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Automatic FSK polarity selection on TX side

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This is done by simulating two cells with different polarities.
On first message from mobile station, the cell with the correct
polarity is used, the other is disabled.

On RX side the polarity is not selected, since FSK decoder detects
polarity for every frame.
This commit is contained in:
Andreas Eversberg
2016-05-10 19:25:07 +02:00
parent 021c34a899
commit e2a9c2c6a5
9 changed files with 211 additions and 98 deletions
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24
src/cnetz/dsp.c
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@@ -37,6 +37,7 @@
#define PI M_PI
#define FSK_DEVIATION 16384
#define BITRATE 5280.0 /* bits per second */
#define BLOCK_BITS 198 /* duration of one time slot including pause at beginning and end */
@@ -56,7 +57,6 @@ static void dsp_init_ramp(cnetz_t *cnetz)
{
double c;
int i;
int16_t deviation = cnetz->fsk_deviation;
PDEBUG(DDSP, DEBUG_DEBUG, "Generating smooth ramp table.\n");
for (i = 0; i < 256; i++) {
@@ -67,13 +67,13 @@ static void dsp_init_ramp(cnetz_t *cnetz)
else
c = sqrt(c);
#endif
ramp_down[i] = (int)(c * (double)deviation);
ramp_down[i] = (int)(c * (double)cnetz->fsk_deviation);
ramp_up[i] = -ramp_down[i];
}
}
/* Init transceiver instance. */
int dsp_init_sender(cnetz_t *cnetz, int measure_speed, double clock_speed[2], double deviation, double noise)
int dsp_init_sender(cnetz_t *cnetz, int measure_speed, double clock_speed[2], double noise)
{
int rc = 0;
double size;
@@ -105,9 +105,7 @@ int dsp_init_sender(cnetz_t *cnetz, int measure_speed, double clock_speed[2], do
}
/* create devation and ramp */
if (deviation > 1.0)
deviation = 1.0;
cnetz->fsk_deviation = (int16_t)(deviation * 32766.9); /* be sure not to overflow -32767 .. 32767 */
cnetz->fsk_deviation = FSK_DEVIATION; /* be sure not to overflow -32767 .. 32767 */
dsp_init_ramp(cnetz);
cnetz->fsk_noise = noise;
@@ -617,10 +615,20 @@ again:
switch (cnetz->dsp_mode) {
case DSP_MODE_OGK:
if (((1 << cnetz->sched_ts) & si.ogk_timeslot_mask)) {
/* if automatic cell selection is used, toggle between
* two cells until a response for one cell is received
*/
if (cnetz->cell_auto)
cnetz->cell_nr = (cnetz->sched_ts & 7) >> 2;
/* send on timeslots depending on the cell_nr:
* cell 0: 0, 8, 16, 24
* cell 1: 4, 12, 20, 28
*/
if (((cnetz->sched_ts & 7) == 0 && cnetz->cell_nr == 0)
|| ((cnetz->sched_ts & 7) == 4 && cnetz->cell_nr == 1)) {
if (cnetz->sched_r_m == 0) {
/* set last time slot, so we can match received message from mobile station */
cnetz->last_tx_timeslot = cnetz->sched_ts;
cnetz->sched_last_ts[cnetz->cell_nr] = cnetz->sched_ts;
PDEBUG(DDSP, DEBUG_DEBUG, "Transmitting 'Rufblock' at timeslot %d\n", cnetz->sched_ts);
bits = cnetz_encode_telegramm(cnetz);
} else {