Shifting the QAM threshold by AMP, instead of shifting the data by AMP_SHIFT

This fixes the errors in bits introduced after LDPC decoding in case of mod_order = 6 and AMO_SHIFT = 9

openair1/PHY/NR_TRANSPORT/nr_ulsch_demodulation.c

@@ -4,7 +4,6 @@
 #include "PHY/NR_TRANSPORT/nr_sch_dmrs.h"
 
 
-
 void nr_ulsch_extract_rbs_single(int **rxdataF,
                                  int **rxdataF_ext,
                                  uint32_t rxdataF_ext_offset,
@@ -35,9 +34,8 @@ void nr_ulsch_extract_rbs_single(int **rxdataF,
 
       if ( (is_dmrs_symbol && ((re&1) != frame_parms->nushift))    ||    (is_dmrs_symbol == 0) ) { // [hna] (re&1) != frame_parms->nushift) assuming only dmrs type 1 and mapping type A
 
-        rxF_ext[rxF_ext_index]     = (rxF[ ((start_re + re)*2)      % (frame_parms->ofdm_symbol_size*2)] << 15) >> AMP_SHIFT;
-        rxF_ext[rxF_ext_index + 1] = (rxF[(((start_re + re)*2) + 1) % (frame_parms->ofdm_symbol_size*2)] << 15) >> AMP_SHIFT;
-        
+        rxF_ext[rxF_ext_index]     = (rxF[ ((start_re + re)*2)      % (frame_parms->ofdm_symbol_size*2)]);
+        rxF_ext[rxF_ext_index + 1] = (rxF[(((start_re + re)*2) + 1) % (frame_parms->ofdm_symbol_size*2)]);
         rxF_ext_index = rxF_ext_index + 2;
     	}
     }

openair1/PHY/NR_TRANSPORT/nr_ulsch_llr_computation.c

@@ -116,8 +116,8 @@ void nr_ulsch_16qam_llr(int32_t *rxdataF_comp,
   nb_re >>= 2;  // length in quad words (4 REs)
   nb_re += (len_mod4 == 0 ? 0 : 1);
 
-  temp_channel = _mm_set1_epi16((int16_t)((QAM16_n1 * one_over_sqrt_2)>>15));
-  
+  temp_channel = _mm_set1_epi16((QAM16_n1 * one_over_sqrt_2)>>(2*15-AMP_SHIFT));
+
   for (i=0; i<nb_re; i++) {
 
 #if defined(__x86_64__) || defined(__i386)
@@ -222,9 +222,8 @@ void nr_ulsch_64qam_llr(int32_t *rxdataF_comp,
   nb_re    = nb_re>>2;  // length in quad words (4 REs)
   nb_re   += ((len_mod4 == 0) ? 0 : 1);
   
-
-  temp_channel[0] = _mm_set1_epi16((int16_t)((QAM64_n1 * one_over_sqrt_2)>>15));
-  temp_channel[1] = _mm_set1_epi16((int16_t)((QAM64_n2 * one_over_sqrt_2)>>15));
+  temp_channel[0] = _mm_set1_epi16((QAM64_n1 * one_over_sqrt_2)>>(2*15-AMP_SHIFT));
+  temp_channel[1] = _mm_set1_epi16((QAM64_n2 * one_over_sqrt_2)>>(2*15-AMP_SHIFT));
 
   for (i=0; i<nb_re; i++) {
 
@@ -362,4 +361,4 @@ void nr_ulsch_compute_llr(int32_t *rxdataF_comp,
       LOG_E(PHY,"nr_ulsch_compute_llr: invalid Qm value, symbol = %d, Qm = %d\n",symbol, mod_order);
       break;
   }
-}
\ No newline at end of file
+}

openair1/PHY/impl_defs_top.h

@@ -245,7 +245,7 @@
 #ifdef BIT8_TX
 #define AMP_SHIFT 7
 #else
-#define AMP_SHIFT 10 // [hna] was 9, but 9 doesn't work in case of mod_order = 6 (problem due to IFFT/FFT)
+#define AMP_SHIFT 9
 #endif
 
 #define AMP ((1)<<AMP_SHIFT)

openair1/SCHED_NR/phy_procedures_nr_gNB.c

@@ -216,8 +216,6 @@ void nr_ulsch_procedures(PHY_VARS_gNB *gNB, gNB_L1_rxtx_proc_t *proc, int UE_id,
   //----------------------------------------------------------
 
   nr_ulsch_unscrambling(gNB->pusch_vars[UE_id]->llr, gNB->ulsch[UE_id+1][0]->harq_processes[harq_pid]->G, 0, Nid_cell, rel15_ul->rnti);
-
-  ////////////////////////////////////////////////////////////
       
 
   //----------------------------------------------------------