Principles of Electronics Communication system.ppt

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DEPARTMENT OF ELECTRONICS AND COMMUNICATION
ENGINEERING
(NBA Accredited)
SUBJECT NAME: PRINCIPLES OF ELECTRONIC COMMUNICATIONS
(OE801EC)
FACULTY NAME: Dr. M.NARESH
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PRINCIPLES OF ELECTRONIC COMMUNICATIONS
COURSE OBJECTIVES:
1. Provide an introduction to fundamental concepts in the understanding of
Communication Systems.
2. Provide an introduction to Network Model and some of the Network Layer
s including Physical Layer, Data link Layer , Network Layer and Transport
Layer.
3. Provide an introduction to the evaluation of Wireless Systems and current
wireless technologies.
COURSE OUTCOMES:
CO1: Learn the basics of signals, Signal transmission concepts and different
Communication parameters
CO2: Demonstrate the working of analog and digital modulation techniques
CO3: Understand the OSI network model and working of data transmission
in different layers.
CO4: Acquire the knowledge on traditional telephony system and optical
communication system..
CO5: Illustrate the evolution of various wireless systems.
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SYLLABUS
UNIT I- Introduction to communication systems: Electromagnetic
Frequency Spectrum, Signal and its representation, Elements of
Electronic Communications System, Types of Communication
Channels.
Signal Transmission Concepts: Baseband transmission and
Broadband transmission.
Communication Parameters: Transmitted power, Channel
bandwidth and Noise, Need for modulation
Signal Radiation and Propagation: Principle of electromagnetic
radiation, Types of Antennas, Antenna Parameters and Mechanisms
of Propagation.
UNIT II- Analog and Digital Communications: Amplitude
modulation and demodulation, FM modulation and demodulation,
Digital converters, Digital modulation schemes – ASK, FSK, PSK,
QPSK, Digital demodulation.
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UNIT IV- Telecommunication Systems: Telephones, Telephone
system, Paging systems, Internet Telephony.
Optical Communications: Optical Principles, Optical
Communication Systems, Fiber –Optic Cables, Optical Transmitters &
Receivers, Wavelength Division Multiplexing.
UNIT III- Data Communication and Networking: Network
Models, OSI Model, Data Link Layer – Media Access control,
Ethernet, Network Layer – Internet Protocol (IPv4/IPv6), Transport
Layer – TCP, UDP.
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UNIT V- Wireless Communications: Evolution of Wireless Systems:
AMPS, GSM, CDMA, WCDMA, OFDM. Current Wireless Technologies:
Wireless LAN, Bluetooth, PAN and ZigBee, Infrared wireless, RFID
communication, UWB, Wireless mesh networks, Vehicular adhoc
networks.

LESSON PLAN:
UNIT I- Introduction to communication systems
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S. No. Topic(S)
No.
of Hrs
Text Book/
Reference
Book
1 Electromagnetic Frequency Spectrum, Signal and
its representation
1 T1
2 Elements of Electronic Communications System,
Types of Communication Channels.
1 T1
3 Baseband transmission and Broadband
transmission.
1 T1
4 Transmitted power, Channel bandwidth and
Noise, Need for modulation
1 T1
5 Principle of electromagnetic radiation, Types of
Antennas
1 T1
6 Antenna Parameters and Mechanisms of
Propagation
1 T1
TOTAL 6

TEXT BOOKS /REFERENCES
TEXT BOOKS:
1. Principles of Electronic Communication Systems, Louis E.
Frenzel, 3e, McGraw Hill, 2008.
2. Data Communications and Networking, Behrouz A. Forouzan,
5e TMH, 2012.
3. Kennady, Davis, Electronic Communications systems,
4e, McGraw Hill, 1999.
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INTRODUCTION:
This unit deals with study of different bands of frequencies for various
applications and types of communication systems that are suitable for
a particular application and also their elements and related parameters
UNIT-I: Introduction to communication systems
OUTCOMES:
Students will be able to
Understand frequency bands and their applications.
Analyze signals and communications systems.
 Define related parameters
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CONTENTS:
1.1 Electromagnetic frequency spectrum
1.2 Signal and its representation
OUTCOMES:
Students will be able:
•To understand different bands of frequencies used for different
applications.
•To identify various types of signals based on their representation.
MODULE-I
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Electromagnetic frequency spectrum
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Applications of different frequencies
Electromagnetic frequency spectrum
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Analog signal
Digital signal
Signal and its representation
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Signal and its representation
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1. Write the typical frequency ranges for the following classification of EM
spectrum: MF, HF, VHF and UHF.
2. Draw the Electromagnetic Frequency Spectrum.
3. Define a signal and write its mathematical expression.
4. What are the different types of signals.
Questions & Answers
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CONTENTS:
1.3 Elements of electronic communications system
1.4 Types of Communication Channels
1.5 Baseband transmission and broadband transmission
OUTCOMES:
Students will learn :
• Functions of different elements of communication system .
• Different types of communication channels
• To understand baseband and broadband transmission concepts
MODULE-2
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•Communication is a process of conveying message at a distance.
If the distance is involved is beyond the direct communication, the communication
engineering comes into the picture. The brain engineering which deals with
communication systems is known as telecommunication engineering.
Telecommunication engineering is classified into two types based on transmission
media. They are:
1. Line communication
2. Radio communication
Introduction to Electronic Communications System
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The transmission of information from source to the destination through a channel or
medium is called communication

BASIC COMMUNICATION BLOCK DIAGRAM:
Elements of Electronic Communication system
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Source: analog or digital
Transmitter: transducer, amplifier, modulator,oscillator, power amp., Antenna
Channel: Like Cable, optical fiber, freespace
Receiver: antenna, amplifier, demodulator, oscillator, power amplifier, Transducer
Destination : Like Person, (loud) speaker,computer

Types of Communication Channels
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TWISTED PAIR

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Optical Fiber cable

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Satellite Microwave

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Terrestrial Microwave

Signal Transmission Concepts
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Base band transmission :
•Baseband technology uses digital signals in data transmission.
•It sends binary values directly as pulses of different voltage levels.
•Digital signals can be regenerated using repeaters in order to travel longer
distances before weakening and becoming unusable because of attenuation.
• Digital signals travelling over base band channel without further
conversion into analog signal by modulation
•Baseband technology transmits a single data signal/stream/channel at a
time

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Broadband transmission:
•Broadband technology uses analog signals in data transmission.
•This technology uses a special analog wave known as the carrier wave.
• A carrier wave does not contain any data but contains all properties of the
analog signal.
•This technology mixes data/digital signal/binary values into the carrier
wave and sends the carrier wave across the channel/medium.
• To transmit data of multiple nodes simultaneously, this technology supports
the Frequency Division Multiplexing

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Base band transmission:
Broad band transmission using Modulation:

Differences between baseband and broadband transmission:
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Baseband transmission Broadband transmission
Transmit digital signals Transmit analog signals
To boost signal strength, use repeaters To boost signal strength, use amplifiers
Can transmit only a single data stream at
a time
Can transmit multiple signal waves at a
time
Support bidirectional communication
simultaneously
Support unidirectional communication
only
Support TDM based multiplexing Support FDM based multiplexing
Use coaxial, twisted-pair, and fiber-optic
cables
Use radio waves, coaxial cables, and fiber
optic cables
Mainly used in Ethernet LAN networks Mainly used in cable and telephone
networks

1. Mention the elements of a communication system. Describe their
functionality with a neat diagram.
2. List the basic functions of a radio transmitter and the corresponding
functions of the receiver.
3. What are types of communication channels.
4. Explain the different types of communication channels
5. Write short notes on base band and broad band transmission.
Questions & Answers
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CONTENTS:
1.6 Communication parameters
- Transmitted Power
- Channel Bandwidth
- Noise
- Need for Modulation
OUTCOMES:
Students will learn communication parameters like transmitted
power, channel bandwidth, noise and need for modulation
MODULE-3
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Transmitted power:
Let be the transmitted power radiated by an isotropic antenna.
The power density at a distance is given by
Where = Average Power
=Surface Area of an imaginary sphere of radius
Communication Parameters
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t
P
R 2
4
t
avg
P
P
R


avg
P
2
4 R
 R
Let be the gain of the transmitting antenna.
Then power density is given by
If is the effective aperture of receiving antenna
Then the received power of receiving antenna is given by
t
G
2
4
t
avg t
P
P G
R


e
A
2
4
t
r t e
P
P G A
R


r
P

Transmitted power:
Where the antenna effective aperture is given by
= Receiving antenna gain
Then the final formula for the power received at the receiving antenna is
given by
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2
4
e r
A G



r
G
 
2
2
4
t t r
r
PG G
P
R




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.W H L
B f f
 
H
f Higher cut off frequency

L
f Lower cut off frequency

Channel Bandwidth:
Bandwidth is the difference between upper and lower frequency limits
and it is represented by
A channel is the medium through which the input signal passes.
I n terms of Analog signal : It is the range of frequencies that the channel can carry.
In terms of Digital signal: the max. bit rate supported by the channel, i. e no. of bits per
second

.
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•The BW of the medium should always be greater than the bandwidth of the
signal to be transmitted else loss of information takes place
•EX: Human voice range is 20Hz -20kHz
• But Voice frequency is 300 Hz-3400Hz
• So Effective speech bandwidth is 3400Hz-300Hz=3100Hz or 3.1kHz

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NOISE:
Noise is an un wanted signal that encounter the message signal at the channel.
noise is an error or undesired random disturbance of a useful information signal.

The noise signal can be understood by taking a look at the following example.
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Most common examples of noise are −
•Hiss sound in radio receivers
•Buzz sound amidst of telephone
conversations
•Flicker in television receivers, etc.

Modulation
Message or Modulating Signal:
The signal which contains a message to be transmitted is called as a message signal.
It is a baseband signal, which has to undergo the process of modulation, to get
transmitted. Hence, it is also called as the modulating signal.
Carrier Signal :
The high frequency signal, which has a certain amplitude, frequency and phase but
contains no information, is called as a carrier signal. It is an empty signal and is used
to carry the signal to the receiver after modulation.
Modulated Signal:
The resultant signal after the process of modulation is called as a modulated signal.
This signal is a combination of modulating signal and carrier signal.
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Need for modulation
 Modulation is the process of changing the characteristics parameters
(amplitude, frequency, phase) of the carrier signal, in accordance with the
instantaneous values of the modulating signal.
 Need for Modulation: Baseband signals are incompatible for direct
transmission. For such a signal, to travel longer distances, its strength has to
be increased by modulating with a high frequency carrier wave, which
doesn’t affect the parameters of the modulating signal.
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Need for modulation
1. Reduce the antenna height.
2. Increases the range of Communication.
3. Allows the multiplexing of signals.
4. Adjustments in the bandwidth is allowed.
5. Avoids the mixing of signals.
6. Improved reception quality
7. Narrow banding of signals.
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Need for modulation:

1. Define transmitted power, channel bandwidth and noise.
2. Mention parameters of any Electronic Communication System.
3. Define noise. Where is it most likely to affect the signal?
Questions & Answers
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CONTENTS:
1.7 Signal radiation and propagation
- Principle of Electromagnetic Radiation
- Types of Antenna
- Antenna parameters
- Mechanisms of Propagation
OUTCOMES:
 Students will learn different types of antennas, antenna parameters
,radiation patterns and propagation mechanisms
MODULE-4
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Principle of electromagnetic radiation:
Electro Magnetic Radiation or EMR is the term used to describe different
types of energies released by electromagnetic process.
Visible light ,Radio Waves, Infrared Rays and X-Rays are all forms of
electromagnetic radiation .
Remote sensing technologies relay on a verity of electromagnetic energy.
Signal Radiation and Propagation
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Electromagnetic energy transferred by radiation is known as Electromagnetic
Radiation or EMR. EMR is the only energy that can travel through a vacuum – i.e.
space.
Light, electromagnetic waves, and radiation all refer to the same physical
phenomenon i.e electromagnetic energy.
All objects warmer than absolute zero (-273° c) emit electromagnetic radiation
(EMR).Objects also reflect and absorb EMR emitted by other objects.
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•Electromagnetic wave consists of both
electric field and magnetic field.
•The electric field and magnetic field are
perpendicular to each other and also
perpendicular to the direction of
propagation

Electromagnetic waves are the oscillations that can propagate through
free space with velocity of light i.e.
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8
3 10 /
m s


Types of antennas:
•An antenna is a transducer, which converts electrical power into
electromagnetic waves and vice versa.
•Antennas are radiating elements that are used to transmit and/or receive
electromagnetic waves.
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TYPES OF ANTENNAS:
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Types of antennas:
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Antenna parameters :
•Gain
•Directivity
•Antenna efficiency
•Effective aperture

ANTENNA PARAMETERS :
1. Gain: Gain of an antenna is the ratio of the radiation intensity in a given
direction to the radiation intensity that would be obtained if the power
accepted by the antenna were radiated isotropically. It is represented by “G”
and measured in decibels (dB).
Gain is given by
where
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e
G D


e Antenna Efficiency
 
D Directivity of Antenna

2. Directivity: The ratio of maximum radiation intensity of the subject
antenna to the radiation intensity of an isotropic or reference antenna, radiating
the same total power is called the directivity. It is represented by “D” and it is
given by :
intensity
intensity
Maximum radiation of subject antenna
D
Radiation of reference antenna

 max
0
,
D
  



3. Antenna efficiency: Antenna Efficiency is the ratio of the radiated
power of the antenna to the input power accepted by the antenna.
Antenna Efficiency is given by
where
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rad
e
input
P
P
 
e Antenna Efficiency
 
rad
P Radiated Power

input
P Input Power

4. Effective aperture: Aperture Efficiency of an antenna is the ratio of the
effective radiating area to the physical area of the aperture.
The mathematical expression for the Aperture Efficiency is given by :
eff
A
p
A
A
  A
eff
p
where
Aperture Efficiency
A Effective Area
A Physical Area





Radiation patterns:
•A radiation pattern is a diagrammatical representation of the distribution
of the radiated energy into a space ,as a function of direction .
•Graphically ,we plot the electric and magnetic fields as a function of the
angular and radial distance from the antenna.
•Which means that we represent then in spherical coordinates as
The radiation pattern has main lobe, side lobes and back lobe.
•The major part of the radiated field, which covers a larger area, is
the main lobe or major lobe. This is the portion where maximum radiated
energy exists. The direction of this lobe indicates the directivity of the
antenna.
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   
, ,
E and H
   

Radiation patterns:
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The other parts of the
pattern where the radiation
is distributed side wards
are known as side
lobes or minor lobes.
These are the areas where
the power is wasted.
There is other lobe, which
is exactly opposite to the
direction of main lobe. It is
known as back lobe, which
is also a minor lobe. A
considerable amount of
energy is wasted even here.

Mechanisms of Propagation : Reflection, Diffraction, Scattering
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Reflection: Occurs When waves impinges
upon an obstruction that is much larger
in size compare to the wavelength of the
signal
Diffraction: Occurs when the radio path
between sender and receiver is
obstructed by an impenetrable body and
by a surface with sharp
irregularities(edges)
Scattering: Occurs when the Channel
contains objects whose sizes are on the
order of the wavelength or less of the
propagation wave and also when the
number of obstacles are quite large

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Wave propagation:
•Ground wave propagation
•Space wave propagation
•Sky wave propagation

1. Describe antenna parameters.
2. Explain in detail non-resonant antennas with applications.
3. An half wave dipole antenna is capable of radiating 1 KW and has 2.15 db
game over an isotropic antenna. How much power must be delivered to the
isotropic antenna to match the field strength directional antenna?
4. What are different types of antennas and explain each type of antenna.
Questions & Answers
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INTRODUCTION:
This unit deals with the study of different modulation and demodulation
schemes in Analog and Digital Communication.
UNIT-II: Analog and Digital Communications
OUTCOMES:
After successful completion of this Unit students will be able to
Define modulation and demodulation.
Analyze various modulation schemes.
 Differentiate analog and digital modulation systems.
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CONTENTS:
2.1. Amplitude modulation and demodulation
OUTCOMES:
 Students will be able to understand different MODULATION AND
DEMODULATION Schemes and their advantages and applications.
MODULE-I
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Amplitude modulation and demodulation
Modulation is the process of changing the characteristics parameters (amplitude,
frequency, phase) of the carrier signal, in accordance with the instantaneous
values of the modulating signal.
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Types of Modulation
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Pulse Modulation:PAM(Pulse Amplitude Modulation)
PWM(Pulse Width Modulation)
PPM(Pulse position Modulation)

Amplitude Modulation:
The amplitude of the carrier signal varies in accordance with the
instantaneous amplitude of the modulating signal is called amplitude modulation .
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Amplitude Modulation
Let the modulating signal be, m(t) = Am cos(2πfmt) eq., 1
and the carrier signal be, c(t)= Ac cos(2πfct) eq., 2
Amplitude Modulated signal S (t) = Ac [1+ka m (t)] cos2πfct eq., 3

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( ) cos
=
m m
m
m
m
m t A t
where A Amplitude of the message signal
Angular frequency of the message signal
f Frequency of the message signal





Message signal
( ) cos
=
c c
c
c
c
c t A t
where A Amplitude of the carrier signal
Angular frequency of the carrier signal
f Frequency of the carrier signal





Carrier Signal
The amplitude modulated signal will be
 
 
( ) ( ) cos
= cos cos
= cos cos cos
c c
c m m c
c c m m c
AM t A m t t
A A t t
A t A t t

 
  
 



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1
( )= cos .2 cos cos
2
c c m m c
AM t A t A t t
  

= cos 2 cos cos
2
m
c c m c
A
A t t t
  
 2cos cos cos( ) cos( - )
A B A B A B
  
 
 
 
= cos cos( ) cos( )
2
= cos cos( ) cos( )
2
= cos cos( ) cos( )
2
= cos cos( ) cos( )
2 2
m
c c c m c m
m c
c c c m c m
c
c m
c c c m c m
c
c a c a
c c c m c m
A
A t t t
A A
A t t t
A
A A
A t t t
A
A m A m
A t t t
    
    
    
    
   
   
   
   
m
a
c
A
where m =modulation index=
A
= cos cos 2 ( ) cos 2 ( )
2 2
c a c a
c c c m c m
A m A m
A t f f t f f t
  
   
By re-arranging

Where µ is “modulation index” or “depth of modulation”
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c
m
A
A


 
  2
/
2
/
m
in
m
ax
m
in
m
ax
A
A
A
A
A
A
c
m



m
in
m
ax
m
in
m
ax
A
A
A
A




then

.
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Amplitude Demodulation: Demodulation is a key process in the
reception of any amplitude modulated signals whether used for
broadcast or two way radio communication systems. Demodulation is the
process by which the original information bearing signal, i.e. the modulation
is extracted from the incoming overall received signal.
Envelope Detector

.
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Envelope Detector
The discharging time constant RLC is very large when compared to the charging time
constant i.e.,
mb
L
c
s
f
C
R
f
c
R
1
1




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Frequency Domain Representation:
Frequency Spectrum of Modulating signal
Frequency Spectrum of Modulated signal

Bandwidth of Amplitude Modulation:
It is defined as the difference between the higher Upper side band frequency and Lower side band
frequency.
Band width (BW)= fUSB-fLSB = fc+fm- (fc-fm)=2fm
= 2 X Message Bandwidth/highest frequency
message signal
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Power Calculation for AMPLITUDE MODULATION
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Let the modulating signal be, m(t) = Am cos(2πfmt)
and the carrier signal be, c(t)= Ac cos(2πfct)
Then AM equation is S (t) = Ac [1+ka m (t)] cos2πfct
S (t) = Ac Cos (2π fct)+Acµ /2[cos2 π(fc+fm)t]+ Acµ /2[cos2π (fc-fm)t]
Total Power: Pt= Pc + PUSB+PLSB
Power of any signal is equal to the mean square value of the signal
Carrier power Pc = Ac2/2
Upper Side Band power PUSB = Ac2 µ2/8
Lower Side Band power P LSB = Ac2 µ2/8
Total power Pt = Pc + PLSB + PUSB
Total power Pt = Ac2/2 + Ac2 µ2/8 + Ac2 µ2/8
= Ac2/2 + Ac2 µ2/4
= Ac2/2[1 + µ2/2]

Amplitude Modulation and Demodulation
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Total power Pt = Ac2/2 + Ac2 µ2/8 + Ac2 µ2/8
= Ac2/2 + Ac2 µ2/4
= Ac2/2[1 + µ2/2]
Total power Pt =
Total power Pt =







2
2
2
1
2

c
A







2
2
1

c
P

1. A transmitter radiates 9kw without modulation and 10.125kw after
modulation. Determine depth of modulation.
2. As related to AM, what is over modulation, under modulation and 100%
modulation?
3. Derive the expression for the amplitude modulated signal.
4.Explain the detection of AM signals using envelope detector
Questions & Answers
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CONTENTS:
2.2. Frequency modulation and Demodulation
OUTCOMES:
Students will be able to define frequency modulation and differentiate
between amplitude modulation and frequency modulation
MODULE-2
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Angle modulation : Angle modulation is the process by which the angle (frequency
or phase) of the carrier signal is changed in accordance with the instantaneous
amplitude of modulating or message signal.
Classified into two types such as
1. Frequency modulation (FM)
2.Phase modulation (PM)
Angle modulation schemes
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Used for :
1. Commercial radio broadcasting
2. Television sound transmission
3. Two way mobile radio
4. Cellular radio
5. Microwave and satellite communication system
Advantages over AM:
1.Freedom from interference: all natural and external noise consist of amplitude
variations, thus receiver usually cannot distinguish between amplitude of noise or
desired signal. AM is noisy than FM.
2. Operate in very high frequency band (VHF): 88MHz-108MHz
3. Can transmit musical programs with higher degree of fidelity

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Frequency modulation and demodulation
Frequency Modulation: The Frequency of the carrier signal varies in accordance with
the instantaneous amplitude of the modulating signal is called amplitude
modulation

During the process of frequency modulations the frequency of carrier signal is changed
in accordance with the instantaneous amplitude of message signal .Therefore the
frequency of carrier after modulation is written as
To find the instantaneous phase angle of modulated signal, integrate equation above
w.r.to ‘t’:
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  t
A
t
m m
m 
cos

Message signal
Carrier signal   t
A
t
c c
c 
cos

Frequency modulation:
  t
A
K
t
A
K m
m
f
C
m
f
c
i 


 cos




  t
A
K
t
dt
t
A
K
dt m
m
m
f
C
m
m
f
C
i
i 





 sin
cos 



 

Thus, we get the FM wave as:
)
sin
cos(
cos
)
( t
A
K
t
A
Ac
t
S m
m
m
f
C
C
i
FM 


 


)
sin
cos(
)
( t
t
A
t
S m
f
C
C
FM 

 

m
m
f
f
A
K

 
Where Modulation index

FREQUENCY DEVIATION:
∆F is the relative placement of carrier frequency (Hz) w. r. t its un-modulated value.
Given as:
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m
f
C A
K

 
max m
f
C A
K

 
min
m
f
C
C
d A
K




 min
max 




m
f
d
A
K
f 




2
m
f
m
f
f
f
A
K
f





;

BANDWIDTH:
The theoretical bandwidth is “infinity”
According to the Carson’s Rule, for large band width of β, the band width of FM
slightly greater than the total frequency execution “2𝜟f”
FM Bandwidth calculation
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.
)
1
(
2
)
1
(
2
)
1
1
(
2
)
1
(
2
)
2
2
)
(
2


















m
m
m
m
m
m
m
m
m
m
m
m
f
f
f
BW
f
BW
f
BW
or
f
f
f
BW
f
f
BW
f
f
BW



GENERATION OF FM WAVE: Direct method:
Generation of FM wave
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)
(
)
(
2
)
(
2
1
)]
(
1
(
)
(
)]
(
1
[
)
(
)
(
1
[
2
1
)
(
)
(
(
2
1
)
(
,
,
0
)
(
,
2
1
0
0
0
0
0
0
2
1
0
0
2
1
0
0
0
0
0
0
0
0
0
0
t
m
kf
f
t
m
c
kf
f
t
m
c
k
t
m
c
k
f
t
f
t
m
c
k
f
t
f
t
m
c
k
C
L
t
f
t
km
C
L
t
f
thenfreq
t
m
when
C
L
f
i
i
i
i




















Detection of FM wave
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Simple Slope Detector:

SIMPLE SLOPE DETECTOR :
It can be seen from the diagram that changes in the slope of the filter, reflect into the linearity of the
demodulation process. The linearity is very dependent not only on the filter slope as it falls away, but
also the tuning of the receiver - it is necessary to tune the receiver off frequency and to a pint where
the filter characteristic is relatively linear.
The final stage in the process is to demodulate the amplitude modulation and this can be achieved
using a simple diode circuit. One of the most obvious disadvantages of this simple approach is the
fact that both amplitude and frequency variations in the incoming signal appear at the output.
However the amplitude variations can be removed by placing a limiter before the detector.
A variety of FM slope detector circuits may be used, but the one below shows one possible circuit
with the applicable waveforms. The input signal is a frequency modulated signal. It is applied to the
tuned transformer (T1, C1, C2 combination) which is offset from the centre carrier frequency. This
converts the incoming signal from just FM to one that has amplitude modulation superimposed upon
the signal.
This amplitude signal is applied to a simple diode detector circuit, D1. Here the diode provides the
rectification, while C3 removes any unwanted high frequency components, and R1 provides a load.
Detection of FM wave
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A phase-locked loop or phase lock loop (PLL) is a control system that generates an
output signal whose phase is related to the phase of an input signal. There are several
different types; the simplest is an electronic circuit consisting of a variable frequency
oscillator and a phase detector in a feed back loop the oscillator generates a periodic
signal, and the phase detector compares the phase of that signal with the phase of the
input periodic signal, adjusting the oscillator to keep the phases matched.
Detection of FM by Phased Lock Loop (PLL)
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Sout ( t )
Sf ( t )
Sphase( t )
Voltage Controlled
Oscillator (VCO)
SVCO ( t ) = AVCO ·sin [ 0 t +  0( t )]
Sf ( t ) = Af ·cos [ c t +  ( t )]
SVCO ( t )
Phase
Detector
Low-pass
filter

1. Compare AM Vs FM.
2. An FM signal with single tone modulation has a frequency deviation
of 15 KHz and a BW of 50 KHz. Find the frequency of modulating
signal.
3. Explain the generation of FM wave and any one method of
demodulating an FM wave.
4. Derive the expression for the frequency modulated signal.
Questions & Answers
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CONTENTS:
2.3 Digital converters
2.4 . Digital Modulation schemes-AK,FSK,PSK,QPSK Modulation and Demodulation
OUTCOMES:
Students will be able:
To define different digital modulation schemes and differentiate them.
To learn functions of different digital demodulation schemes
MODULE-3
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.
Basic Digital Communication System
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.
Digital communication is the physical transfer of data over Point-To-
Point or Point-To-Multipoint communication channel. It is transfer of
discrete messages

.
Digital Converters
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Digital Converters: A converter that is used to change the analog signal to digital
is known as an analog to digital converter or ADC converter.
This converter is one kind of integrated circuit or IC that converts the signal directly
from continuous form to discrete form.
This converter can be expressed in A/D, ADC, A to D. The inverse function of DAC is
nothing but ADC

Digital Converters
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Steps for Convert Analog to Digital:
• Sampling
• Quantizing
• Encoding

AMPLITUDE SHIFT KEYING(ASK)
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Amplitude-shift keying (ASK) is a form of amplitude modulation that
represents digital data as variations in the amplitude of a carrier
wave. In an ASK system, a symbol, representing one or more bits, is sent
by transmitting a fixed-amplitude carrier wave at a fixed frequency for a
specific time duration

AMPLITUDE SHIFT KEYING(ASK):
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( )
( )
( ) [1 ( )] cos( )
2
( ) inf (mod ) ( )
mod ( )
2
ask m c
ask
m
A
v t v t t
where v amplitude shift keying wave
v t digital ormatio ulating signal volts
A
un ulated carrier amplitude volts

 
   
 
 


log ( sec , 2 )
c c
ana carrier radian frequency radians per ond f t
 

( )
( ) 1 1 ( ) 1 0
( ) 1 ( ) 1
( ) [1 1] cos( )
2
m m
m m
ask c
Let v t V for Logic and v t V for Logic
For v t V For v t V
A
v t t

   
   
 
   
 
( ) ( ) [1 1] cos( )
2
cos( ) =0
ask c
c
A
v t t
A t


 
   
 

AMPLITUDE SHIFT KEYING(ASK)

ASK Modulation and Demodulation
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FREQUENCY SHIFT KEYING(FSK)
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Frequency-shift keying (FSK) is a frequency modulation scheme in
which digital information is transmitted through discrete frequency
changes of a carrier signal.

FREQUENCY SHIFT KEYING(FSK):
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  

( )
( )
( ) cos 2 ( ) t
( ) (mod ) ( )
log ( )
fsk c c m
fsk
m
c
c
v t V f v t f
where v frequncy shift keying wave
v t binary input ulating signal volts
V ana carrier amplitude volts
f ana

  
 


 log ( )
( ) log ( )
carrier center frequency hertz
f peak change shift in ana carrier center frequency hertz
 
  

( )
( ) 1 1 ( ) 1 0
( ) 1 ( ) 1
( ) cos 2 t
m m
m m
fsk c c
Let v t V for Logic and v t V for Logic
For v t V For v t V
v t V f f

   
   
     

( ) ( ) cos 2 t
hertz
2
- ( )
fsk c c
m s
m s
v t V f f
f f
frequency Deviation f
f f absolute difference between mark and space frequency hertz

  

 


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FSK, in the most basic case, represents a 1 (a mark) by one frequency and
a 0 (a space) by another. These frequencies lie within the bandwidth of the
transmission channel.

FSK Modulation and Demodulation
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FSK Modulator

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PHASE SHIFT KEYING(PSK)
Phase-shift keying is a digital modulation process which conveys data by
changing the phase of a constant frequency reference signal.

Binary phase shift keying(BPSK):
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Binary Phase Shift Keying( BPSK)

BINAR PHASE SHIFT KEYING(BPSK):
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Generation:
Detection:
Generation and Detection of Binary Phase Shift Keying( BPSK)

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Quadrature Phase Shift Keying(QPSK)
QPSK is a form of Phase Shift Keying in which two bits are modulated at
once, selecting one of four possible carrier phase shifts.
QPSK allows the signal to carry twice as much information as ordinary PSK
using the same bandwidth

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Quadrature Phase Shift Keying(QPSK)
Constellation Diagram
QPSK

Quadrature Phase Shift Keying(QPSK):
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Generation:
Detection:
Generation and Detection of Quadrature Phase Shift Keying(QPSK)

1. Define ASK, FSK and PSK modulation schemes and draw them.
2. Sketch the waveform of PSK for binary sequence 1100101.
3. Differentiate QPSK and BPSK.
4. Differentiate ASK and FSK.
5. Explain the Generation of BPSK with neat diagram.
6. Draw the block diagrams of ASK & FSK and explain with wave forms.
7. Explain the Demodulation of BASK with neat diagram.
8. Explain the Demodulation of BPSK with neat diagram.
Questions & Answers
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INTRODUCTION:
This unit describes data communications components, data representation,
data flow, network structure, topologies, categories and network models.
.
OUTCOMES:
Understand the concepts of data communications and networking.
 Understand the principles and concepts of network models.
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UNIT-III: Data Communication and Networking

CONTENTS:
3.1Components of a data communications system
3.2 Network Models
OUTCOMES:
Students will be able
To understand the Data Communications System and its components.
Familiarize with the basic taxonomy and terminology of the computer
networking area.
To identify the different types of network topologies
MODULE-1
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.
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Data communications are the exchange of data between two devices
via some form of transmission medium such as a wire cable.
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). The effectiveness of a data
communications system depends on four fundamental characteristics:
delivery, accuracy, timeliness, and jitter

Components of Data Communication system:
Message is the information (data) include text, numbers, pictures, audio, and video.
Sender can be a computer, workstation, telephone handset, video camera, and so on.
Receiver can be a computer, workstation, telephone handset, television, and so on.
Ttransmission medium include twisted-pair wire, coaxial cable, fiber-optic cable, and
radio waves
Protocol is a set of rules that govern data communications. it represents an agreement
between the communicating devices.
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Data Flow:

.
Network models
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A network is a set of devices (often referred to as 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 can be a cable, air, optical fiber, or any medium which can transport
a signal carrying information.
•Performance
•Depends on Network Elements
•Measured in terms of Delay and Throughput
•Reliability
•Failure rate of network components
•Measured in terms of availability/robustness
•Security
•Data protection against corruption/loss of data due to:
•Errors
•Malicious users

Type of connection
1. Point to point - single transmitter and receiver
2. Multipoint - multiple recipients of single transmission
Network models
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.
Physical Topology
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The term physical topology refers to the way in which a network is laid out
physically.: one or more devices connect to a link; two or more links form a
topology.
The topology of a network is the geometric representation of the relationship
of all the links and linking devices (usually called nodes) to one another.
There are four basic topologies possible:

Mesh and Star Topology
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1.Fully connected
2. Robust
3. Not flexible
1. Every node has its own dedicated
connection
2. Acts as a repeater for data flow.
3. Used with twisted cable, optical fiber or
coaxial cable.
Mesh: Star:

Bus and Ring Topology
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1. Transmits data only in one direction.
2. Every device is connected to single cable only.
1. A number of repeaters are used with large number of nodes to prevent data loss.
2. Data is transferred in a sequential manner.
Bus:
Ring:

1. Combination of two or topologies.
2. A star backbone with bus networks
3. Inherits the advantages and disadvantages of the topologies included
Hybrid Topology
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.
•Local Area Networks (LANs)
•Short distances
•Designed to provide local interconnectivity
•Wide Area Networks (WANs)
•Long distances
•Provide connectivity over large areas
•Metropolitan Area Networks (MANs)
•Provide connectivity over areas such as a city, a campus
Categories of Networks
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1. Private networks, not subject to
tariffs or other regulatory controls.
2. Operate at relatively high speed
when compared to the typical WAN.
3. Different types of media access
control methods in a LAN, the
prominent ones are Ethernet, token
ring.
4. Connects computers in a single
building, block or campus, i.e. they
work in a restricted geographical
area.
Local Area Network (LAN)
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1. Covers towns and cities (50 km)
2. Communication medium used
are optical fibers, cables etc.
3. Data rates adequate for
distributed computing applications.
Metropolitan Area Network (MAN)
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1. Covers large distances(states, countries, continents).
2. Communication medium used are satellite, public telephone networks which are
connected by routers.
Wide Area Network (WAN)
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1. Draw & explain the functionality of different blocks of a data
communication system.
2. What is network topology and explain the different network
topologies.
3. What are the different type of networks? Explain in detail.
4. Comparison of different type of networks
Questions & Answers
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CONTENTS:
OSI MODEL
Layered Architecture
Peer-to-peer Processes
Encapsulation
OUTCOMES:
Student will able to enumerate the layers of the OSI model and explain the
function(s) of each layer.
MODULE-2
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OSI model
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1. Established in 1947, the International Standards Organization (ISO) is a
multinational body dedicated to worldwide agreement on international
standards.
2. An ISO standard that covers all aspects of network communications is
the Open Systems Interconnection (OSI) model.
3. It was first introduced in the late 1970s.
Responsibilities of layer in OSI Reference Model

Interaction between layers in the OSI model
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An exchange using the OSI model
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The physical layer is responsible for movements of individual bits from one
hop (node) to the next.
Functions of Physical Layer
1. Representation of Bits
2. Data Rate
3. Synchronization
4. Interface
5. Line Configuration
6. Topologies
7. Transmission Modes
Physical layer
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The data link layer is responsible for moving frames from one hop (node) to
the next.
Functions of Data Link Layer
1. Framing
2. Physical Addressing
3. Flow Control
4. Error Control
5. Access Control
Data link layer
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The network layer is responsible for the delivery of individual packets from
the source host to the destination host.
Functions of Network Layer:
1. Internetworking
2. Addressing
3. Routing
4. Packetizing
Network layer
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Source-to-destination delivery
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The transport layer is responsible for the delivery of a message from one
process to another.
Functions of Transport Layer
1. Service-point addressing
2. Segmentation and reassembly
3. Connection control
4. Flow control
5. Error control
Transport layer
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Process-to-process delivery
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The session layer is responsible for dialog control and synchronization.
Functions of Session Layer
1. Dialog Control
2. Token Management
3. Synchronization
Session layer
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The presentation layer is responsible for translation, compression, and
encryption
Functions of Presentation layer
1. Translation
2. Encryption
3. Compression
Presentation layer
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The application layer is responsible for providing services to the user.
Application layer
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1. Explain the OSI reference model with neat diagram.
2. Explain the functions of physical layer and data link layer in brief.
3. Explain the functions of network layer and transport layer in brief.
4. Explain the functions of session layer and application layer in brief.
Questions & Answers
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CONTENTS:
Data link layer – media access control
Ethernet
OUTCOMES:
Student will able to enumerate the data link layer
MODULE-3
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Data link layer
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The data link layer transforms the physical layer, a raw transmission facility, to a reliable
link. It makes the physical layer appear error-free to the upper layer
Communication at the data link layer occurs between two adjacent nodes.
To send data from A to F, three partial deliveries are made.
First, the data link layer at A sends a frame to the data link layer at B (a router).
Second, the data link layer at B sends a new frame to the data link layer at E.
Finally, the data link layer at E sends a new frame to the data link layer at F.
Note that the frames that are exchanged between the three nodes have different values
in the headers.
The frame from A to B has B as the destination address and A as the source address.
The frame from B to E has E as the destination address and B as the source address.
The frame from E to F has F as the destination address and E as the source address.
The values of the trailers can also be different if error checking includes the header of
the frame.

Media Access control
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In IEEE 802 LAN/MAN standards, the medium access control (MAC, also called media
access control) sub-layer is the layer that controls the hardware responsible for
interaction with the wired, optical or wireless transmission medium
The MAC sub layer and the logical link control (LLC) sub layer together make up
the data link layer.
Within the data link layer, the LLC
provides flow control and multiplexing
for the logical link , while the MAC
provides flow control and multiplexing
for the transmission medium.

Media Access Control
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CSMA / CD
Carrier Sense: wait till medium is idle before sending frame.
Multiple Access: multiple computers use the same shared media. Each uses same access algorithm.
Collision Detection: Listen to medium – detect if another station’s signal interferes – back off and try again later.
If collision occurs: wait a random time t1 - 0< t1<d.
D depends on transmission speed – time for frame width or 512 bits.
If second collision occurs, wait a random time t2 - 0< t2<2d.
Double range for each succesive collision.
Exponential backoff
No acknowledgement like TCP.
CSMA/CA used in wireless networks where not all stations receive message.
Both sides send small message followed by data:
X is about to send to Y
Y is about to receive from X
Data frame sent from X to Y.
Shared medium – stations take turns at sharing the medium.
Media access control ensures fairness.

Ethernet
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Invented in 1973 @ Xerox (IEEE 802.3)
Originally a LAN technology – extended to MAN / WAN.
Same frame format, different wiring schemes, data rates across generations.
Most common version (10BaseT) – 1990

Ethernet
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Ethernet Generations:
NIC – Network Interface Card
MAU – Media Attachment Unit
AUI – Attachment Unit
Interface
MII – Media Independent
Interface
.

Ethernet
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Ethernet Frame
48-bit address
Address assigned when NIC card is manufactured.
Packets can be sent to
Single address – Unicast
All stations on network – Broadcast (address = all 1s.)
Subset of stations – Multicast
Broadcast (address = all 1s.)
All receivers accepts unicast / broadcats.
Half addresses reserved for multicast (247)
NIC can accepts zero or more multicasts.
Ethernet Addressing:

.
Ethernet
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.
100Base-FX
LED light source / MMF / 2 km
max distance.
Modal dispersion – limited
bandwidth
100Base-SX (IEEE 802.3z)
Short wavelength laser (850 nm)
Max distance = 5 km.
100Base-LX
Long wavelength laser (1310
nm)
Max distance = 5 km.
Beyond Gigabit Ethernet: Recent Developments:
10 Gb/s Ethernet
No CSMS/CD, same frame format.
Applications
Upgrade LANs / Backbone.
MAN applications.

CONTENTS:
Network Layer-Intent Protocol (IPv4/IPv6)
OUTCOMES:
Understand the principles and concepts of internet protocols .
MODULE-4
MATRUSRI
ENGINEERING COLLEGE

MATRUSRI
ENGINEERING COLLEGE
Transport segment from sending to receiving host
on sending side encapsulates segments into datagrams
on receiving side, delivers segments to transport layer
network layer protocols in every host, router
router examines header fields in all IP datagrams passing through it
Network Layer
Network Layer: Internet
host, router network layer functions:

.
Network Layer- Internet Protocol (IPv4/IPv6)
MATRUSRI
ENGINEERING COLLEGE
.
IP Datagram format
IP: the Internet Protocol
datagram format
addressing

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ENGINEERING COLLEGE
IP address: 32-bit identifier associated with each host or router interface
 Interface: connection between
host/router and physical link.
 router’s typically have multiple
interfaces.
 host typically has one or two
interfaces (e.g., wired Ethernet, wireless
802.11)

.
MATRUSRI
ENGINEERING COLLEGE
Pv4 stands for Internet Protocol version 4. It is the underlying technology that
makes it possible for us to connect our devices to the web. Whenever a device
accesses the Internet, it is assigned a unique, numerical IP address such as 99.48.
227.22
IPv4 frame format

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ENGINEERING COLLEGE
priority: identify priority among datagrams in flow
flow Label: identify datagrams in same “flow.” concept of“flow” not well defined).
next header: identify upper layer protocol for data
IPv6 datagram format

.
MATRUSRI
ENGINEERING COLLEGE
.
Not all routers can be upgraded simultaneously
no “flag days”
how will network operate with mixed IPv4 and IPv6 routers?
tunneling: IPv6 datagram carried as payload in IPv4 datagram among IPv4
routers
Transition from IPv4 to IPv6

Network layer- internet protocol (ipv4/ipv6)
MATRUSRI
ENGINEERING COLLEGE
IPv4 and IPv6 are the actual protocols tasked with data transmission in the form of
packets and datagrams. IPv4 protocol is mainly used with ethernets during packet
switching in the link-layer networks. IPv6 protocol being more newfangled has improved
capabilities as compared to IPV4

CONTENTS:
Transport layer – TCP, UDP
OUTCOMES:
Student will able to enumerate the layers of the TCP/IP model and explain the
function(s) of each layer.
MODULE-5
MATRUSRI
ENGINEERING COLLEGE

Transport layer -TCP/IP model
MATRUSRI
ENGINEERING COLLEGE

Transport layer -TCP/IP model
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ENGINEERING COLLEGE
TCP, like UDP, is a process-to-process (program-to-program) protocol. TCP, therefore,
like UDP, uses port numbers.
TCP is called a connection-oriented, reliable transport protocol. It adds connection-
oriented and reliability features to the services of IP.
TCP Services:
Process-to-Process Communication
Stream Delivery Service
Full-Duplex Communication
Connection-Oriented Service
Reliable Service
TCP Features:
Numbering System
Flow Control
Error Control
Congestion Control
Format

OSI Vs TCP/IP
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Open System Interconnection(OSI) Transmission Control Protocol(TCP)
OSI model has been developed by ISO (International
Standard Organization).
It was developed by ARPANET (Advanced Research Project
Agency Network).
It is an independent standard and generic protocol
used as a communication gateway between the
network and the end user.
It consists of standard protocols that lead to the
development of an internet. It is a communication protocol
that provides the connection among the hosts.
The transport layer provides a guarantee for the
delivery of the packets.
The transport layer does not provide the surety for the
delivery of packets. But still, we can say that it is a reliable
model.
It is also known as a reference model through which
various networks are built.
It is an implemented model of an OSI model.
The network layer provides both connection-
oriented and connectionless service.
The network layer provides only connectionless service.
Protocols are hidden and can be easily replaced
when the technology changes.
The protocol cannot be easily replaced.
It consists of 7 layers. It consists of 4 layers.
Defines the services, protocols, and interfaces as well
as provides a proper distinction between them. It is
protocol independent.
In the TCP/IP model, services, protocols, and interfaces are
not properly separated. It is protocol dependent.
The usage of this model is very low. This model is highly used.
It provides standardization to the devices like router,
motherboard, switches, and other hardware devices.
It does not provide the standardization to the devices. It
provides a connection between various computers.

Transport layer - User datagram protocol (UDP)
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The original TCP/IP protocol suite specifies two protocols for the transport layer:
UDP and TCP
The User Datagram Protocol (UDP) is called a connectionless, unreliable transport
protocol.
It does not add anything to the services of IP except to provide process-to process
communication instead of host-to-host communication.
Also, it performs very limited error checking.

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The following lists some uses of the UDP protocol:
o UDP is suitable for a process that requires simple request-response communication
with little concern for flow and error control. It is not usually used for a process
such as FrP that needs to send bulk data .
o UDP is suitable for a process with internal flow and error control mechanisms. For
example, the Trivial File Transfer Protocol (TFTP) process includes flow and error
control. It can easily use UDP.
o UDP is a suitable transport protocol for multicasting. Multicasting capability is
embedded in the UDP software but not in the TCP software.
o UDP is used for management processes such as SNMP .
o UDP is used for some route updating protocols such as Routing Information Protocol
(RIP).
UDP Process:
Connectionless Services
Flow and Error Control
Encapsulation and De-capsulation

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Pseudo header for checksum calculation
The UDP checksum calculation is different from the one for IP and ICMP. Here the
checksum includes three sections: a pseudo header, the UDP header, and the data
coming from the application layer
If the checksum does not include the pseudo
header, a user datagram may arrive safe and
sound.
However, if the IP header is corrupted, it
may be delivered to the wrong host.
The protocol field is added to ensure that
the packet belongs to UDP, and not
to other transport-layer protocols.
If this value is changed during transmission,
the checksum calculation at the receiver will
detect it and UDP drops the packet. It is not
delivered to the wrong protocol.

1. Explain the TCP/IP reference model with neat diagram.
2. Comparison between OSI model and TCP/IP model.
Questions & Answers
MATRUSRI
ENGINEERING COLLEGE

INTRODUCTION:
The telephone system is the largest and most complex electronic communication system
in the world. It uses just about every type of electronic communication technique
available including virtually all the ones described in this chapter
UNIT IV- Telecommunication Systems
OUTCOMES:
Acquire the knowledge of Electronic telephone system.
Describe the operation of a PBX.
Explain the operation of a facsimile machine and operation of an Internet
Protocol telephone.
 Understand the concepts of Optical communication and wavelength division
multiplexing
MATRUSRI
ENGINEERING COLLEGE

CONTENTS:
4.1. Telephones, telephone system
OUTCOMES:
Name and described the components in conventional and electronic telephones.
 Described the characteristics of the various signals used in telephone communication.
Understand the general operation of a cordless telephone.
MODULE-I
MATRUSRI
ENGINEERING COLLEGE

Telephones
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ENGINEERING COLLEGE
- The original telephone system was designed for full-duplex analog communication
of voice signals.
- Today, this system is still primarily used for voice, but it employs mostly digital
techniques, not only in signal transmission but also in control operations.
The basic telephone system:

Telephones
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It also contains a ringer and a dialing mechanism. Overall, the
telephone set fuli lls the following basic functions. The receive
mode provides:
1. An incoming signal that rings a bell or produces an audio tone indicating that a
call
is being received
2. A signal to the telephone system indicating that the signal has been answered
3. Transducers to convert voice to electric signals and electric signals to voice
The transmit mode:
1. Indicates to the telephone system that a call is to be made when the handset is
lifted
2. Indicates that the telephone system is ready to use by generating a signal
called the
dial tone
3. Provides a way of transmitting the telephone number to be called to the
telephone
system
4. Receives an indication that the call is being made by receiving a ringing tone
5. Provides a means of receiving a special tone indicating that the called line is
busy
6. Provides a means of signaling the telephone system that the call is complete

.
Telephones
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ENGINEERING COLLEGE
Basic telephone set
Basic telephone set:
Ringer Hybrid
Hook switch Dialing circuit
DTMF

Telephones
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ENGINEERING COLLEGE
DTMF
Most modern telephones use a dialing system known as Touch- Tone.
It uses pairs of audio tones to create signals representing the numbers to be dialed.
This dialing system is referred to as the dual-tone multi frequency (DTMF) system

Telephones
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ENGINEERING COLLEGE
Standard Telephone and Local Loop:
Transmitter Central office Pulse dialing
Receiver Ring Tone dialing
Hook Switch Tip Hybrid

Telephone System
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ENGINEERING COLLEGE
The telephone system refers to the organizations and facilities involved in connecting a telephone to
the called telephone regardless of where it might be in the united states or anywhere else in the
world.
Telephone Hierarchy:
•Whenever you make a telephone call, your voice is connected through your local exchange to the
telephone system.
• From there it passes through at least one other local exchange, which is connected to the telephone
you are calling.
• Several other facilities may provide switching, multiplexing, and other services required to transmit
your voice.
• The telephone system is referred to as the public switched telephone network (PSTN).
• The central office or local exchange is the facility to which your telephone is directly connected by a
twisted-pair cable.
• Regional Bell operating companies (RBOCs), also called local exchange carriers (LECs), provide local
telephone service. Independent phone companies provide local service in rural areas not served by
RBOCs.
•The LECs provide telephone services to designated geographical areas referred to as local access
and transport areas (LATAs).
•Long-distance service is provided by long-distance carriers known as interexchange carriers (IXCs).
•The IXCs are the familiar long-distance carriers such as AT&T (now SBC), WorldCom (now Verizon),
and US Sprint.
•Long-distance carriers must be used for the interconnection for any inter-LATA connections.

.
Telephone System
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ENGINEERING COLLEGE
Subscriber interface : The subscriber interface or the subscriber line interface circuit (SLIC) is
comprised of a group of basic circuits that power the telephone and provide all the basic functions
such as ringing, dial tone, and dialing supervision.
BORSCHT functions in the subscriber line interface at the central office

.
Telephone System
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ENGINEERING COLLEGE
Organization of the telephone system in the United States
The POP provides the connections to the long-distance carriers, or IXCs. The “cloud” represents the
long-distance networks of the IXCs. The long-distance network connects to the remote POPs, which
in turn are connected to other central offices and local exchanges.

.
Telephone System
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ENGINEERING COLLEGE
Private Telephone System:
Key Systems serve 2–50 user telephones within an organization.
Individual telephone units called stations, all of which are connected to a central answering
station
The central answering station is connected to one or more local loop lines, or trunks, back to
the local exchange.
The telephone sets in a key system typically have a group of pushbuttons that allow each phone
to select two or more outgoing trunking lines.
Private Telephone System: Private Branch Exchange
For larger organizations: thousands of individual telephones within an organization.
private automatic branch exchanges (PABXs)
computer branch exchanges (CPXs).
Advantages of efficiency and cost reduction when many telephones are required.
An alternative to PBX is Centrex.
This service performs the function of a PBX but uses special equipment and special trunk
lines.

Telephone System
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ENGINEERING COLLEGE
PBX: PBX provides baseband interconnections to all the telephones in an organization.
The PBX offers the advantages of efficiency and cost reduction when many telephones are required.
The modern PBX is usually fully automated by computer control.

1. Draw And Explain about telephone hierarchy.
2. Write short notes on telephone SYSTEM.
Questions & Answers
MATRUSRI
ENGINEERING COLLEGE

CONTENTS:
Paging systems,
Internet telephony
OUTCOMES:
Students will be able to Understand
the operation of paging systems
Operation of an internet protocol telephone.
MODULE-2
MATRUSRI
ENGINEERING COLLEGE

.
Paging systems
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ENGINEERING COLLEGE
Paging is a radio communication system designed to signal individuals wherever they may be.
Paging systems operate in the simplex mode. They broadcast signals or messages to individuals
who carry small battery-operated receivers.
To contact an individual with a pager, make a telephone call.
A paging company will send a radio signal that will be received by the pager.
The paging receiver has a built-in audible signaling device or silent vibrator that inform the
person that he or she is being paged.
 Some paging receivers have a small LCD screen on which a telephone number is displayed. This
tells the paged individual which number to call.
 The newest pagers are two-way devices that receive data or send data in the form of numerically
coded messages or short alphanumeric text.

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ENGINEERING COLLEGE
Paging systems
The paging business is closely allied with the telephone business, because the telephone system
provides the initial and final communication process.
 To contact a person via a pager, an individual dials the telephone number assigned to that person.
 The call is received at the office of the paging company.
The paging company responds with one or more signaling tones that tell the caller to
enter the telephone number the paged person should call.
 Once the number is entered, the caller presses the pound sign key to signal the end
of the telephone entry
The paging system records the telephone number in a computer and translates this
number into a serial binary-coded message.
 The message is transmitted as a data bit stream to the paging receiver.
 Paging systems usually operate in the VHF and UHF frequency ranges.
 Most paging systems can locate an individual within a 30-mi radius

Paging systems
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ENGINEERING COLLEGE
Each paging receiver is assigned a special code called a cap code, which is a sequence of
numbers or a combination of letters and numbers.
 The cap code is broadcast over a paging region and if the pager is in the region, it will pick up
and recognize its unique code.
 Thus the most widely used digital paging format is the FLEX system, developed by Motorola.
 REFLEX and INFLEXION are newer, two-way forms of FLEX.

.
Paging systems
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Paging Receiver
 A paging receiver is a small battery-powered superheterodyne receiver.
 Most pagers use a single-chip IC receiver.
 Single- and double-conversion models are available.
 Direct conversion receivers (ZIF) are also used.
 Most basic paging systems use some form of frequency modulation.

.
Internet telephony
MATRUSRI
ENGINEERING COLLEGE
.
Internet telephony, also called Internet Protocol (IP) telephony or Voice over Internet
Protocol (VoIP), uses the Internet to carry digital voice telephone calls.
 VoIP almost completely bypasses the existing telephone system.
 VoIP is a highly complex digital voice system that relies on high-speed Internet connections
from cable TV companies, phone companies supplying DSL, and other broadband systems
including wireless.
VoIP uses the Internet’s vast fiber-optic cabling network to carry phone calls without phone
company charges.
 In large companies, VoIP is replacing traditional telephone service because:
It offers the benefits of lower long-distance calling charges
It reduces the amount of new equipment needed, since phone service is provided over
the same LAN that interconnects the PCs.
There are two basic parts to an IP phone call:
 The “dialing” process which establishes an initial connection
 The voice signal flow.

Internet telephony
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ENGINEERING COLLEGE
Voice Signal Flow
Link Establishment
Home VoIP
Enterprise IP Phones

1. Explain the concept of internet telephony.
2. Explain the operation of an internet protocol telephone.
Questions & Answers
MATRUSRI
ENGINEERING COLLEGE

CONTENTS:
Optical communications: Optical principles
OUTCOMES:
MODULE-3
MATRUSRI
ENGINEERING COLLEGE

.
Optical principles
MATRUSRI
ENGINEERING COLLEGE
.
Optical communication systems use light to transmit information from one place to another.
Light is a type of electromagnetic radiation like radio waves.
Today, infrared light is being used increasingly as the carrier for information in communication
systems.
The transmission medium is either free space or a light-carrying cable called a fiber-optic cable.
Because the frequency of light is extremely high, it can accommodate very high rates of data
transmission with excellent reliability.
Physical Optics: Reflection
The simplest way of manipulating light is to reflect it.
When light rays strike a reflective surface, the light waves are thrown back or reflected.
By using mirrors, the direction of a light beam can be changed.
The law of reflection states that if the light ray strikes a mirror at some angle A from the normal,
the reflected light ray will leave the mirror at the same angle B to the normal.
In other words, the angle of incidence is equal to the angle of reflection.
A light ray from the light source is called an incident ray.

.
Optical principles
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Physical Optics: Refraction
The direction of the light ray can also be changed by refraction, which is the bending of a
light ray that occurs when the light rays pass from one medium to another.
Refraction occurs when light passes through transparent material such as air, water, and
glass.
Refraction takes place at the point where two different substances come together.
Refraction occurs because light travels at different speeds in different materials
The amount of refraction of the light of a material is usually expressed in terms of the index
of refraction n.
This is the ratio of the speed of light in air to the speed of light in the substance.
It is also a function of the light wavelength.

Optical communication systems
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Light Wave Communication in Free Space:
An optical communication system consists of:
A light source modulated by the signal to be transmitted.
A photo detector to pick up the light and convert it back into an electrical signal.
An amplifier.
A demodulator to recover the original information signal.

Optical communication systems
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ENGINEERING COLLEGE
Fiber-Optic Communication System
Fiber-optic cables many miles long can be constructed and interconnected for the purpose of
transmitting information.
Fiber-optic cables have immense information-carrying capacity (wide bandwidth).
Many thousands of signals can be carried on a light beam through a fiber-optic cable.

FIBER-OPTIC CABLES
MATRUSRI
ENGINEERING COLLEGE
Types of Fiber-Optic cables:
Step Index cable
Graded Index cable
Multi mode graded index cable

Optical Transmitters & Receivers
MATRUSRI
ENGINEERING COLLEGE
In an optical communication system, transmission begins with the transmitter, which consists of a
carrier generator and a modulator. The carrier is a light beam that is usually modulated by turning it
on and off with digital pulses. The basic transmitter is essentially a light source.
The receiver is a light or photo detector that converts the received light back to an electric signal. In
this section, the types of light sources used in fiber-optic systems and the transmitter circuitry, as
well as the various light detectors and the related receiver circuits,

MATRUSRI
ENGINEERING COLLEGE
(a) Typical LED construction. (b) Light radiation pattern
Light-Emitting Diodes.:
A light-emitting diode (LED) is a PN-junction semi
conductor device that emits light when forward-biased.
When a free electron encounters a hole in the
semiconductor structure, the two combine, and in the
process they give up energy in the form of light.
Semiconductors such as gallium arsenide (GaAs) are
superior to silicon in light emission.
Most LEDs are GaAs devices optimized for producing red light.
LEDs are widely used for displays indicating whether a circuit is off or on, or for displaying
decimal and binary data.
However, because an LED is a fast semiconductor device, it can be turned off and on very quickly and is
capable of transmitting the narrow light pulses required in a digital Fiber optic system.

MATRUSRI
ENGINEERING COLLEGE
Laser Diodes.:
The other commonly used light transmitter is a laser, which is a
light source that emits coherent monochromatic light.
Monochromatic light is a pure single frequency light.
Although an LED emits red light, that light covers a narrow
spectrum around the red frequencies.
Coherent refers to the fact that all the light waves emitted are in
phase with one another.
Coherence produces a focusing effect on a beam so that it is narrow and, as a result, extremely intense.
The effect is somewhat similar to that of using a highly directional antenna to focus radio waves into a
narrow beam that also increases the intensity of the signal.
The most widely used light source in i ber-optic systems is the injection laser diode (ILD), also known
as a Fabry-Perot (FP) laser. Like the LED, it is a PN junction diode usually made of GaAs.

OPTICAL TRANSMITTERS & RECEIVERS
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ENGINEERING COLLEGE
Light Detectors
The receiver part of the optical communication system is relatively simple.
It consists of a detector that senses the light pulses and converts them to an electric signal.
This signal is amplified and shaped into the original serial digital data.
The most critical component is the light sensor
Photodiode:
The most widely used light sensor is a photodiode. It is a silicon PN-junction diode that is sensitive to
light. This diode is normally reverse-biased,.
The only current that flows through it is an extremely small reverse leakage current. When light
strikes the diode, this leakage current increases significantly. This current flows through a resistor and
develops a voltage drop across it. The result is an output voltage pulse.
Phototransistor:
The reverse current in a diode is extremely small even when exposed to light. The resulting voltage
pulse is very small and so must be amplified.
The base collector junction is exposed to light.
The base leakage current produced causes a larger emitter-to-collector current to flow. Thus the
transistor amplifies the small leakage current into a larger, more useful output . Phototransistor
circuits are far more sensitive to small light levels, but they are relatively slow. Thus further
amplification and pulse shaping are normally used.

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ENGINEERING COLLEGE
PIN Diode:
The sensitivity of a standard PN-junction photodiode can be increased and the response time decreased
by creating a new device that adds an un doped or intrinsic (I) layer between the P and N semiconductors.
The thin P layer is exposed to the light, which penetrates to the junction, causing electron flow
proportional to the amount of light. The diode is reverse-biased, and the current is very low until light
strikes the diode, which significantly increases the current. PIN diodes are significantly faster in response
to rapid light pulses of high frequency. And their light sensitivity is far greater than that of an ordinary
photodiode.
Structure of a PIN photodiode.

MATRUSRI
ENGINEERING COLLEGE
Avalanche Diode:
The avalanche photodiode (APD) is a more widely used photo sensor.
It is the fastest and most sensitive photodiode available, but it is expensive and its circuitry is complex.
Like the standard photodiode, the APD is reverse-biased. However, the operation is different.
The APD uses the reverse breakdown mode of operation that is commonly found in zener and IMPATT
microwave diodes.
When a sufficient amount of reverse voltage is applied, an extremely high current flows because of the
avalanche effect.
Normally, several hundred volts of reverse bias, just below the avalanche threshold, are applied.
When light strikes the junction, breakdown occurs and a large current flows.
This high reverse current requires less amplification than the small current in a standard photodiode.
Germanium APDs are also significantly faster than the other photodiodes and are capable of handling
the very high gigabit-per-second data rates possible in some systems.

MATRUSRI
ENGINEERING COLLEGE
Wavelength Division Multiplexing(WDM)
Data is most easily multiplexed on i ber-optic cable by using time-division multiplexing (TDM), as in the
T1 system or in the SONET system .
However, developments in optical components make it possible to use frequency- division multiplexing
(FDM) on Fuber-optic cable (called wavelength-division multiplexing, or WDM), which permits multiple
channels of data to operate over the cable’s light wave bandwidth.
Wavelength-division multiplexing, another name for frequency-division multiplexing, has been widely
used in radio, TV, and telephone systems. The best example today is the multiplexing of dozens of TV
signals on a common coaxial cable coming into the home

MATRUSRI
ENGINEERING COLLEGE
Wavelength Division Multiplexing(WDM
In WDM, different frequencies or “colors’’ of infrared light are employed to carry individual data streams.
These are combined and carried on a single Fiber.
Although frequency as a parameter is more widely used to distinguish the location of wireless signals
below 300 GHz, at light frequencies the wavelength parameter is the preferred measure.
Coarse Wavelength-Division Multiplexing
The first coarse WDM (CWDM) systems used two channels operating on 1310 and 1550 nm.
Later, four channels of data were multiplexed.
A separate serial data source controls each laser. The data source may be a single data source or a
multiple TDM source. Current systems use light in the 1550-nm range.
A typical four channel system uses laser wavelengths of 1534, 1543, 1550, and 1557.4 nm.
Each laser is switched off and on by the input data.
The laser beams are then optically combined and transmitted over a single Fiberc able. At the
receiving end of the cable, special optical Filters are used to separate the light beams into individual
channels. Each light beam is detected with an optical sensor and then filtered into the four data
streams.

Questions & Answers
MATRUSRI
ENGINEERING COLLEGE
1. Draw the block diagram of fiber optics communication system? Explain in detail.
2. What are the advantages of wavelength division multiplexing?
3. Explain classification of fibers.

INTRODUCTION:
This unit describes the cell phone operational concepts, the two most
common second-generation digital cell phone systems and different
wireless technologies with different applications.
UNIT-V
OUTCOMES:
Understand the concepts of cell phone systems.
 Understand the different wireless technologies.
MATRUSRI
ENGINEERING COLLEGE

CONTENTS:
CELLULAR TELEPHONE SYSTEMS
OUTCOMES:
DESCRIBED THE ARCHITECTURE AND OPERATION OF A CELL
PHONE BASE STATION.
MODULE-I
MATRUSRI
ENGINEERING COLLEGE

INTRODUCTION
• Wireless refers primarily to the cellular telephone industry.
• The cell phone is the largest-volume consumer electronics device.
• It has changed the way that we communicate.
• In 2005, cell phone subscribers numbered more than wired telephone
subscribers.
• As the data speed of the newer digital cell phone transmissions
increases, more cell phone applications are possible, including
cameras, Internet access, e-mails, audio, gaming, and video.
• A cellular radio system provides standard telephone service by two-
way radio at remote locations.
• Cellular radios or telephones were originally installed in cars or trucks,
but today most of them are available in handheld models.
MATRUSRI
ENGINEERING COLLEGE

INTRODUCTION
• Cellular telephones permit users to link up with the
standard telephone system, which permits calls to any part
of the world.
• Cellular radio telephone service is available worldwide.
• The original U.S. cell phone system, known as the
advanced mobile phone system, or AMPS, was based on
analog technologies.
• AMPS has been phased out and replaced by second-
generation (2G) and third-generation (3G) digital cell
phone systems.
MATRUSRI
ENGINEERING COLLEGE

CELLULAR CONCEPTS
• The basic concept behind the cellular radio system is that rather
than serving a given geographical area with a single transmitter and
receiver, the system divides the service area into many small areas
known as cells.
• The typical cell covers only several square miles and contains its
own receiver and low-power transmitter.
• The coverage of a cell depends upon the density (number) of users
in a given area.
• Each cell is connected by telephone lines or a microwave radio relay
link to a master control center known as the mobile telephone
switching office (MTSO).
• The MTSO controls all the cells and provides the interface between
each cell and the main telephone office.
MATRUSRI
ENGINEERING COLLEGE

CELLULAR CONCEPTS
• As the person with the cell phone passes through a cell, it is served by the cell
transceiver.
• The telephone call is routed through the MTSO and to the standard telephone
system.
• As the person moves, the system automatically switches from one cell to the
next.
• The receiver in each cell station continuously monitors the signal strength of
the mobile unit.
• When the signal strength drops below a desired level, it automatically seeks a
cell where the signal from the mobile unit is stronger.
• The computer at the MTSO causes the transmission from the person to be
switched from the weaker cell to the stronger cell. This is called a handoff.
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The area served by a cellular telephone system is divided into small
areas called cells. Note: cells are shown as ideal hexagons, but in reality
they have circular to other geometric shapes. These areas may overlap,
and the cells may be of different sizes.
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FREQUENCY ALLOCATION
• Cellular radio systems operate in the UHF and microwave bands as
assigned by the Federal Communications Commission (FCC).
• The original frequency assignments were in the 800- to 900-MHz
range previously occupied by the mostly unused UHF TV channels 68
through 83.
• The frequencies between 824 and 849 MHz are reserved for the
uplink transmissions from the cell phone to the base station. These are
also called the reverse channels.
• The frequencies between 869 and 894 MHz are the downlink bands
from base station to cell phone.
• Two blocks of 60 MHz between 1850 and 1990 MHz are referred to
as the personal communications systems (PCS) channels.
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Additional U.S. Cell phone spectrum. (A) 890 to 960 mhz and (b) 1850 to 1990
mhz are called the personal communication system PCS band.
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MULTIPLE ACCESS
Multiple access refers to how the subscribers are allocated to the
assigned frequency spectrum.
Access methods are the ways in which many users share a limited
amount of spectrum.
The techniques include:
1. Frequency reuse
2. Frequency-division multiple access (FDMA)
3. Time-division multiple access (TDMA)
4. Code-division multiple access (CDMA)
5. Spatial-division multiple access (SDMA).
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FREQUENCY REUSE
• In frequency reuse, individual frequency bands are
shared by multiple base stations and users.
• This is possible by ensuring that one subscriber or base
station does not interfere with any others.
• This separation achieved by controlling such factors as
transmission power, base station spacing, and antenna
height and radiation patterns.
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FREQUENCY-DIVISION MULTIPLE ACCESS
• FDMA systems are like frequency-division multiplexing.
• They allow many users to share a block of spectrum by dividing it up
into many smaller channels.
• Each channel of a band is given an assigned number or is designated
by the center frequency of the channel.
• One subscriber is assigned to each channel.
Time-Division Multiple Access
• TDMA relies on digital signals and operates on a single channel.
• Multiple users use different time slots.
• Because the audio signal is sampled at a rapid rate, the data words
can be interleaved into different time slots.
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CODE-DIVISION MULTIPLE ACCESS
• CDMA is just another name for spread spectrum.
• A high percentage of cell phone systems use direct sequence spread spectrum
(DSSS).
• Here the digital audio signals are encoded in a circuit called a vocoder to produce
a 13-kbps serial digital compressed voice signal.
• It is then combined with a higher-frequency chipping signal.
• A unique pseudo-random chipping code is used to identify multiple subscribers
who use the same spectrum.
Spatial-Division Multiple Access
• This form of access is actually an extension of frequency reuse.
• It uses highly directional antennas to pinpoint users and reject others on the
same frequency.
• Very narrow antenna beams at the cell site base station are able to lock in on
one subscriber but block another while both subscribers are using the same
frequency.
• Modern antenna technology using adaptive phased arrays makes this
possible.
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DUPLEXING
• Duplexing refers to the ways in which two-way radio or telephone
conversations are handled.
• Telephone communications have always been full duplex, where both
parties can simultaneously send and receive. All cell phone systems are full
duplex.
• To achieve full duplex operation, frequency-division duplexing (FDD) or
time-division duplexing (TDD) must be implemented.
• In FDD, separate frequency channels are assigned for the transmit and
receive functions.
• The transmit and receive channels are spaced so that they do not interfere
with one another inside the cell phone or base station circuits.
• TDD is less common. The system assigns the transmit and receive data to
different time slots, both on the same frequency.
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1. WRITE SHORT NOTES ON MULTIPLE ACCESS.
2. EXPLAIN THE CELLULAR CONCEPTS.
Questions & Answers
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CONTENTS:
THE ADVANCED MOBILE PHONE SYSTEM (AMPS)
DIGITAL CELL PHONE SYSTEMS
OUTCOMES:
DESCRIBED THE BLOCK DIAGRAM ARCHITECTURE OF A MODERN
DIGITAL CELL PHONE.
MODULE-II
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TYPICAL AMPS HANDSET
Although AMPS cell phones are due to be phased out beginning in
2007, millions are still in use.
An AMPS unit consists of five major sections: transmitter, receiver,
synthesizer, logic unit, and control unit.
Mobile radios derive their operating power from built-in rechargeable
batteries.
The transmitter and receiver share a single antenna.
Advanced Mobile Phone System (AMPS)
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GENERAL BLOCK DIAGRAM OF A TYPICAL AMPS UNIT (CELLULAR
RADIO).
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TYPICAL AMPS HANDSET: TRANSMITTER & RECEIVER
• The transmitter is a low-power FM unit operating in the frequency
range of 825 to 845 MHz.
• The transmitter’s output power is controllable by the cell site and
MTSO.
• Special control signals picked up by the receiver are sent to an
automatic power control (APC) circuit that sets the transmitter to
one of eight power output levels.
• The APC feature permits optimum cell site reception with minimal
power and helps minimize interference from other stations in the
same or adjacent cells.
• The receiver is typically a dual-conversion superheterodyne.
• The frequency synthesizer section develops all the signals used by
the transmitter and receiver.
• The logic unit contains the master control circuitry.
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TYPICAL AMPS HANDSET
• All cellular radios contain a programmable read-only
memory (PROM) chip called the number assignment
module (NAM).
• The NAM contains the mobile identification number
(MIN), which is the telephone number assigned to the unit.
• The control unit contains the handset with speaker and
microphone.
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• All new cell phones and systems use digital rather than analog
methods.
• All-digital systems were developed to expand the capacity of existing
cell phone systems.
• Digital techniques provide several ways to multiplex many users into
the same spectrum space.
• Digital systems are more reliable in a noisy environment.
• Digital circuits can be made smaller and more power-efficient, so
handsets can be compact and can operate for longer times on a single
battery charge.
• Digital cell phones greatly facilitate the transmission of data, so
services such as e-mail and Internet access are possible with a cell
phone.
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2G CELL PHONE SYSTEMS
• Three basic second-generation (2G) digital cell phone systems are in
wide use today.
• Two of them use time-division multiplexing (TDM), and the third uses
spread spectrum (SS).
• The TDM systems are the Global System for Mobile Communications
(GSM) and the IS-136 standard for time division multiple access (TDMA).
• The SS system is code-division multiple access (CDMA).
Vocoder
• To use digital data transmission techniques first requires that the voice
be digitized.
• The circuit that does this is a vocoder, a special type of analog-to-digital
(A/D) converter and digital-to-analog (D/A) converter.
• The converted serial data signal, representing the voice, modulates the
carrier and the composite signal transmitted over the assigned channel.
• The main function of a vocoder is data compression.
• All 2G and 3G phones contain a vocoder.
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IS-136 TDMA
• IS-136 is the Telecommunications Industry Association (TIA) standard that
describes the time-division multiple-access (TDMA) cell phone system.
• IS-136 operates concurrently on the same 800- to 900-MHz band channels used
by AMPS and is also used in the PCS-1900 bands.
• The IS-136 system provides for six time slots in the TDMA frame. Two time slots
are assigned to each of three users.
• Spectral efficiency is achieved with π/4-DQPSK modulation, one of the most
efficient modulation methods currently available.
GSM
• The most widely used 2G digital system is GSM, or Global System for Mobile
Communications.
• In the US, GSM is widely implemented in both the 800- and 1900-MHz personal
communication system band.
• It has mostly replaced the IS-136 systems in the US.
• Like IS-136, GSM uses TDMA.
• The modulation method, known as Gaussian minimum shift keying (GMSK), is
similar to FSK but allows higher speeds to be transmitted in a narrower channel.
• GSM is the dominant cell phone technology in the world.
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IS-95 CDMA
• The IS-95 CDMA TIA cell phone standard is called code-division multiple
access (CDMA) and is also known as CDMA One.
• CDMA uses direct sequence spread spectrum (DSSS) with a 1.2288-MHz
chipping rate that spreads the signal over a 1.25-MHz channel.
• Up to 64 users can use this band simultaneously with little or no interference
or degradation of service.
• The CDMA system uses FDD for duplexing.
• A key part of a CDMA system is APC.
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2.5G CELL PHONE SYSTEMS
• The designation 2.5G refers to a generation of cell phones between
the original second-generation (2G) digital phones and newer third-
generation (3G) phones.
• 2.5G phones bring data transmission capability to 2G phones in
addition to normal voice service.
• A 2.5G phone permits subscribers to exchange emails and access the
Internet by cell phone.
• The three technologies used in 2.5G systems are GPRS, EDGE, and
CDMA2000.
• One popular 2.5G technology is the general packet radio service
(GPRS).
• This system is designed to work with GSM phones.
• It uses one or more of the eight time slots in a GSM phone system to
transmit data rather than digitized voice.
• A faster 2.5G technology is enhanced data rate for GSM evolution
(EDGE).
• It uses 8-PSK modulation instead of GMSK to achieve data rates up to
384 kbps.
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2.5G CELL PHONE SYSTEMS
CDMA2000
• A third, different form of 2.5G digital cell phone is designated
CDMA2000. This standard is an extension of the widely used IS-95
CDMA standard (CDMA One).
• The basic CDMA2000 data transmission method uses 1.25-MHz-wide
channels but changes the modulation and coding formats to double the
voice capacity.
• The data capability is packet-based and permits a data rate of up to
144 kbps which is comparable to EDGE.
• The more recent version is called 1×EV-DO or Evolution-Data
Optimized. It has a data rate of about 3.1 Mbps downlink and an uplink
rate up to 1.8 Mbps.
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• Third-generation (3G) cell phones are true packet data phones.
• 3G phones feature enhanced digital voice and high-speed data transmission
capability.
• 3G applications include fast e-mail and Internet access.
• 3G phones are being packaged with personal digital assistants (PDAs).
• High speed also permits the transmission of video.
UMTS 3G
• The ITU recommended one worldwide version known as wideband CDMA
(WCDMA) in implementing 3G.
• This system is also known as the Universal Mobile Telecommunications
Service (UMTS).
• WCDMA is a direct sequence spread spectrum technology.
• In the most popular configuration, it is designed to use a 3.84-MHz chipping
rate in 5-MHz-wide bands.
• Duplexing is FDD, requiring the matching of 5-MHz channels. The modulation
is QPSK.
• It can achieve a packet data rate up to 2 Mbps.
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3G CELL PHONE SYSTEMS- UMTS 3G
• A key problem in implementing 3G is the need for huge portions of spectrum.
• The exact 3G spectrum varies widely depending on which part of the world
you are in, making it extremely difficult to design a cell phone that is fully
operable worldwide.
• The UMTS 3G standard also defines a TDD version known as TD-SCDMA for
time-division synchronous code-division multiple access.
• The primary benefit of TD-SCDMA is that less spectrum is needed.
• Because of the need for faster systems, a new system compatible with
WCDMA has been developed.
• Known as high-speed downlink packet access (HSDPA), this so-called 3.5G
technology is an add-on to WCDMA systems.
• HSDPA uses an adaptive coding and modulation scheme with QPSK and 16-
QAM.
• When a fast uplink is needed, a companion standard known as high-speed
uplink packet access (HSUPA) is used.
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Principles of Electronics Communication system.ppt

Principles of Electronics Communication system.ppt

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