Kwame Nkrumah University of
Science & Technology, Kumasi, Ghana
COE 241
COMMUNICATION SYSTEMS
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Kwame Nkrumah University of
Science & Technology, Kumasi, Ghana
Dr. Bright Yeboah-Akowuah
Email: b.yeboahakowuah@knust.edu.gh
akowuah2000@yahoo.co.uk
Phone: 0240728535
Office: Vodafone building Room 420
Office Hours: Mondays 12pm – 4pm
(Appointments can also be scheduled)
Website : www.bryeak.co.uk
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Kwame Nkrumah University of
Science & Technology, Kumasi, Ghana
Course Objectives
After completing this course, students
will be able to:
§ Describe the components of modern communication systems
§ Explain linear systems and signal processing techniques
§ Explain analog modulation (AM), angular modulation (FM & PM)
§ Demonstrate the basic principles of modulation and demodulation used
in radio communication systems
§ Design simple impedance matching networks and low-pass & high-pass
filters to meet a given specification
§ Investigates the bit error rate (BER) and symbol error rate (SER)
performance of M-PSK modulation schemes
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Kwame Nkrumah University of
Science & Technology, Kumasi, Ghana
Course Content
§ Introduction to Communication System
§ Signals and Systems
§ Modulations: AM, FM and PM
§ Analog,Pulse and Digital
Communications
§ Filters
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Kwame Nkrumah University of
Science & Technology, Kumasi, Ghana
Course Outline
Lecture
Activity
1
Introduction to Communication
System
2-3
Signals and Systems
4-5
Modulations: AM, FM and PM
6-7
Pulse and Digital Communications
8-9
Filters
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Kwame Nkrumah University of
Science & Technology, Kumasi, Ghana
Reading list
1. Modern Digital and Analog Communication Systems, 4th
ed., B.P. Lathi, Oxford University Press, 2009
2. Introduction to Analog and Digital Communications, S.
Haykin and M. Moher, Wiley, 2nd edition, 2007
3. Digital Communication, J. G. Proakis and M Salehi,
McGraw-Hill, 5th edition, 2008
4. Principles of Electronic Communication Systems, L. E.
Frenzel Jr., McGraw-Hill Education, 4th ed., 2016.
ISBN 978007337385-0
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Kwame Nkrumah University of
Science & Technology, Kumasi, Ghana
Marks Distribution
§ Attendance 5% ( Note: You MUST attend ALL lectures )
§ Assignments 5%
§ Mid-Semester 20%
§ Final Examination 70%
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Kwame Nkrumah University of
Science & Technology, Kumasi, Ghana
Introduction…
COMMUNICATION SYSTEMS
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Introduction…
What is communication ??
Ø Transmission of information from one point to another through
succession of processes:
Ø The generation of message signal: voice, image, video, text,
computer data
Ø Encoding of the message suitable for transmission
Ø Transmission of the encoded message
Ø Decoding and reproduction of the original message
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Introduction…
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Communication block
Three main
components:
• Transmitter
• Channel
• Receiver
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Transmitter
Ø Electronic components and circuits designed
to convert the electrical signal to a signal suitable for
transmission over a given communication medium.
Ø Transmitters are made up of oscillators, amplifiers,
tuned circuits and filters, modulators, frequency
mixers, frequency synthesizers, and other circuits.
Ø Typically this process involves carrier generation,
modulation, amplification, and coupling to an antenna
by cable or waveguide.
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Transmitter Continued…
Basic transmitter in block diagram
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Transmitter Continued…
Ø The radio-frequency oscillator is the carrier source,
and is sometimes known as the master oscillator to
distinguish it from local oscillators in receivers. The
modulator depends on the modulation system in use
(e.g. AM, FM etc.)
Ø Power amplifiers to boost the modulator output to
the necessary power level for transmission
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Communication Channel
Ø The communication channel is the medium by which
the electronic signal is sent from one place to another.
Many different types of media are used in
communication systems, including wire conductors,
fiber-optic cable, and free space.
Channel Constraints!!!
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Channel Constraints!!!
Ø
Bandwidth (B)
Ø that portion of the frequency spectrum
occupied by a signal
Ødifference between the upper and lower
frequency limits of the signal
ØHigher bandwidth leads to greater cost
ØLower bandwidth leads to distortion
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Channel Constraints!!!
Ø
Signal-to-noise ratio (SNR)
Ø presence of noise affects received signal
quality
Ø noise cannot be totally eliminated but
minimise its effect
Ø Increasing bandwidth increases the rate of
transmission but also allows more noise to
pass, so the choice of a bandwidth is a
tradeoff
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Shannon-Hartley theorem
How fast can we transfer
information
over a communication
channel ?
What about the channel
capacity?
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Shannon-Hartley theorem
The theorem states that
the channel capacity is
given by:
C = B log2 (1+ S/N)
where:
C is the channel capacity
B is the bandwidth in Hertz
in bits per second
S/N signal-to-noise ratio
NOTE !!! S/N not in dB
Convert to power ratio if in dB
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Shannon-Hartley theorem…
For example:
Calculate the maximum channel
P = antilog (30/10)= 1000
capacity of a voice telephone with a
The channel capacity is
bandwidth of 3100 Hz and S/N 30 dB
C =B log2 (1+S/N)
= 3100 log2 ( 1+ 1000)
= 3100 log2 (1001)
Solution:
First convert S/N from dB to power ratio
using
dB= 10 log P where P is power ratio
But remember
log2 N = (log10 N)/ (log10 2) = 3.32 log10 N
therefore,
log2 1001 =3.32 log10 1001 = 3.32(3) ≈ 10
Therefore, the channel capacity
C = 3100( 10) = 31000 bps
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Multiple Coding Levels
Channel capacity can be
modified by using multiplelevel encoding schemes that
permit more bits per symbol
to be transmitted.
This makes it possible to
transmit data using symbols
that represent more than just
1 bit
Consider the equation:
C =2B log2 N
where C is channel capacity
B is channel bandwidth
N is the number of
different encoding levels
per time interval.
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Multiple Coding Levels…
Solution:
For example;
If the bandwidth of a
communication channel is 12.5
kHz and the channel capacity is
103.8 kps, Calculate the number
of coding levels N needed to
achieve the maximum speed
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Types of Electronic
Communication
Electronic communications are classified
according to whether they are:
(1)one-way (simplex)
(2)two-way (full duplex or half duplex)
transmissions
(3) (2) analog or digital signals.
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Types of Electronic
Communication
Simplex
One-way
communication
e.g. Tv
broadcasting
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Types of Electronic
Communication
Duplex
Two-way
communication
e.g. Telephone
conversation
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Types of Electronic
Communication
Half duplex
The form of two-way
communication in
which only one party
transmits at a time.
Parties take turns in
transmitting and
receiving
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Types of Electronic
Communication
Analog Signal
Continuous timevarying waveform. For
example, voltage,
current, voice signals.
Sine wave
Voice signal
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Types of Electronic
Communication
Voltage reading ??
Digital Signal
. Discrete time signal.
Deals with on/off, 1/0
situations.
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Digital Signal…
Data used in computers are digital. Most digital signals use
binary or two-state codes. For example, telegraph
(Morse code), serial binary code etc.
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