channels also called transmission media carry data from one computer to another.
o Two categories of communication channels
 Physical connection (Guided)
 Wireless connection (Unguided)
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10. Guided media
 Guided transmission media are more commonly known
as the wired communication or bounded transmission
media.
 The electromagnetic signals travel between the
communicating devices through a physical
medium/conductor.
 As the medium for transmission is a physical conductor,
it also provides direction to the signal.
Dr. Ibrahim A. S.
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11. 11
Physical Connections
 Example of the physical connection media/guided media
 Telephone lines – Rj 15
 Twisted pair cables – Rj 45
 Coaxial cable
 Fiber-optic cable
Dr. Ibrahim A. S.

12. Unguided media
 The unguided media is also called wireless
communication.
 It does not require any physical medium to transmit
electromagnetic signals.
 In unguided media, the electromagnetic signals are
broadcasted through air to everyone.
 These signals are available to one who has the device
capable of receiving those signal.
Dr. Ibrahim A. S.
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13. 13
Wireless Connections
Infrared
Broadcast radio
 Wi-FI (wireless
fidelity) 802.11
Microwave
 Stations
 Bluetooth
Satellite
 GPS
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Microwave dish
GPS
Satellite

14. Description of Communication
channel/media
S/N Transmission media Description
1 Twisted pair cable (Rj15 &
Rj45)
Copper wires e.g standard telephone lines
2 Coaxial cable Solid copper wire more than 80 times the
capacity of twisted pair cable
3 Fiber optic cable Made of glass thread. Light carries data more
26,000 times the capacity of twisted pair cable
4 Infrared Short range signal. Infrared light carried data
and travels in a straight line
5 Bluetooth Short range wireless signal using UHF radio
waves, from 2.402 GHz to 2.480 GHz
6 Broadcast radio Radio waves used by cellular phones and other
wireless devices. Usually travel long distance
7 Microwave Uses antenna and satellite. High frequency
radio waves that moves in straight line
Dr. Ibrahim A. S.
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15. Comparison of Communication
media
 The key difference between guided and unguided media
is that guided media uses a physical path or conductor to
transmit the signals whereas, the unguided media
broadcast the signal through the air.
 The guided media is also called wired communication or
bounded transmission media. However, the unguided
media is also called wireless communication or
unbounded transmission media.
 The guided media provide direction to the signal
whereas, the unguided media does not direct the signal.
 Categories of guided media are twisted pair cable,
coaxial cable and optical fibre. On the other hands, the
categories of unguided media are radio wave, microwave,
and infrared signal.
Dr. Ibrahim A. S.
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16. 16
◆ A set of communication elements connected
by communication links
➭ Communication elements
● Computers, printers, mobile phones, …
● Routers, switches, ...
➭ Communication links
● optic fiber
● coaxial cable
● twisted pair
● wireless (radio, microwave, satellite)
➭ Topologies
● Ring, Star, Bus, Tree, Mesh
What is a Computer Network
local ISP
company
network
regional ISP
router
workstation
server
mobile
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17. 17
◆ A software/hardware infrastructure
➭ Share resources
● data, files, computing power, video,…
➭ Information highway
● communication between geographically dispersed users
➭ Electronic Society
● Cyberspace
● Virtual global nation
What is a Computer Network
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18. 18
Computer Networks
 A computer network is a communication system
 Connects two or more computers
 Network provides “connectivity”
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19. What is “Connectivity” ?
 Direct or indirect access to every other node in the
network
 Connectivity is the magic needed to communicate
if you do not have a direct pt-pt physical link.
 Allows information exchange
 Potential of networking:
 move bits everywhere, cheaply, and with desired
performance characteristics
 Tradeoff: Performance characteristics worse than true physical link!

20. 20
Computer Networks
Common network terms
• Node
• Client
• Server
• Hub
• Network interface cards (NIC)
• Network operating system
(NOS)
• Distributed processing
• Host computer
• Network administrator
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Computer Networks Connect Computers
Dr. Ibrahim A. S.

21.  Other important networks include the voice telephone
 network and the cable TV network used to
disseminate video signals.
 The main things these networks have in common are
that they are specialized to handle one particular kind
of data (keystrokes, voice, or video) and
 they typically connect to special-purpose devices
 (terminals, hand receivers, and television sets).
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Dr. Ibrahim A. S.

22.  What distinguishes a computer network from these other types
of networks?
 Probably the most important characteristic of a computer
network is its generality.
 Computer networks are built primarily from general-purpose
programmable hardware, and
 they are not optimized for a particular application like making
phone calls or delivering television signals.
 Instead, they are able to carry many different types of data, and
they support a wide, and ever growing, range of applications
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Dr. Ibrahim A. S.

23. 23
 Computer Network
– an interconnected collection of autonomous
computers
Internet: “network of networks”
– loosely hierarchical
– public Internet versus private intranet
WWW a distributed systems run on the top of Internet
 Distributed System
– High degree of cohesiveness and transparency
– A software system built on top of a network
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24. 24
Uses of Computer Networks
• Business Applications
• Home Applications
• Mobile Users
• Social Issues
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25. 25
Business Applications of
Networks
a. Resource sharing (hardware, software, information, …)
b. Providing communication medium (e-mail, video
conferenceing)
c. Doing business electronically (B2B, B2C, e-commerce)
 A network with two clients and one server.
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26. 26
Business Applications of Networks (2)
a. Two processes are involved
b. A communication network is needed
 The client-server model involves requests and
replies.
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27. 27
Goals of Networks for Companies
 Resource sharing: equipment, programs, data
 high reliability
– replicated data
– hardware
 Saving money
– mainframe: 10 times faster, but 1000 times more
expensive than PC
– client-server model
 Scalability
– mainframe: replace a larger one
– client-server model: add more servers
 Communication medium for separated employees
Dr. Ibrahim A. S.

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Home Network Applications
• Access to remote information
• Person-to-person communication
• Interactive entertainment
• Electronic commerce
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Home Network Applications (2)
 In peer-to-peer system there are no fixed clients
and servers.
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30. 30
Home Network Applications (3)
 Some forms of e-commerce.
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 Networks for People
– Access to remote information
• e.g.: financial, shopping, customized newspapers,
on-line digital library, WWW
– Person-to-person communication
• email, video conference, newsgroup
– Interactive entertainment
• VOD, interactive movies or TVs, game playing
Dr. Ibrahim A. S.

32. Summary
 Data communication is the process of sharing data,
programs, and information between two or more
computers.
 Data communication rely on connectivity.
 Connectivity uses computer networks to link
people and resources.
 Computer network is a set of communication
elements connected by communication links.
 Computer network is used for various purposes
such as business, home, office, e.t.c.
Dr. Ibrahim A. S.
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34. Review Questions
Dr. Ibrahim A. S.
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