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// This example demonstrates the basic interface to the dsssframe64gen and
// dsssframe64sync objects.
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>
#include <time.h>
#include <getopt.h>
#include <assert.h>
#include "liquid.h"
// static callback function
static int callback(unsigned char * _header,
int _header_valid,
unsigned char * _payload,
unsigned int _payload_len,
int _payload_valid,
framesyncstats_s _stats,
void * _context)
{
printf("*** callback invoked (%s) ***\n", _payload_valid ? "pass" : "FAIL");
framesyncstats_print(&_stats);
// save recovered symbols to file
unsigned int i;
FILE * fid = (FILE*)_context;
for (i=0; i<_stats.num_framesyms; i++) {
fprintf(fid,"s(%3u) = %12.8f + %12.8fj;\n", i+1,
crealf(_stats.framesyms[i]), cimagf(_stats.framesyms[i]));
}
return 0;
}
int main(int argc, char *argv[])
{
// options
unsigned int nfft = 2400;
float SNRdB = -10.0f;
const char * filename = "dsssframe64sync_example.m";
// create dsssframe64gen object
dsssframe64gen fg = dsssframe64gen_create();
// generate the frame in blocks
unsigned int buf_len = dsssframe64gen_get_frame_len(fg);
float complex * buf_tx = (float complex *)malloc(buf_len*sizeof(float complex));
float complex * buf_rx = (float complex *)malloc(buf_len*sizeof(float complex));
// export results to file
FILE * fid = fopen(filename,"w");
fprintf(fid,"%% %s : auto-generated file\n", filename);
fprintf(fid,"clear all; close all;\n");
fprintf(fid,"s=[];\n");
// generate in one step (for now)
dsssframe64gen_execute(fg, NULL, NULL, buf_tx);
// apply channel (AWGN)
float nstd = powf(10.0f,-SNRdB/20.0f);
unsigned int i;
for (i=0; i<buf_len; i++)
buf_rx[i] = buf_tx[i]*M_SQRT1_2 + nstd*(randnf() + _Complex_I*randnf())/M_SQRT2;
// run through sync
dsssframe64sync fs = dsssframe64sync_create(callback, (void*)fid);
dsssframe64sync_execute(fs, buf_rx, buf_len);
dsssframe64sync_destroy(fs);
// push resulting sample through periodogram
spgramcf periodogram = spgramcf_create_default(nfft);
spgramcf_write(periodogram, buf_rx, buf_len);
float psd[nfft];
spgramcf_get_psd(periodogram, psd);
spgramcf_destroy(periodogram);
// plot results
fprintf(fid,"nfft=%u; Y=zeros(1,nfft);\n", nfft);
for (i=0; i<nfft; i++)
fprintf(fid,"Y(%4u) = %12.8f;\n", i+1, psd[i]);
fprintf(fid,"figure('position',[100 100 1200 400]);\n");
fprintf(fid,"subplot(1,5,1:3);\n");
fprintf(fid," f=[0:(nfft-1)]/nfft-0.5; plot(f,Y); xlim([-0.5 0.5]); grid on;\n");
fprintf(fid," xlabel('Normalized Frequency [f/Fs]'); ylabel('PSD [dB]');\n");
fprintf(fid,"subplot(1,5,4:5);\n");
fprintf(fid," plot(real(s),imag(s),'.','MarkerSize',6); grid on; axis([-1 1 -1 1]*1.5)\n");
fprintf(fid," axis('square'); xlabel('I'); ylabel('Q');\n");
fclose(fid);
printf("results written to %s\n", filename);
// destroy allocated objects and free memory
dsssframe64gen_destroy(fg);
free(buf_tx);
free(buf_rx);
return 0;
}
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