Prepared by:-
Abdirrahman sheikh Hassan
Dahir Suleiman Aqil

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Introduction
During the past several years , traditional analog communication systems that use traditional amplitude modulation ( AM ) , frequency modulation ( FM ) and phase modulation ( PM ) have gradually been replaced with more modern digital communication systems.
Digital communication systems offer several outstanding advantages over traditional analog systems : ease of processing , ease of multiplexing and noise immunity .
Introduction (cont.)
Digital modulation applies a digital data stream to the carrier and makes the data stream compatible with the radio frequency (RF) communications channel.
The process of converting data signal to a sinusoidal waveform where its amplitude, phase or frequency, or a combination of them, is varied in accordance with the transmitting data is called Bandpass modulation.
Project objectives
In light of previous considerations, the objectives of the project are:-
To study different types of digital modulation techniques and their detectors.
To highlight the importance of the signal constellation and Gray coding.
To estimate or calculate the performance of these techniques and compare them.
To simulate different types of digital modulation techniques.
Methodology
The project is divided in to two phases:
The first phase will involve and comparative study of the different modulation (both binary &M-ary) techniques, also their detections and their constellation diagrams thoroughly to understand clearly the basic principles of the digital modulation techniques.
Methodology (cont.)
Second phase will focus on the performance of the different techniques by testing different types of modulation and comparing their performance. The implementation of this phase will involve the use software simulation (MATLAB program).
Expected Outcomes
After this project the researchers will become familiar with some of the digital modulation techniques.
Since the choice of the modulation technique depends on its performance , we will simulate different techniques and will compare them ,than we shall know the suitable one.
Literature Review
In the past 20 years or so, research and development in digital modulation techniques have been very active and have yielded many promising results. However, these results are scattered all over the literature.
In 2002 - turbo-coded satellite digital TV broadcast during a satellite test in "France Telecom Services International" . was based on Phase Shift Keying (PSK) and Quadrature PSK (QPSK).
In 2009 - [Computer-Aided Engineering] Analyze BER Performance Of Wireless FSK Systems Modern communication systems employ digital modulation for a variety of reasons, including improved immunity to noise and channel impairments as well as enhanced security compared to analog modulation.
Overview of the digital modulation:
Modulation and demodulation concepts
Modulation is the process of converting a baseband signal in to a bandpass signal.
A high frequency “carrier” is modulated by the original “modulating” signal to give a “modulated” wave.
Modulation and demodulation concepts(cont.)
Demodulation is the process of extracting the baseband message from the carrier.
The receiver implementation can affect the performance.
Coherent ( synchronous ) detection: in coherent detection , the local carrier generated at the receiver is phase locked with the carrier at transmitter .
Non coherent ( envelope ) detection : this type of detection does not need receiver carrier to be phase locked with transmitter carrier .
Some basic definitions
The bit rate defines the rate at which information is passed.
The baud (or signaling) rate defines the number of symbols per second. Each symbol represents N bits, and has M signal states, where M = 2^N.This is called M-ary signaling.
Bandwidth efficiency: the number of bits per second that can be transmitted per Hertz of channel bandwidth.
Bit Error Rate(BER) defines the probability of receiving the transmitted bit over channel incorrectly.(transmit 1 and receive 0; transmit 0 and receive 1)
Signal Constellation
Given any modulation scheme, it is possible to obtain its signal constellation.
If we know the signal constellation, we can estimate the performance in terms of the probability of symbol error or probability of bit error given the noise parameters.
Probability of error
depends on the minimum
distance between the
constellation points.
Types of digital modulation:
Binary modulation
Each bit on the input is responsible for the change of one symbol (in one of the 3-parametrs of carrier wave) on output.
Consequently, the output rate of changes is equal to input rate of changes.
The change at the input is known as bit rate (bps). where the change at the output is known as baud or baud rate .
1) Binary Amplitude Shift keying(BASK)
Amplitude of the carrier is switched between two levels according to the digital data.
One bit is transmitted at a time.
Very simple,
The frequency and the phase are constant and
very susceptible to interference.
BASK transmitter(OOK)
An OOK signal can be produced as shown in Figure:
When b(t) is bit ‘1’,symbol 1 is transmitted
When b(t) is bit ‘0’,symbol 0 is transmitted.
Signal representation of the OOK.
 Detection of the (OOK) 
2) Binary Frequency Shift Keying(BFSK)
If the frequency of the sinusoidal carrier is switched depending on the incoming digital signal ,then it is called frequency shift keying(FSK)
As the binary input signal changes from logic 0 to logic 1 and vice versa, the FSK output shifts between two frequencies : a mark or logic 1 frequency and a space or logic 0 frequency.
BFSK transmitter
Signal constellation
BFSK detector
Coherent detector
3.Binary Phase Shift Keying (PSK)
If the phase of the carrier is switched depending on the input digital signal , then it is called phase shift keying ( PSK ).
We know that phase modulation has constant amplitude envelope . Hence the effect of nonlinearities , noise interference is minimum on signal detection.
PSK transmitter
PSK detection
M-ary modulation
Two or more bits are transmitted simultaneously .
Each number(N) of bits on the input are responsible for the change of one symbol on the output.
Thus ,the symbol rate is equal to bit rate divided by the number(N) of bits.
M-ary schemes are more bandwidth efficient, but more susceptible to noise.
1)M-ary PSK
Quadrature PSK (QPSK)
Is an other form of angle-modulation , constant-envelope digital modulation.
QPSK is an M-ary encoding where M=4 (hence the name ‘ quadrature ’meaning ‘4’).
Whith a QPSK four output phases are possible for a single carrier frequency
QPSK transmitter
Signal constellation
Signal constellation(cont.)
QPSK receiver
M-ary QAM
Quadrature Amplitude modulation(QAM) is the combination of amplitude modulation and phase shift keying.
QASK transmitter
Signal constellation
64-QAM This modulation scheme can be used to transmit 16 bits per symbol.
16-QAM receiver
What we will do next….?
This is what we have covered so far in the project and in the upcoming period we will do the following tasks:
From 20 February to 10 march we will estimate or calculate the performance of these techniques in detail.
From 12 march to 15 may we will simulate different types of digital modulation techniques
And compare their performance.
From 16 may to 30 may we will analyze the results of the simulation.
From 1st June to 30 June we will do the documentation.