1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
|
// This example tests the performance for detecting and decoding frames
// with the framegen64 and framesync64 objects.
// SEE ALSO: framesync64_example.c
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include "liquid.h"
#define OUTPUT_FILENAME "framesync64_performance_example.m"
// add noise to channel
void frame64_add_noise(float complex * _buf, 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<LIQUID_FRAME64_LEN; i++)
_buf[i] += nstd*( randnf() + _Complex_I*randnf() ) * M_SQRT1_2;
}
int main(int argc, char*argv[])
{
// create frame generator, synchronizer objects
framegen64 fg = framegen64_create();
framesync64 fs = framesync64_create(NULL,NULL);
unsigned int min_errors = 50;
unsigned int min_trials = 500;
unsigned int max_trials = 5000;
float per_target = 1e-2f;
// create buffer for the frame samples
float complex frame[LIQUID_FRAME64_LEN];
float SNRdB = -3.0f;
float per_0 =-1.0f, per_1 = -1.0f;
float snr_0 = 0.0f, snr_1 = 0.0f;
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 %6s %6s %12s\n", "SNR", "detect", "valid", "trials", "PER");
while (SNRdB < 10.0f) {
framesync64_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
framesync64_reset(fs);
// generate the frame with random header and payload
framegen64_execute(fg, NULL, NULL, frame);
// add channel effects
frame64_add_noise(frame, SNRdB);
// synchronize/receive the frame
framesync64_execute(fs, frame, LIQUID_FRAME64_LEN);
}
num_trials += min_trials;
num_errors = num_trials - framesync64_get_framedatastats(fs).num_payloads_valid;
if (num_errors >= min_errors)
break;
if (num_trials >= max_trials)
break;
}
// print results
framedatastats_s stats = framesync64_get_framedatastats(fs);
float per = (float)(num_trials - stats.num_payloads_valid)/(float)num_trials;
if (per >= per_target) { per_0 = per; snr_0 = SNRdB; }
else if (per_1 < 0.0f ) { per_1 = per; snr_1 = SNRdB; }
printf(" %8.3f %6u %6u %6u %12.4e\n",
SNRdB,stats.num_frames_detected,stats.num_payloads_valid,num_trials,per);
fprintf(fid,"SNR(end+1)=%g; pdetect(end+1)=%g; pvalid(end+1)=%g;\n",
SNRdB,
(float)stats.num_frames_detected / (float)num_trials,
(float)stats.num_payloads_valid / (float)num_trials);
if (num_errors < min_errors)
break;
SNRdB += 0.5f;
}
float m = (logf(per_1) - logf(per_0)) / (snr_1 - snr_0);
float snr_target = snr_0 + (logf(per_target) - logf(per_0)) / m;
printf("per:{%12.4e,%12.4e}, snr:{%5.2f,%5.2f} => %.3f dB for PER %12.4e\n",
per_0, per_1, snr_0, snr_1, snr_target, per_target);
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([-6 10 1e-3 1]);\n");
fprintf(fid,"grid on;\n");
fclose(fid);
printf("results written to %s\n", OUTPUT_FILENAME);
// clean up allocated objects
framegen64_destroy(fg);
framesync64_destroy(fs);
return 0;
}
|
