Corrected LBRM functionality

lib/include/srsran/phy/phch/sch_cfg_nr.h

@@ -19,8 +19,11 @@ typedef struct SRSRAN_API {
   srsran_mcs_table_t mcs_table; ///< @brief Indicates the MCS table the UE shall use for PDSCH and/or PUSCH without
                                 ///< transform precoding
 
-  srsran_xoverhead_t xoverhead; ///< Accounts for overhead from CSI-RS, CORESET, etc. If the field is absent, the UE
+  srsran_xoverhead_t xoverhead; ///< @brief Accounts for overhead from CSI-RS, CORESET, etc. If the field is absent, the
-                                ///< applies value xOh0 (see TS 38.214 [19], clause 5.1.3.2).
+                                ///< UE applies value xOh0 (see TS 38.214 [19], clause 5.1.3.2).
+
+  bool limited_buffer_rm; ///< @brief Enables LBRM (Limited buffer rate-matching). Given by rateMatching parameter in
+                          ///< PUSCH-ServingCellConfig or PDSCH-ServingCellConfig ASN1 sequences
 } srsran_sch_cfg_t;
 
 typedef struct SRSRAN_API {

lib/src/phy/phch/sch_nr.c

@@ -87,7 +87,7 @@ static int sch_nr_Nref(uint32_t N_rb, srsran_mcs_table_t mcs_table, uint32_t max
   uint32_t           N_re_lbrm = SRSRAN_MAX_NRE_NR * sch_nr_n_prb_lbrm(N_rb);
   double             TCR_lbrm  = 948.0 / 1024.0;
   uint32_t           Qm_lbrm   = (mcs_table == srsran_mcs_table_256qam) ? 8 : 6;
-  uint32_t           TBS_LRBM  = srsran_ra_nr_tbs(N_re_lbrm, 1.0, TCR_lbrm, Qm_lbrm, max_mimo_layers);
+  uint32_t           TBS_LRBM  = srsran_ra_nr_tbs(N_re_lbrm, 1.0, TCR_lbrm, Qm_lbrm, SRSRAN_MIN(4, max_mimo_layers));
   double             R         = 2.0 / 3.0;
   srsran_basegraph_t bg        = srsran_sch_nr_select_basegraph(TBS_LRBM, R);
 
@@ -141,11 +141,15 @@ int srsran_sch_nr_fill_tb_info(const srsran_carrier_nr_t* carrier,
   cfg->Nl   = tb->N_L;
 
   // Calculate Nref
-  int Nref = sch_nr_Nref(carrier->nof_prb, sch_cfg->mcs_table, carrier->max_mimo_layers);
+  if (sch_cfg->limited_buffer_rm) {
+    int Nref = sch_nr_Nref(carrier->nof_prb, sch_cfg->mcs_table, 4);
     if (Nref < SRSRAN_SUCCESS) {
       ERROR("Error computing N_ref");
     }
     cfg->Nref = (uint32_t)Nref;
+  } else {
+    cfg->Nref = SRSRAN_LDPC_MAX_LEN_ENCODED_CB;
+  }
 
   // Calculate number of code blocks after applying CBGTI... not implemented, activate all CB
   for (uint32_t r = 0; r < cbsegm.C; r++) {

lib/test/phy/phy_dl_nr_test.c

@@ -30,6 +30,7 @@ static float                     cfo_hz            = 0.0f; // CFO Hz
 static srsran_dmrs_sch_type_t    dmrs_type                        = srsran_dmrs_sch_type_1;
 static srsran_dmrs_sch_add_pos_t dmrs_add_pos                     = srsran_dmrs_sch_add_pos_2;
 static bool                      interleaved_pdcch                = false;
+static uint32_t                  nof_dmrs_cdm_groups_without_data = 1;
 
 static void usage(char* prog)
 {
@@ -79,7 +80,7 @@ static int parse_args(int argc, char** argv)
             dmrs_type = srsran_dmrs_sch_type_2;
             break;
         }
-        switch (strtol(argv[optind], NULL, 10)) {
+        switch (strtol(argv[optind++], NULL, 10)) {
           case 0:
             dmrs_add_pos = srsran_dmrs_sch_add_pos_0;
             break;
@@ -93,6 +94,7 @@ static int parse_args(int argc, char** argv)
             dmrs_add_pos = srsran_dmrs_sch_add_pos_3;
             break;
         }
+        nof_dmrs_cdm_groups_without_data = (uint32_t)strtol(argv[optind], NULL, 10);
         break;
       case 'T':
         pdsch_cfg.sch_cfg.mcs_table = srsran_mcs_table_from_str(argv[optind]);
@@ -357,7 +359,7 @@ int main(int argc, char** argv)
   pdsch_cfg.grant.L                                = 13;
   pdsch_cfg.grant.nof_layers                       = carrier.max_mimo_layers;
   pdsch_cfg.grant.dci_format                       = srsran_dci_format_nr_1_0;
-  pdsch_cfg.grant.nof_dmrs_cdm_groups_without_data = 1;
+  pdsch_cfg.grant.nof_dmrs_cdm_groups_without_data = nof_dmrs_cdm_groups_without_data;
   pdsch_cfg.grant.beta_dmrs                        = srsran_convert_dB_to_amplitude(3);
   pdsch_cfg.grant.rnti_type                        = srsran_rnti_type_c;
   pdsch_cfg.grant.rnti                             = 0x4601;