Simulation of Line Coding Schemes in Matlab

Objectives

How to write Matlab code that encodes a digital data into digital signal?

Study sample Matlab program for unipolar NRZ, NRZ-L, and Bipolar AMI

Program Code

Unipolar NRZ

 A positive voltage represents a binary 1, and zero volts indicates a binary 0. It is the simplest line code.

% Unipolar NRZ

clc

message = [0 1 1 0 1 0 1];

data = [0 0 1 0 1 0 0 0 1 0 0 0 1 0];

i = 1 : 7;

j = 1.99 : 7.99;

time = [ ];

for k = 1 : 7

time = [time i(k), j(k)];

end

% Digital Signal Generation:

signal = [ ];

for t=1:2:13

    if (data(t) == 0)

        signal (t : t+1) = 0;

    else

        signal (t : t+1) = -1;

    end

end

subplot(2,1,1);

plot (time, signal)      % Plotting PCM Signal

xlabel ('Time (t)')

ylabel ('Amplitude (A)')

title('Digital Signal')

Simulation Results

 

NRZ-L

In this encoding schemes, 0 is represented by +ve volt and 1 is represented by negative volt.

Program Code

% NRZ-L

 

message = [0 1 0 1 1 1 0 0 1 1 1 1 ];

data = message;

i = 1:length(messgae);

j=1.99:length(message+0.99);

time = []

for (k = 1 : length(message))

    time= [time i(k) j(k)]

end

 

% Generating signal 

signal = [];

N = length(data);

for (t=1:2:N)

    if(data(t)==1)

        signal(t:t+1)=1;

    else

        signal(t:t+1)=-1;

    end

end

% display the signal

 

figure(1);

plot(time,signal,'linewidth',2)

title('NRZ-LZ')

xlabel('time')

ylabel('voltage level')

 

axis([1 8 -0.5 1.5 ])

Simulation Results

 

 

Pseudo Ternary Encoding

A multilevel binary encoding that complements the bipolar-AMI encoding: binary 1 is represented by a lack of pulse, and a binary 0 is represented by a positive or a negative pulse. The binary 0 pulses must alternate in polarity.

Program Code

clc

message = [0 1 1 0 1 1 1 0 0 0 1];   

data = zeros(1,2*length(message)-1);           

data (1 : 2 : end) = message;

i = 1 : 11;

j = 1.99 : 11 + 0.99;

time = [ ];

for (k = 1 : length(message));

    time = [time i(k), j(k)];   

end

% Gnerating Signal

signal = [ ];            

n = length(data);

prebit = 1;

for t = 1 : 2 : n                  

    if (data(t) == 0)

        signal(t : t+1) = 0;

    else if (data(t) == 1 & prebit == 1)

            signal (t : t+1) = 1;

            prebit = -1;

        else

            signal (t : t+1) = -1;

            prebit = 1;

        end

    end

end

subplot(2,1,1)

plot (time, signal)            % Plotting …

title ('Digital Signal')

xlabel ('Time')

ylabel ('Amplitude')