NR MAC: enable MIMO beamforming with multiple CSI-RS ports

Add beam_id_polarization_offset config parameter to assign one beam index
per antenna port in CSI-RS and PDSCH scheduling, enabling MIMO operation
with dual-polarization and larger port configurations.

openair2/GNB_APP/MACRLC_nr_paramdef.h

@@ -51,10 +51,12 @@
 #define MACRLC_BEAMS_PERIOD                  "beams_per_period"
 #define MACRLC_BEAM_WEIGHTS_LIST             "beam_weights"
 #define MACRLC_DBT_FILE                      "dbt_file"
+#define MACRLC_BEAM_POL_OFFSET               "beam_id_polarization_offset"
 #define MACRLC_PUSCH_RSSI_THRESHOLD          "pusch_RSSI_Threshold"
 #define MACRLC_PUCCH_RSSI_THRESHOLD          "pucch_RSSI_Threshold"
 #define MACRLC_STATS_MAX_UE                  "stats_max_ue"
 
+
 #define HLP_MACRLC_UL_PRBBLACK "SNR threshold to decide whether a PRB will be blacklisted or not"
 #define HLP_MACRLC_DL_BLER_UP "Upper threshold of BLER to decrease DL MCS"
 #define HLP_MACRLC_DL_BLER_LO "Lower threshold of BLER to increase DL MCS"
@@ -72,6 +74,7 @@
 #define HLP_MACRLC_BEAM_DURATION "number of consecutive slots for a given set of beams"
 #define HLP_MACRLC_BEAMS_PERIOD "set of beams that can be simultaneously allocated in a period"
 #define HLP_MACRLC_DBT_FILE "File path to CSV file to read digital beamforming table"
+#define HLP_MACRLC_BEAM_POL_OFFSET "beamID offset for dual polarization (0=disable, 1=consecutive IDs)"
 #define HLP_MACRLC_PUSCH_RSSI_THRESHOLD "Limits PUSCH TPC commands based on RSSI to prevent ADC railing. Value range [-1280, 0], unit 0.1 dBm/dBFS"
 #define HLP_MACRLC_PUCCH_RSSI_THRESHOLD "Limits PUCCH TPC commands based on RSSI to prevent ADC railing. Value range [-1280, 0], unit 0.1 dBm/dBFS"
 #define HLP_MACRLC_STATS_MAX_UE "Maximum number of UEs before disabling periodical output (0 to disable)"
@@ -118,6 +121,7 @@
   {MACRLC_BEAMS_PERIOD,                HLP_MACRLC_BEAMS_PERIOD,  0, .u8ptr=NULL,  .defintval=1,               TYPE_UINT8,   0}, \
   {MACRLC_BEAM_WEIGHTS_LIST,           NULL,                     0, .iptr=NULL,   .defintarrayval=0,          TYPE_INTARRAY,0}, \
   {MACRLC_DBT_FILE,                    HLP_MACRLC_DBT_FILE,      0, .strptr=NULL, .defstrval=NULL,            TYPE_STRING,  0}, \
+  {MACRLC_BEAM_POL_OFFSET,             HLP_MACRLC_BEAM_POL_OFFSET, 0, .u8ptr=NULL, .defintval=0,              TYPE_UINT8,   0}, \
   {MACRLC_PUSCH_RSSI_THRESHOLD,        HLP_MACRLC_PUSCH_RSSI_THRESHOLD, \
                                                                                0, .iptr=NULL,   .defintval=0,               TYPE_INT,     0}, \
   {MACRLC_PUCCH_RSSI_THRESHOLD,        HLP_MACRLC_PUCCH_RSSI_THRESHOLD, \
@@ -166,6 +170,7 @@
   { .s5 = { NULL } }, \
   { .s5 = { NULL } }, \
   { .s5 = { NULL } }, \
+  { .s5 = { NULL } }, /* beam_id_polarization_offset */ \
   { .s2 =  { config_check_intrange, {-1280, 0}} }, /* PUSCH RSSI threshold range */ \
   { .s2 =  { config_check_intrange, {-1280, 0}} }, /* PUCCH RSSI threshold range */ \
   { .s5 = { NULL } }, \

openair2/GNB_APP/gnb_config.c

@@ -1747,6 +1747,7 @@ void RCconfig_nr_macrlc(configmodule_interface_t *cfg)
         beam_info->beam_allocation = malloc16(beams_per_period * sizeof(beam_info->beam_allocation));
         beam_info->beam_duration = *gpd(params, np, MACRLC_BEAM_DURATION)->u8ptr;
         beam_info->beams_per_period = beams_per_period;
+        beam_info->beam_id_polarization_offset = *gpd(params, np, MACRLC_BEAM_POL_OFFSET)->u8ptr;
         beam_info->beam_allocation_size = -1; // to be initialized once we have information on frame configuration
       }
       bool das_enabled = false;

openair2/LAYER2/NR_MAC_gNB/gNB_scheduler_dlsch.c

@@ -992,9 +992,21 @@ nfapi_nr_dl_tti_pdsch_pdu_rel15_t *prepare_pdsch_pdu(nfapi_nr_dl_tti_request_pdu
   // Precoding and beamforming
   pdsch_pdu->precodingAndBeamforming.num_prgs = 1;
   pdsch_pdu->precodingAndBeamforming.prg_size = pdsch_pdu->rbSize;
-  pdsch_pdu->precodingAndBeamforming.dig_bf_interfaces = 1;
-  pdsch_pdu->precodingAndBeamforming.prgs_list[0].pm_idx = sched_pdsch->pm_index; 
-  pdsch_pdu->precodingAndBeamforming.prgs_list[0].dig_bf_interface_list[0].beam_idx = beam_index;
+  pdsch_pdu->precodingAndBeamforming.prgs_list[0].pm_idx = sched_pdsch->pm_index;
+  const int pol_offset = mac->beam_info.beam_id_polarization_offset;
+  
+  const int numPorts = mac->radio_config.pdsch_AntennaPorts.XP * mac->radio_config.pdsch_AntennaPorts.N1 * mac->radio_config.pdsch_AntennaPorts.N2;
+  if (numPorts > 1 && pol_offset > 0) {  
+    pdsch_pdu->precodingAndBeamforming.dig_bf_interfaces = numPorts;
+    for (int port = 0; port < numPorts; port++){
+      pdsch_pdu->precodingAndBeamforming.prgs_list[0].dig_bf_interface_list[port].beam_idx = beam_index + 1 + (port * pol_offset);
+    }
+  }
+  
+  else {
+    pdsch_pdu->precodingAndBeamforming.dig_bf_interfaces = 1;
+    pdsch_pdu->precodingAndBeamforming.prgs_list[0].dig_bf_interface_list[0].beam_idx = beam_index;
+  }
   return pdsch_pdu;
 }
 

openair2/LAYER2/NR_MAC_gNB/gNB_scheduler_primitives.c

@@ -3287,10 +3287,27 @@ void nr_csirs_scheduling(int Mod_idP, frame_t frame, slot_t slot, nfapi_nr_dl_tt
           nfapi_nr_dl_tti_csi_rs_pdu_rel15_t *csirs_pdu_rel15 = &dl_tti_csirs_pdu->csi_rs_pdu.csi_rs_pdu_rel15;
           csirs_pdu_rel15->precodingAndBeamforming.num_prgs = 1;
           csirs_pdu_rel15->precodingAndBeamforming.prg_size = resourceMapping.freqBand.nrofRBs; //1 PRG of max size
-          csirs_pdu_rel15->precodingAndBeamforming.dig_bf_interfaces = 1;
           csirs_pdu_rel15->precodingAndBeamforming.prgs_list[0].pm_idx = 0;
-          const uint16_t fapi_beam = convert_to_fapi_beam(UE->UE_beam_index, gNB_mac->beam_info.beam_mode);
-          csirs_pdu_rel15->precodingAndBeamforming.prgs_list[0].dig_bf_interface_list[0].beam_idx = fapi_beam;
+
+          uint16_t fapi_beam = convert_to_fapi_beam(UE->UE_beam_index, gNB_mac->beam_info.beam_mode);
+          const int nrofPorts_to_num[] = {1, 2, 4, 8, 12, 16, 24, 32};
+          const int numPorts = nrofPorts_to_num[resourceMapping.nrofPorts];
+          int pol_offset = gNB_mac->beam_info.beam_id_polarization_offset;
+          if (numPorts > 1 && pol_offset > 0) {
+            csirs_pdu_rel15->precodingAndBeamforming.dig_bf_interfaces = numPorts;
+            for (int port = 0; port < numPorts; port++) {
+              // For SISO Beam with ID n, [n+p for p in numPorts] is the set of MIMO beams associated to it
+              // MIMO beams can be spliting the array in subarrays, use different polarizations, etc
+              int new_beam = UE->UE_beam_index + 1 + (port * pol_offset);
+              fapi_beam = convert_to_fapi_beam(new_beam, gNB_mac->beam_info.beam_mode);
+              csirs_pdu_rel15->precodingAndBeamforming.prgs_list[0].dig_bf_interface_list[port].beam_idx = fapi_beam;
+            }
+          } else {
+            csirs_pdu_rel15->precodingAndBeamforming.dig_bf_interfaces = 1;
+            csirs_pdu_rel15->precodingAndBeamforming.prgs_list[0].dig_bf_interface_list[0].beam_idx = fapi_beam;
+          }
+
+          
           csirs_pdu_rel15->bwp_size = dl_bwp->BWPSize;
           csirs_pdu_rel15->bwp_start = dl_bwp->BWPStart;
           csirs_pdu_rel15->subcarrier_spacing = dl_bwp->scs;

openair2/LAYER2/NR_MAC_gNB/main.c

@@ -118,7 +118,12 @@ size_t dump_mac_stats(gNB_MAC_INST *gNB, char *output, size_t strlen, bool reset
     const int avg_rsrp = stats->num_rsrp_meas > 0 ? stats->cumul_rsrp / stats->num_rsrp_meas : 0;
     const int avg_sinrx10 = stats->num_sinr_meas > 0 ? stats->cumul_sinrx10 / stats->num_sinr_meas : 0;
 
-    output = st_append(output, end, "UE RNTI %04x CU-UE-ID ", UE->rnti);
+    //Display beam information when beamforming is active
+    if (gNB->beam_info.beam_mode != NO_BEAM_MODE) {
+      output = st_append(output, end, "UE RNTI %04x BeamId %d CU-UE-ID ", UE->rnti, UE->UE_beam_index);
+    } else {
+      output = st_append(output, end, "UE RNTI %04x CU-UE-ID ", UE->rnti);
+    }
     if (du_exists_f1_ue_data(UE->rnti)) {
       f1_ue_data_t ued = du_get_f1_ue_data(UE->rnti);
       output = st_append(output, end, "%d", ued.secondary_ue);

openair2/LAYER2/NR_MAC_gNB/nr_mac_gNB.h

@@ -819,6 +819,8 @@ typedef struct {
   int beams_per_period;
   int beam_allocation_size;
   nr_beam_mode_t beam_mode;
+  /// beamID offset for dual polarization (0=disabled, typical value is 1)
+  int beam_id_polarization_offset;
 } NR_beam_info_t;
 
 #define UE_iterator(BaSe, VaR) for (NR_UE_info_t **VaR##pptr=BaSe, *VaR=*VaR##pptr; VaR; VaR=*(++VaR##pptr))