Write DL ToA into circular buffer

In a future commit, we will look up the maximum ToA over the last
transmissions. Introduce a buffer in which we write the last
16 measurements.

openair1/PHY/INIT/nr_init_ue.c

@@ -157,6 +157,8 @@ void init_nr_prs_ue_vars(PHY_VARS_NR_UE *ue)
       for (int j=0; j<fp->nb_antennas_rx; j++) {
         prs_vars[idx]->prs_resource[k].prs_meas[j] = malloc16_clear(sizeof(prs_meas_t));
         AssertFatal((prs_vars[idx]->prs_resource[k].prs_meas[j]!=NULL), "%s: PRS measurements malloc failed for gNB_id %d, rx_ant %d\n", __FUNCTION__, idx, j);
+        prs_meas_t *m = prs_vars[idx]->prs_resource[k].prs_meas[j];
+        m->next_dl_toa = m->dl_toa;
       }
     }
   }

openair1/PHY/NR_UE_ESTIMATION/nr_dl_channel_estimation.c

@@ -73,7 +73,10 @@ void peak_estimator(c16_t *buffer, int32_t buf_len, int32_t *peak_idx, int32_t *
 
 void set_prs_dl_toa(prs_meas_t *prs_meas, float dl_toa)
 {
-  prs_meas->dl_toa = dl_toa;
+  *prs_meas->next_dl_toa++ = dl_toa;
+  if (prs_meas->next_dl_toa >= prs_meas->dl_toa + sizeofArray(prs_meas->dl_toa))
+    prs_meas->next_dl_toa = prs_meas->dl_toa;
+  LOG_D(NR_PHY, "next_dl_toa %p\n", prs_meas->next_dl_toa);
 }
 
 int nr_prs_channel_estimation(uint8_t gNB_id,

openair1/PHY/defs_nr_common.h

@@ -312,7 +312,9 @@ typedef struct {
     int32_t sfn;
     int8_t  slot;
     int8_t  rxAnt_idx;
-    float dl_toa;
+    // circular buffer to be able to read maximum of last estimations
+    float dl_toa[128]; // set through set_prs_dl_toa()
+    float *next_dl_toa;
     int32_t dl_aoa;
     float snr;
     float rsrp;