An implementation of Analog cellular networks like A-Netz, B-Netz, C-Netz, NMT, AMPS, TACS, JTACS, Radiocom 2000, IMTS, MPT1327, Eurosignal and more http://osmocom-analog.eversberg.eu/
You can not select more than 25 topics Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
osmocom-analog/src/bnetz/dsp.c

422 lines
14 KiB

/* B-Netz signal processing
*
* (C) 2016 by Andreas Eversberg <jolly@eversberg.eu>
* All Rights Reserved
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#define CHAN bnetz->sender.kanal
#include <stdio.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <math.h>
#include "../libsample/sample.h"
#include "../libdebug/debug.h"
#include "../libmobile/call.h"
#include "bnetz.h"
#include "dsp.h"
#define PI 3.1415927
/* Notes on TX_PEAK_FSK level:
*
* At 2000 Hz the deviation shall be 4 kHz, so with emphasis the deviation
* at 1000 Hz would be theoretically 2 kHz. This is factor 0.714 below
* 2.8 kHz deviation we want at dBm0.
*/
/* signaling */
#define MAX_DEVIATION 4000.0
#define MAX_MODULATION 3000.0
#define DBM0_DEVIATION 2800.0 /* deviation of dBm0 at 1 kHz */
#define TX_PEAK_FSK (4000.0 / 2000.0 * 1000.0 / DBM0_DEVIATION)
#define TX_PEAK_METER (2000.0 / 2900.0 * 1000.0 / DBM0_DEVIATION) /* FIXME: what is the metering pulse deviation??? we use half of the 4kHz deviation, so we can still use -6dB of the speech level */
#define DAMPEN_METER 0.5 /* use -6dB to dampen speech while sending metering pulse (according to FTZ 1727 Pfl 32 Clause 3.2.6.6.5) */
#define MAX_DISPLAY 1.4 /* something above dBm0 */
#define BIT_RATE 100.0
#define BIT_ADJUST 0.5 /* full adjustment on bit change */
#define F0 2070.0
#define F1 1950.0
#define METERING_HZ 2900 /* metering pulse frequency */
#define TONE_DETECT_CNT 7 /* 70 milliseconds to detect continuous tone */
#define TONE_LOST_CNT 14 /* we use twice of the detect time, so we bridge a loss of "TONE_DETECT_CNT duration" */
#define TONE_STDDEV_TH 0.2 /* threshold of bad quality (standard deviation) to reject tone */
/* carrier loss detection */
#define MUTE_TIME 0.1 /* time to mute after loosing signal */
#define LOSS_TIME 12.5 /* duration of signal loss before release (according to FTZ 1727 Pfl 32 Clause 3.2.3.2) */
/* table for fast sine generation */
static sample_t dsp_metering[65536];
/* global init for FSK */
void dsp_init(void)
{
int i;
PDEBUG(DDSP, DEBUG_DEBUG, "Generating sine table for metering tone.\n");
for (i = 0; i < 65536; i++)
dsp_metering[i] = sin((double)i / 65536.0 * 2.0 * PI) * TX_PEAK_METER;
}
static int fsk_send_bit(void *inst);
static void fsk_receive_bit(void *inst, int bit, double quality, double level);
/* Init transceiver instance. */
int dsp_init_sender(bnetz_t *bnetz, double squelch_db)
{
PDEBUG_CHAN(DDSP, DEBUG_DEBUG, "Init DSP for 'Sender'.\n");
if (TONE_DETECT_CNT > sizeof(bnetz->rx_tone_quality) / sizeof(bnetz->rx_tone_quality[0])) {
PDEBUG_CHAN(DDSP, DEBUG_ERROR, "buffer for tone quality is too small, please fix!\n");
return -EINVAL;
}
/* init squelch */
squelch_init(&bnetz->squelch, bnetz->sender.kanal, squelch_db, MUTE_TIME, LOSS_TIME);
/* set modulation parameters */
sender_set_fm(&bnetz->sender, MAX_DEVIATION, MAX_MODULATION, DBM0_DEVIATION, MAX_DISPLAY);
PDEBUG(DDSP, DEBUG_DEBUG, "Using FSK level of %.3f (%.3f KHz deviation @ 2000 Hz)\n", TX_PEAK_FSK, 4.0);
/* init fsk */
if (fsk_init(&bnetz->fsk, bnetz, fsk_send_bit, fsk_receive_bit, bnetz->sender.samplerate, BIT_RATE, F0, F1, TX_PEAK_FSK, 0, BIT_ADJUST) < 0) {
PDEBUG_CHAN(DDSP, DEBUG_ERROR, "FSK init failed!\n");
return -EINVAL;
}
bnetz->tone_detected = -1;
/* metering tone */
bnetz->meter_phaseshift65536 = 65536.0 / ((double)bnetz->sender.samplerate / METERING_HZ);
PDEBUG(DDSP, DEBUG_DEBUG, "dial_phaseshift = %.4f\n", bnetz->meter_phaseshift65536);
bnetz->dmp_tone_level = display_measurements_add(&bnetz->sender.dispmeas, "Tone Level", "%.1f %%", DISPLAY_MEAS_LAST, DISPLAY_MEAS_LEFT, 0.0, 150.0, 100.0);
bnetz->dmp_tone_stddev = display_measurements_add(&bnetz->sender.dispmeas, "Tone Stddev", "%.1f %%", DISPLAY_MEAS_LAST, DISPLAY_MEAS_LEFT, 0.0, 100.0, 100.0);
bnetz->dmp_tone_quality = display_measurements_add(&bnetz->sender.dispmeas, "Tone Quality", "%.1f %%", DISPLAY_MEAS_LAST, DISPLAY_MEAS_LEFT, 0.0, 100.0, 100.0);
bnetz->dmp_frame_level = display_measurements_add(&bnetz->sender.dispmeas, "Frame Level", "%.1f %% (last)", DISPLAY_MEAS_LAST, DISPLAY_MEAS_LEFT, 0.0, 150.0, 100.0);
bnetz->dmp_frame_stddev = display_measurements_add(&bnetz->sender.dispmeas, "Frame Stddev", "%.1f %% (last)", DISPLAY_MEAS_LAST, DISPLAY_MEAS_LEFT, 0.0, 100.0, 100.0);
bnetz->dmp_frame_quality = display_measurements_add(&bnetz->sender.dispmeas, "Frame Quality", "%.1f %% (last)", DISPLAY_MEAS_LAST, DISPLAY_MEAS_LEFT, 0.0, 100.0, 100.0);
return 0;
}
/* Cleanup transceiver instance. */
void dsp_cleanup_sender(bnetz_t *bnetz)
{
PDEBUG_CHAN(DDSP, DEBUG_DEBUG, "Cleanup DSP for 'Sender'.\n");
fsk_cleanup(&bnetz->fsk);
}
/* If good tone is received, we just set this tone, if not already and reset counters.
* If band tone was received, we just unset this tone, if not already.
* Count duration of tone and indicate detection/loss to protocol handler.
*/
static void fsk_receive_tone(bnetz_t *bnetz, int tone, int goodtone, double level_avg, double level_stddev, double quality_avg)
{
/* count duration of the tone being detected */
bnetz->tone_duration++;
/* check if we have a good tone that was not previously detected
* in the previous function we already checked for TONE_DETECT_CNT intervals so we directly mark the tone as detected */
if (goodtone) {
bnetz->tone_count = 0;
/* if tone was undetected or has changed, we set new detected tone */
if (tone != bnetz->tone_detected) {
/* set duration to TONE_DETECT_CNT, because it took that long to detect the tone */
bnetz->tone_duration = TONE_DETECT_CNT;
bnetz->tone_detected = tone;
PDEBUG_CHAN(DDSP, DEBUG_INFO, "Detecting continuous tone: F%d Level=%3.0f%% standard deviation=%.0f%% Quality=%3.0f%%\n", bnetz->tone_detected, level_avg * 100.0, level_stddev / level_avg * 100.0, quality_avg * 100.0);
bnetz_receive_tone(bnetz, bnetz->tone_detected);
}
}
/* lost detected tone because it is not good anymore or has changed */
if (!goodtone && bnetz->tone_detected > -1) {
bnetz->tone_count++;
if (bnetz->tone_count == TONE_LOST_CNT) {
/* subtract TONE_LOST_CNT from duration, because it took that long to detect loss of tone */
PDEBUG_CHAN(DDSP, DEBUG_INFO, "Lost F%d tone after %.2f seconds.\n", bnetz->tone_detected, (double)(bnetz->tone_duration - TONE_LOST_CNT) / 100.0);
bnetz->tone_detected = -1;
bnetz_receive_tone(bnetz, -1);
}
}
}
/* 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_stddev, quality_avg;
bnetz_t *bnetz = (bnetz_t *)inst;
int i;
/* normalize FSK level */
level /= TX_PEAK_FSK;
/* store level and quality to tone buffer */
bnetz->rx_tone_quality[bnetz->rx_tone_qualidx] = quality;
bnetz->rx_tone_level[bnetz->rx_tone_qualidx] = level;
if (++bnetz->rx_tone_qualidx == TONE_DETECT_CNT)
bnetz->rx_tone_qualidx = 0;
/* average level and quality of tone */
level_avg = level_stddev = quality_avg = 0;
for (i = 0; i < TONE_DETECT_CNT; i++) {
level_avg += bnetz->rx_tone_level[i];
quality_avg += bnetz->rx_tone_quality[i];
}
level_avg /= TONE_DETECT_CNT; quality_avg /= TONE_DETECT_CNT;
for (i = 0; i < TONE_DETECT_CNT; i++) {
level = bnetz->rx_tone_level[i];
level_stddev += (level - level_avg) * (level - level_avg);
}
level_stddev = sqrt(level_stddev / TONE_DETECT_CNT);
/* update tone measurements */
display_measurements_update(bnetz->dmp_tone_level, level_avg * 100.0, 0.0);
display_measurements_update(bnetz->dmp_tone_stddev, level_stddev / level_avg * 100.0, 0.0);
display_measurements_update(bnetz->dmp_tone_quality, quality_avg * 100.0, 0.0);
/* collect bits, and check for level and continuous tone */
bnetz->rx_tone = (bnetz->rx_tone << 1) | bit;
for (i = 0; i < TONE_DETECT_CNT; i++) {
if (((bnetz->rx_tone >> i) & 1) != bit)
break;
if (bnetz->rx_tone_level[i] < 0.05)
break;
}
/* continuous tone detection:
* 1. The quality must be good enough.
* 2. All bits must be the same (continuous tone).
*/
if (level_stddev / level_avg > TONE_STDDEV_TH || i < TONE_DETECT_CNT)
fsk_receive_tone(bnetz, bit, 0, level_avg, level_stddev, quality_avg);
else
fsk_receive_tone(bnetz, bit, 1, level_avg, level_stddev, quality_avg);
/* store level and quality to telegram buffer */
bnetz->rx_telegramm_quality[bnetz->rx_telegramm_qualidx] = quality;
bnetz->rx_telegramm_level[bnetz->rx_telegramm_qualidx] = level;
if (++bnetz->rx_telegramm_qualidx == 16)
bnetz->rx_telegramm_qualidx = 0;
/* average level and quality of frame */
level_avg = level_stddev = quality_avg = 0;
for (i = 0; i < 16; i++) {
level_avg += bnetz->rx_telegramm_level[i];
quality_avg += bnetz->rx_telegramm_quality[i];
}
level_avg /= 16.0; quality_avg /= 16.0;
for (i = 0; i < 16; i++) {
level = bnetz->rx_telegramm_level[i];
level_stddev += (level - level_avg) * (level - level_avg);
}
level_stddev = sqrt(level_stddev / 16.0);
/* collect bits */
bnetz->rx_telegramm = (bnetz->rx_telegramm << 1) | bit;
/* check if pattern 01110xxxxxxxxxxx matches */
if ((bnetz->rx_telegramm & 0xf800) != 0x7000)
return;
/* collect bits, and check for level */
for (i = 0; i < 16; i++) {
if (bnetz->rx_telegramm_level[i] < 0.05)
break;
}
if (i == 16)
PDEBUG_CHAN(DDSP, DEBUG_DEBUG, "FSK Valid bits: %d / %d Level: %.0f%% Stddev: %.0f%%\n", i, 16, level_avg * 100.0, level_stddev / level_avg * 100.0);
/* drop any telegramm that is too bad */
if (level_stddev / level_avg > TONE_STDDEV_TH || i < 16)
return;
/* update telegramm measurements */
display_measurements_update(bnetz->dmp_frame_level, level_avg * 100.0 , 0.0);
display_measurements_update(bnetz->dmp_frame_stddev, level_stddev / level_avg * 100.0, 0.0);
display_measurements_update(bnetz->dmp_frame_quality, quality_avg * 100.0, 0.0);
PDEBUG_CHAN(DDSP, DEBUG_INFO, "Telegramm RX Level: average=%.0f%% standard deviation=%.0f%% Quality: %.0f%%\n", level_avg * 100.0, level_stddev / level_avg * 100.0, quality_avg * 100.0);
/* receive telegramm */
bnetz_receive_telegramm(bnetz, bnetz->rx_telegramm);
}
/* Process received audio stream from radio unit. */
void sender_receive(sender_t *sender, sample_t *samples, int length, double rf_level_db)
{
bnetz_t *bnetz = (bnetz_t *) sender;
sample_t *spl;
int pos;
int i;
/* fsk/tone signal */
fsk_receive(&bnetz->fsk, samples, length);
/* process signal mute/loss, without signalling tone / FSK frames */
switch (squelch(&bnetz->squelch, rf_level_db, (double)length / (double)bnetz->sender.samplerate)) {
case SQUELCH_LOSS:
bnetz_loss_indication(bnetz, LOSS_TIME);
/* FALLTHRU */
case SQUELCH_MUTE:
memset(samples, 0, sizeof(*samples) * length);
break;
default:
break;
}
if ((bnetz->dsp_mode == DSP_MODE_AUDIO
|| bnetz->dsp_mode == DSP_MODE_AUDIO_METER) && bnetz->callref) {
int count;
count = samplerate_downsample(&bnetz->sender.srstate, samples, length);
spl = bnetz->sender.rxbuf;
pos = bnetz->sender.rxbuf_pos;
for (i = 0; i < count; i++) {
spl[pos++] = samples[i];
if (pos == 160) {
call_up_audio(bnetz->callref, spl, 160);
pos = 0;
}
}
bnetz->sender.rxbuf_pos = pos;
} else
bnetz->sender.rxbuf_pos = 0;
}
static int fsk_send_bit(void *inst)
{
bnetz_t *bnetz = (bnetz_t *)inst;
/* send frame bit (prio) */
switch (bnetz->dsp_mode) {
case DSP_MODE_TELEGRAMM:
if (!bnetz->tx_telegramm || bnetz->tx_telegramm_pos == 16) {
/* request frame */
bnetz->tx_telegramm = bnetz_get_telegramm(bnetz);
if (!bnetz->tx_telegramm) {
PDEBUG_CHAN(DDSP, DEBUG_DEBUG, "Stop sending 'Telegramm'.\n");
return -1;
}
bnetz->tx_telegramm_pos = 0;
}
return bnetz->tx_telegramm[bnetz->tx_telegramm_pos++];
case DSP_MODE_0:
return 0; /* F0 */
case DSP_MODE_1:
return 1; /* F1 */
default:
return -1; // should never happen
}
}
/* Add metering pulse tone to audio stream. Keep phase for next call of function. */
static void metering_tone(bnetz_t *bnetz, sample_t *samples, int length)
{
double phaseshift, phase;
int i;
phaseshift = bnetz->meter_phaseshift65536;
phase = bnetz->meter_phase65536;
for (i = 0; i < length; i++) {
/* Add metering pulse, also dampen audio level by 6 dB */
*samples = (*samples) * DAMPEN_METER + dsp_metering[(uint16_t)phase];
samples++;
phase += phaseshift;
if (phase >= 65536)
phase -= 65536;
}
bnetz->meter_phase65536 = phase;
}
/* Provide stream of audio toward radio unit */
void sender_send(sender_t *sender, sample_t *samples, uint8_t *power, int length)
{
bnetz_t *bnetz = (bnetz_t *) sender;
int count;
memset(power, 1, length);
again:
switch (bnetz->dsp_mode) {
case DSP_MODE_SILENCE:
memset(samples, 0, length * sizeof(*samples));
break;
case DSP_MODE_AUDIO:
case DSP_MODE_AUDIO_METER:
jitter_load(&bnetz->sender.dejitter, samples, length);
if (bnetz->dsp_mode == DSP_MODE_AUDIO_METER)
metering_tone(bnetz, samples, length);
break;
case DSP_MODE_0:
case DSP_MODE_1:
case DSP_MODE_TELEGRAMM:
/* Encode tone/frame into audio stream. If frames have
* stopped, process again for rest of stream. */
count = fsk_send(&bnetz->fsk, samples, length, 0);
samples += count;
length -= count;
if (length)
goto again;
break;
}
}
const char *bnetz_dsp_mode_name(enum dsp_mode mode)
{
static char invalid[16];
switch (mode) {
case DSP_MODE_SILENCE:
return "SILENCE";
case DSP_MODE_AUDIO:
return "AUDIO";
case DSP_MODE_AUDIO_METER:
return "AUDIO + METERING PULSE";
case DSP_MODE_0:
return "TONE 0";
case DSP_MODE_1:
return "TONE 1";
case DSP_MODE_TELEGRAMM:
return "TELEGRAMM";
}
sprintf(invalid, "invalid(%d)", mode);
return invalid;
}
void bnetz_set_dsp_mode(bnetz_t *bnetz, enum dsp_mode mode)
{
/* reset telegramm */
if (mode == DSP_MODE_TELEGRAMM && bnetz->dsp_mode != mode) {
bnetz->tx_telegramm = 0;
fsk_tx_reset(&bnetz->fsk);
}
PDEBUG_CHAN(DDSP, DEBUG_DEBUG, "DSP mode %s -> %s\n", bnetz_dsp_mode_name(bnetz->dsp_mode), bnetz_dsp_mode_name(mode));
bnetz->dsp_mode = mode;
}