enb,nsa: fix deriviation of UL ARFCN from DL ARFCN for FDD bands

srsenb/src/enb_cfg_parser.cc

@@ -1194,12 +1194,9 @@ int set_derived_args(all_args_t* args_, rrc_cfg_t* rrc_cfg_, phy_cfg_t* phy_cfg_
       // auto-detect UL frequency
       if (cfg.ul_earfcn == 0) {
         // derive UL ARFCN from given DL ARFCN
-        uint16_t             nr_band   = band_helper.get_band_from_dl_freq_Hz(phy_cell_cfg.dl_freq_hz);
-        srsran_duplex_mode_t nr_duplex = band_helper.get_duplex_mode(nr_band);
-        if (nr_duplex == SRSRAN_DUPLEX_MODE_TDD) {
-          cfg.ul_earfcn = cfg.dl_earfcn;
-        } else {
-          ERROR("Can't derive UL ARFCN from DL ARFCN");
+        cfg.ul_earfcn = band_helper.get_ul_arfcn_from_dl_arfcn(cfg.dl_earfcn);
+        if (cfg.ul_earfcn == 0) {
+          ERROR("Can't derive UL ARFCN from DL ARFCN %d", cfg.dl_earfcn);
           return SRSRAN_ERROR;
         }
       }