NR UE: enable CSI report for SISO case

Correct precoded_sinr_dB wrongly set to 0 for SISO case.
Also correct ri_restriction is 0 when calculating CQI bit length for SISO.

openair1/PHY/NR_UE_TRANSPORT/csi_rx.c

@@ -592,7 +592,33 @@ int nr_csi_rs_pmi_estimation(const PHY_VARS_NR_UE *ue,
   // The first column is applicable if the UE is reporting a Rank = 1, whereas the second column is applicable if the
   // UE is reporting a Rank = 2.
 
-  if(N_ports == 1 || interference_plus_noise_power == 0) {
+  if (interference_plus_noise_power == 0) {
+    return 0;
+  }
+
+  if (N_ports == 1) {
+    // SISO case: SINR = E[|h|^2] / noise_power. No PMI to estimate.
+    int64_t signal_power = 0;
+    int count = 0;
+
+    for (int rb = csirs_config_pdu->start_rb; rb < (csirs_config_pdu->start_rb + csirs_config_pdu->nr_of_rbs); rb++) {
+      if (csirs_config_pdu->freq_density <= 1 && csirs_config_pdu->freq_density != (rb % 2)) {
+        continue;
+      }
+      uint16_t k = (frame_parms->first_carrier_offset + rb * NR_NB_SC_PER_RB) % frame_parms->ofdm_symbol_size;
+      uint16_t k_offset = k + mem_offset;
+
+      const c16_t h = csi_rs_estimated_channel_freq[0][0][k_offset];
+      signal_power += (int64_t)h.r * h.r + (int64_t)h.i * h.i;
+      count++;
+    }
+
+    if (count > 0) {
+      const int64_t avg_signal_power = signal_power / count;
+      const uint32_t sinr = avg_signal_power / interference_plus_noise_power;
+      *precoded_sinr_dB = dB_fixed(sinr);
+    }
+
     return 0;
   }
 

openair2/LAYER2/NR_MAC_COMMON/nr_mac_common.c

@@ -4480,7 +4480,7 @@ static uint8_t compute_ri_bitlen(const NR_CSI_ReportConfig_t *csi_reportconfig,
 
   if (codebookConfig == NULL) {
     csi_report->csi_meas_bitlen.ri_bitlen = 0;
-    return 0;
+    return 1;
   }
 
   struct NR_CodebookConfig__codebookType__type1__subType__typeI_SinglePanel *type1single = NULL;