EE 361

Communication Theory
Course Information
Course Info
Pre-requisite: Signals and Systems (EE341)
Textbook
B. P. Lathi & Z. Ding, Modern Digital and Analog
Communication Systems. Int. 5th Ed., Oxford
University Press, 2019.
References
1.Hsu, H. P. (2009). Schaum's outline of signals
and systems (2nd ed.). Columbus, OH: McGraw-Hill
Education.
2.Haykin, S. (2009). Communication systems (2nd
ed.). John Wiley & Sons.
3.Couch, II, L. W. (2007). Digital and analog
communication systems (7th ed.). Upper Saddle
River, NJ: Prentice Hall.
4.Proakis, J. G., & Salehi, M. (2005). Fundamentals
of Communication Systems. Upper Saddle River,
NJ: Prentice Hall.
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 Blooms
CLOs Course Learning Outcomes PLOs
Taxonomy

CLO-1 Be able to conduct analysis of baseband signals in PLO-2 C4

time domain and in frequency domains. (Analyzing)
CLO-2 Be able to analyze linear and non-linear modulated PLO-2 C4
signals in time and frequency domains. (Analyzing)
CLO-3 Be able to analyze systems such as quantizers using PLO-2 C4
the principle of digital communication systems. (Analyzing)
CLO-4 Be able to design analog and digital systems under PLO-3 C4
various constraints. (Analyzing)

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 Tentative Grade Distribution

Assessment Tools Percentage

Quizzes (Surprise + Scheduled) 15%
Assignments 05%
Midterm Examination 30%
Complex Engineering Problem 10%
Final Examination 40%

Students are encouraged to solve some assigned homework problems

using the available engineering software, such as MATLAB
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 Weekly Lecture Breakdown
Week# Topic Related Preparation

1 Introduction to Communication Systems Chapter 1 & 2 Text Book

2 Introduction to Signals Chapter 2 Text Book

3 Analysis and Transmission of Signals Chapter 3 Text Book
4 Analysis and Transmission of Signals Chapter 3 Text Book
5 Amplitude Modulation (AM), Baseband and carrier, Double Side Band (DSB) Chapter 4 Text Book

6 DSB-LC, Quadrature Amplitude Modulation (QAM) Chapter 4 Text Book

7 Single Side Band (SSB), Vestigial Side Band (VSB), Carrier Acquisition, Chapter 4 Text Book
Superhetrodyne AM Receiver
8 Angle Modulation: Concept of Instantaneous Frequency Chapter 4 Text Book
Mid Exam To be decided
9 Bandwidth of Angle Modulated Waves, FM generation, Chapter 4 Text Book
10 Demodulation of FM, Interference in Angle Modulated Systems FM receiver Chapter 4 Text Book

11 Sampling Theorem, Pulse Code Modulation (PCM) Chapter 5 Text Book

12 PCM, Differential PCM (DPCM), Delta Modulation Chapter 5 Text Book
13 Selected topics in principles of digital transmission Chapter 6 Text Book
14 Selected topics on the analysis of noise impairments in Wireless Chapter 6 Text Book
Communication Systems
15 Selected topics on 5G and beyond 5G Communication Systems Research Papers
Final Exam To be decided
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 Administrative Policies

▪ According to institute policy, 80% attendance is mandatory to appear in the

final examination.
▪ In any case, there will be no retake of (scheduled/surprise) quizzes.
▪ Assignments are due as instructed. Late submission are not allowed.

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 EE 361
Communication Theory
CHAPTER 1
INTRODUCTION

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 What is Communication?
• Communication = Transfer of Information
• Old Forms of Communication (Non Electrical)
– Using Couriers; human messengers, carrier pigeons, post
– Using sound; drum beats, gun shots
– Using Fire; torches, smoke, SOS
– Using light; flashlight, flags
• Non-Electrical Communication: Slow and over short distances
• Electrical Communication = Using electrical signals
– Long distances, Fast, Reliable, Economical
• Modes of Communication
– Simplex – One directional
– Half-Duplex- Two directional but at different times.
– Full-Duplex – Two directional simultaneously.

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Applications – Cell Phones

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Albert Einstein’s fear

Remember! You are here to understand

the theory and not its ecology.
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The Pakistan Market

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Emerging Technologies

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 Applications – Health Care

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 A General Block Diagram for a Communication System
Input Input Input Transmitter Transmitte Channel Received Receiver Output Output Output Destination
Source d
Message Transducer Signal Signal Signal Signal Transducer Message

Channel Impairments
• Delay
• Attenuation (loss of power)
• Distortion (system imperfections)
• Noise (usually from natural
sources)
• Interference (non-hostile human
sources)
• Jamming (hostile human sources)
Message Input
Transducer
• Source:
Human Microphone
– Generates a message (often in a non-electrical form) Voice
• Human voice (acoustic signal)
Printed Scanner
• Printed page Page
• Photograph
Photograph Digital Camera
• Video
• Text message Video Video Camera

• Input Transducer Text Keyboard

Message
– Converts the non-electrical message into an
electrical waveform that is called a baseband signal.
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 A General Block Diagram for a Communication System
Source Input Input Input Transmitter Transmitte Channel Received Receiver Output Output Output Destination
d
Message Transducer Signal Signal Signal Signal Transducer Message

Channel Impairments
• Delay
• Attenuation (loss of power)
• Distortion (system imperfections)
• Noise (usually from natural sources)
• Interference (non-hostile human sources)
• Jamming (hostile human sources)

• Transmitter:
– Modifies the baseband signal into a form suitable for the channel, for
efficient transmission
• Channel
– is the medium of transmission
• e.g. wire, coaxial cable, optical fiber, air, free space, etc.
– Can cause many types of impairment to the signal
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 A General Block Diagram for a Communication System
Source Input Input Input Transmitter Transmitte Channel Received Receiver Output Output Output Destination
d
Message Transducer Signal Signal Signal Signal Transducer Message

Channel Impairments
• Delay
• Attenuation (loss of power)
• Distortion (system imperfections)
• Noise (usually from natural
sources) Message Output
• Interference (non-hostile human
sources) Transducer
•
• Receiver:
Jamming (hostile human sources)
Human Loudspeaker
Voice
– “Recovers” the input signal from the received
signal by undoing the signal modifications made Printed Printer
Page
by the transmitter and the channel
• Output Transducer Photograph Printer/Still
Monitor
– Converts the output electrical signal into its Video Video
original form (message) Monitor/TV
• Destination Text Text Printer, e.g.
– The unit to which the message is communicated, Message telex machine
e.g., the user of the information
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 Noise
• Noise is a random and unpredictable signal, usually, from natural sources
– External noise; lightning, solar noise, interference
– Internal noise; thermal motion of electrons in conductors, random emission,
diffusion and recombination of electrons and holes.
• Proper care can minimize or even eliminate external noise
• Proper care can reduce the effect of internal noise but can never
eliminate it
• Noise is one of the basic factors that fundamentally limits the
communication rate
• Other factors are power and bandwidth
• The signal-to-noise ratio (SNR) is defined as the ratio of signal power to
noise power
• The SNR is continuously decreasing along the length of the channel.
• Amplification of the received signal to compensate for attenuation cannot
help improve the SNR, because the noise will be amplified in the same
proportion. On the contrary, an amplifier may decrease the SNR.
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 Analog and Digital Messages
• Messages are analog or digital.
• Analog messages
• Characterized by data whose values vary over a continuous
range of time.
• For example, a particular speech waveform has amplitudes
that vary over a continuous range.
• Digital Messages
• constructed with a finite number of symbols.
• For example, printed English consists of 26 letters, 10
number, a space and several punctuation marks. Thus, a text
document written in English is a digital message constructed
from about 128 symbols.
• A digital message constructed with M symbols is called an
M-ary message.
• More Code and Regenerative Repeaters.
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Analog to Digital Conversion

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 Modulation
• Modulation is the process by which the baseband signal is included in the
properties of a high-frequency carrier.
• A carrier is a high-frequency sinusoid and it has the following parameters:
– Amplitude
– Frequency
– Phase
• Modulation is performed by varying one of the carrier parameters in
proportion to the baseband signal.
• Accordingly, we have
– Amplitude Modulation (AM)
– Frequency Modulation (FM)
– Phase Modulation (PM)
• At the receiver, the inverse operation is performed. This is called
“Demodulation.”
• Demodulation is the process of recovering the baseband signal from the
modulated carrier.
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 Modulation
Carrier

Baseband Signal=Modulating Signal=Message Signal=Information Signal

Amplitude-Modulated Carrier

Freqency-Modulated Carrier

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 Why do we need modulation?
• We need modulation for three main reasons:
1. Efficient Radiation:
• For efficient radiation, the length of the antenna must be at least one
tenth of the wavelength
• For practical antenna size, the signal frequency must be “high”
• For speech signal, most of the power is concentrated in the frequency
range of 100-3000 Hz. Audible signals have content in the frequency range
of 20-20000 Hz. These frequencies correspond to wavelengths in the range
of 15 km to 1500 km. Thus, a speech signal cannot be radiated from an
antenna of a practical size.
• Using a carrier frequency of 500 kHz (MW range), an antenna of length 60
m is needed (AM Broadcast Station). Frequency Wavelength Minimum Antenna
Length
• Using a carrier frequency of 800 MHz, 60 Hz 5000 km 500 km
an antenna of length 3.8 cm is needed 20 kHz 15 km 1.5 km
(Mobile Phone) 450 kHz 666 m 66.6 m
1 MHz 300 m 30 m
100 MHz 3m 30 cm
1 GHz 30 cm 3 cm

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 Why do we need modulation?
• We need modulation for three main reasons:
2. Simultaneous Transmission of Several Signals:
• To transmit several signals using the same channel without interference,
these signals must occupy separate frequency bands
• This can be achieved by modulating the signals using different carrier
frequencies, so that the modulated carriers occupy separate frequency
bands.
• This can allow many users to share the same channel.
• This is called Multiplexing or Multiple Access.
• Multiplexing is a technique that combines multiple signals into one signal for
transmission over a shared medium. This is used in telephony systems.
• Multiple access is a technique that allows multiple devices to access a
shared medium for data transfer. The modulated signals are combined
in the channel. This is the case in radio broadcasting.

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 Why do we need modulation?
• We need modulation for three main reasons:
3. Obtaining Better Tradeoff between SNR and B:
• Modulation can be used to obtain better SNR at the expense of bandwidth.
• Some types of modulation provide better SNR vs. bandwidth tradeoff.

• More reasons:
– Moving the signal to a better frequency slot (e.g. for lower attenuation
or interference)
– Shifting the signal to a more suitable frequency (e.g. optical range for
optical fibers)
– etc.

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 Broadcast
Systems: TV
Broadcast
Systems

https://www.mathworks.com/help/comm/ug/atsc-digital-television.html, Date Accessed 28/1/25 39

 Assignment # 1 (Hand Written)

1. On Slide 10, a time line of 1G to 6G is mentioned. Draw a table

comparing these technologies. Select any 5 features to compare
the 5 generations.
2. Draw PSTN, GSM and LTE architecture diagrams. The
architectures are often asked as interview questions.
3. In terms of your experience with telecommunication sector as a
user, identify at least 1 problem that you have faced as a user.
Next, see if you can find the solution for such a problem in
literature using Google Scholar and report if applicable.
• Note:
• 1) In handwritten form and to be handed over in the first class
of 2nd week of semester.
• 2) All identical submissions will be marked as zero.

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