1

EC8561 – COMMUNICATION SYSTEMS LABORATORY

GRACE COLLEGE OF ENGINEERING, THOOTHUKUDI
SYLLABUS
LIST OF EXPERIMENTS:
Signal Sampling and reconstruction
1.

Time Division Multiplexing

2.

AM Modulator and Demodulator

3.

FM Modulator and Demodulator

4.

Pulse Code Modulation and Demodulation

5.

Delta Modulation and Demodulation

6.

Line coding schemes

7.

Simulation of ASK, FSK, and BPSK generation schemes

8.

Simulation of DPSK, QPSK and QAM generation schemes

9.

Simulation of signal constellations of BPSK, QPSK and QAM

10.

Simulation of ASK, FSK and BPSK detection schemes

11.

Simulation of Linear Block and Cyclic error control coding schemes

12.

Simulation of Convolutional coding scheme

13.

Communication link simulation

14.

TOTAL: 45 PERIODS

2
 EC8561 – COMMUNICATION SYSTEMS LABORATORY
GRACE COLLEGE OF ENGINEERING, THOOTHUKUDI
LIST OF EXPERIMENTS
S.NO DATE NAME OF THE EXPERIMENT PAGE MARKS SIGNATURE
NO
1 Signal Sampling and reconstruction

2 Time Division Multiplexing

3 AM Modulator and Demodulator

4 FM Modulator and Demodulator

5 Pulse Code Modulation and Demodulation

6 Delta Modulation and Demodulation

7 Line coding schemes

8 Simulation of ASK, FSK, and BPSK

generation schemes

9 Simulation of DPSK, QPSK

and QAM generation schemes

10 Simulation of signal constellations of

BPSK, QPSK and QAM

11 Simulation of ASK, FSK and BPSK

detection schemes

12 Simulation of Linear Block and Cyclic

error control coding schemes

13 Simulation of Convolutional coding

scheme
14. Communication link simulation

SIGNATURE OF LAB IN CHARGEEX

3
 EC8561 – COMMUNICATION SYSTEMS LABORATORY
GRACE COLLEGE OF ENGINEERING, THOOTHUKUDI
EX.NO.1 SAMPLING AND RECONSTRUCTION OF ANALOG SIGNAL DATE:

AIM:
To perform the signal sampling and Reconstruction of the Analog signal.

APPARATUS REQUIRED:
1. VCT- 23 Kit
2. Patch Cord
3. Probe
4. CRO

THEORY:
A band limited signal of finite energy has no frequency components higher than ‘W’
hertz is completely described by specified the values of the signal of instants of time separated by
1/2W seconds, where ‘W’ is the higher frequency content. The zero order hold circuit is used for
practical reconstruction. It simply hold the value x(n) for ‘T’ seconds . Here ‘T’ is the sampling
period; The output of zero order hold is stair case signal. The reconstructed signal is the
succession of sinc pulses weighted by x(nTs) these pulses are interpolated with the help of a
LPF. It is also called reconstruction filter or interpolation filter Natural sampling is chopper
sampling because the waveform of the sampled signal appears to be chopped off from the
original signal waveform. The top of the samples remains constant and equal to instantaneous
value of x(t) at start of sampling fs
= 1/Ts

PROCEDURE:
1. Connect the main plug in to the main board. Keep the power switch in OFF position.
2. Put the duty cycle selector switch in position 50%
3. Link 25 Hz sine wave output to analog input.
4. Turn on the trainer.
5. Turning on the trainer select 250 Hz sampling rate by default.
6. Display 25Hz sine wave and sampled output on t oscilloscope. This display shows 25Hz
sine wave being sampled at 200 Hz there are 10 samples for every cycle of the sinewave.
7. Link the sample output to the fourth order low pass filter display sample output and
output of the filter in the oscilloscope. The display shows the reconstructed original 21
Hz sine wave.
8. We had used sampling frequency greater than twice the maximum input frequency.
9. Remove the line from 25KHz sine wave output to the modulating input.
10. By successive process of frequency selector switch change the sampling frequency 32
KHz, 16KHz, 8 KHz,4 KHz,2 KHz,1 KHz,50 Hz and back to 250 Hz
11. Observe how sample output changes in each cases and how the lower sampling
frequencies introduce distortion in to the filter output waveform. This is due to the fact
that the filter does not attenuate the unwanted next frequency component significantly use
of higher order filter would improve the output waveform.

4
 EC8561 – COMMUNICATION SYSTEMS LABORATORY
GRACE COLLEGE OF ENGINEERING, THOOTHUKUDI

TABULATION

AMPLITUDE TIME PERIOD FREQUENCY

MODULATION
SIGNAL
SAMPLED OUTPUT
SAMPLED & HOLD
OUTPUT
FLAT TOP OUTPUT
DEMODUALTED
SIGNAL

5
 EC8561 – COMMUNICATION SYSTEMS LABORATORY
GRACE COLLEGE OF ENGINEERING, THOOTHUKUDI

2. So far we have used sampling frequencies greater than twice the maximum input
frequency. To set the nquist criteria set sampling rate 4 Hz 50% duty cycle.
13. Remove the link 25 Hz sine wave output to the modulating input.
14. Connect the link from 250 Hz or 500 Hz sine wave output to the modulating input and
link the sampled output to fourth order LPF. Display sample output and output of the filter on
the oscilloscope. The display shows the reconstruction signal 250 Hz or 500 Hz sine wave.
15. Now decrease the sampling rate to 32 KHz and then to 500 Hz. Observe the distortedfact
that we under sampled the input waveform overlooking the nyquist criteria and thus the
output was distorted even though the signal below the cutoff frequency of the filter. This is
also describes the phenomenon of aliasing.

MODEL OUTPUT GRAPH

RESULT
Thus the signal sampling and reconstruction techniques was performed and graph was plotted

6
 EC8561 – COMMUNICATION SYSTEMS LABORATORY
GRACE COLLEGE OF ENGINEERING, THOOTHUKUDI
EX.NO .2 TIME DIVISION MULTIPLEXING (TDM) DATE:

AIM:
To understand and to study TDM of signals.

APPARATUS REQUIRED:

1. TDM – PAM kit

2. Patch cord
3. Probe
4. CRO
5. Function generator
6. RPS

THEORY:
TDM:
Time division multiplexing (TDM) is the process of sending more than one source
information over a same channel in different time slot which helps in efficient channel utilization
and saves bandwidth. Time-division multiplexing (TDM) is a type of digital or (rarely) analog
multiplexing in which two or more signals or bit streams are transferred apparently
simultaneously as sub-channels in one communication channel, but are physically taking turns on
the channel. The time domain is divided into several recurrent timeslots of fixed length, one for
each sub-channel. A sample byte or data block of subchannel 1 is transmitted during timeslot 1,
sub-channel 2 during timeslot 2, etc. One TDM frame consists of one timeslot per sub-channel.
After the last sub-channel the cycle starts all over again with a new frame, starting with the
second sample, byte or data block from sub-channel 1. It's often practical to combine a set of
low-bit-rate streams, each with a fixed and pre-defined bit rate, into a single high-speed bit
stream that can be transmitted over a single channel. This technique is called time division
multiplexing (TDM) and has many applications, including wire line telephone systems and some
cellular telephone systems. The main reason to use TDM is to take advantage of existing
transmission lines. It would be very expensive if each low-bit-rate stream were assigned a costly
physical channel (say, an entire fiber optic line) that extended over a long distance.

7
 EC8561 – COMMUNICATION SYSTEMS LABORATORY
GRACE COLLEGE OF ENGINEERING, THOOTHUKUDI

PATCHING DIAGRAM-TDM

PROCEDURE:
1. Switch ON the power supply to the board

2. Display the multiplexed signal at testpoint T14 on channel 1 and 250Hz sinewave at test point
T2 on channel 2 of CRO note down waveform
3. Display 500Hz sine wave at testpoint T3 on channel 2 in place of 250Hz identify
sampled version of this sinewave in TDM signal and note down
4. Similarly observe 1KHz and 2KHZ waveforms at testpoints T4 and T5 respectively on
oscilloscope and notedown
5. Display the TDM waveform(T14) on channel 1 and channel synchronization
signal (T13) on channel 2 of CRO and note down the waveforms
6. Display 250KHz sinewave at T2 on channel 1 and output sinewave at T16 on channel 2 of CRO
note down waveform

8
 EC8561 – COMMUNICATION SYSTEMS LABORATORY
GRACE COLLEGE OF ENGINEERING, THOOTHUKUDI

Amplitude in Time Frequency

volts period
TDM output signal
Transmitter channel
signal
Receiver channel signal

RESULT:
Thus the time division multiplexed outputs are observed and studied.

9
 EC8561 – COMMUNICATION SYSTEMS LABORATORY
GRACE COLLEGE OF ENGINEERING, THOOTHUKUDI
EXP.NO.; 3 AMPLITUDE MODULATION AND DEMODULATION DATE:

AIM:

To perform the amplitude modulation and demodulation a using AM Kit.

APPARATUS REQUIRED:

1. Amplitude modulation kit

2. CRO
3. Probe
4. Patch cord

MODULATION THEORY:
Modulation is defined as the process by which some characteristics of a carrier signal is
varied in accordance with a modulating signal. The base band signal is referred to as the
modulating signal and the output of the modulation process is called as the modulation signal.
Amplitude modulation is defined as the process in which is the amplitude of the carrier
wave is varied about a means values linearly with the base band signal. The envelope of the
modulating wave has the same shape as the base band signal provided the following two
requirements are satisfied
The carrier frequency fc must be much greater than the highest frequency components fm
of the message signal m (t)
i.e. fc >>fm

The modulation index must be less than unity. if the modulation index is greater than
unity, the carrier wave becomes over modulated.

DEMODULATION THEORY:
The process of detection provides a means of recovering the modulating Signal from
modulating signal. Demodulation is the reverse process of modulation. The detector circuit is
employed to separate the carrier wave and eliminate the side bands. Since the envelope of an AM
wave has the same shape as the message, independent of the carrier frequency and phase,
demodulation can be accomplished by extracting envelope.
PROCEDURE:
1. Switch ON the power supply
2. Make wiring connection on VCT-26 as shown in patching diagram
3. Set the carrier signal frequency to be 25khz
4. Check the modulating signal frequency varies from 100hz to 1.5khz at modulating signal
output P2 by varying POT3
5. Connect the carrier signal output P1 to carrier signal input P4 of modulator
6. Connect the modulating signal output P2 to modulating signal input P5 of modulator
7. Display the AM wave at CRO and notedown the readings
8. Convert the modulated output P7 to demodulated input P9 of demodulator
9. Observe the amplified demodulated ouput at testpoint P13

10
 EC8561 – COMMUNICATION SYSTEMS LABORATORY
GRACE COLLEGE OF ENGINEERING, THOOTHUKUDI
PATCHING DIAGRAM -AM MODULATION

PATCHING DIAGRAM -DM DEMODULATION

11
 EC8561 – COMMUNICATION SYSTEMS LABORATORY
GRACE COLLEGE OF ENGINEERING, THOOTHUKUDI

MODEL GRAPH

TABULATION:
Amplitude in Time Frequency
volts period
Message signal
Carrier signal
Modulated signal
Demodulated signal

RESULT:

Thus the amplitude modulation and demodulation were performed.

12
 EC8561 – COMMUNICATION SYSTEMS LABORATORY
GRACE COLLEGE OF ENGINEERING, THOOTHUKUDI

EXP.NO.; 4 FREQUENCY MODULATION AND DEMODULATION DATE:

AIM:
To perform Frequency modulation technique.

APPARATUS REQUIRED:
1. Frequency modulation kit
2. CRO
3. Probe
4. Patch cord

THEORY:
Frequency modulation is a process of changing the frequency of a carrier wave in
accordance with the slowly varying base band signal. The main advantage of this modulation is
that it can provide better discrimination against noise.

PROCEDURE:
1. Switch ON the power supply

2. Connect the sinewave generator output to frequency modulator input

3. DPDT switch(SW1) is used to select the low frequency carrier or hign frequency carrier

4. Set the deviation switch (SW2) in high deviation mode

5. Connect the CRO input to frequency modulator output
6. Now vary the amplitude potmeter from minimun to maximum to findout the frequency
deviation for FM
7. Now observe the frequency modulated output , draw the graph

8. Connect the frequency modulated output to the PLL detector input

9. Now set the DPDT switch in low frequency mode

10. Set the deviation switch in low deviation mode

11. Connect CRO input to PLLdetector output

12. Observe the demodulated ouput and then compare with the original input

13
 EC8561 – COMMUNICATION SYSTEMS LABORATORY
GRACE COLLEGE OF ENGINEERING, THOOTHUKUDI
PATCHNG DIAGRAM FM MODULATOR

PATCHING DIAGRAM-FM DEMODULATOR

14
 EC8561 – COMMUNICATION SYSTEMS LABORATORY
GRACE COLLEGE OF ENGINEERING, THOOTHUKUDI

MODEL GRAPH

TABULATION:
Amplitude in Time Frequency
volts period
Message signal
Carrier signal
Modulated signal
Demodulated signal

RESULT:

Thus the FM performed and the modulation index was found.

15
 EC8561 – COMMUNICATION SYSTEMS LABORATORY
GRACE COLLEGE OF ENGINEERING, THOOTHUKUDI
EX.NO.; 5 PULSE CODE MODULATION AND DEMODULATION DTAE:

Aim:
To perform Pulse code Modulation and demodulation and to plot the waveform forbinary data at different
frequencies

Apparatus Required:

1. PCM kit
2. CRO
3. Probe
4. Patch cord

THEORY:

PCM is a method of converting an analog in to digita signals . Information in a analog

form cannot be processes by digital computers so its necessary to convert them in to digital PCM
is term which was formed during the development of digital audio transmission standards. Digital
data can be transported robustly over long distances unlike the analog data and can be interleaved
with other digital data sos various combinations of transmission channels can be used.

Procedure:
1. Make wiring connection on VCT-07 as shown oin figure / simply connect the test points P! to P8 and P21 to P22 using
patch card
2. Ensure all the switches in switched faults block in OFF position and potentiometers POT1 and POT@ in
minimum position
3. Keep 87Khz of sampling rate
4. Display the modulating signal at test point P1 using CRO probe. Increase the sinewave amplitude by rotating POT1 in
clockwise directions and set sinewave amplitude and note down
5. Display the sample and hold ouput waveform on CRO and note down the waveform
6. Observe the recovered waveform at test point P34 note down the waveform

16
 EC8561 – COMMUNICATION SYSTEMS LABORATORY
GRACE COLLEGE OF ENGINEERING, THOOTHUKUDI

TABULATION

AMPLITUDE IN TIME PERIOD IN FRQUENCY IN

PARAMETERS
(VOLTS) (ms) (Hz)
MESSAGE SIGNAL

MODULATED
SIGNAL
DEMODULATED
SIGNAL

17
 EC8561 – COMMUNICATION SYSTEMS LABORATORY
GRACE COLLEGE OF ENGINEERING, THOOTHUKUDI

MODEL GRAPH

RESULT

Thus the Pulse Code Modulation and Demodulation was performed and output is verified

18
 EC8561 – COMMUNICATION SYSTEMS LABORATORY
GRACE COLLEGE OF ENGINEERING, THOOTHUKUDI

EX.NO.;6. DELTA MODULATION AND DEMODULATION DATE:

AIM:

To perform Delta Modulation and Demodulation.

APPARATUS REQUIRED:

1. DM kit
2. CRO
3. Probe
4. Patch cord

THEORY:

Delta Modulation is a form of pulse modulation where a sample value is represented as a single
bit. This is almost similar to differential PCM, as the transmitted bit is only one per sample just to
indicate whether the present sample is larger or smaller than the previous one. The encoding,
decoding and quantizing process become extremely simple but this system cannot handle rapidly
varying samples. This increases the quantizing noise.

PROCEDURE:

1. Plugin AC power cord into 230v,5A mains power supply

2. Connect P1 to input of DM selection P9
3. Connect P2 to clock input of DM section P14
4. Connect p12 with P10
5. Connect output P15 of delta modulator to input of delta demodulator section
6. Connect the test point P1 with CRO turn POT1 in clockwise directions and set amplitude
7. Observe and notedown the output wave form from CRO

19
 EC8561 – COMMUNICATION SYSTEMS LABORATORY
GRACE COLLEGE OF ENGINEERING, THOOTHUKUDI
PATCHING DIAGRAM- DM MODULATION &DEMODULATION

20
 EC8561 – COMMUNICATION SYSTEMS LABORATORY
GRACE COLLEGE OF ENGINEERING, THOOTHUKUDI

TABULATION

Amplitude in Time Frequency

volts period
Message signal
Demodulated signal

MODEL GRAPH

RESULT
Thus the Delta modulation and demodulation were performed and graphs were
plotted.

21
 EC8561 – COMMUNICATION SYSTEMS LABORATORY
GRACE COLLEGE OF ENGINEERING, THOOTHUKUDI

EX.NO.7. LINE CODING SCHEMES DATE:

AIM :
To perform different line coding schemes.

APPARATUS REQUIRED:
1. VCT -37 trainer kit
2. Patch chords.
3. CRO

THEORY:
We need to represent PCM binary digits by electrical pulses in order to transmit them
through a base band channel. The most commonly used PCM popular data formats are being
realized here. Line coding refers to the process of representing the bit stream (1‟s and 0‟s) in the
form of voltage or current variations optimally tuned for the specific properties of the physical
channel being used. The selection of a proper line code can help in so many ways: One
possibility is to aid in clock recovery at the receiver. A clock signal is recovered by observing
transitions in the received bit sequence, and if enough transitions exist, a good recovery of the
clock is guaranteed, and the signal is said to be self-clocking.
Some common types of line encoding in common-use nowadays are unipolar, polar, bipolar,
Manchester and Duobinary encoding.
PROCEDURE
1. Connect the PRBS (test point P5) to various line coding formats. Obtain the coded
output as per the requirement.
2. Connect coded signal test point to corresponding decoding test point as inputs.
3. Set the SW1 as per the requirement.
4. Set the potentiometer P1 in minimum position.
5. Switch ON the power supply. Press the switch SW2 once.
6. Display the encoded signal and decoded signal on the CRO.

22
 EC8561 – COMMUNICATION SYSTEMS LABORATORY
GRACE COLLEGE OF ENGINEERING, THOOTHUKUDI

PATCHING DIAGRAM-UNIPOLAR RZ

PATCHING DIAGRAM-POLAR RZ

23
 EC8561 – COMMUNICATION SYSTEMS LABORATORY
GRACE COLLEGE OF ENGINEERING, THOOTHUKUDI

PATCHING DIAGRAM-POLAR NRZ

PATCHING DIAGRAM-BIPOLAR RZ

24
 EC8561 – COMMUNICATION SYSTEMS LABORATORY
GRACE COLLEGE OF ENGINEERING, THOOTHUKUDI

PATCHING DIAGRAM-MANCHESTER

25
 EC8561 – COMMUNICATION SYSTEMS LABORATORY
GRACE COLLEGE OF ENGINEERING, THOOTHUKUDI
TABULAR COLUMN

ENCODED SIGNAL DECODED SIGNAL

S.No Name of the signal Amplitude in V Time period in Amplitude in Time period in
Sec V Sec
1

RESULT

Thus the line coding and decoding techniques were performed.

26
 EC8561 – COMMUNICATION SYSTEMS LABORATORY
GRACE COLLEGE OF ENGINEERING, THOOTHUKUDI
EX.NO.8 ASK, FSK AND PSK SIMULATION USING MATLAB DATE:

AIM:

To simulate ASK FSK and PSK using MAT Lab .

APPARATUS REQUIRED:

4. Computer
5. Matlab software Version 2013b

PROCEDURE:

1. Open Matlab version 2013b

2. Open new file and enter the program and save it.
3. Add the path to the location of the file in the system.
4. Compile the program and check for any error and debug it.
5. Note down the output.

MATLAB CODING:

MATLAB CODE FOR ASK FSK PSK

%matlab code for digital modulation(ask, fsk and psk)

pi=3.14;
f=5;
f2=10;
phi=pi;
x=[1 0 1 1 0];
nx=size(x,2);
i=1;
while i<nx+1
t = i:0.001:i+1;
if x(i)==1
ask=sin(2*pi*f*t);
fsk=sin(2*pi*f*t);
psk=sin(2*pi*f*t);
else
ask=0;
fsk=sin(2*pi*f2*t);
psk=sin(2*pi*f*t+phi);
end
subplot(3,1,1);
plot(t,ask);
xlabel('time')
ylabel('amplitude')
title('amplitude shift keying')
hold on;
grid on;

27
 EC8561 – COMMUNICATION SYSTEMS LABORATORY
GRACE COLLEGE OF ENGINEERING, THOOTHUKUDI

axis([1 10 -2 2]);
subplot(3,1,2);
plot(t,fsk);
xlabel('time')
ylabel('amplitude')
title('frequency shift keying')
hold on;
grid on;
axis([1 10 -2 2]);
subplot(3,1,3);
plot(t,psk);
xlabel('time')
ylabel('amplitude')
title('Phase shift keying')
hold on;
grid on;
axis([1 10 -2 2]);
i=i+1;
end
MODEL OUTPUT

RESULT:

The simulation of ASK FSK and PSK were done using MATLAB and the outputs were
recorded.

28
 EC8561 – COMMUNICATION SYSTEMS LABORATORY
GRACE COLLEGE OF ENGINEERING, THOOTHUKUDI
EX.NO.;9 Simulation of DPSK, QPSK and QAM generation schemes DATE:

AIM:

To simulate DPSK using MATLAB.

APPARATUS REQUIRED:

6. Computer
7. Matlab software Version 2013b

PROCEDURE:

1. Open Matlab version 2013b

2. Open new file and enter the program and save it.
3. Add the path to the location of the file in the system.
4. Compile the program and check for any error and debug it.
5. Note down the output.

MATLAB CODING
DPSK
%dpsk
clc;
clear all ;
close all;
%input bits
b=[1 0 1 1 0 1 ];
N=6;
%differential encoding
d=1;%initial bit

dc=[];
for i=1:length(b)
dc=[dc d];
d= not(xor(d,b(i)));
end
dc=[dc d];
%bit to symbol mapping
for ii=1:length(dc)
if dc(ii)==1;
nn(ii)=1;
else
nn(ii)=-1;
end
end
%pulse shaping
S=100;
i=1;
t=0:1/S:length(dc);
for j=1:length(t)
if t(j)<=i;
m(j)=nn(i);
else
m(j)=nn(i);

29
 EC8561 – COMMUNICATION SYSTEMS LABORATORY
GRACE COLLEGE OF ENGINEERING, THOOTHUKUDI
i=i+1;
end
end
%plot
subplot(411);
plot(t,m,'k-');
xlabel('time');
ylabel('amplitude');
title('polar signal');
%%carrier
c=cos(2*pi*2*t);
subplot(412);
plot(t,c,'k-');
xlabel('time');
ylabel('amplitude');
title('carrier signal');
%dpsk modulation
x=m.*c;
subplot(413);
plot(t,x,'k-');
xlabel('time');
ylabel('amplitude');
title('bpsk signal');
%coherent detection
y=x;
y1=y.*c;%product modulator
subplot(414);
plot(t,y1,'k-');
xlabel('time');
ylabel('amplitude');
title('dpsk detection signal');
int_op =[];
for ii=0:S:length(y1)-S;
int_op=(1/S)*trapz(y1(ii+1:ii+S));
int_op =[int_op int_op];
end
%harddetection
det=(round(int_op,1)>=0);
%diffenetial detection
for ii=1:length(det)-1
if det(ii)==det(ii+1);
op(ii)=1;
else
op(ii)=0;
end
end
disp('diffenetial detection')
op

QPSK
% QPSK Modulation
clc;
clear all;
close all;
%GENERATE QUADRATURE CARRIER SIGNAL
Tb=1;t=0:(Tb/100):Tb;fc=1;
c1=sqrt(2/Tb)*cos(2*pi*fc*t);
c2=sqrt(2/Tb)*sin(2*pi*fc*t);

30
 EC8561 – COMMUNICATION SYSTEMS LABORATORY
GRACE COLLEGE OF ENGINEERING, THOOTHUKUDI
%generate message signal
N=8;m=rand(1,N);
t1=0;t2=Tb
for i=1:2:(N-1)
t=[t1:(Tb/100):t2]
if m(i)>0.5
m(i)=1;
m_s=ones(1,length(t));
else
m(i)=0;
m_s=-1*ones(1,length(t));
end
%odd bits modulated signal
odd_sig(i,:)=c1.*m_s;
if m(i+1)>0.5
18
m(i+1)=1;
m_s=ones(1,length(t));
else
m(i+1)=0;
m_s=-1*ones(1,length(t));
end
%even bits modulated
signal
even_sig(i,:)=c2.*m_s;
%qpsk signal
qpsk=odd_sig+even_sig;
%Plot the QPSK modulated signal
subplot(3,2,4);plot(t,qpsk(i,:));
title('QPSK signal');xlabel('t---->');ylabel('s(t)');grid on; hold on;
t1=t1+(Tb+.01); t2=t2+(Tb+.01);
end
hold off
%Plot the binary data bits and carrier signal
subplot(3,2,1);stem(m);
title('binary data bits');xlabel('n---->');ylabel('b(n)');grid on;
subplot(3,2,2);plot(t,c1);
title('carrier signal-1');xlabel('t---->');ylabel('c1(t)');grid on;
subplot(3,2,3);plot(t,c2);
title('carrier signal-2');xlabel('t---->');ylabel('c2(t)');grid on;
% QPSK Demodulation
t1=0;t2=Tb
for i=1:N-1
t=[t1:(Tb/100):t2]
%correlator
x1=sum(c1.*qpsk(i,:));
x2=sum(c2.*qpsk(i,:));
%decision device
if (x1>0&&x2>0)
demod(i)=1;
demod(i+1)=1;
elseif (x1>0&&x2<0)
demod(i)=1;
demod(i+1)=0;
elseif (x1<0&&x2<0)
demod(i)=0;
demod(i+1)=0;
elseif (x1<0&&x2>0)
demod(i)=0;
demod(i+1)=1;
end
31
 EC8561 – COMMUNICATION SYSTEMS LABORATORY
GRACE COLLEGE OF ENGINEERING, THOOTHUKUDI
t1=t1+(Tb+.01); t2=t2+(Tb+.01)end

32
 EC8561 – COMMUNICATION SYSTEMS LABORATORY
GRACE COLLEGE OF ENGINEERING, THOOTHUKUDI
subplot(3,2,5);stem(demod);
title('qpsk demodulated bits');xlabel('n---->');ylabel('b(n)');grid on;

QAM
clc;
clear all;
close all;
t = -0.04:1.e-4:0.04;
t1 = -0.02:1.e-4:0;
t2 = 0:1.e-4:0.02;
Ta = 0.01;
mu1 = 1 - abs((t1+Ta)/Ta);
mu1 = [zeros([1 200]),mu1,zeros([1 400])];
mu2 = 1 - abs((t2-Ta)/Ta);
mu2 = [zeros([1 400]),mu2,zeros([1 200])];
m2 = mu1 - mu2;
m1 = sinc(2*t/Ta) + 2*sinc(2*t/Ta+1) + sinc(2*t/Ta-1);
f = 400;
c1 = cos(2*f*pi*t);
c2 = cos(2*f*pi*t - pi/2);
qam = 2*m1.*c1 + 2*m2.*c2;
dem1 = qam.*c1;
dem2 = qam.*c2;
a = fir1(50,10*1.e-4);
b = 1;
rec1 = filter(a,b,dem1);
rec2 = filter(a,b,dem2);
fl = length(t);
fl = 2^ceil(log2(fl));
f = (-fl/2:fl/2-1)/(fl*1.e-4);
m1F = fftshift(fft(m1,fl));
m2F = fftshift(fft(m2,fl));
qamF = fftshift(fft(qam,fl));
rec1F = fftshift(fft(rec1,fl));
rec2F = fftshift(fft(rec2,fl));
figure(1);
subplot(3,2,1);
plot(t,m1);
title('Message 1');
xlabel('{\it t} (sec)');
ylabel('m-1(t)');
grid;
subplot(3,2,2);
plot(t,m2);
title('Message 2');
xlabel('{\it t} (sec)');
ylabel('m-2(t)');
grid; subplot(3,2,
[3 4]);
plot(t,qam);
title('QAM'); xlabel('{\
it t} (sec)');
ylabel('QAM');
grid;
subplot(3,2,5);
plot(t,rec1); xlabel('{\
it t} (sec)');
ylabel('m-1(t)');

33
 EC8561 – COMMUNICATION SYSTEMS LABORATORY
GRACE COLLEGE OF ENGINEERING, THOOTHUKUDI
title('Recovered Signal 1');
grid;
subplot(3,2,6);
plot(t,rec2); xlabel('{\
it t} (sec)');
ylabel('m-2(t)');
title('Recovered Signal 2');
grid;
figure(2);
subplot(3,2,1);
plot(f,abs(m1F));
title('Freq Responce of Message Signal 1');
xlabel('f(Hz)');
ylabel('M-1(f)');
grid;
axis([-600 600 0 200]);
subplot(3,2,2);
plot(f,abs(m2F));
title('Freq Responce of Message Signal 1');
xlabel('f(Hz)');
ylabel('M-2(f)');
grid;
axis([-600 600 0 200]);
subplot(3,2,[3 4]);
plot(f,abs(qamF));
title('Freq Responce of QAM');
xlabel('f(Hz)');
ylabel('QAM(f)');
grid;
axis([-600 600 0 400]);
subplot(3,2,5);
plot(f,abs(rec1F));
title('Freq Responce of Recoverd Signal');
xlabel('f(Hz)');
ylabel('M-1(f)');
grid;
axis([-600 600 0 200]);
subplot(3,2,6);
plot(f,abs(rec2F));
title('Freq Responce of Recoverd Signal');
xlabel('f(Hz)');
ylabel('M-2(f)');
grid;
axis([-600 600 0 200]);

34
 EC8561 – COMMUNICATION SYSTEMS LABORATORY
GRACE COLLEGE OF ENGINEERING, THOOTHUKUDI
MODEL OUTPUT
DPSK

QPSK

35
 EC8561 – COMMUNICATION SYSTEMS LABORATORY
GRACE COLLEGE OF ENGINEERING, THOOTHUKUDI

QAM

RESULT:
Thus the simulation of DPSK,QPSK,QAM was performed in MATLAB and corresponding
waveforms were plotted successfully.

36
 EC8561 – COMMUNICATION SYSTEMS LABORATORY
GRACE COLLEGE OF ENGINEERING, THOOTHUKUDI

EX.NO.:10 SIMULATION OF SIGNAL CONSTELLATIONS OF BPSK, QPSK AND QAM DATE:

AIM:

To simulate BPSK QPSK and QAM using MAT Lab software.

APPARATUS REQUIRED:

8. Computer
9. Matlab software Version 2013b

PROCEDURE:

2. Open Matlab version 2013b

3. Open new file and enter the program and save it.
4. Add the path to the location of the file in the system.
5. Compile the program and check for any error and debug it.
6. Note down the output.

MATLAB CODING:
Bpsk conctellation

clc;
clear all;
close all;
M=2;
k=log2(M);
n=3*1e5;
nsamp=8;
X=randint(n,1);
xsym = bi2de(reshape(X,k,length(X)/k).','left-msb');
Y_psk= modulate(modem.pskmod(M),xsym);
Ytx_psk = Y_psk;
EbNo=30;
SNR=EbNo+10*log10(k)-10*log10(nsamp);
Ynoisy_psk = awgn(Ytx_psk,SNR,'measured');
Yrx_psk = Ynoisy_psk;
h1=scatterplot(Yrx_psk(1:nsamp*5e3),nsamp,0,'r.');
hold on;
scatterplot(Yrx_psk(1:5e3),1,0,'k*',h1);
title('constellation diagram BPSK');
legend('Received signal' ,'signal constellation'); axis([-5 5 -5 5]);
hold off;
QPSK QAM
clc;
clear all;
close all;
M=16;
k=log2(M);

37
 EC8561 – COMMUNICATION SYSTEMS LABORATORY
GRACE COLLEGE OF ENGINEERING, THOOTHUKUDI
n=3*1e5;
nsamp=8;
X=randint(n,1);
xsym = bi2de(reshape(X,k,length(X)/k).','left-msb');
Y_qam= modulate(modem.qammod(M),xsym);
Y_qpsk= modulate(modem.pskmod(M),xsym);
Ytx_qam = Y_qam;
Ytx_qpsk = Y_qpsk;
EbNo=30;
SNR=EbNo+10*log10(k)-10*log10(nsamp);
Ynoisy_qam = awgn(Ytx_qam,SNR,'measured');
Ynoisy_qpsk = awgn(Ytx_qpsk,SNR,'measured');
Yrx_qam = Ynoisy_qam;
Yrx_qpsk = Ynoisy_qpsk;
h1=scatterplot(Yrx_qam(1:nsamp*5e3),nsamp,0,'r.');
hold on;
scatterplot(Yrx_qam(1:5e3),1,0,'k*',h1);
title('constellation diagram 16 QAM');
legend('Received signal' ,'signal constellation');
axis([-5 5 -5 5]);
hold off;
h2=scatterplot(Yrx_qpsk(1:nsamp*5e3),nsamp,0,'r.');
hold on;
scatterplot(Yrx_qpsk(1:5e3),1,0,'k*',h2);
title('constellation diagram 16 PSK');
legend('Received signal' ,'signal constellation');
axis([-5 5 -5 5]);
hold off;
title('constellation diagram 16 PSK');
legend('Received signal' ,'signal constellation');
axis([-5 5 -5 5]);
hold off;

MODEL OUPUT
BPSK

38
 EC8561 – COMMUNICATION SYSTEMS LABORATORY
GRACE COLLEGE OF ENGINEERING, THOOTHUKUDI

QPSK

QAM

RESULT

Thus the Signal Constellation of BPSK, QPSK And QAM observed using MATLAB and
corresponding waveforms were plotted successfully.

39
 EC8561 – COMMUNICATION SYSTEMS LABORATORY
GRACE COLLEGE OF ENGINEERING, THOOTHUKUDI
EX.NO., 11 SIMULATION OF ASK, FSK AND BPSK DETECTION SCHEMES DATE
AIM:

To simulate ASK FSK and PSK using MAT Lab .

APPARATUS REQUIRED:

3. Computer
4. Matlab software Version 2013b

PROCEDURE:

6. Open Matlab version 2013b

7. Open new file and enter the program and save it.
8. Add the path to the location of the file in the system.
9. Compile the program and check for any error and debug
it. Note down the output.
MATLAB CODING:
ASK
%ASK Modulation
clc;
clear all;
close all;
%GENERATE CARRIER SIGNAL
Tb=1; fc=10;
t=0:Tb/100:1;
c=sqrt(2/Tb)*sin(2*pi*fc*t);
%generate message signal
N=8;
m=rand(1,N);
t1=0;t2=Tb
for i=1:N
t=[t1:.01:t2]
if m(i)>0.5
m(i)=1;
m_s=ones(1,length(t));
else
m(i)=0;
m_s=zeros(1,length(t));
end
message(i,:)=m_s;
%product of carrier and
message ask_sig(i,:)=c.*m_s;
t1=t1+(Tb+.01); t2=t2+
(Tb+.01);
%plot the message and ASK signal
subplot(5,1,2);axis([0 N -2 2]);plot(t,message(i,:),'r');
title('message signal');xlabel('t--->');ylabel('m(t)');grid on
hold on
subplot(5,1,4);plot(t,ask_sig(i,:));
title('ASK signal');xlabel('t--->');ylabel('s(t)');grid on
hold onend
hold off
%Plot the carrier signal and input binary data
subplot(5,1,3);plot(t,c);
title('carrier signal');xlabel('t--->');ylabel('c(t)');grid on
40
 EC8561 – COMMUNICATION SYSTEMS LABORATORY
GRACE COLLEGE OF ENGINEERING, THOOTHUKUDI
subplot(5,1,1);stem(m);
title('binary data bits');xlabel('n--->');ylabel('b(n)');grid on
2
% ASK Demodulation
t1=0;t2=Tb
for i=1:N
t=[t1:Tb/100:t2]
%correlator
x=sum(c.*ask_sig(i,:));
%decision device
if x>0
demod(i)=1;
else
demod(i)=0;
end t1=t1+
(Tb+.01);
t2=t2+(Tb+.01);
end
%plot demodulated binary data bits
subplot(5,1,5);stem(demod);
title('ASK demodulated signal'); xlabel('n--->');ylabel('b(n)');grid on
FSK
clc;
clear all;
close all;
%GENERATE CARRIER SIGNAL
Tb=1; fc1=2;fc2=5; t=0:
(Tb/100):Tb;
c1=sqrt(2/Tb)*sin(2*pi*fc1*t);
c2=sqrt(2/Tb)*sin(2*pi*fc2*t);
%generate message signal
N=8;
m=rand(1,N);
t1=0;t2=Tb
for i=1:N
t=[t1:(Tb/100):t2]
if m(i)>0.5
m(i)=1;
m_s=ones(1,length(t));
invm_s=zeros(1,length(t));
else
m(i)=0;
m_s=zeros(1,length(t));
invm_s=ones(1,length(t));
end
message(i,:)=m_s;
%Multiplier
fsk_sig1(i,:)=c1.*m_s;
fsk_sig2(i,:)=c2.*invm_s;
fsk=fsk_sig1+fsk_sig2;
%plotting the message signal and the modulated signal
subplot(3,2,2);axis([0 N -2
2]);plot(t,message(i,:),'r');title('message
signal');xlabel('t---->');ylabel('m(t)');grid on;hold
on;subplot(3,2,5);plot(t,fsk(i,:));
title('FSK signal');xlabel('t---->');ylabel('s(t)');grid on;hold on;
t1=t1+(Tb+.01); t2=t2+(Tb+.01);
end
hold off
%Plotting binary data bits and carrier signal
subplot(3,2,1);stem(m);

41
 EC8561 – COMMUNICATION SYSTEMS LABORATORY
GRACE COLLEGE OF ENGINEERING, THOOTHUKUDI
title('binary data');xlabel('n---->'); ylabel('b(n)');grid on;
subplot(3,2,3);plot(t,c1);
title('carrier signal-1');xlabel('t---->');ylabel('c1(t)');grid on;
subplot(3,2,4);plot(t,c2);
title('carrier signal-2');xlabel('t---->');ylabel('c2(t)');grid on;
13
% FSK Demodulation
t1=0;t2=Tb
for i=1:N
t=[t1:(Tb/100):t2]
%correlator
x1=sum(c1.*fsk_sig1(i,:));
x2=sum(c2.*fsk_sig2(i,:));
x=x1-x2;
%decision device
if x>0
demod(i)=1; else
demod(i)=0;
end t1=t1+
(Tb+.01);
t2=t2+(Tb+.01);
end
%Plotting the demodulated data bits
subplot(3,2,6);stem(demod);
title(' demodulated data');xlabel('n---->');ylabel('b(n)'); grid on;
BPSK
clc;
clear all;
close all;
%GENERATE CARRIER SIGNAL
Tb=1;
t=0:Tb/100:Tb;
fc=2;
c=sqrt(2/Tb)*sin(2*pi*fc*t);
%generate message signal
N=8;
m=rand(1,N);
t1=0;t2=Tb
for i=1:N
t=[t1:.01:t2]
if m(i)>0.5
m(i)=1;
m_s=ones(1,length(t));
else
m(i)=0;
m_s=-1*ones(1,length(t));
end
message(i,:)=m_s;
%product of carrier and message signal
bpsk_sig(i,:)=c.*m_s;
%Plot the message and BPSK modulated signal
subplot(5,1,2);axis([0 N -2 2]);plot(t,message(i,:),'r');
title('message signal(POLAR form)');xlabel('t--->');ylabel('m(t)');
grid on; hold on;

42
 EC8561 – COMMUNICATION SYSTEMS LABORATORY
GRACE COLLEGE OF ENGINEERING, THOOTHUKUDI
subplot(5,1,4);plot(t,bpsk_sig(i,:));
title('BPSK signal');xlabel('t--->');ylabel('s(t)');
grid on; hold on;
t1=t1+1.01; t2=t2+1.01;
end
hold off
%plot the input binary data and carrier signal
subplot(5,1,1);stem(m);
title('binary data bits');xlabel('n--->');ylabel('b(n)');
grid on;
subplot(5,1,3);plot(t,c);
title('carrier signal');xlabel('t--->');ylabel('c(t)');
grid on;
7
% PSK Demodulation
t1=0;t2=Tb
for i=1:N
t=[t1:.01:t2]
%correlator
x=sum(c.*bpsk_sig(i,:));
%decision device
if x>0
demod(i)=1;
else
demod(i)=0;
end
t1=t1+1.01;
t2=t2+1.01;
end
%plot the demodulated data bits
subplot(5,1,5);stem(demod);
title('demodulated data');xlabel('n--->');ylabel('b(n)');
grid on

MODEL OUTPUT
ASK

43
 EC8561 – COMMUNICATION SYSTEMS LABORATORY
GRACE COLLEGE OF ENGINEERING, THOOTHUKUDI

FSK

BPSK

RESULT:

The simulation of ASK FSK and PSK were done using MATLAB and the outputs were
recorded.

44
 EC8561 – COMMUNICATION SYSTEMS LABORATORY
GRACE COLLEGE OF ENGINEERING, THOOTHUKUDI
EX.NO.12 LINEAR BLOCK AND CYCLIC ERROR CONTROL CODING
TECHNIQUES DATE:

AIM:

To simulate error linear block code error control coding technique using MATLAB.

APPARATUS REQUIRED:

10. Computer
11. Matlab software Version 2013b

THEORY:

In coding theory, a linear code is an error-correcting code for which any linear
combination of codewords is also a codeword. Linear codes are traditionally partitioned into
block codes and convolutional codes, although turbo codes can be seen as a hybrid of these
two types. Linear codes allow for more efficient encoding and decoding algorithms than other
codes.Linear codes are used in forward error correction and are applied in methods for
transmitting symbols (e.g., bits) on a communications channel so that, if errors occur in the
communication, some errors can be corrected or detected by the recipient of a message block.
The codewords in a linear block code are blocks of symbols which are encoded using more
symbols
than the original value to be sent. A linear code of length n transmits blocks containing n
symbols. For example, the [7,4,3] Hamming code is a linear binary code which represents 4-bit
messages using 7-bit codewords. Two distinct codewords differ in at least three bits. As a
consequence, up to two errors per codeword can be detected while a single error can be
corrected.

PROCEDURE:

1. Open Matlab version 2013b

2. Open new file and enter the program and save it.
3. Add the path to the location of the file in the system.
4. Compile the program and check for any error and debug it.
5. Note down the output.
MATLAB CODING:

clc;
clearall;
%g=input('Enter The Generator Matrix: ');%row value separate by semicolon
disp('The Generator Matrix is : ');
g= [1 1 0 1 0 0 0 ;0 1 1 0 1 0 0;1 1 1 0 0 1 0;1 0 1 0 0 0 1];
disp(g);
disp ('The Order of Linear Block Code for given Generator Matrix is:');
[n,k] = size(transpose(g));
disp('The Code Word Length is : ');disp(n);
disp('The Parity Bit Length is : ');disp(k);
45
 EC8561 – COMMUNICATION SYSTEMS LABORATORY
GRACE COLLEGE OF ENGINEERING, THOOTHUKUDI
for i = 1:2^k

46
 EC8561 – COMMUNICATION SYSTEMS LABORATORY
GRACE COLLEGE OF ENGINEERING, THOOTHUKUDI
for j = k:-1:1
if rem(i-1,2^(-j+k+1))>=2^(-j+k)
m(i,j)=1;
else
m(i,j)=0;
end
end
end
disp('The Possible Message Bits are :
'); disp(' c0 c1 c2 c3');
disp(m);
disp('The Possible Codewords are :')
disp(' b0 b1 b2 c0 c1 c2 c3 Hamming weight')
c = rem(m*g,2);
d_min = sum((c(1:2^k,:))');
d_min2=d_min';
s= [ c d_min2];
disp(s);
disp('The Minimum Hamming Weight for the given Block Code is= ');
d_min1 = min(sum((c(2:2^k,:))'));
disp(d_min1);
% DECode
p = [g(:,1:n-k)];
h = [eye(n-k),transpose(p)];
disp('The H Matrix is ');
disp(h);
ht = transpose(h);
disp('The H Transpose Matrix is ');
disp(ht);
r=[0 0 1 1 1 0 1];
e=rem(r*ht,2);
disp('Syndrome of a Given Codeword is :');
disp(e);
for i = 1:1:size(ht)
if(ht(i,1:3)==e)
r(i) = 1-r(i);
break;
end
end
disp('The Error is in
bit:'); disp(i);
disp('The Corrected Codeword is
:'); disp(r);

47
 EC8561 – COMMUNICATION SYSTEMS LABORATORY
GRACE COLLEGE OF ENGINEERING, THOOTHUKUDI
OUTPUT:
The Generator Matrix is :
1 1 0 1 0 0 0
0 1 1 0 1 0 0
1 1 1 0 0 1 0
1 0 1 0 0 0 1
The Order of Linear Block Code for given Generator Matrix is:

The Code Word Length is :

7
The Parity Bit Length is :
4
The Possible Message Bits are :
c0 c1 c2 c3
0 0 0 0
0 0 0 1
0 0 1 0
0 0 1 1
0 1 0 0
0 1 0 1
0 1 1 0
0 1 1 1
1 0 0 0
1 0 0 1

1 0 1 0
1 0 1 1
1 1 0 0
1 1 0 1
1 1 1 0
1 1 1 1
The Possible Codewordsare :
b0 b1 b2 c0 c1 c2 c3 Hamming weight
0 0 0 0 0 0 0 0
1 0 1 0 0 0 1 3
1 1 1 0 0 1 0 4
0 1 0 0 0 1 1 3
0 1 1 0 1 0 0 3
1 1 0 0 1 0 1 4
1 0 0 0 1 1 0 3
0 0 1 0 1 1 1 4
1 1 0 1 0 0 0 3
0 1 1 1 0 0 1 4
0 0 1 1 0 1 0 3
1 0 0 1 0 1 1 4
1 0 1 1 1 0 0 4
0 0 0 1 1 0 1 3
0 1 0 1 1 1 0 4
1 1 1 1 1 1 1 7

48
 EC8561 – COMMUNICATION SYSTEMS LABORATORY
GRACE COLLEGE OF ENGINEERING, THOOTHUKUDI

The Minimum Hamming Weight for the given Block Code is= 3
The H Matrix is
1 0 0 1 0 1 1
0 1 0 1 1 1 0
0 0 1 0 1 1 1
The H Transpose Matrix is
1 0 0
0 1 0
0 0 1
1 1 0
0 1 1
1 1 1
1 0 1
Syndrome of a Given Codewordis :
0 0 1
The Error is in bit:
3
The Corrected Codewordis :

0 0 0 1 1 0 1

CYCLIC CODE
%Generation of parity check matrix and generator matrix for a (7, 4) Hamming code.
[h,g,n,k] = hammgen(3);
%Generation of parity check matrix for the generator polynomial g(x) = 1+x+x3
h1 = hammgen(3,[1 0 1 1])
%Computation of code vectors for a cyclic code
clc;
close
all; n=7;
k=4;
msg=[1 0 0 1; 1 0 1 0; 1 0 1 1];
code = encode(msg,n,k,'cyclic');
msg
code
%Syndrome decoding
clc;
close
all; q=3;
n=2^q-1; k=n-q;
parmat = hammgen(q); % produce parity-check matrix
trt = syndtable(parmat); % produce decoding table
recd = [1 0 1 1 1 1 0 ] %received vector
syndrome = rem(recd * parmat',2);
syndrome_de = bi2de(syndrome, 'left-msb'); %convert to decimal
disp(['Syndrome = ',num2str(syndrome_de),.....
' (decimal), ',num2str(syndrome),' (binary) ']);
corrvect = trt(1+syndrome_de, :);%correction vector
correctedcode= rem(corrvect+recd,2);
parmat
corrvect
correctedcode

49
 EC8561 – COMMUNICATION SYSTEMS LABORATORY
GRACE COLLEGE OF ENGINEERING, THOOTHUKUDI

RESULT:
Thus the program for error control coding is done using MATLAB and the output is verified.

50
 EC8561 – COMMUNICATION SYSTEMS LABORATORY
GRACE COLLEGE OF ENGINEERING, THOOTHUKUDI

EX.NO. 13 SIMULATION OF CONVOLUTIONAL CODING DATE:

AIM:

To perform the simulation of convolutional coding scheme using MATLAB.

APPARATUS REQUIRED:

1. Computer
2. Matlab software Version 2013b

PROCEDURE:

1. Open Matlab version 2013b

2. Open new file and enter the program and save it.
3. Add the path to the location of the file in the system.
4. Compile the program and check for any error and debug it.
5. Note down the output.

THEORY

Convolutional Code:

Convolutional codes are commonly described using two parameters: the code rate and
the constraint length. The code rate, k/n, is expressed as a ratio of the number of bits into the
convolutional encoder (k) to the number of channel symbols output by the convolutional
encoder (n) in a given encoder cycle. The constraint length parameter, K, denotes the "length"
of the convolutional encoder, i.e. how many k-bit stages are available to feed the
combinatorial logic that produces the output symbols. Closely related to K is the parameter
m, which indicates how many encoder cycles an input bit is retained and used for encoding
after it first appears at the input to the convolutional encoder. The m parameter can be
thought of as the memory length of the encoder. Convolutional codes are widely used as
channel codes in practical communication systems for error correction. The encoded bits
depend on the current k input bits and a few past input bits. The main decoding strategy for
convolutional codes is based on the widely used Viterbi algorithm. As a result of the wide
acceptance of convolutional codes, there have been several approaches to modify and extend
this basic coding scheme. Trellis coded modulation (TCM) and turbo codes are two such
examples. The operation of a convolutional encoder can be explained in several but
equivalent ways such as, by a) state diagram representation, b) tree diagram representation
and c) trellis diagram representation

MATLAB CODING
clc; clear
all; close
all;
m=[1 0 1 1];%messagesequence
p=2%%no of flipflop
z=zeros(1,p);
mm=horzcat(m,z);%additional zeros add
d1=0;d2=0; %inital content x=[];
51
 EC8561 – COMMUNICATION SYSTEMS LABORATORY
GRACE COLLEGE OF ENGINEERING, THOOTHUKUDI
%initialcontent flipflop states

52
 EC8561 – COMMUNICATION SYSTEMS LABORATORY
GRACE COLLEGE OF ENGINEERING, THOOTHUKUDI
c=[];%codevector
for i=1:1:length(mm)
d1(i+1)=mm(i);
d2(i+1)=d1(i);
x=[x; d1(i) d2(i)];
u(i)=xor(x(i,1),x(i,2));
c1(i)=xor(u(i),mm(i));%1st output bit
c2(i)=xor(mm(i),x(i,2));%2nd output bit
c=[c c1(i) c2(i)];
end
disp('state of the shift register:')
x
disp('code vector')
c

OUTPUT

RESULT:

Thus the simulation of convolutional coding scheme was performed in MATLAB

successfully.

53
 EC8561 – COMMUNICATION SYSTEMS LABORATORY
GRACE COLLEGE OF ENGINEERING, THOOTHUKUDI
EX.NO. 14 COMMUNICATION LINK SIMULATION DATE:

AIM:

To perform communication Link using MATLAB.

APPARATUS REQUIRED:
PC with MATLAB Software with Simulink tool

PROCEDURE:
1. Start simulink section
2. Select fileNew Model in the simulink library to construct a new model
3. Go to simulink library select appropriate module and add to model
4. Connect all the inserted models
5. Set the simulation parameters
6. Run the simulation and observe and save all the plots and values.

AM MODULATION

54
 EC8561 – COMMUNICATION SYSTEMS LABORATORY
GRACE COLLEGE OF ENGINEERING, THOOTHUKUDI

MODEL OUTPUT

FREQUENCY MODULATION & DEMODULATION

55
 EC8561 – COMMUNICATION SYSTEMS LABORATORY
GRACE COLLEGE OF ENGINEERING, THOOTHUKUDI

MODEL GRAPH

RESULT:
Thus the Simulink block diagram for communication link is done using MATLAB and the output is
verified.

56