In this example we will introduce a few new features compared to the BPSK example. We will use the it_ifile class to store the results of the simulation. We will use the Real_Timer class to measure the execution time of our program. Furthermore we will use one of the channel classes, the AWGN_Channel. We will also show how to read the results in to Matlab with the load_it function. The program is as follows:
using std::cout;
using std::endl;
{
Ec = 1.0;
EbN0dB = linspace(0.0, 9.0, 10);
RNG_randomize();
cout <<
"Now simulating Eb/N0 value number " <<
i + 1 <<
" of " <<
EbN0dB.
length() << endl;
}
cout << endl;
cout <<
"EbN0dB = " <<
EbN0dB <<
" [dB]" << endl;
cout << "Saving results to ./qpsk_result_file.it" << endl;
cout << endl;
ff.open(
"qpsk_result_file.it");
return 0;
}
Ordinary AWGN Channel for cvec or vec inputs and outputs.
void set_size(int n, bool copy=false)
Resizing an Array<T>.
int length() const
Returns the number of data elements in the array object.
Bit Error Rate Counter (BERC) Class.
Automatic naming when saving.
The IT++ file format reading and writing class.
Include file for the IT++ communications module.
When you run this program, the output will look something like this:
Now simulating Eb/N0 value number 1 of 10
Now simulating Eb/N0 value number 2 of 10
Now simulating Eb/N0 value number 3 of 10
Now simulating Eb/N0 value number 4 of 10
Now simulating Eb/N0 value number 5 of 10
Now simulating Eb/N0 value number 6 of 10
Now simulating Eb/N0 value number 7 of 10
Now simulating Eb/N0 value number 8 of 10
Now simulating Eb/N0 value number 9 of 10
Now simulating Eb/N0 value number 10 of 10
Elapsed time = 0.460899 seconds
EbN0dB = [0 1 2 3 4 5 6 7 8 9] [dB]
BER = [0.07968 0.0559 0.03729 0.02294 0.01243 0.0058 0.0025 0.00076 0.00013 6e-05]
Saving results to ./qpsk_result_file.it
Now it is time to plot the simulation results in Matlab and compare with theory using the Matlab code below. The results will be stored in a file called "qpsk_result_file.it". Make sure load_it.m is in your Matlab path (look in /matlab) and that you run the example code below from the directory where qpsk_result_file.it is located
figure(1); clf;
load_it qpsk_result_file.it
h1 = semilogy(EbN0dB,ber,'*-r'); hold on
ebn0db = 0:.1:10;
ebn0 = 10.^(ebn0db/10);
Pb = 0.5 * erfc(sqrt(ebn0));
h2 = semilogy(ebn0db,Pb);
set(gca,'fontname','times','fontsize',16);
xlabel('{\it E_b} / {\it N}_0 [dB]');
ylabel('BER')
title('QPSK on an AWGN Channel');
legend([h1 h2],'Simulation','Theory');
grid on;