cfo: srslte_sync_get_cfo() returns PSS-based CFO estimation. Gives better results than CP-based

srslte/examples/pdsch_ue.c

@@ -511,12 +511,6 @@ int main(int argc, char **argv) {
             if (n < 0) {
              // fprintf(stderr, "Error decoding UE DL\n");fflush(stdout);
             } else if (n > 0) {
-
-              /*
-              printf("Saving signal...\n");
-              srslte_ue_dl_save_signal(&ue_dl, &ue_dl.softbuffer, sfn*10+srslte_ue_sync_get_sfidx(&ue_sync), rv, prog_args.rnti);
-              exit(-1);
-              */
               
               /* Send data if socket active */
               if (prog_args.net_port > 0) {

srslte/include/srslte/sync/sync.h

@@ -76,6 +76,7 @@ typedef struct SRSLTE_API {
   uint32_t max_offset;
   bool enable_cfo_corr;
   float mean_cfo;
+  float mean_cfo2; 
   int cfo_i;
   bool find_cfo_i; 
   bool find_cfo_i_initiated; 
@@ -93,6 +94,7 @@ typedef struct SRSLTE_API {
   float m1_value;
   float M_norm_avg; 
   float M_ext_avg; 
+  cf_t  *temp;
 
 }srslte_sync_t;
 

srslte/lib/rf/rf_blade_imp.c

@@ -341,6 +341,10 @@ double rf_blade_set_rx_freq(void *h, double freq)
             (uint32_t) freq, bladerf_strerror(status));
     return -1;
   }
+  f_int=0;
+  bladerf_get_frequency(handler->dev, BLADERF_MODULE_RX, &f_int);
+  printf("set RX frequency to %u\n", f_int);
+  
   return freq;
 }
 
@@ -355,6 +359,9 @@ double rf_blade_set_tx_freq(void *h, double freq)
     return -1;
   }
   
+  f_int=0;
+  bladerf_get_frequency(handler->dev, BLADERF_MODULE_TX, &f_int);
+  printf("set TX frequency to %u\n", f_int);
   return freq;
 }
 

srslte/lib/sync/sync.c

@@ -61,6 +61,7 @@ int srslte_sync_init(srslte_sync_t *q, uint32_t frame_size, uint32_t max_offset,
     q->detect_cp = true;
     q->sss_en = true;
     q->mean_cfo = 0; 
+    q->mean_cfo2 = 0; 
     q->N_id_2 = 1000; 
     q->N_id_1 = 1000;
     q->cfo_i = 0; 
@@ -78,8 +79,8 @@ int srslte_sync_init(srslte_sync_t *q, uint32_t frame_size, uint32_t max_offset,
       goto clean_exit;
     }
     
-    // Set a CFO tolerance of approx 100 Hz
-    srslte_cfo_set_tol(&q->cfocorr, 100.0/(15000.0*q->fft_size));
+    // Set a CFO tolerance of approx 50 Hz
+    srslte_cfo_set_tol(&q->cfocorr, 50.0/(15000.0*q->fft_size));
 
     for (int i=0;i<2;i++) {
       q->cfo_i_corr[i] = srslte_vec_malloc(sizeof(cf_t)*q->frame_size);
@@ -89,6 +90,12 @@ int srslte_sync_init(srslte_sync_t *q, uint32_t frame_size, uint32_t max_offset,
       }
     }
     
+    q->temp = srslte_vec_malloc(sizeof(cf_t)*2*q->frame_size);
+    if (!q->temp) {
+      perror("malloc");
+      goto clean_exit;
+    }
+    
     srslte_sync_set_cp(q, SRSLTE_CP_NORM);
     
     if (srslte_pss_synch_init_fft(&q->pss, max_offset, fft_size)) {
@@ -131,6 +138,9 @@ void srslte_sync_free(srslte_sync_t *q) {
       }
       srslte_pss_synch_free(&q->pss_i[i]);
     }
+    if (q->temp) {
+      free(q->temp);
+    }
   }
 }
 
@@ -185,7 +195,7 @@ uint32_t srslte_sync_get_sf_idx(srslte_sync_t *q) {
 }
 
 float srslte_sync_get_cfo(srslte_sync_t *q) {
-  return q->mean_cfo + q->cfo_i;
+  return q->mean_cfo2 + q->cfo_i;
 }
 
 void srslte_sync_set_cfo(srslte_sync_t *q, float cfo) {
@@ -413,6 +423,8 @@ srslte_sync_find_ret_t srslte_sync_find(srslte_sync_t *q, cf_t *input, uint32_t
     if (peak_position) {
       *peak_position = 0; 
     }
+    
+    cf_t *input_cfo = input; 
 
     if (q->enable_cfo_corr) {
       float cfo = cfo_estimate(q, input); 
@@ -421,19 +433,21 @@ srslte_sync_find_ret_t srslte_sync_find(srslte_sync_t *q, cf_t *input, uint32_t
       q->mean_cfo = SRSLTE_VEC_EMA(cfo, q->mean_cfo, q->cfo_ema_alpha);
       
       /* Correct CFO with the averaged CFO estimation */
-      srslte_cfo_correct(&q->cfocorr, input, input, -q->mean_cfo / q->fft_size);                                   
+      srslte_cfo_correct(&q->cfocorr, input, q->temp, -q->mean_cfo / q->fft_size);      
+      
+      input_cfo = q->temp; 
     }
     
     /* If integer CFO is enabled, find max PSS correlation for shifted +1/0/-1 integer versions */
     if (q->find_cfo_i && q->enable_cfo_corr) {
-      q->cfo_i = cfo_i_estimate(q, input, find_offset, &peak_pos);   
+      q->cfo_i = cfo_i_estimate(q, input_cfo, find_offset, &peak_pos);   
       if (q->cfo_i != 0) {
-        srslte_vec_prod_ccc(input, q->cfo_i_corr[q->cfo_i<0?0:1], input, q->frame_size);
+        srslte_vec_prod_ccc(input_cfo, q->cfo_i_corr[q->cfo_i<0?0:1], input_cfo, q->frame_size);
         INFO("Compensating cfo_i=%d\n", q->cfo_i);
       }
     } else {      
       srslte_pss_synch_set_N_id_2(&q->pss, q->N_id_2);
-      peak_pos = srslte_pss_synch_find_pss(&q->pss, &input[find_offset], &q->peak_value);
+      peak_pos = srslte_pss_synch_find_pss(&q->pss, &input_cfo[find_offset], &q->peak_value);
       if (peak_pos < 0) {
         fprintf(stderr, "Error calling finding PSS sequence\n");
         return SRSLTE_ERROR; 
@@ -449,7 +463,7 @@ srslte_sync_find_ret_t srslte_sync_find(srslte_sync_t *q, cf_t *input, uint32_t
       // Set an invalid N_id_1 indicating SSS is yet to be detected
       q->N_id_1 = 1000; 
       
-      if (sync_sss(q, input, find_offset + peak_pos, q->cp) < 0) {
+      if (sync_sss(q, input_cfo, find_offset + peak_pos, q->cp) < 0) {
         DEBUG("No space for SSS processing. Frame starts at %d\n", peak_pos);
       }
     }
@@ -459,13 +473,16 @@ srslte_sync_find_ret_t srslte_sync_find(srslte_sync_t *q, cf_t *input, uint32_t
       
       if (q->detect_cp) {
         if (peak_pos + find_offset >= 2*(q->fft_size + SRSLTE_CP_LEN_EXT(q->fft_size))) {
-          srslte_sync_set_cp(q, srslte_sync_detect_cp(q, input, peak_pos + find_offset));
+          srslte_sync_set_cp(q, srslte_sync_detect_cp(q, input_cfo, peak_pos + find_offset));
         } else {
           DEBUG("Not enough room to detect CP length. Peak position: %d\n", peak_pos);
         }
       }
   
       if (peak_pos + find_offset >= 2*(q->fft_size + SRSLTE_CP_LEN_EXT(q->fft_size))) {
+        float cfo2   = srslte_pss_synch_cfo_compute(&q->pss, &input[find_offset + peak_pos - q->fft_size]);
+        q->mean_cfo2 = SRSLTE_VEC_EMA(cfo2, q->mean_cfo2, q->cfo_ema_alpha);
+        
         ret = SRSLTE_SYNC_FOUND;
       } else {
         ret = SRSLTE_SYNC_FOUND_NOSPACE; 

srslte/lib/ue/ue_dl.c

@@ -302,6 +302,13 @@ int srslte_ue_dl_decode_rnti(srslte_ue_dl_t *q, cf_t *input, uint8_t *data, uint
         fprintf(stderr, "Error calling srslte_pdsch_decode()\n");      
       } 
     }
+    
+    printf("Saving signal...\n");
+    srslte_vec_save_file("input", input, sizeof(cf_t)*SRSLTE_SF_LEN_PRB(q->cell.nof_prb));
+    srslte_ue_dl_save_signal(q, &q->softbuffer, sf_idx, rvidx, rnti, cfi);
+    //exit(-1);
+
+  
   }
 
   q->pkts_total++;

srslte/lib/ue/ue_sync.c

@@ -605,14 +605,12 @@ int srslte_ue_sync_zerocopy(srslte_ue_sync_t *q, cf_t *input_buffer) {
             } 
                       
             q->frame_total_cnt++;       
-          } else {
-            if (q->correct_cfo) {
-              srslte_cfo_correct(&q->sfind.cfocorr, 
+          } 
+          if (q->correct_cfo) {
+            srslte_cfo_correct(&q->sfind.cfocorr, 
                           input_buffer, 
                           input_buffer, 
-                          -srslte_sync_get_cfo(&q->strack) / q->fft_size);               
-                          
-            }            
+                          -srslte_sync_get_cfo(&q->strack) / q->fft_size);                         
           }          
         break;
       }