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//
// flexframesync_reconfig_example.c
//
// Demonstrates the reconfigurability of the flexframegen and
// flexframesync objects.
//
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>
#include <time.h>
#include <getopt.h>
#include "liquid.h"
#define OUTPUT_FILENAME "flexframesync_reconfig_example.m"
void usage()
{
printf("flexframesync_example [options]\n");
printf(" u/h : print usage\n");
printf(" s : signal-to-noise ratio [dB], default: 30\n");
printf(" n : number of frames, default: 3\n");
}
int main(int argc, char *argv[]) {
srand( time(NULL) );
// define parameters
float SNRdB = 30.0f;
float noise_floor = -30.0f;
unsigned int num_frames = 3;
// get options
int dopt;
while((dopt = getopt(argc,argv,"uhvqs:f:m:p:n:")) != EOF){
switch (dopt) {
case 'u':
case 'h': usage(); return 0;
case 's': SNRdB = atof(optarg); break;
case 'n': num_frames = atoi(optarg); break;
default:
exit(1);
}
}
// create flexframegen object
flexframegenprops_s fgprops;
flexframegenprops_init_default(&fgprops);
flexframegen fg = flexframegen_create(NULL);
// frame data
unsigned char header[14];
unsigned char * payload = NULL;
// create flexframesync object with default properties
flexframesync fs = flexframesync_create(NULL,NULL);
// channel
float nstd = powf(10.0f, noise_floor/20.0f); // noise std. dev.
float gamma = powf(10.0f, (SNRdB+noise_floor)/20.0f); // channel gain
unsigned int i;
// initialize header, payload
for (i=0; i<14; i++)
header[i] = i;
// frame buffers, properties
unsigned int buf_len = 256;
float complex buf[buf_len];
unsigned int j;
for (j=0; j<num_frames; j++) {
// configure frame generator properties
unsigned int payload_len = (rand() % 256) + 1; // random payload length
fgprops.check = LIQUID_CRC_NONE; // data validity check
fgprops.fec0 = LIQUID_FEC_NONE; // inner FEC scheme
fgprops.fec1 = LIQUID_FEC_NONE; // outer FEC scheme
fgprops.mod_scheme = (rand() % 2) ? LIQUID_MODEM_QPSK : LIQUID_MODEM_QAM16;
// reallocate memory for payload
payload = realloc(payload, payload_len*sizeof(unsigned char));
// initialize payload
for (i=0; i<payload_len; i++)
payload[i] = rand() & 0xff;
// set properties and assemble the frame
flexframegen_setprops(fg, &fgprops);
flexframegen_assemble(fg, header, payload, payload_len);
printf("frame %u, ", j);
flexframegen_print(fg);
// write the frame in blocks
int frame_complete = 0;
while (!frame_complete) {
// write samples to buffer
frame_complete = flexframegen_write_samples(fg, buf, buf_len);
// add channel impairments (gain and noise)
for (i=0; i<buf_len; i++)
buf[i] = buf[i]*gamma + nstd * (randnf() + _Complex_I*randnf()) * M_SQRT1_2;
// push through sync
flexframesync_execute(fs, buf, buf_len);
}
} // num frames
// print frame data statistics
flexframesync_print(fs);
// clean up allocated memory
flexframegen_destroy(fg);
flexframesync_destroy(fs);
free(payload);
printf("done.\n");
return 0;
}
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