Compute LLR for QPSK for ML

openair1/PHY/NR_TRANSPORT/nr_transport_proto.h

@@ -292,6 +292,18 @@ void nr_ulsch_compute_llr(int32_t *rxdataF_comp,
 void reset_active_stats(PHY_VARS_gNB *gNB, int frame);
 void reset_active_ulsch(PHY_VARS_gNB *gNB, int frame);
 
+void nr_ulsch_compute_ML_llr(int32_t **rxdataF_comp,
+                             int32_t ***rho,
+                             int16_t **llr_layers,
+                             uint8_t nb_antennas_rx,
+                             uint32_t rb_size,
+                             uint32_t nb_re,
+                             uint8_t symbol,
+                             uint32_t rxdataF_ext_offset,
+                             uint8_t mod_order);
+
+void nr_ulsch_shift_llr(int16_t **llr_layers, uint32_t nb_re, uint32_t rxdataF_ext_offset, uint8_t mod_order, int shift);
+
 void nr_fill_ulsch(PHY_VARS_gNB *gNB,
                    int frame,
                    int slot,

openair1/PHY/NR_TRANSPORT/nr_ulsch_demodulation.c

@@ -12,6 +12,7 @@
 //#define DEBUG_CH_COMP
 //#define DEBUG_RB_EXT
 //#define DEBUG_CH_MAG
+//#define ML_DEBUG
 
 #define INVALID_VALUE 255
 
@@ -1898,6 +1899,9 @@ void nr_rx_pusch(PHY_VARS_gNB *gNB,
                  unsigned char harq_pid)
 {
 
+  // Temporary flag: (true) ML receiver, (false) MMSE receiver
+  bool ml_rx = true;
+
   uint8_t aarx, aatx;
   uint32_t nb_re_pusch, bwp_start_subcarrier;
   int avgs = 0;
@@ -2001,8 +2005,8 @@ void nr_rx_pusch(PHY_VARS_gNB *gNB,
   int ad_shift = 0;
   if (rel15_ul->nrOfLayers == 1) {
     ad_shift = 1 + log2_approx(frame_parms->nb_antennas_rx >> 2);
-  } else {
-    ad_shift = -3; // For 2-layers, we are already doing a bit shift in the nr_ulsch_zero_forcing_rx_2layers() function, so we can use more bits
+  } else if (ml_rx == false) {
+    ad_shift = -3; // For 2-layers, we are already doing a bit shift in the nr_ulsch_mmse_2layers() function, so we can use more bits
   }
 
   for(uint8_t symbol = rel15_ul->start_symbol_index; symbol < (rel15_ul->start_symbol_index + rel15_ul->nr_of_symbols); symbol++) {
@@ -2108,7 +2112,7 @@ void nr_rx_pusch(PHY_VARS_gNB *gNB,
                              nb_re_pusch);
 
       // Apply MMSE for 2 Tx layers
-      if (rel15_ul->nrOfLayers == 2) {
+      if (ml_rx == false && rel15_ul->nrOfLayers == 2) {
         nr_ulsch_mmse_2layers(frame_parms,
                               pusch_vars->rxdataF_comp,
                               pusch_vars->ul_ch_mag0,
@@ -2159,17 +2163,46 @@ void nr_rx_pusch(PHY_VARS_gNB *gNB,
       /*--------------------  LLRs computation  -------------------------------------------------------------*/
       /*-----------------------------------------------------------------------------------------------------*/
       start_meas(&gNB->ulsch_llr_stats);
+      if (ml_rx == false || rel15_ul->nrOfLayers == 1) {
         for (aatx=0; aatx < rel15_ul->nrOfLayers; aatx++) {
-        nr_ulsch_compute_llr(&pusch_vars->rxdataF_comp[aatx*frame_parms->nb_antennas_rx][symbol * (off + rel15_ul->rb_size * NR_NB_SC_PER_RB)],
-                             pusch_vars->ul_ch_mag0[aatx*frame_parms->nb_antennas_rx],
-                             pusch_vars->ul_ch_magb0[aatx*frame_parms->nb_antennas_rx],
-                             pusch_vars->ul_ch_magc0[aatx*frame_parms->nb_antennas_rx],
+          nr_ulsch_compute_llr(&pusch_vars->rxdataF_comp[aatx * frame_parms->nb_antennas_rx][symbol * (off + rel15_ul->rb_size * NR_NB_SC_PER_RB)],
+                               pusch_vars->ul_ch_mag0[aatx * frame_parms->nb_antennas_rx],
+                               pusch_vars->ul_ch_magb0[aatx * frame_parms->nb_antennas_rx],
+                               pusch_vars->ul_ch_magc0[aatx * frame_parms->nb_antennas_rx],
                                &pusch_vars->llr_layers[aatx][rxdataF_ext_offset * rel15_ul->qam_mod_order],
                                rel15_ul->rb_size,
                                pusch_vars->ul_valid_re_per_slot[symbol],
                                symbol,
                                rel15_ul->qam_mod_order);
         }
+      } else {
+        nr_ulsch_compute_ML_llr(pusch_vars->rxdataF_comp,
+                                pusch_vars->rho,
+                                pusch_vars->llr_layers,
+                                frame_parms->nb_antennas_rx,
+                                rel15_ul->rb_size,
+                                nb_re_pusch,
+                                symbol,
+                                rxdataF_ext_offset,
+                                rel15_ul->qam_mod_order);
+
+        if (rel15_ul->qam_mod_order == 2) {
+          nr_ulsch_shift_llr(pusch_vars->llr_layers, nb_re_pusch, rxdataF_ext_offset, rel15_ul->qam_mod_order, 4);
+        }
+
+#ifdef ML_DEBUG
+        c16_t *llr_layers0 = (c16_t *)&pusch_vars->llr_layers[0][rxdataF_ext_offset * rel15_ul->qam_mod_order];
+        c16_t *llr_layers1 = (c16_t *)&pusch_vars->llr_layers[1][rxdataF_ext_offset * rel15_ul->qam_mod_order];
+        printf("===============================\n");
+        printf("AFTER nr_ulsch_compute_ML_llr()\n");
+        printf("===============================\n");
+        for (int k = 0; k < nb_re_pusch; k++) {
+          printf("[%3i] llr_layers0 = (%6i, %6i), llr_layers1 = (%6i, %6i)\n",
+                 k, llr_layers0[k].r, llr_layers0[k].i, llr_layers1[k].r, llr_layers1[k].i);
+        }
+        printf("\n");
+#endif
+      }
       stop_meas(&gNB->ulsch_llr_stats);
       rxdataF_ext_offset += pusch_vars->ul_valid_re_per_slot[symbol];
     }