Automatic update of USRP RX gain during initial search using --agc option

- if search fails, keeps increasing the rx gain (set by --ue-rxgain) by
  3 db until USRP max rx gain
- if initial sync is success, sets the rxgain to the value of
  (TARGET_RX_POWER (50) - pbch digital power in dB/RE)

openair1/PHY/NR_UE_ESTIMATION/nr_estimation.h

@@ -115,6 +115,12 @@ void nr_ue_measurements(PHY_VARS_NR_UE *ue,
                         uint32_t pdsch_est_size,
                         int32_t dl_ch_estimates[][pdsch_est_size]);
 
+int nr_ue_calculate_ssb_rsrp(const NR_DL_FRAME_PARMS *fp,
+                             const UE_nr_rxtx_proc_t *proc,
+                             const c16_t rxdataF[][fp->samples_per_slot_wCP],
+                             int symbol_offset,
+                             int ssb_start_subcarrier);
+
 void nr_ue_ssb_rsrp_measurements(PHY_VARS_NR_UE *ue,
                                  uint8_t gNB_index,
                                  const UE_nr_rxtx_proc_t *proc,
@@ -146,9 +152,9 @@ void nr_pdsch_ptrs_processing(PHY_VARS_NR_UE *ue,
 
 float_t get_nr_RSRP(module_id_t Mod_id,uint8_t CC_id,uint8_t gNB_index);
 
-void nr_sl_psbch_rsrp_measurements(sl_nr_ue_phy_params_t *sl_phy_params,
-                                   NR_DL_FRAME_PARMS *fp,
-                                   c16_t rxdataF[][fp->samples_per_slot_wCP],
-                                   bool use_SSS);
+int nr_sl_psbch_rsrp_measurements(sl_nr_ue_phy_params_t *sl_phy_params,
+                                  NR_DL_FRAME_PARMS *fp,
+                                  c16_t rxdataF[][fp->samples_per_slot_wCP],
+                                  bool use_SSS);
 /** @}*/
 #endif

openair1/PHY/NR_UE_TRANSPORT/nr_initial_sync.c

@@ -291,6 +291,11 @@ void nr_scan_ssb(void *arg)
                                                          &ssbInfo->pbchResult,
                                                          nr_gold_pbch_ref,
                                                          rxdataF); // start pbch detection at first symbol after pss
+      if (ssbInfo->syncRes.cell_detected) {
+        int rsrp_db_per_re = nr_ue_calculate_ssb_rsrp(ssbInfo->fp, ssbInfo->proc, rxdataF, 0, ssbInfo->gscnInfo.ssbFirstSC);
+        ssbInfo->adjust_rxgain = TARGET_RX_POWER - rsrp_db_per_re;
+        LOG_I(PHY, "pbch rx ok. rsrp:%d dB/RE, adjust_rxgain:%d dB\n", rsrp_db_per_re, ssbInfo->adjust_rxgain);
+      }
     }
   }
 }
@@ -370,6 +375,7 @@ nr_initial_sync_t nr_initial_sync(UE_nr_rxtx_proc_t *proc,
     fp->ssb_index = res.ssbIndex;
     ue->symbol_offset = res.symbolOffset;
     ue->common_vars.freq_offset = res.freqOffset;
+    ue->adjust_rxgain = res.adjust_rxgain;
   }
 
   // In initial sync, we indicate PBCH to MAC after the scan is complete.

openair1/PHY/NR_UE_TRANSPORT/nr_initial_sync_sl.c

@@ -512,7 +512,7 @@ nr_initial_sync_t sl_nr_slss_search(PHY_VARS_NR_UE *UE, UE_nr_rxtx_proc_t *proc,
                 sync_params->DFN,
                 sync_params->slot_offset);
 
-          nr_sl_psbch_rsrp_measurements(sl_ue, frame_parms, rxdataF, false);
+          UE->adjust_rxgain = nr_sl_psbch_rsrp_measurements(sl_ue, frame_parms, rxdataF, false);
 
           UE->init_sync_frame = sync_params->remaining_frames;
           result.rx_offset = sync_params->rx_offset;

openair1/PHY/defs_nr_UE.h

@@ -600,6 +600,9 @@ typedef struct PHY_VARS_NR_UE_s {
 
   notifiedFIFO_t tx_resume_ind_fifo[NR_MAX_SLOTS_PER_FRAME];
 
+  // Gain change required for automation RX gain change
+  int adjust_rxgain;
+
   // Sidelink parameters
   sl_nr_sidelink_mode_t sl_mode;
   sl_nr_ue_phy_params_t SL_UE_PHY_PARAMS;
@@ -645,6 +648,7 @@ typedef struct {
   fapiPbch_t pbchResult;
   int pssCorrPeakPower;
   int pssCorrAvgPower;
+  int adjust_rxgain;
 } nr_ue_ssb_scan_t;
 
 typedef struct nr_phy_data_tx_s {

openair1/PHY/impl_defs_top.h

@@ -181,6 +181,9 @@
 #define TARGET_RX_POWER_MAX 65    // Maximum digital power, such that signal does not saturate (value found by simulation)
 #define TARGET_RX_POWER_MIN 35    // Minimum digital power, anything below will be discarded (value found by simulation)
 
+// Increase USRP rx gain in steps of 3dB during Initial search
+#define INCREASE_IN_RXGAIN 3
+
 //the min and max gains have to match the calibrated gain table
 //#define MAX_RF_GAIN 160
 //#define MIN_RF_GAIN 96

openair1/SCHED_NR_UE/phy_procedures_nr_ue_sl.c

@@ -223,7 +223,7 @@ int psbch_pscch_processing(PHY_VARS_NR_UE *ue, const UE_nr_rxtx_proc_t *proc, nr
       sym = (sym == 0) ? 5 : sym + 1;
     }
 
-    nr_sl_psbch_rsrp_measurements(sl_phy_params, fp, rxdataF, false);
+    ue->adjust_rxgain = nr_sl_psbch_rsrp_measurements(sl_phy_params, fp, rxdataF, false);
 
     LOG_D(NR_PHY, " ------  Decode SL-MIB: frame.slot %d.%d ------  \n", frame_rx % 1024, nr_slot_rx);