Initial NR OFDM symbol size compatibility

lib/include/srslte/phy/common/phy_common_nr.h

@@ -311,6 +311,14 @@ SRSLTE_API const char* srslte_mcs_table_to_str(srslte_mcs_table_t mcs_table);
  */
 SRSLTE_API srslte_mcs_table_t srslte_mcs_table_from_str(const char* str);
 
+/**
+ * @brief Computes the minimum valid symbol size for a given amount of PRB
+ * @attention The valid FFT sizes are radix 2 and radix 3 between 128 to 4096 points.
+ * @param nof_prb Number of PRB
+ * @return The minimum valid FFT size if the number of PRB is in range, 0 otherwise
+ */
+SRSLTE_API uint32_t srslte_min_symbol_sz_rb(uint32_t nof_prb);
+
 #ifdef __cplusplus
 }
 #endif

lib/include/srslte/phy/dft/ofdm.h

@@ -76,8 +76,28 @@ typedef struct SRSLTE_API {
   cf_t*             window_offset_buffer;
 } srslte_ofdm_t;
 
+/**
+ * @brief Initialises or reconfigures OFDM receiver
+ *
+ * @note The reconfiguration of the OFDM object considers only CP, number of PRB and optionally the FFT size
+ * @attention The OFDM object must be zeroed externally prior calling the initialization for first time
+ *
+ * @param q OFDM object
+ * @param cfg OFDM configuration
+ * @return SRSLTE_SUCCESS if the initialization/reconfiguration is successful, SRSLTE_ERROR code otherwise
+ */
 SRSLTE_API int srslte_ofdm_rx_init_cfg(srslte_ofdm_t* q, srslte_ofdm_cfg_t* cfg);
 
+/**
+ * @brief Initialises or reconfigures OFDM transmitter
+ *
+ * @note The reconfiguration of the OFDM object considers only CP, number of PRB and optionally the FFT size
+ * @attention The OFDM object must be zeroed externally prior calling the initialization for first time
+ *
+ * @param q OFDM object
+ * @param cfg OFDM configuration
+ * @return SRSLTE_SUCCESS if the initialization/reconfiguration is successful, SRSLTE_ERROR code otherwise
+ */
 SRSLTE_API int srslte_ofdm_tx_init_cfg(srslte_ofdm_t* q, srslte_ofdm_cfg_t* cfg);
 
 SRSLTE_API int

lib/src/phy/common/phy_common_nr.c

@@ -74,3 +74,25 @@ srslte_mcs_table_t srslte_mcs_table_from_str(const char* str)
   }
   return srslte_mcs_table_N;
 }
+
+#define PHY_COMMON_NR_NOF_VALID_SYMB_SZ 10U
+
+static const uint32_t phy_common_nr_valid_symbol_sz[PHY_COMMON_NR_NOF_VALID_SYMB_SZ] =
+    {128, 256, 384, 512, 768, 1024, 1536, 2048, 3072, 4096};
+
+uint32_t srslte_min_symbol_sz_rb(uint32_t nof_prb)
+{
+  uint32_t nof_re = nof_prb * SRSLTE_NRE;
+
+  if (nof_re == 0) {
+    return 0;
+  }
+
+  for (uint32_t i = 0; i < PHY_COMMON_NR_NOF_VALID_SYMB_SZ; i++) {
+    if (phy_common_nr_valid_symbol_sz[i] > nof_re) {
+      return phy_common_nr_valid_symbol_sz[i];
+    }
+  }
+
+  return 0;
+}

lib/src/phy/dft/ofdm.c

@@ -276,15 +276,11 @@ int srslte_ofdm_tx_init(srslte_ofdm_t* q, srslte_cp_t cp, cf_t* in_buffer, cf_t*
 
 int srslte_ofdm_tx_init_cfg(srslte_ofdm_t* q, srslte_ofdm_cfg_t* cfg)
 {
-  bzero(q, sizeof(srslte_ofdm_t));
-
   return ofdm_init_mbsfn_(q, cfg, SRSLTE_DFT_BACKWARD);
 }
 
 int srslte_ofdm_rx_init_cfg(srslte_ofdm_t* q, srslte_ofdm_cfg_t* cfg)
 {
-  bzero(q, sizeof(srslte_ofdm_t));
-
   return ofdm_init_mbsfn_(q, cfg, SRSLTE_DFT_FORWARD);
 }
 

lib/src/phy/ue/ue_dl_nr.c

@@ -138,7 +138,11 @@ int srslte_ue_dl_nr_set_carrier(srslte_ue_dl_nr_t* q, const srslte_carrier_nr_t*
 
   if (carrier->nof_prb != q->carrier.nof_prb) {
     for (uint32_t i = 0; i < q->nof_rx_antennas; i++) {
-      srslte_ofdm_rx_set_prb(&q->fft[i], SRSLTE_CP_NORM, carrier->nof_prb);
+      srslte_ofdm_cfg_t cfg = {};
+      cfg.nof_prb           = carrier->nof_prb;
+      cfg.symbol_sz         = srslte_min_symbol_sz_rb(carrier->nof_prb);
+      cfg.cp                = SRSLTE_CP_NORM;
+      srslte_ofdm_rx_init_cfg(&q->fft[i], &cfg);
     }
   }