Added comment to clarify cross-correlation in PSS

srslte/lib/sync/pss.c

@@ -304,7 +304,12 @@ int srslte_pss_synch_find_pss(srslte_pss_synch_t *q, cf_t *input, float *corr_pe
       return SRSLTE_ERROR;
     }
 
-    /* Correlate input with PSS sequence */
+    /* Correlate input with PSS sequence
+     * 
+     * We do not reverse time-domain PSS signal because it's conjugate is symmetric.
+     * The conjugate operation on pss_signal_time has been done in srslte_pss_synch_init_N_id_2
+     * This is why we can use FFT-based convolution
+     */
     if (q->frame_size >= q->fft_size) {
     #ifdef CONVOLUTION_FFT
       memcpy(q->tmp_input, input, q->frame_size * sizeof(cf_t));