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//
// complementary_codes_example.c
//
// This example demonstrates how to generate complementary binary
// codes in liquid. A pair of codes is generated using the bsequence
// interface, their auto-correlations are computed, and the result is
// summed and printed to the screen. The results are also printed to an
// output file, which plots the sequences and their auto-correlations.
//
// SEE ALSO: bsequence_example.c
// msequence_example.c
#include <stdio.h>
#include <stdlib.h>
#include <getopt.h>
#include "liquid.h"
#define OUTPUT_FILENAME "complementary_codes_example.m"
// print usage/help message
void usage()
{
printf("complementary_codes_example [options]\n");
printf(" u/h : print usage\n");
printf(" n : sequence length, 8,16,32,64,... (default: 32)\n");
}
int main(int argc, char*argv[])
{
// options
unsigned int n = 32;
int dopt;
while ((dopt = getopt(argc,argv,"uhn:")) != EOF) {
switch (dopt) {
case 'u':
case 'h': usage(); return 0;
case 'n': n = atoi(optarg); break;
default:
exit(1);
}
}
// validate input
if ( (1<<liquid_nextpow2(n)) != n ) {
fprintf(stderr,"error: %s, sequence length must be a power of 2\n", argv[0]);
exit(1);
}
// create and initialize codes
bsequence a = bsequence_create(n);
bsequence b = bsequence_create(n);
bsequence_create_ccodes(a, b);
// print
bsequence_print(a);
bsequence_print(b);
// generate test sequences
bsequence ax = bsequence_create(n);
bsequence bx = bsequence_create(n);
bsequence_create_ccodes(ax, bx);
// compute auto-correlations
unsigned int i;
int raa[n];
int rbb[n];
for (i=0; i<n; i++) {
raa[i] = 2*bsequence_correlate(a,ax) - n;
rbb[i] = 2*bsequence_correlate(b,bx) - n;
bsequence_circshift(ax);
bsequence_circshift(bx);
// print to screen
printf(" raa[%4u] = %4d, rbb[%4u] = %4d, sum = %4d\n",
i, raa[i], i, rbb[i], raa[i] + rbb[i]);
}
// print results to file
FILE * fid = fopen(OUTPUT_FILENAME,"w");
if (!fid) {
fprintf(stderr,"error: %s, cannot open output file '%s' for writing\n", argv[0], OUTPUT_FILENAME);
exit(1);
}
fprintf(fid,"%% %s : auto-generated file\n", OUTPUT_FILENAME);
fprintf(fid,"clear all;\n");
fprintf(fid,"close all;\n\n");
fprintf(fid,"n = %u;\n", n);
fprintf(fid,"a = zeros(1,n);\n");
fprintf(fid,"b = zeros(1,n);\n");
fprintf(fid,"raa = zeros(1,n);\n");
fprintf(fid,"rbb = zeros(1,n);\n");
for (i=0; i<n; i++) {
fprintf(fid,"a(%6u) = %1u;\n", i+1, bsequence_index(a,n-i-1));
fprintf(fid,"b(%6u) = %1u;\n", i+1, bsequence_index(b,n-i-1));
fprintf(fid,"raa(%6u) = %12.8f;\n", i+1, raa[i] / (float)n);
fprintf(fid,"rbb(%6u) = %12.8f;\n", i+1, rbb[i] / (float)n);
}
// plot results
fprintf(fid,"figure;\n");
fprintf(fid,"t = 0:(n-1);\n");
fprintf(fid,"subplot(3,1,1);\n");
fprintf(fid," stairs(t,a);\n");
fprintf(fid," axis([-1 n -0.2 1.2]);\n");
//fprintf(fid," xlabel('delay (samples)');\n");
fprintf(fid," ylabel('a');\n");
fprintf(fid,"subplot(3,1,2);\n");
fprintf(fid," stairs(t,b);\n");
fprintf(fid," axis([-1 n -0.2 1.2]);\n");
//fprintf(fid," xlabel('delay (samples)');\n");
fprintf(fid," ylabel('b');\n");
fprintf(fid,"subplot(3,1,3);\n");
fprintf(fid," plot(t,raa,t,rbb,t,[raa+rbb]/2);\n");
fprintf(fid," axis([-1 n -0.5 1.2]);\n");
fprintf(fid," xlabel('delay (samples)');\n");
fprintf(fid," ylabel('auto-correlation');\n");
fclose(fid);
printf("results written to %s.\n", OUTPUT_FILENAME);
// clean up memory
bsequence_destroy(a);
bsequence_destroy(b);
bsequence_destroy(ax);
bsequence_destroy(bx);
return 0;
}
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