CLASS 1.pptx

DEPARTMENT OF COMPUTER ENGINEERING
UNIVERSITY OF GHANA
DATA COMMUNICATION/FUNDAMENTALS OF
INFORMATION TRANSMISSION

 History and overview of information transmission
 Building blocks of a telecommunication systems
 Data communication
 Data communication and networks
 Reasons for studying data transmission
 Modern trends in telecommunication technology for data transmission
 The internet
GENERAL INTRODUCTION

HISTORY AND OVERVIEW OF INFORMATION TRANSMISSION
Communication and networks were developed in the pre-industrial age. These systems
transmitted information over line-of-sight distances using smoke signals, torch signaling,
flashing mirrors, signal flares, or semaphore flags.
The modulator was the hand of the sender and the detector was the eye of the receiver.
The processor was the brain of the receiver.
Figure 1: Early forms of wireless communications. (a) Smoke signals (b) semaphore (c) heliograph (d) drums
Properties of early optical
communications systems:
 Slow data rate
 Poor integrity
 High error rate

The first form of telecommunications was the Telegraph, which was invented in 1837 by
Morse.
Alexander Graham Bell invented the telephone in 1876. Soon afterward, the World’s first
telephone exchange was opened in 1878 in New Haven, Connecticut, USA.
Since then, telephony has become the universal means of communicating for humankind.
In 1935, Edwin Armstrong demonstrated frequency modulation (FM) for the first time, and
since the late 1930s, FM has been the primary modulation technique used for mobile
communication systems throughout the world.
HISTORY AND OVERVIEW OF INFORMATION TRANSMISSION

BUILDING BLOCKS OF TELECOMMUNICATION SYSTEMS
Communication is the activity of conveying information through the exchange of thoughts,
messages, or information, as by speech, visuals, signals, writing, or behavior.
Communication requires a sender, a message, and a recipient. The communication process is
complete once the receiver has understood the message of the sender.
Communication theory is a field of information and mathematics that studies the
technical process of information and human process of human communication. It studies
the principle of transmitting information and the methods by which it is delivered.
The basic elements of a communication system are source, transmitter, channel, receiver,
and destination.

BASIC ELEMENTS OF COMMUNICATION
Basic elements of communication in communication theory are:
Information source: “Produces a message or sequence of messages to be communicated to the
receiving terminal”.
Sender(transmitter): “Operates on the message in some way to produce a signal suitable for
transmission over the channel”.
Channel: “A medium used to transmit the signal from transmitter to receiver.
Receiver: “Performs the inverse operation of that done by the transmitter, reconstructing the
message from the signal”.
Destination: “The person (or thing) for whom the message is intended.

Input
transducer
Transmitter Channel
Distortion
and noise
Receiver
Output
transducer
Input message Input signal Transmitted signal
Received signal
Output signal
Output message
Electrical or
nonelectrical,
such as a human
voice, a
television picture
or data.
Converting the
nonelectrical
message into an
electrical
waveform.
Referred to as
the baseband
signal or
message signal.
Modifying the
input signal for
efficient
transmission.
A medium,
such as a
wire, a radio
link.
Undoing the signal
modifications made
at the transmitter
and the channel.
Converting the
electrical signal
to its original
form.
The waveform is distorted because of
different amounts of attenuation and
phase shift suffered by different
frequency components.
Noise are random
and unpredictable
signals from causes
external and
internal.
The transmitter consists of one or more
of the following subsystems: a pre-
emphasizer, a sampler, a quantizer, a
coder and a modulator.
The receiver may consist of a
demodulator, a decoder, a filter and a
de-emphasizer.
Influence of noise on
various modulation
methods
BUILDING BLOCKS OF TELECOMMUNICATION SYSTEMS
Figure 2: Building blocks of
Telecom. Systems

SIMPLIFIED DATA COMMUNICATIONS MODEL
m(t)
t
m
g(t)
t
g
t
r
t
s
t
g
t
m
ing
approximat
signal
ted
reconstruc
:
)
(
~
ing
approximat
signal
d
demodulate
:
)
(
~
frequency)
(shifted
channel
in the
corrupted
signal
modulated
:
)
(
frequency)
(shifted
ed
transmitt
be
to
signal
modulated
:
)
(
(baseband)
modulated
be
n to
informatio
processed
:
)
(
(baseband)
source
by
sent
be
n to
informatio
:
)
(
Figure 3: Simplified Data Communications Model

SIGNALANALYSIS
 Signal analyses and processing may be thought of as letting signals through systems.
h(t)
f(t) y(t)
From f(t) and h(t), find y(t), Signal processing
From f(t) and y(t), find h(t), System design
From y(t) and h(t), find f(t), Signal reconstruction
f(t) – Input signal
h(t)- System processor
y(t)- Output signal

DATA COMMUNICATIONS
 Data refers to information presented in whatever form as agreed upon by the parties creating
and using the data.
 Data communications are the exchange of data between two devices via some form of
transmission medium such as a wire cable.
 Data and information from one computer system can be transmitted to other systems across
geographical areas.
 For data communications to occur, the communicating devices must be part of a
communication system made up of a combination of hardware (physical equipment) and
software (programs).
 A data communications system has five components: Message, Sender, Receiver, Transmission
medium, and Protocol.

 The effectiveness of data communication depends on:
 Delivery: The system must deliver data to the correct destination. Data must be received by
only the intended device or user.
 Accuracy: the system must deliver data accurately
 Timelines: the system must deliver data in a timely manner. Data delivered later are useless.
 Jitter: variation in the packet arrival time. It is the uneven delay in the delivery of audio or
video packets.
EFFECTIVENESS OF DATA COMMUNICATION

DATA COMMUNICATION CIRCUITS
The underlying purpose of a digital communications circuit is to provide a transmission path
between locations and to transfer digital information from one station (node, where computers
or other digital equipment are located) to another using electronic circuits.
Data communications circuits utilize electronic communications equipment and facilities to
interconnect digital computer equipment.
Communication facilities are physical means of interconnecting stations and are provided to
data communications users through public telephone networks (PTN), public data networks
(PDN), and a multitude of private data communications systems.
Figure 4: Data Communication Circuits

Transmitter: A transmitter transforms and encodes the information in such a way as to produce
electromagnetic signals that can be transmitted across some sort of transmission system. For
example, a modem takes a digital bit stream from an attached device such as a personal
computer and transforms that bit stream into an analog signal that can be handled by the
telephone network.
Transmission medium: The transmission medium carries the encoded signals from the
transmitter to the receiver. Different types of transmission media include free-space radio
transmission (i.e. all forms of wireless transmission) and physical facilities such as metallic and
optical fiber cables.
Receiver: The receiver accepts the signal from the transmission medium and converts it into a
form that can be handled by the destination device. For example, a modem will accept an
analog signal coming from a network or transmission line and convert it into a digital bit
stream.
Destination: Takes the incoming data from the receiver and can be any kind of digital
equipment like the source.
DATA COMMUNICATION CIRCUITS

Antennas are our electronic eyes and ears in the world. Antennas are a very important
component of communication systems. An antenna is an electrical conductor or a system of
conductors that radiates/collects (transmits or receives) electromagnetic energy into/from space.
OR
 An antenna is a device that provides a transition between guided electromagnetic waves in
wires and electromagnetic waves in free space. An antenna can be a length of wire, a metal rod,
or a piece of metal tubing. Antennas radiate most effectively when their length is directly
related to the wavelength of the transmitted signal.
OR
 An antenna converts the guided waves present in a waveguide, feeder cable, or transmission
line into radiating waves traveling in free space, or vice versa. It is a passive structure that
serves as a transition between a transmission line and air used to transmit and/or receive
electromagnetic waves. It is a transducer that interfaces a circuit and free-space
BASIC ANTENNA

BASIC ANTENNA
 Only accelerated (or decelerated)
charges radiate EM waves. A current
with a time-harmonic variation (AC)
satisfies this requirement.
 They are used in systems such as:
 radio broadcasting
 broadcast television
 Radar
 cell phones
 satellite communications
 garage door openers
 wireless microphones
 blue-tooth-enabled devices
 RFID tags on merchandise, etc.
Figure 5: Transmitter and Receiver Antenna

 Radiation Patterns: A radiation pattern is a graphical representation of the radiation
properties of an antenna.
 An idealized isotropic antenna radiates equally in all directions. Power from an isotropic point
source is equally distributed in all directions. It is completely unfocused. The isotropic antenna
is a theoretical reference antenna.
 The directivity of an antenna is captured by its beam width; it is the angle within which power
radiated is at least half of that in the most preferred direction.
BASIC ANTENNA

Wire antennas: Dipole, monopole, loop
antenna, helix antennas:- Usually used in
personal applications, automobiles, buildings,
ships, aircraft, and spacecraft.
TYPES OF ANTENNAS
Aperture antennas:
Horn antennas, waveguide opening:- Usually used
in aircraft and space crafts, because these
antennas can be flush.
Reflector antennas: Parabolic reflectors, and
corner reflectors:- These are high-gain
antennas usually used in radio astronomy,
microwave communication, and satellite
tracking.
Lens antennas: Convex-plane, convex-
convex, convex-concave, and concave-
plane lenses. These antennas are
usually used for very high frequency
applications.
Array antennas: Yagi-Uda antenna, microstrip
patch array, aperture array, slotted waveguide
array :- Used for very high gain applications with
added advantage, such as controllable radiation
pattern.
Microstrip antennas: Rectangular, circular, etc.
shaped metallic patch above a ground plane:- Used
in aircraft, spacecraft, satellites, missiles, cars,
mobile phones, etc.

WAVELENGTH AND ANTENNAS
 The dimensions of an antenna are usually expressed in terms of wavelength .
• Low frequencies imply long wavelengths, hence low-frequency antennas are very large.
• High frequencies imply short wavelengths, hence high-frequency antennas are usually small.
 You may recall from physics that the wavelength and frequency of an electromagnetic wave in
free space are related to the speed of light.
 Calculate the wavelength of the signal if a radio station is broadcasting at a frequency of 100
MHz.

The ability of an antenna to focus electromagnetic energy is defined by its gain. Antenna gain is
the power output, in a particular direction, compared to that produced in any direction by an
idealized omnidirectional (isometric) antenna. If f is the carrier frequency and Ae is the
effective area of the antenna, then the antenna gain is given by:
Antenna gain is expressed as a ratio of the effective radiated output power (Pout) to the input
power (Pin)
The gain of an antenna is a measure of power transmitted relative to that transmitted by an
isometric source
Antenna gain relative to an isotropic source is expressed in decibels as dBi.
ANTENNA GAIN

DATA COMMUNICATION AND NETWORKS
 Any group of computers connected together can be called a data communications network, and
the process of sharing resources between computers over a data communications network is
called networking.
 The most important considerations of a data communications network are performance,
transmission rate, reliability, and security.
 The major components of a network are end stations, applications, and a network that will
support traffic between the end stations.
 Computer networks all share common devices, functions, and features, including servers,
clients, transmission media, shared data, shared printers and other peripherals, hardware and
software resources, network interface card (NIC), local operating system (LOS), and the
network operating system (NOS).

Servers: Servers are devices that hold shared files, programs, and the network operating
system. Servers provide access to network resources to all the users of the network. Examples
include file servers, print servers, mail servers, communication servers etc.
Clients: Clients are computers that access and use the network and shared network resources.
Client computers are basically the customers (users) of the network, as they request and receive
service from the servers.
Shared Data: Shared data are data that file servers provide to clients, such as data files, printer
access programs, and e-mail.
Shared Printers and other peripherals: these are hardware resources provided to the users of
the network by servers. Resources provided include data files, printers, software, or any other
items used by the clients on the network.
Network interface card: Every computer in the network has a special expansion card called a
network interface card (NIC), which prepares and sends data, receives data, and controls data
flow between the computer and the network. While transmitting, NIC passes frames of data
onto the physical layer and on the receiver side, the NIC processes bits received from the
physical layer and processes the message based on its contents.

 Local operating system: A local operating system allows personal computers to access files,
print to a local printer, and have and use one or more disk and CD drives that are located on the
computer. Examples are MS-DOS, PC-DOS, UNIX, Macintosh, OS/2, Windows 95, 98, XP,
and Linux.
 Network operating system (NOS): the NOS is a program that runs on computers and servers
that allows the computers to communicate over a network. The NOS provides services to
clients such as log-in features, password authentication, printer access, network administration
functions, and data file sharing.

NETWORK MODELS
 Computer networks can be represented with two basic network models: peer-to-peer
client/server and dedicated client/server. The client/server method specifies the way in which
two computers can communicate with software over a network.
Peer-to-peer client/server network:
Here, all the computers share their resources, such as hard drives, printers, and so on with all
the other computers on the network.
Individual resources like disk drives, CD-ROM drives, and even printers are transformed into
shared, collective resources that are accessible from every PC.
The information stored across the peer-to-peer network is uniquely decentralized. The peer-to-
peer network is an appropriate choice when there are fewer than 10 users on the network,
security is not an issue and all the users are located in the same general area.
 Advantages of a peer-to-peer network include:
 No need for a network administrator
 Network is inexpensive to set up and maintain
 Each PC can make backup copies of its data to other PCs for security.
 Easiest type of network to build

 Dedicated client/server network:
 Here, one computer is designated as a server and the rest of the computers are clients.
 Dedicated Server Architecture can improve the efficiency of client-server systems by using
one server for each application that exists within an organization.
 The designated servers store all the network shared files and applications programs and
function only as servers and are not used as a client or workstation.
 Client computers can access the servers and have shared files transferred to them over the
transmission medium. In general, the dedicated client/server model is preferable to the peer-
to-peer client/server model for general-purpose data networks.
NETWORK MODELS

NETWORK TOPOLOGIES
Topology refers to the layout of connected devices, i.e. how the computers, cables, and other
components within a data communications network are interconnected.
Physical topology describes how the network is actually laid out.
Logical topology describes how the data actually flow through the network.
Two most basic topologies are point-to-point and multipoint. A point-to-point topology usually
connects two mainframe computers for high-speed digital information. A multipoint topology
connects more stations through a single transmission medium. Examples are a star, bus, ring,
mesh, and hybrid.

NETWORK TOPOLOGIES-STAR TOPOLOGY
A star topology is designed with each node (workstations and peripherals) connected directly to
a central network hub or switch. Data on a star network passes through the hub or switch before
continuing to its destination. The hub or switch manages and controls all functions of the
network.
Advantages Disadvantages
Easily extended without
disruption to the network
Requires more cables
Cable failure affects only a
single user
A central connecting
device allows for a single
point of failure
Easy to troubleshoot and
isolate problems
More difficult to
implement Figure 5: Star Topology

Bus networks use a common backbone to connect all devices. A single cable, (the backbone)
functions as a shared communication medium that devices attach or tap into with an interface
connector. A device wanting to communicate with another device on the network sends a
broadcast message onto the wire that all other devices see, but only the intended recipient
actually accepts and processes the message. The bus topology is the simplest and most common
method of interconnecting computers. The two ends of the transmission line never touch to
form a complete loop. A bus topology is also known as a linear bus or a horizontal bus.
Cheap and easy to implement Network disruption when
computers are added or
removed
Requires less cable A break in the cable will
prevent all systems from
assessing the network
Does not use a specialized
network equipment
Difficult to troubleshoot
NETWORK TOPOLOGIES-BUS TOPOLOGY
Figure 6: Bus Topology

In a ring network (sometimes called a loop), every device has exactly two neighbors for
communication purposes. All messages travel through a ring in the same direction (either
"clockwise" or "counterclockwise"). All the stations are interconnected to form a closed loop or
circle. Transmissions are unidirectional and must propagate through all the stations in the loop.
Each computer acts like a repeater.
NETWORK TOPOLOGIES-RING TOPOLOGY
Cable faults are easily
located making
troubleshooting easier
Expansion to the network
can cause network
disruption
Ring networks are
moderately easy to install
A single break in the cable
can disrupt the entire
network
Figure 7: Ring Topology

The mesh topology incorporates a unique network design in which each computer on the
network connects to every other, creating a point-to-point connection between every device on
the network. Unlike each of the previous topologies, messages sent on a mesh network can take
any of several possible paths from source to destination. A mesh network in which every device
connects to every other is called a full mesh.
NETWORK TOPOLOGIES-MESH TOPOLOGY
Provides redundant paths
between devices
Requires more cables
than the other topologies
The network can be
explained without
disruption to current uses
Complicated
implementation
Figure 8: Mesh Topology

This topology is simply combining two or more of the traditional topologies to form a larger,
more complex topology. The main aim is to be able to share the advantages of different
topologies.
NETWORK TOPOLOGIES-HYBRID TOPOLOGY
Figure 9: Hybrid Topology

NETWORK CLASSIFICATIONS
 One way to categorize the different types of computer network designs is by their scope or
scale. Common examples of area network types are:
 Local Area Network (LAN)
 Wide Area Network (WAN)
 Metropolitan Area Network (MAN)
 Campus Area Network (CAN)
 Personal Area Network (PAN)

A local area network (LAN) is a network that connects computers and devices in a limited
geographical area such as a home, school, computer laboratory, office building, or closely
positioned group of buildings. LANs use a network operating system to provide two-way
communications at bit rates in the range of 10 Mbps to 100 Mbps. In addition to operating in a
limited space, LANs are also typically owned, controlled, and managed by a single person or
organization. They also tend to use certain connectivity technologies, primarily Ethernet and
Token Ring.
LOCALAREA NETWORK (LAN)
Advantages of LAN
 Share resources efficiently
 Individual workstation might survive network failure
if it doesn’t rely upon others
 Component evolution independent of system
evolution
 Supports heterogeneous hardware/software
 Access to other LANs and WANs
 High transfer rates with low error rates
Figure 10: Local Area Network

CHARACTERISTICS OF LAN
Every computer has the potential to communicate with any other computers of the network
High degree of connection between computers
Easy physical connection of computers in a network
Inexpensive medium of data transmission
High data transmission rate
Usually connected using Ethernet
USES OF LAN
 File transfers and Access
 Word and text processing
 Electronic message handling
 Remote database access
 Personal computing
 Digital voice transmission and storage

Wide area networks are the oldest type of data communications network that provide relatively
slow-speed, long-distance transmission of data, voice, and video information over relatively
large and widely dispersed geographical areas, such as countries or the entire continent. WANs
interconnect routers in different locations. A WAN differs from a LAN in several important
ways. Most WANs (like the Internet) are not owned by any one organization but rather exist
under collective or distributed ownership and management.
WIDE AREA NETWORK (WLAN)
Figure 11: Wide Area Network

USES OF WAN
 Communication Facility: For a big company spanning over the country the employees can save
long-distance phone calls and it overcomes the time lag in overseas communications.
 Computer conferencing is another use of WAN where users communicate with each other
through their computer system.
 Remote Data Entry is possible in WAN. It means sitting at any location you can enter data,
update data, and query other information of any computer attached to the WAN.
 Centralized Information: This means if the organization is spread over many cities, they keep
their important business data in a single place. WAN permits the collection of this data from
different sites and saving at a single site.

DIFFERENCE BETWEEN LAN AND WAN
. LAN WAN
LAN is restricted to a limited geographical
area of few kilometers.
WAN covers great distance and operate
nationwide or even worldwide.
The computer terminals and peripheral
devices are connected with wires and coaxial
cables.
There is no physical connection.
Communication is done through telephone
lines and satellite links.
Cost of data transmission in LAN is less
because the transmission medium is owned
by a single organization.
The cost of data transmission is very high
because the transmission medium used are
hired, either telephone lines or satellite links.
The speed of data transmission is much faster
Few data transmission errors
The speed of data transmission is slower
Less data transmission errors

METROPOLITAN AREA NETWORK (MAN)
The communication infrastructures that have been developed in and around large cities. It is a
middle ground network between LAN and WAN. The purpose of MANs is to interconnect
various LANs within a metropolitan area, that is, within approximately a 50-mile range.
Generally, the speed of MANs is equal to that of LANs and they use similar technology. It
provides connectivity over areas such as a campus.
Figure 12: Metropolitan Area Network

THE USES OFA NETWORK
 File Management (Sharing, transferring)
 Data files are shared (Access can be limited)
 Shared files stored on a server
 Application sharing (software can be shared)
 Shared peripheral devices (printers, modems)
 Personal communication(Email, Instantaneous communication)
 Conferencing (teleconferencing, video-conferencing, audio-conferencing, data-conferencing)
 Voice over IP (Phone communication over network wires)
 Easier data backup

BENEFITS OF DATA TRANSMISSION
Central Storage of Data: Files can be stored on a central node (the file server) that can be
shared and made available to each and every user in an organization.
Anyone can connect to a computer network: There is a negligible range of abilities required
to connect to a modern computer network. The effortlessness of joining makes it workable for
even youthful kids to start exploiting the data.
It is highly flexible: This innovation is known to be truly adaptable, as it offers clients the
chance to investigate everything about fundamental things, for example, programming without
influencing their usefulness.
Security through Authorization: Security and protection of information is additionally settled
through the system. As just the system clients are approved to get to specific records or
applications, no other individual can crack the protection or security of information.
It boosts storage capacity: Since you will share data, records, and assets wit other individuals,
you need to guarantee all information and substance are legitimately put away in the
framework. With this systems administration innovation, you can do the majority of this with
no issue, while having all the space you require for capacity.

MODERN TRENDS IN TELECOMMUNICATION TECHNOLOGY
FOR DATA TRANSMISSION
Reading assignment
1. 5G Communication
2. Electronic signature
3. Artificial intelligence
4. Smart cities
5. Big data
6. Internet of things
7. Cloud computing
8. Cyber security

HISTORY OF INTERNET DEVELOPMENT
About 54-year History since 1969
Pentagon & Cold War
Original Use:
Military installations
Universities
Business firms with defense department contracts
Initial Goal:
Design a network that maintains the safe transition of data between military computers

EVOLUTION OF THE INTERNET
 Advanced Research Projects Agency Network (ARPANET) became functional in September
1969, linking scientific and academic researchers across the United States.
 The original ARPANET consisted of four main computers, one each located at the University
of California at Los Angeles, the University of California at Santa Barbara, the Stanford
Research Institute, and the University of Utah.
 In 1986, the National Science Foundation (NSF) connected its huge network of five
supercomputer centers called NSFnet to ARPANET.
 This configuration of complex networks and hosts became known as the Internet.
 In 1995, NSFnet terminated its network on the Internet and resumed its status as a research
network.
 In 1996 Internet2 was founded, the goal of Internet2 was to develop and test advanced network
technologies that will benefit Internet users in the short-term future.
Examples of Internet2 projects that are now mainstream include telemedicine, and digital
libraries (online books, magazines, music, movies, speeches, etc.). Today, More than 2 billion
hosts connect to the Internet.

EVOLUTION OF THE INTERNET
1969
ARPANET
becomes
functional
1984 ARPANET
has more than
1,000 individual
computers linked
as hosts
1986 NSF
connects
NSFnet to
ARPANET and
becomes
known as the
Internet
1995
NSFNet
terminates its
network on the
Internet and
resumes its
status as a
research network
1996
Internet2
was
founded
Today
More
than 2
billion
hosts
connect
to the
Internet
Figure 13: Evolution of the Internet

WHO OWNS THE INTERNET
No single person, company, institution, or government agency owns the Internet. Each
organization on the Internet is responsible only for maintaining its own network.

METHODS OF INTERNET CONNECTIONS
Many homes and small business users connect to the Internet via high-speed broadband Internet
service:
Cable Internet service: provides high-speed Internet access through the cable television
network via a cable modem.
Digital Subscriber Line (DSL): provides high-speed Internet connections using regular copper
telephone lines.
Fiber to the Premises (FTTP): uses fiber-optic cable to provide high-speed Internet access to
home and business users.
Fixed wireless: provides high-speed Internet connections using a dish-shaped antenna on your
house or business to communicate with a tower location via radio signals.
Cellular Radio Network: offers high-speed Internet connections to devices with built-in
compatible technology or computers with wireless modems.
Wi-Fi network uses radio signals to provide high-speed Internet connections to compatible or
properly equipped wireless computers and devices.
Satellite Internet Service: provides high-speed Internet connections via satellite to a satellite
dish that communicates with a satellite modem.

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