Merge remote-tracking branch 'sakthivelvelumani/ue-trs-support' into integration_2026_w28

UE: implement TRS processing in PHY (#199)

This PR implements PHY layer processing for CSI-RS tracking signal that
estimates the CFO and sends a frequency correction command to the radio
when CFO goes above a threshold of 500Hz.

A CI test is added with a GNU radio script between OCUDU gNB and the UE
that simulates a continuous frequency offset. The test passes if the UE
sends a frequency correction command.
Reviewed-by: Robert Schmidt <robert.schmidt@openairinterface.org>
Reviewed-by: Bartosz Podrygajlo <bartosz.podrygajlo@openairinterface.org>
Reviewed-by: Francesco Mani <email@francescomani.it>

executables/nr-ue.c

@@ -215,9 +215,8 @@ static void UE_synch(void *arg) {
         ((ret.rx_offset << 1) / fp->samples_per_subframe * fp->slots_per_subframe)
         + round((float)((ret.rx_offset << 1) % fp->samples_per_subframe) / fp->samples_per_slot0);
 
-    if (get_nrUE_params()->cont_fo_comp) {
-      UE->freq_offset = freq_offset - UE->dl_Doppler_shift;
-    } else {
+    UE->freq_offset = freq_offset - UE->dl_Doppler_shift;
+    if (!get_nrUE_params()->cont_fo_comp) {
       // rerun with new cell parameters and frequency-offset
       nrue_ru_set_freq(UE, ul_carrier, dl_carrier, freq_offset);
     }
@@ -711,6 +710,18 @@ static inline int get_readBlockSize(uint16_t slot, const NR_DL_FRAME_PARMS *fp)
   return rem_samples + next_slot_first_symbol;
 }
 
+void trs_freq_correction(PHY_VARS_NR_UE *ue, int cfo)
+{
+  if (abs(cfo) > TRS_CFO_THRESH) {
+    LOG_A(PHY, "CFO estimated (%d) from TRS exceeded threshold (%d). Adjusting radio CF\n", cfo, TRS_CFO_THRESH);
+    ue->freq_offset += cfo;
+    uint64_t dl_carrier;
+    uint64_t ul_carrier;
+    nr_get_carrier_frequencies(ue, &dl_carrier, &ul_carrier);
+    nrue_ru_set_freq(ue, ul_carrier, dl_carrier, ue->freq_offset);
+  }
+}
+
 void *UE_thread(void *arg)
 {
   //this thread should be over the processing thread to keep in real time

nfapi/open-nFAPI/nfapi/public_inc/fapi_nr_ue_interface.h

@@ -463,6 +463,7 @@ typedef struct {
   uint8_t power_control_offset;     // Ratio of PDSCH EPRE to NZP CSI-RSEPRE [3GPP TS 38.214, sec 5.2.2.3.1], Value: 0->23 representing -8 to 15 dB in 1dB steps; 255: L1 is configured with ProfileSSS
   uint8_t power_control_offset_ss;  // Ratio of NZP CSI-RS EPRE to SSB/PBCH block EPRE [3GPP TS 38.214, sec 5.2.2.3.1], Values: 0: -3dB; 1: 0dB; 2: 3dB; 3: 6dB; 255: L1 is configured with ProfileSSS
   uint8_t measurement_bitmap;       // bit 0 RSRP, bit 1 RI, bit 2 LI, bit 3 PMI, bit 4 CQI, bit 5 i1
+  uint8_t last_trs_slot;            // indicates to PHY if the slot is end of TRS burst
 } fapi_nr_dl_config_csirs_pdu_rel15_t;
 
 typedef enum{vrb_to_prb_mapping_non_interleaved = 0, vrb_to_prb_mapping_interleaved = 1} vrb_to_prb_mapping_t;

openair1/PHY/defs_nr_UE.h

@@ -56,6 +56,11 @@
 //       (0  + 0 * 20) % 512 = 0
 #define NUM_PROCESS_SLOT_TX_BARRIERS 512
 
+// CSI for tracking can have up to 2 resources per slot
+#define MAX_CSI_RES_SLOT 2
+// Threshold to change radio frequency
+#define TRS_CFO_THRESH 500
+
 #include "impl_defs_nr.h"
 #include "time_meas.h"
 #include "PHY/CODING/coding_defs.h"
@@ -553,7 +558,8 @@ typedef struct nr_phy_data_s {
   int n_dlsch_codewords;
   // Sidelink Rx action decided by MAC
   sl_nr_rx_config_type_enum_t sl_rx_action;
-  NR_UE_CSI_RS csirs_vars;
+  int num_csirs;
+  NR_UE_CSI_RS csirs_vars[MAX_CSI_RES_SLOT];
   NR_UE_CSI_IM csiim_vars;
 } nr_phy_data_t;
 

openair1/PHY/nr_phy_common/inc/nr_ue_phy_meas.h

@@ -38,7 +38,8 @@
   FN(ULSCH_INTERLEAVING_STATS),\
   FN(ULSCH_ENCODING_STATS),\
   FN(OFDM_MOD_STATS),\
-  FN(PRACH_GEN_STATS)
+  FN(PRACH_GEN_STATS),\
+  FN(TRS_PROCESSING)
 
 typedef enum {
   FOREACH_NR_PHY_CPU_MEAS(NOOP),

openair1/SCHED_NR_UE/defs.h

@@ -134,7 +134,12 @@ void nr_ue_csi_im_procedures(PHY_VARS_NR_UE *ue,
 void nr_ue_csi_rs_procedures(PHY_VARS_NR_UE *ue,
                              const UE_nr_rxtx_proc_t *proc,
                              const c16_t rxdataF[][ue->frame_parms.samples_per_slot_wCP],
-                             fapi_nr_dl_config_csirs_pdu_rel15_t *csirs_config_pdu);
+                             fapi_nr_dl_config_csirs_pdu_rel15_t *csirs_config_pdu,
+                             c16_t trs_estimates[][1][ue->frame_parms.ofdm_symbol_size],
+                             const int res_idx,
+                             const int trs_sym0);
+
+void trs_freq_correction(PHY_VARS_NR_UE *ue, int cfo);
 
 int psbch_pscch_processing(PHY_VARS_NR_UE *ue, const UE_nr_rxtx_proc_t *proc, nr_phy_data_t *phy_data);
 void phy_procedures_nrUE_SL_TX(PHY_VARS_NR_UE *ue, const UE_nr_rxtx_proc_t *proc, nr_phy_data_tx_t *phy_data, c16_t **txp);

openair1/SCHED_NR_UE/fapi_nr_ue_l1.c

@@ -150,8 +150,14 @@ static void nr_ue_scheduled_response_dl(NR_UE_MAC_INST_t *mac,
         phy_data->csiim_vars.active = true;
         break;
       case FAPI_NR_DL_CONFIG_TYPE_CSI_RS:
-        phy_data->csirs_vars.csirs_config_pdu = pdu->csirs_config_pdu.csirs_config_rel15;
-        phy_data->csirs_vars.active = true;
+        AssertFatal(phy_data->num_csirs < MAX_CSI_RES_SLOT, "CSI resources per slot exceeded limit\n");
+        const int c = phy_data->num_csirs;
+        if (phy_data->csirs_vars[c].active) {
+          AssertFatal(false, "Resource should not be active before its configured\n");
+        }
+        phy_data->csirs_vars[c].csirs_config_pdu = pdu->csirs_config_pdu.csirs_config_rel15;
+        phy_data->csirs_vars[c].active = true;
+        phy_data->num_csirs++;
         break;
       case FAPI_NR_DL_CONFIG_TYPE_RA_DLSCH:
       case FAPI_NR_DL_CONFIG_TYPE_SI_DLSCH:

openair1/SCHED_NR_UE/phy_procedures_nr_ue.c

@@ -1184,16 +1184,35 @@ void pdsch_processing(PHY_VARS_NR_UE *ue, const UE_nr_rxtx_proc_t *proc, nr_phy_
   }
 
   // do procedures for CSI-RS
-  if (phy_data->csirs_vars.active == 1) {
-    for(int symb = 0; symb < ue->frame_parms.symbols_per_slot; symb++) {
-      if(is_csi_rs_in_symbol(phy_data->csirs_vars.csirs_config_pdu, symb)) {
-        if (!slot_fep_map[symb]) {
-          nr_slot_fep(ue, &ue->frame_parms, proc->nr_slot_rx, symb, rxdataF, link_type_dl, 0, ue->common_vars.rxdata);
-          slot_fep_map[symb] = true;
+  {
+    /*
+    CSI-RS for tracking use only one port.
+    Number of CSI-RS resources for tracking is always 2 per slot.
+    Computed estimates from first resource is saved and used while estimating second resource.
+    */
+    c16_t trs_estimates[ue->frame_parms.nb_antennas_rx][1][ue->frame_parms.ofdm_symbol_size];
+    for (int res = 0; res < MAX_CSI_RES_SLOT; res++) {
+      if (phy_data->csirs_vars[res].active == 1) {
+        for (int symb = 0; symb < ue->frame_parms.symbols_per_slot; symb++) {
+          if (is_csi_rs_in_symbol(phy_data->csirs_vars[res].csirs_config_pdu, symb)) {
+            if (!slot_fep_map[symb]) {
+              nr_slot_fep(ue, &ue->frame_parms, proc->nr_slot_rx, symb, rxdataF, link_type_dl, 0, ue->common_vars.rxdata);
+              slot_fep_map[symb] = true;
+            }
+          }
         }
+        if (res > 0 && phy_data->csirs_vars[res].csirs_config_pdu.csi_type == 0) // tracking CSI
+          AssertFatal(phy_data->csirs_vars[res - 1].active && (phy_data->csirs_vars[res - 1].csirs_config_pdu.csi_type == 0),
+                      "CSI-RS for tracking must have two consecutive active resources\n");
+        nr_ue_csi_rs_procedures(ue,
+                                proc,
+                                rxdataF,
+                                &phy_data->csirs_vars[res].csirs_config_pdu,
+                                trs_estimates,
+                                res,
+                                (res == 1) ? phy_data->csirs_vars[0].csirs_config_pdu.symb_l0 : -1);
       }
     }
-    nr_ue_csi_rs_procedures(ue, proc, rxdataF, &phy_data->csirs_vars.csirs_config_pdu);
   }
 
   int16_t *llr[2];

openair1/SIMULATION/NR_PHY/nr_unitary_common.c

@@ -68,3 +68,7 @@ void configure_nr_nfapi_vnf(eth_params_t params)
 {
   UNUSED(params);
 }
+
+void trs_freq_correction(PHY_VARS_NR_UE *ue, int cfo)
+{
+}

openair2/LAYER2/NR_MAC_UE/nr_ue_scheduler.c

@@ -1114,7 +1114,8 @@ static void schedule_ta_command(fapi_nr_dl_config_request_t *dl_config, NR_UE_MA
 
 static NR_CSI_ResourceConfigId_t find_CSI_resourceconfig(NR_CSI_MeasConfig_t *csi_measconfig,
                                                          NR_BWP_Id_t dl_bwp_id,
-                                                         NR_NZP_CSI_RS_ResourceId_t csi_id)
+                                                         NR_NZP_CSI_RS_ResourceId_t csi_id,
+                                                         bool *is_last_res)
 {
   bool found = false;
   for (int csi_list = 0; csi_list < csi_measconfig->csi_ResourceConfigToAddModList->list.count; csi_list++) {
@@ -1139,14 +1140,14 @@ static NR_CSI_ResourceConfigId_t find_CSI_resourceconfig(NR_CSI_MeasConfig_t *cs
           AssertFatal(csi_res->nzp_CSI_RS_Resources.list.array[k], "NZP_CSI_RS_ResourceId shoulan't be NULL\n");
           if (csi_id == *csi_res->nzp_CSI_RS_Resources.list.array[k]) {
             found = true;
+            *is_last_res = (k == (csi_res->nzp_CSI_RS_Resources.list.count - 1));
             break;
           }
         }
         if (found && csi_res->trs_Info)
-          // CRI-RS for Tracking (not implemented yet)
-          // in this case we there is no associated CSI report
-          // therefore to signal this we return a value higher than
-          // maxNrofCSI-ResourceConfigurations
+          /* CRI-RS for Tracking. In this case there is no associated CSI report
+           * therefore to signal this we return a value higher than
+           * maxNrofCSI-ResourceConfigurations. */
           return NR_maxNrofCSI_ResourceConfigurations + 1;
         else if (found)
           return csires->csi_ResourceConfigId;
@@ -1216,7 +1217,8 @@ static void nr_schedule_csirs_reception(NR_UE_MAC_INST_t *mac, int frame, int sl
     csi_period_offset(NULL, nzpcsi->periodicityAndOffset, &period, &offset);
     if((frame * mac->frame_structure.numb_slots_frame + slot-offset) % period != 0)
       continue;
-    NR_CSI_ResourceConfigId_t csi_res_id = find_CSI_resourceconfig(csi_measconfig, dl_bwp_id, nzpcsi->nzp_CSI_RS_ResourceId);
+    bool is_last_res = false;
+    NR_CSI_ResourceConfigId_t csi_res_id = find_CSI_resourceconfig(csi_measconfig, dl_bwp_id, nzpcsi->nzp_CSI_RS_ResourceId, &is_last_res);
     // do not schedule reseption of this CSI-RS if not associated with current BWP
     if(csi_res_id < 0)
       continue;
@@ -1226,9 +1228,12 @@ static void nr_schedule_csirs_reception(NR_UE_MAC_INST_t *mac, int frame, int sl
     csirs_config_pdu->subcarrier_spacing = mu;
     csirs_config_pdu->cyclic_prefix = current_DL_BWP->cyclicprefix ? *current_DL_BWP->cyclicprefix : 0;
 
-    if (csi_res_id > NR_maxNrofCSI_ResourceConfigurations)
+    if (csi_res_id > NR_maxNrofCSI_ResourceConfigurations) {
+      /* According to 38.214 5.1.6.1.1, the number of resources indicate if one
+       * or two consequtive slots for TRS is used. We indicate to phy the last slot. */
+      csirs_config_pdu->last_trs_slot = is_last_res;
       csirs_config_pdu->csi_type = 0; // TRS
-    else
+    } else
       csirs_config_pdu->csi_type = 1; // NZP-CSI-RS
 
     csirs_config_pdu->scramb_id = nzpcsi->scramblingID;