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B-Netz: Use standard deviation to determine if an FSK frame is valid or not

This commit is contained in:
Andreas Eversberg 2017-08-13 14:15:53 +02:00
parent 41bd9999b1
commit ee61c4362b
3 changed files with 22 additions and 10 deletions
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10
src/bnetz/bnetz.c
View File

@ -445,21 +445,23 @@ void bnetz_receive_tone(bnetz_t *bnetz, int bit)
}
/* A digit was received. */
void bnetz_receive_telegramm(bnetz_t *bnetz, uint16_t telegramm, double level, double quality)
void bnetz_receive_telegramm(bnetz_t *bnetz, uint16_t telegramm, double level_avg, double level_dev, double quality_avg)
{
struct impulstelegramm *it;
int digit = 0;
/* drop any telegramm that is too bad */
if (quality < 0.2)
if (level_dev / level_avg > 0.2)
return;
PDEBUG_CHAN(DDSP, DEBUG_INFO, "RX Level: average=%.0f%% deviation=%.0f%% Quality: %.0f%%\n", level_avg * 100.0, level_dev / level_avg * 100.0, quality_avg * 100.0);
it = bnetz_telegramm2digit(telegramm);
if (it) {
digit = it->digit;
PDEBUG(DBNETZ, (bnetz->sender.loopback) ? DEBUG_NOTICE : DEBUG_INFO, "Received telegramm '%s' (RX Level: %.0f%% Quality=%.0f)\n", it->description, level * 100.0 + 0.5, quality * 100.0 + 0.5);
PDEBUG(DBNETZ, (bnetz->sender.loopback) ? DEBUG_NOTICE : DEBUG_INFO, "Received telegramm '%s'\n", it->description);
} else {
PDEBUG(DBNETZ, DEBUG_DEBUG, "Received unknown telegramm digit '0x%04x' (RX Level: %.0f%% Quality=%.0f) (might be radio noise)\n", telegramm, level * 100.0 + 0.5, quality * 100.0 + 0.5);
PDEBUG(DBNETZ, DEBUG_DEBUG, "Received unknown telegramm digit '0x%04x' (might be radio noise)\n", telegramm);
return;
}

2
src/bnetz/bnetz.h
View File

@ -103,6 +103,6 @@ int bnetz_create(int kanal, const char *audiodev, int use_sdr, int samplerate, d
void bnetz_destroy(sender_t *sender);
void bnetz_loss_indication(bnetz_t *bnetz);
void bnetz_receive_tone(bnetz_t *bnetz, int bit);
void bnetz_receive_telegramm(bnetz_t *bnetz, uint16_t telegramm, double level, double quality);
void bnetz_receive_telegramm(bnetz_t *bnetz, uint16_t telegramm, double level_avg, double level_dev, double quality_avg);
const char *bnetz_get_telegramm(bnetz_t *bnetz);

20
src/bnetz/dsp.c
View File

@ -161,6 +161,7 @@ static void fsk_receive_tone(bnetz_t *bnetz, int bit, int goodtone, double level
/* Collect 16 data bits (digit) and check for sync mark '01110'. */
static void fsk_receive_bit(void *inst, int bit, double quality, double level)
{
double level_avg, level_dev, quality_avg;
bnetz_t *bnetz = (bnetz_t *)inst;
int i;
@ -187,15 +188,24 @@ static void fsk_receive_bit(void *inst, int bit, double quality, double level)
return;
/* average level and quality */
level = quality = 0;
level_avg = level_dev = quality_avg = 0;
for (i = 0; i < 16; i++) {
level += bnetz->rx_telegramm_level[i];
quality += bnetz->rx_telegramm_quality[i];
level_avg += bnetz->rx_telegramm_level[bnetz->rx_telegramm_qualidx];
quality_avg += bnetz->rx_telegramm_quality[bnetz->rx_telegramm_qualidx];
if (++bnetz->rx_telegramm_qualidx == 16)
bnetz->rx_telegramm_qualidx = 0;
}
level /= 16.0; quality /= 16.0;
level_avg /= 16.0; quality_avg /= 16.0;
for (i = 0; i < 16; i++) {
level = bnetz->rx_telegramm_level[bnetz->rx_telegramm_qualidx];
level_dev += (level - level_avg) * (level - level_avg);
if (++bnetz->rx_telegramm_qualidx == 16)
bnetz->rx_telegramm_qualidx = 0;
}
level_dev = sqrt(level_dev / 16.0);
/* send telegramm */
bnetz_receive_telegramm(bnetz, bnetz->rx_telegramm, level, quality);
bnetz_receive_telegramm(bnetz, bnetz->rx_telegramm, level_avg, level_dev, quality_avg);
}
/* Process received audio stream from radio unit. */