Delay compensation for PUCCH2

openair1/PHY/nr_phy_common/src/nr_phy_common.c

@@ -25,6 +25,8 @@
 #define USE_128BIT
 #endif
 
+#define PEAK_DETECT_THRESHOLD 15
+
 int16_t saturating_sub(int16_t a, int16_t b)
 {
   int32_t result = (int32_t)a - (int32_t)b;
@@ -367,20 +369,28 @@ void nr_est_delay(int ofdm_symbol_size, const c16_t *ls_est, c16_t *ch_estimates
   int max_val = delay->delay_max_val;
   const int sync_pos = 0;
 
+  uint64_t mean_val = 0;
   for (int i = 0; i < ofdm_symbol_size; i++) {
     int temp = c16amp2(ch_estimates_time[i]) >> 1;
+    mean_val += temp;
     if (temp > max_val) {
       max_pos = i;
       max_val = temp;
     }
   }
+  mean_val /= ofdm_symbol_size;
 
   if (max_pos > ofdm_symbol_size / 2)
     max_pos = max_pos - ofdm_symbol_size;
 
   delay->delay_max_pos = max_pos;
   delay->delay_max_val = max_val;
-  delay->est_delay = max_pos - sync_pos;
+
+  // The peak in general is quite clear. It only gives a small peak when the noise is high, generally obtaining an incorrect
+  // estimated delay, and causing the delay compensation to worsen the result instead of improving it. After analyzing several
+  // peaks, and doing many tests, a PEAK_DETECT_THRESHOLD = 15 is an adequate value, to apply delay compensation only when there is
+  // clearly a peak
+  delay->est_delay = mean_val > 0 && max_val / mean_val > PEAK_DETECT_THRESHOLD ? max_pos - sync_pos : 0;
 }
 
 unsigned int nr_get_tx_amp(int power_dBm, int power_max_dBm, int total_nb_rb, int nb_rb)