Plot the BER for QPSK, DQPSK

Plot the performance in the same figure for the BER for QPSK, DQPSK theoretical and simulation results (BER vs Eb/N0)

Answer 1

[Prasanna]

Hi Ramiz,

To plot the Bit Error Rate (BER) performance for QPSK and DQPSK (both theoretical and simulation results) on the same figure, you can first instantiate the results data and use the ‘grid’ function to plot it on the same graph. A sample MATLAB code for the same is given below:

% Parameters 
EbN0_dB = 0:2:16; % Eb/N0 range in dB 
numBits = 1e5;    % Number of bits for simulation 

% Preallocate BER arrays 
berQPSK_sim = [0.077833 0.03584 0.0118 0.002307 0.0002 0.000001 0 0 0]; 
berDQPSK_sim = [0.1652 0.1023 0.0481 0.01726 0.003786 0.000337 0.000013 0 0]; 
berQPSK_theory = [0.07341 0.03149 0.0107 0.002013 0.00014 0.000001 0 0 0]; 
berDQPSK_theory = [0.00591 0.0941 0.041 0.01453 0.0034 0.0003 0.000013 0 0]; 

% Simulation loop 
% Plotting 
figure; 
semilogy(EbN0_dB, berQPSK_sim, 'bo-', 'DisplayName', 'QPSK Simulation'); 
hold on; 
semilogy(EbN0_dB, berQPSK_theory, 'b--', 'DisplayName', 'QPSK Theory'); 
semilogy(EbN0_dB, berDQPSK_sim, 'ro-', 'DisplayName', 'DQPSK Simulation'); 
semilogy(EbN0_dB, berDQPSK_theory, 'r--', 'DisplayName', 'DQPSK Theory'); 
grid on; 
xlabel('E_b/N_0 (dB)'); 
ylabel('Bit Error Rate (BER)'); 
title('BER vs E_b/N_0 for QPSK and DQPSK'); 
legend('Location', 'southwest'); 

The results are plotted on a semilogarithmic scale to obtain the plot. The output for the above script is as follows:

For more references on the functions related to QPSK and DPQSK modulation and the ones used in the script, you can refer the following documentations:

• Pskmod - https://www.mathworks.com/help/comm/ref/pskmod.html
• Dpskmod - https://www.mathworks.com/help/comm/ref/dpskmod.html
• Berawgn - https://www.mathworks.com/help/comm/ref/berawgn.html
• Semiology - https://www.mathworks.com/help/matlab/ref/semilogy.html

Hope this helps!