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// This example demonstrates the interfaces to the framegen64 and
// framesync64 objects used to completely encapsulate data for
// over-the-air transmission. A 64-byte payload is generated, and then
// encoded, modulated, and interpolated using the framegen64 object.
// The resulting complex baseband samples are corrupted with noise and
// moderate carrier frequency and phase offsets before the framesync64
// object attempts to decode the frame. The resulting data are compared
// to the original to validate correctness.
//
// SEE ALSO: flexframesync_example.c
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <time.h>
#include "liquid.h"
#define OUTPUT_FILENAME "framesync64_example.m"
// 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 * _userdata)
{
printf("*** callback invoked ***\n");
framesyncstats_print(&_stats);
return 0;
}
int main(int argc, char*argv[])
{
// create frame generator, synchronizer objects
framegen64 fg = framegen64_create();
framesync64 fs = framesync64_create(callback,NULL);
// create buffer for the frame samples
unsigned int frame_len = LIQUID_FRAME64_LEN; // fixed frame length
float complex frame[frame_len];
// generate the frame with random header and payload
framegen64_execute(fg, NULL, NULL, frame);
// add minor channel effects
unsigned int i;
for (i=0; i<frame_len; i++) {
frame[i] *= cexpf(_Complex_I*(0.01f*i + 1.23456f));
frame[i] *= 0.1f;
frame[i] += 0.02f*( randnf() + _Complex_I*randnf())*M_SQRT1_2;
}
// synchronize/receive the frame
framesync64_execute(fs, frame, frame_len);
framesync64_print(fs);
// clean up allocated objects
framegen64_destroy(fg);
framesync64_destroy(fs);
// export results
FILE* fid = fopen(OUTPUT_FILENAME, "w");
fprintf(fid,"%% %s: auto-generated file\n", OUTPUT_FILENAME);
fprintf(fid,"clear all; close all;\n");
fprintf(fid,"frame_len = %u;\n", frame_len);
for (i=0; i<frame_len; i++)
fprintf(fid,"y(%4u)=%12.4e+j*%12.4e;\n", i+1, crealf(frame[i]), cimagf(frame[i]));
fprintf(fid,"t=0:(length(y)-1);\n");
fprintf(fid,"plot(t,real(y),t,imag(y));\n");
fclose(fid);
printf("results written to %s\n", OUTPUT_FILENAME);
printf("done.\n");
return 0;
}
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