[develop] Added: LUT for sin/cos and function nr_apply_Doppler()

common/utils/nr/nr_common.c

@@ -738,3 +738,10 @@ uint32_t get_ssb_offset_to_pointA(uint32_t absoluteFrequencySSB,
   AssertFatal(sco % scs_scaling == 0, "ssb offset %d can create frequency offset\n", sco);
   return ssb_offset_point_a;
 }
+
+uint16_t LUTSin[ResolSinCos+1];
+void InitSinLUT( void ) {
+  for ( int i=0; i<(ResolSinCos+1); i++ ) {
+    LUTSin[i] = sin((double)M_PI/2/ResolSinCos*i) * (1<<14); //Format: Q14
+  }
+}

common/utils/nr/nr_common.h

@@ -131,4 +131,10 @@ int get_ssb_subcarrier_offset(uint32_t absoluteFrequencySSB, uint32_t absoluteFr
 #define min(a,b) cmin(a,b)
 #endif
 
+//look-up table for the sine (cosine) function
+#define ResolSinCos 100
+extern uint16_t LUTSin[ResolSinCos+1];
+void InitSinLUT( void );
+
+
 #endif

executables/nr-ru.c

@@ -1224,7 +1224,7 @@ void *ru_thread( void *param ) {
 	//slot_duration.tv_nsec = 0.5e6;
 	slot_duration.tv_nsec = 0.5e6;
 
-  
+  InitSinLUT();
 
   while (!oai_exit) {
     

openair1/PHY/MODULATION/nr_modulation.h

@@ -140,4 +140,9 @@ int nr_layer_precoder_cm(int16_t **datatx_F_precoding,
                 int *prec_matrix,
                 uint8_t n_layers,
                 int32_t re_offset);
+
+
+// apply frequency offset compensation
+void nr_apply_Doppler( void *in, uint32_t len, int32_t fDoppler, uint32_t *SampIdxDoppler, NR_DL_FRAME_PARMS *fp );
+
 #endif

openair1/PHY/MODULATION/slot_fep_nr.c

@@ -26,6 +26,7 @@
 #include "PHY/LTE_ESTIMATION/lte_estimation.h"
 #include "PHY/NR_UE_ESTIMATION/nr_estimation.h"
 #include <common/utils/LOG/log.h>
+#include "nr/nr_common.h"
 
 //#define DEBUG_FEP
 
@@ -330,3 +331,45 @@ void apply_nr_rotation_RX(NR_DL_FRAME_PARMS *frame_parms,
     }
   }
 }
+
+typedef struct complex16 sample_t; // 2*16 bits complex number
+//Apply the givin Doppler shift to the input signal with a fixed number of samples
+void nr_apply_Doppler( void *in, uint32_t len, int32_t fDoppler, uint32_t *SampIdxDoppler, NR_DL_FRAME_PARMS *fp ) {
+
+  int16_t SinDopper, CosDopper; // sine/cosine value from the LUT
+  sample_t *sigComp = (sample_t *)in;
+  for ( int k=0; k < len; k++ ) {
+    int64_t IdxInt = (int64_t)*SampIdxDoppler * fDoppler * ResolSinCos*4;
+    IdxInt = IdxInt>0 ? IdxInt+fp->samples_per_frame*100/2 : IdxInt-fp->samples_per_frame*100/2; //rounding
+    IdxInt = IdxInt / (fp->samples_per_frame*100);
+    int16_t IdxModulo = IdxInt % (ResolSinCos*4);
+    IdxModulo = IdxModulo<0 ? IdxModulo+ResolSinCos*4 : IdxModulo;
+
+    if ( IdxModulo < 2*ResolSinCos  ) {
+      if ( IdxModulo < ResolSinCos ) {
+        SinDopper = LUTSin[IdxModulo];
+        CosDopper = LUTSin[ResolSinCos-IdxModulo];
+      }
+      else {
+        SinDopper = LUTSin[2*ResolSinCos-IdxModulo];
+        CosDopper = -LUTSin[IdxModulo-ResolSinCos];
+      }
+    }
+    else {
+      if ( IdxModulo < 3*ResolSinCos ) {
+        SinDopper = -LUTSin[IdxModulo-2*ResolSinCos];
+        CosDopper = -LUTSin[3*ResolSinCos-IdxModulo];
+      }
+      else {
+        SinDopper = -LUTSin[4*ResolSinCos-IdxModulo];
+        CosDopper = LUTSin[IdxModulo-3*ResolSinCos];
+      }
+    }
+
+    sample_t sigTmp = sigComp[k];
+    sigComp[k].r= ( (int32_t)sigTmp.r*CosDopper - (int32_t)sigTmp.i*SinDopper )>>14;
+    sigComp[k].i= ( (int32_t)sigTmp.i*CosDopper + (int32_t)sigTmp.r*SinDopper )>>14;
+    (*SampIdxDoppler)++;
+  }
+
+}
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