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fixing "making SFN dependent on GPS time"

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in fact it syncs the USRP time to GPS time when available and then derives the SFN from the USRP time.
a side effect is that now SFN does not necessarily start at 0 and this also required other changes
 - initialization of the future_ul_tti_request.
 - fixing a bug in get_samples_per_slot
This commit is contained in:
Florian Kaltenberger
2022-04-06 17:40:14 +02:00
parent 5b22d94d37
commit 367ad780a4
4 changed files with 37 additions and 27 deletions
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executables/nr-ru.c
+14 -4
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@@ -604,6 +604,7 @@ void *emulatedRF_thread(void *param) {
void rx_rf(RU_t *ru,int *frame,int *slot) {
RU_proc_t *proc = &ru->proc;
NR_DL_FRAME_PARMS *fp = ru->nr_frame_parms;
openair0_config_t *cfg = &ru->openair0_cfg;
void *rxp[ru->nb_rx];
unsigned int rxs;
int i;
@@ -641,8 +642,8 @@ void rx_rf(RU_t *ru,int *frame,int *slot) {
if (rxs != samples_per_slot) LOG_E(PHY, "rx_rf: Asked for %d samples, got %d from USRP\n",samples_per_slot,rxs);
if (proc->first_rx == 1) {
ru->ts_offset = proc->timestamp_rx;
proc->timestamp_rx = 0;
//ru->ts_offset = proc->timestamp_rx;
//proc->timestamp_rx = 0;
} else {
samples_per_slot_prev = fp->get_samples_per_slot((*slot-1)%fp->slots_per_frame,fp);
@@ -653,13 +654,22 @@ void rx_rf(RU_t *ru,int *frame,int *slot) {
}
}
//compute system frame number (SFN) according to O-RAN-WG4-CUS.0-v02.00 (using alpha=beta=0)
// this assumes that the USRP has been synchronized to the GPS time
// OAI uses timestamps in sample time stored in int64_t, but it will fit in double precision for many years to come.
double gps_sec = ((double) ts)/cfg->sample_rate;
//proc->frame_rx = ((int64_t) (gps_sec/0.01)) & 1023;
// in fact the following line is the same as long as the timestamp_rx is synchronized to GPS.
proc->frame_rx = (proc->timestamp_rx / (fp->samples_per_subframe*10))&1023;
proc->tti_rx = fp->get_slot_from_timestamp(proc->timestamp_rx,fp);
// synchronize first reception to frame 0 subframe 0
LOG_D(PHY,"RU %d/%d TS %llu , frame %d, slot %d.%d / %d\n",
LOG_D(PHY,"RU %d/%d TS %ld, GPS %f, SR %f, frame %d, slot %d.%d / %d\n",
ru->idx,
0,
(unsigned long long int)(proc->timestamp_rx+ru->ts_offset),
ts, //(unsigned long long int)(proc->timestamp_rx+ru->ts_offset),
gps_sec,
cfg->sample_rate,
proc->frame_rx,proc->tti_rx,proc->tti_tx,fp->slots_per_frame);
// dump VCD output for first RU in list