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 {
+    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/NR_UE_TRANSPORT/csi_rx.c

@@ -262,6 +262,8 @@ static int nr_csi_rs_channel_estimation(
     int16_t *log2_maxh,
     uint32_t *noise_power)
 {
+  const int meas_bitmap = csirs_config_pdu->measurement_bitmap;
+  AssertFatal(meas_bitmap != 1, "No need to do CSI-RS channel estimation for only RSRP measurment\n");
   *noise_power = 0;
   int maxh = 0;
   int count = 0;
@@ -301,10 +303,16 @@ static int nr_csi_rs_channel_estimation(
               const c16_t *rx_csi_rs_signal = &csi_rs_received_signal[ant_rx][symbol_offset];
               c16_t tmp =
                   c16MulConjShift(tx_csi_rs_signal[k_tx], rx_csi_rs_signal[k_rx], nr_csi_info->csi_rs_generated_signal_bits);
+              if (csirs_config_pdu->csi_type != 0) {
                 // This is not just the LS estimation for each (k,l), but also the sum of the different contributions
                 // for the sake of optimizing the memory used.
                 csi_rs_ls_estimated_channel[ant_rx][port_tx][kinit_tx].r += tmp.r;
                 csi_rs_ls_estimated_channel[ant_rx][port_tx][kinit_tx].i += tmp.i;
+              } else {
+                // for tracking we want estimates of all sub carriers having CSI-RS
+                csi_rs_ls_estimated_channel[ant_rx][port_tx][k_tx].r = tmp.r;
+                csi_rs_ls_estimated_channel[ant_rx][port_tx][k_tx].i = tmp.i;
+              }
             }
           }
         }
@@ -362,6 +370,10 @@ static int nr_csi_rs_channel_estimation(
       }
     }
 
+    // we need only ls estimates for tracking CSI. So stop here.
+    if (meas_bitmap == 0)
+      continue;
+
     /// Power noise estimation
     AssertFatal(csirs_config_pdu->nr_of_rbs > 0, " nr_of_rbs needs to be greater than 0\n");
     uint16_t noise_real[fp->nb_antennas_rx][csi_mapping->ports][csirs_config_pdu->nr_of_rbs];
@@ -406,9 +418,11 @@ static int nr_csi_rs_channel_estimation(
 
   }
 
+  if (meas_bitmap > 1) {
     *noise_power /= (fp->nb_antennas_rx * csi_mapping->ports);
     *log2_maxh = log2_approx(maxh - 1);
     *log2_re = log2_approx(count - 1);
+  }
 
 #ifdef NR_CSIRS_DEBUG
   LOG_I(NR_PHY, "Noise power estimation based on CSI-RS: %i\n", *noise_power);
@@ -774,6 +788,61 @@ static void nr_csi_im_power_estimation(const PHY_VARS_NR_UE *ue,
 #endif
 }
 
+static double get_cfo(const double phase_diff, const int sym0, const int sym1, const NR_DL_FRAME_PARMS *fp)
+{
+  const double one_fs = 1.0 / (fp->samples_per_frame * 100);
+  int sample_count = 0;
+  for (int s = sym0 + 1; s <= sym1; s++) {
+    const int prefix = (s % (7 * (1 << fp->numerology_index))) ? fp->nb_prefix_samples : fp->nb_prefix_samples0;
+    sample_count += (fp->ofdm_symbol_size + prefix);
+  }
+  const double delta_time = sample_count * one_fs;
+  const double cfo = phase_diff / (2 * M_PI * delta_time);
+  return cfo;
+}
+
+static void nr_ue_trs_processing(PHY_VARS_NR_UE *ue,
+                                 const c16_t res0_est[][1][ue->frame_parms.ofdm_symbol_size],
+                                 const c16_t res1_est[][1][ue->frame_parms.ofdm_symbol_size],
+                                 const c16_t freq_interp_est[][1][ue->frame_parms.ofdm_symbol_size],
+                                 const fapi_nr_dl_config_csirs_pdu_rel15_t *csirs_config_pdu,
+                                 const csi_mapping_parms_t *csi_mapping,
+                                 const int sym0,
+                                 const int sym1,
+                                 int *cfo,
+                                 int *time_offset)
+{
+  AssertFatal((sym0 > -1) && (sym1 > -1) && (sym1 > sym0), "Invalid symbol index for TRS estimation\n");
+  const NR_DL_FRAME_PARMS *fp = &ue->frame_parms;
+  // CFO estimation
+  const int ant_rx = 0; // Estimate only on first antenna port
+  cd_t phase_diff = {0.0};
+  AssertFatal(csirs_config_pdu->freq_density == 3,
+              "CSI-RS for tracking must have freq density of 3 but has %d\n",
+              csirs_config_pdu->freq_density);
+  AssertFatal(csi_mapping->kprime == 0 && csi_mapping->lprime == 0, "Invalid kprime, lprime for CSI-RS for tracking (row 1)\n");
+  for (int rb = csirs_config_pdu->start_rb; rb < (csirs_config_pdu->start_rb + csirs_config_pdu->nr_of_rbs); rb++) {
+    for (int cdm_id = 0; cdm_id < csi_mapping->size; cdm_id++) {
+      uint16_t kinit = rb * NR_NB_SC_PER_RB;
+      uint16_t k = kinit + csi_mapping->koverline[cdm_id];
+
+      const c16_t *res0 = res0_est[ant_rx][0];
+      const c16_t *res1 = res1_est[ant_rx][0];
+      phase_diff.r += res1[k].r * res0[k].r + res1[k].i * res0[k].i;
+      phase_diff.i += res1[k].i * res0[k].r - res1[k].r * res0[k].i;
+    }
+  }
+  *cfo = (int)get_cfo(atan2(phase_diff.i, phase_diff.r), sym0, sym1, fp);
+
+  if (time_offset) {
+    // Time offset estimation
+    __attribute__((aligned(32))) c16_t time_est[fp->ofdm_symbol_size];
+    delay_t delay = {0};
+    nr_est_delay(fp->ofdm_symbol_size, freq_interp_est[ant_rx][0], time_est, &delay);
+    *time_offset = delay.delay_max_pos;
+  }
+}
+
 void nr_ue_csi_im_procedures(PHY_VARS_NR_UE *ue,
                              const c16_t rxdataF[][ue->frame_parms.samples_per_slot_wCP],
                              const fapi_nr_dl_config_csiim_pdu_rel15_t *csiim_config_pdu)
@@ -796,7 +865,10 @@ 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)
 {
 
 #ifdef NR_CSIRS_DEBUG
@@ -816,11 +888,6 @@ void nr_ue_csi_rs_procedures(PHY_VARS_NR_UE *ue,
   LOG_I(NR_PHY, "csirs_config_pdu->power_control_offset_ss = %i\n", csirs_config_pdu->power_control_offset_ss);
 #endif
 
-  if(csirs_config_pdu->csi_type == 0) {
-    LOG_E(NR_PHY, "Handling of CSI-RS for tracking not handled yet at PHY\n");
-    return;
-  }
-
   if(csirs_config_pdu->csi_type == 2) {
     LOG_E(NR_PHY, "Handling of ZP CSI-RS not handled yet at PHY\n");
     return;
@@ -870,17 +937,12 @@ void nr_ue_csi_rs_procedures(PHY_VARS_NR_UE *ue,
                        &rsrp_dBm,
                        rxdataF);
 
-
-  if (csirs_config_pdu->measurement_bitmap == 0) {
-    LOG_D(NR_PHY, "No CSI-RS measurements configured\n");
-    return;
-  }
-
   uint32_t noise_power = 0;
   int16_t log2_re = 0;
   int16_t log2_maxh = 0;
   // if we need to measure only RSRP no need to do channel estimation
-  if (csirs_config_pdu->measurement_bitmap > 1)
+  if (csirs_config_pdu->measurement_bitmap != 1) {
+    const bool use_trs_buff = (csirs_config_pdu->csi_type == 0 && res_idx == 0);
     nr_csi_rs_channel_estimation(frame_parms,
                                 csirs_config_pdu,
                                 csi_info,
@@ -888,11 +950,12 @@ void nr_ue_csi_rs_procedures(PHY_VARS_NR_UE *ue,
                                 csi_rs_received_signal,
                                 &mapping_parms,
                                 CDM_group_size,
-                                 csi_rs_ls_estimated_channel,
+                                (use_trs_buff) ? trs_estimates : csi_rs_ls_estimated_channel,
                                 csi_rs_estimated_channel_freq,
                                 &log2_re,
                                 &log2_maxh,
                                 &noise_power);
+  }
 
   uint8_t rank_indicator = 0;
   // bit 1 in bitmap to indicate RI measurment
@@ -926,9 +989,34 @@ void nr_ue_csi_rs_procedures(PHY_VARS_NR_UE *ue,
       nr_csi_rs_cqi_estimation(precoded_sinr_dB, &cqi);
   }
 
+  int trs_cfo = 0;
+  const bool do_trs_est = (csirs_config_pdu->csi_type == 0) && (res_idx == 1);
+  if (do_trs_est) {
+    start_meas_nr_ue_phy(ue, TRS_PROCESSING);
+    nr_ue_trs_processing(ue,
+                         trs_estimates,
+                         csi_rs_ls_estimated_channel,
+                         csi_rs_estimated_channel_freq,
+                         csirs_config_pdu,
+                         &mapping_parms,
+                         trs_sym0,
+                         csirs_config_pdu->symb_l0,
+                         &trs_cfo,
+                         NULL); // Time offset not estimated because it is corrected using PBCH DMRS
+    stop_meas_nr_ue_phy(ue, TRS_PROCESSING);
+  }
+
   switch (csirs_config_pdu->measurement_bitmap) {
-    case 1 :
-      LOG_I(NR_PHY, "[UE %d] RSRP = %i dBm\n", ue->Mod_id, rsrp_dBm);
+    case 0:
+      if (do_trs_est)
+        LOG_I(NR_PHY,
+              "%d.%d TRS estimated CFO: %d Hz\n",
+              proc->frame_rx,
+              proc->nr_slot_rx,
+              trs_cfo);
+      break;
+    case 1:
+      LOG_I(NR_PHY, "%d.%d [UE %d] RSRP = %i dBm\n", proc->frame_rx, proc->nr_slot_rx, ue->Mod_id, rsrp_dBm);
       break;
     case 26 :
       LOG_I(NR_PHY, "RI = %i i1 = %i.%i.%i, i2 = %i, SINR = %i dB, CQI = %i\n",
@@ -942,6 +1030,10 @@ void nr_ue_csi_rs_procedures(PHY_VARS_NR_UE *ue,
       AssertFatal(false, "Not supported measurement configuration\n");
   }
 
+  if (!ue->cont_fo_comp && do_trs_est && csirs_config_pdu->last_trs_slot) {
+    trs_freq_correction(ue, trs_cfo);
+  }
+
   // Send CSI measurements to MAC
   if (!ue->if_inst || !ue->if_inst->dl_indication)
     return;

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)) {
+  {
+    /*
+    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;
             }
           }
         }
-    nr_ue_csi_rs_procedures(ue, proc, rxdataF, &phy_data->csirs_vars.csirs_config_pdu);
+        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);
+      }
+    }
   }
 
   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;