Improved channel estimates around DC

Ignored 1 pilot before and after DC

openair1/PHY/NR_UE_ESTIMATION/filt16a_32.c

@@ -123,6 +123,24 @@ short filt8_m0[8] = {
 short filt8_mm0[8]= {
 0,0,0,8192,16384,8192,0,0};
 
+short filt8_dcma[8]= {
+16384,12288,8192,4096,4096,0,0,0};
+
+short filt8_dcmb[8]= {
+0,4096,8192,4096,4096,0,0,0};
+
+short filt8_dcmc[8]= {
+0,0,0,4096,4096,8192,4096,0};
+
+short filt8_dcmd[8]= {
+0,0,0,4096,4096,8192,12288,16384};
+
+short filt8_dcl[8]= {
+0,8192,16384,12288,8192,4096,0,0};
+
+short filt8_dcr[8]= {
+0,0,0,4096,8192,12288,16384,0};
+
 short filt8_l1[8] = {
 24576,16384,0,0,0,0,0,0};
 
@@ -136,4 +154,4 @@ short filt8_m1[8] = {
 0,0,8192,16384,8192,0,0,0};
 
 short filt8_mm1[8]= {
-0,0,0,0,8192,16384,8192,0};
+0,0,0,0,8192,16384,8192,0};

openair1/PHY/NR_UE_ESTIMATION/filt16a_32.h

@@ -91,6 +91,18 @@ extern short filt8_m0[8];
 
 extern short filt8_mm0[8];
 
+extern short filt8_dcma[8];
+
+extern short filt8_dcmb[8];
+
+extern short filt8_dcmc[8];
+
+extern short filt8_dcmd[8];
+
+extern short filt8_dcl[8];
+
+extern short filt8_dcr[8];
+
 extern short filt8_l1[8];
 
 extern short filt8_ml1[8];
@@ -101,4 +113,4 @@ extern short filt8_m1[8];
 
 extern short filt8_mm1[8];
 
-#endif
+#endif

openair1/PHY/NR_UE_ESTIMATION/nr_dl_channel_estimation.c

@@ -884,7 +884,72 @@ int nr_pdsch_channel_estimation(PHY_VARS_NR_UE *ue,
                                          dl_ch,
                                          8);
     //}
+    
+    // check if PRB crosses DC and improve estimates around DC
+    if ((bwp_start_subcarrier >= ue->frame_parms.ofdm_symbol_size/2) && (bwp_start_subcarrier+nb_rb_pdsch*12 >= ue->frame_parms.ofdm_symbol_size)) {
+      dl_ch = (int16_t *)&dl_ch_estimates[aarx][ch_offset];
+      uint16_t idxDC = 2*(ue->frame_parms.ofdm_symbol_size - bwp_start_subcarrier);
+      uint16_t idxPil = idxDC/2;
+      printf("idxDC %d idxPil %d\n",idxDC,idxPil);
+      re_offset = k;
+      pil = (int16_t *)&pilot[rb_offset*((config_type==0) ? 6:4)];
+      pil += (idxPil-4);
+      dl_ch += (idxDC-8);
+      dl_ch = memset(dl_ch, 0, sizeof(int16_t)*16);
+      
+      re_offset = (re_offset+idxDC/2-4)&(ue->frame_parms.ofdm_symbol_size-1);
+      rxF   = (int16_t *)&rxdataF[aarx][(symbol_offset+nushift+re_offset)];
+      ch[0] = (int16_t)(((int32_t)pil[0]*rxF[0] - (int32_t)pil[1]*rxF[1])>>15);
+      ch[1] = (int16_t)(((int32_t)pil[0]*rxF[1] + (int32_t)pil[1]*rxF[0])>>15);
+      
+      multadd_real_vector_complex_scalar(filt8_dcma,
+                                         ch,
+                                         dl_ch,
+                                         8);
 
+      pil += 2;
+      re_offset = (re_offset+2)&(ue->frame_parms.ofdm_symbol_size-1);
+      rxF   = (int16_t *)&rxdataF[aarx][(symbol_offset+nushift+re_offset)];
+      ch[0] = (int16_t)(((int32_t)pil[0]*rxF[0] - (int32_t)pil[1]*rxF[1])>>15);
+      ch[1] = (int16_t)(((int32_t)pil[0]*rxF[1] + (int32_t)pil[1]*rxF[0])>>15);
+
+      multadd_real_vector_complex_scalar(filt8_dcmb,
+                                         ch,
+                                         dl_ch,
+                                         8);
+      
+      pil += 4;
+      re_offset = (re_offset+4)&(ue->frame_parms.ofdm_symbol_size-1);
+      rxF   = (int16_t *)&rxdataF[aarx][(symbol_offset+nushift+re_offset)];
+      ch[0] = (int16_t)(((int32_t)pil[0]*rxF[0] - (int32_t)pil[1]*rxF[1])>>15);
+      ch[1] = (int16_t)(((int32_t)pil[0]*rxF[1] + (int32_t)pil[1]*rxF[0])>>15);
+      
+      multadd_real_vector_complex_scalar(filt8_dcmc,
+                                         ch,
+                                         dl_ch,
+                                         8);
+
+      pil += 2;
+      re_offset = (re_offset+2)&(ue->frame_parms.ofdm_symbol_size-1);
+      rxF   = (int16_t *)&rxdataF[aarx][(symbol_offset+nushift+re_offset)];
+      ch[0] = (int16_t)(((int32_t)pil[0]*rxF[0] - (int32_t)pil[1]*rxF[1])>>15);
+      ch[1] = (int16_t)(((int32_t)pil[0]*rxF[1] + (int32_t)pil[1]*rxF[0])>>15);
+
+      multadd_real_vector_complex_scalar(filt8_dcmd,
+                                         ch,
+                                         dl_ch,
+                                         8);
+    }
+
+//#ifdef DEBUG_PDSCH
+    dl_ch = (int16_t *)&dl_ch_estimates[aarx][ch_offset];
+    for(uint16_t idxP=0; idxP<(nb_rb_pdsch*12/8); idxP++) {
+      for(uint8_t idxI=0; idxI<16; idxI+=2) {
+        printf("%d\t%d\t",dl_ch[idxP*16+idxI],dl_ch[idxP*16+idxI+1]);
+      }
+      printf("\n");
+    }
+//#endif    
   }
 
   return(0);