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// This example tests the performance for detecting and decoding frames
// with the dsssframe64gen and dsssframe64sync objects.
// SEE ALSO: dsssframe64sync_example.c
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include "liquid.h"
#define OUTPUT_FILENAME "dsssframe64sync_performance_example.m"
// add noise to channel
void frame64_add_noise(float complex * _buf,
unsigned int _buf_len, float _SNRdB)
{
float nstd = powf(10.0f, -_SNRdB/20.0f);
nstd *= M_SQRT2; // scale noise to account for signal being over-sampled by 2
unsigned int i;
for (i=0; i<_buf_len; i++)
_buf[i] += nstd*( randnf() + _Complex_I*randnf() ) * M_SQRT1_2;
}
int main(int argc, char*argv[])
{
// create frame generator, synchronizer objects
dsssframe64gen fg = dsssframe64gen_create();
dsssframe64sync fs = dsssframe64sync_create(NULL,NULL);
unsigned int min_errors = 5;
unsigned int min_trials = 80;
unsigned int max_trials = 1000;
// create buffer for the frame samples
unsigned int frame_len = dsssframe64gen_get_frame_len(fg);
float complex * frame = (float complex *)malloc(frame_len*sizeof(float complex));
float SNRdB = -25.0f;
FILE* fid = fopen(OUTPUT_FILENAME, "w");
fprintf(fid,"%% %s: auto-generated file\n", OUTPUT_FILENAME);
fprintf(fid,"clear all; close all;\n");
fprintf(fid,"SNR=[]; pdetect=[]; pvalid=[];\n");
printf("# %8s %6s (%7s) %6s (%7s) %6s\n", "SNR", "missed", "percent", "errors", "percent", "trials");
fclose(fid);
while (SNRdB < -5.0f) {
dsssframe64sync_reset_framedatastats(fs);
unsigned int num_trials = 0, num_errors = 0;
while (1) {
unsigned int i;
for (i=0; i<min_trials; i++) {
// reset frame synchronizer
dsssframe64sync_reset(fs);
// generate the frame with random header and payload
dsssframe64gen_execute(fg, NULL, NULL, frame);
// add channel effects
frame64_add_noise(frame, frame_len, SNRdB);
// synchronize/receive the frame
dsssframe64sync_execute(fs, frame, frame_len);
}
num_trials += min_trials;
num_errors = num_trials - dsssframe64sync_get_framedatastats(fs).num_payloads_valid;
if (num_errors >= min_errors)
break;
if (num_trials >= max_trials)
break;
}
// print results
framedatastats_s stats = dsssframe64sync_get_framedatastats(fs);
unsigned int num_misses = num_trials - stats.num_frames_detected;
float pmd = (float) num_misses / (float) num_trials;
float per = (float) num_errors / (float) num_trials;
printf(" %8.3f %6u (%6.2f%%) %6u (%6.2f%%) %6u\n",
SNRdB,num_misses,pmd*100,num_errors,per*100,num_trials);
fid = fopen(OUTPUT_FILENAME,"a");
fprintf(fid,"SNR(end+1)=%g; pdetect(end+1)=%12g; pvalid(end+1)=%12g;\n",
SNRdB,
(float)stats.num_frames_detected / (float)num_trials,
(float)stats.num_payloads_valid / (float)num_trials);
fclose(fid);
if (num_errors < min_errors)
break;
SNRdB += 1.0f;
}
fid = fopen(OUTPUT_FILENAME,"a");
fprintf(fid,"figure;\n");
fprintf(fid,"hold on;\n");
fprintf(fid," semilogy(SNR, 1-pdetect+eps,'-o', 'LineWidth',2, 'MarkerSize',2);\n");
fprintf(fid," semilogy(SNR, 1-pvalid +eps,'-o', 'LineWidth',2, 'MarkerSize',2);\n");
fprintf(fid,"hold off;\n");
fprintf(fid,"xlabel('SNR [dB]');\n");
fprintf(fid,"ylabel('Prob. of Error');\n");
fprintf(fid,"legend('detect','decoding','location','northeast');\n");
fprintf(fid,"axis([-30 10 1e-3 1]);\n");
fprintf(fid,"grid on;\n");
fclose(fid);
printf("results written to %s\n", OUTPUT_FILENAME);
// clean up allocated objects and memory blocks
dsssframe64gen_destroy(fg);
dsssframe64sync_destroy(fs);
free(frame);
return 0;
}
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