RRC: add SIB3/SIB4 neighbour offsets and inter-frequency SIB4 config

Introduce typed SIB3/SIB4 neighbour and inter-frequency carrier
configuration structures, wire them into the RRC neighbour and gNB
instances, and centralise parsing and bounds checking of per-frequency
SIB4 parameters from the gNB frequency list.

Changes:
- Define SIB3/SIB4 reselection and offset bound macros in gnb_config.c
  and apply them when parsing SIB4 frequency_config and
  per-carrier q_RxLevMin/t_ReselectionNR.
- Add add_inter_freq and parse_inter_freq_list helpers in gnb_config.c
  to populate a shared inter_freqs seq_arr_t from gNB_CONFIG_STRING_GNB_LIST
  frequency_list entries, enforcing unique (ARFCN,SCS) combinations and
  logging duplicates.
- Extend neighbour cell parameters in gnb_paramdef.h with SIB3 per-
  neighbour offset fields and define frequency_list/frequency_config
  option names, descriptor tables, and index constants for SIB4 inter-
  frequency configuration.
- Introduce nr_neighbour_cell_neighbor_offset_t, nr_neighbour_cell_sib3_t,
  nr_neighbour_cell_sib4_freq_t, nr_neighbour_cell_sib4_t, and
  nr_inter_freq_cfg_t in nr_rrc_defs.h, and extend nr_neighbour_cell_t
  and gNB_RRC_INST with sib3/sib4 and inter_freqs members respectively.
- udpated fill_neighbour_cell_configuration to use GET_PARAMS_LIST
  with params bound check

openair2/GNB_APP/gnb_config.c

@@ -2012,6 +2012,108 @@ static nr_neighbour_cell_t *get_neighbour_by_pci(seq_arr_t *neighbour_cells, int
   return NULL;
 }
 
+/** @brief Parse gNB-level inter-frequency list (frequency_list) into a shared array.
+ * This parses gNBs.[gnb_idx].frequency_list once and validates per-frequency SIB4
+ * parameters. The resulting list can then be reused for all serving cells.
+ * @param[out] inter_freqs Sequence array of nr_inter_freq_cfg_t to populate
+ * @param[in]  gnb_idx     gNB index */
+static bool eq_inter_freq_arfcn_scs(const void *vval, const void *vit)
+{
+  const nr_inter_freq_cfg_t *key = (const nr_inter_freq_cfg_t *)vval;
+  const nr_inter_freq_cfg_t *cur = (const nr_inter_freq_cfg_t *)vit;
+  return key->arfcn == cur->arfcn && key->scs == cur->scs;
+}
+
+/** @brief Insert an inter-frequency config if (ARFCN,SCS) is unique in the list.
+ * Fails fast if a duplicate is found.
+ * @param[in,out] inter_freqs Existing inter-frequency list
+ * @param[in]     f           Candidate entry to insert (by value)
+ * @param[in]     gnb_idx     gNB index for logging
+ */
+static void add_inter_freq(seq_arr_t *inter_freqs, const nr_inter_freq_cfg_t *f, uint8_t gnb_idx)
+{
+  const nr_inter_freq_cfg_t key = {.arfcn = f->arfcn, .scs = f->scs};
+  elm_arr_t dup = find_if(inter_freqs, (void *)&key, eq_inter_freq_arfcn_scs);
+  if (dup.found) {
+    AssertFatal(false, "gNB %d: duplicate inter-freq carrier ARFCN %d, SCS %d in frequency_list\n", gnb_idx, f->arfcn, f->scs);
+  }
+
+  seq_arr_push_back(inter_freqs, (void *)f, sizeof(*f));
+}
+
+static void parse_inter_freq_list(seq_arr_t *inter_freqs, const uint8_t gnb_idx)
+{
+  seq_arr_init(inter_freqs, sizeof(nr_inter_freq_cfg_t));
+
+  char freq_path[MAX_OPTNAME_SIZE + 8];
+  snprintf(freq_path, sizeof(freq_path), "%s.[%i]", GNB_CONFIG_STRING_GNB_LIST, gnb_idx);
+  GET_PARAMS_LIST(freq_list, freq_params, GNBFREQUENCYPARAMS_DESC, GNB_CONFIG_STRING_FREQUENCY_LIST, freq_path);
+
+  for (int i = 0; i < freq_list.numelt; ++i) {
+    const paramdef_t *freq_item = freq_list.paramarray[i];
+    nr_inter_freq_cfg_t f = {0};
+    f.arfcn = *gpd(freq_item, sizeofArray(freq_params), GNB_CONFIG_STRING_FREQUENCY_ABS_FREQ_SSB)->i64ptr;
+    f.scs = *gpd(freq_item, sizeofArray(freq_params), GNB_CONFIG_STRING_FREQUENCY_SCS)->uptr;
+
+    char cfg_path[MAX_OPTNAME_SIZE + 16];
+    snprintf(cfg_path,
+             sizeof(cfg_path),
+             "%s.[%i].%s.[%i]",
+             GNB_CONFIG_STRING_GNB_LIST,
+             gnb_idx,
+             GNB_CONFIG_STRING_FREQUENCY_LIST,
+             i);
+    GET_PARAMS(freq_cfg, GNBFREQUENCYCONFIGPARAMS_DESC, cfg_path);
+
+    nr_neighbour_cell_sib4_freq_t *p = &f.freq_cfg;
+
+    p->cellReselectionPriority = *freq_cfg[GNB_CONFIG_FREQUENCY_CELL_RESEL_PRIO_IDX].iptr;
+    p->threshX_HighP = *freq_cfg[GNB_CONFIG_FREQUENCY_THRESH_X_HIGH_P_IDX].iptr;
+    p->threshX_LowP = *freq_cfg[GNB_CONFIG_FREQUENCY_THRESH_X_LOW_P_IDX].iptr;
+    p->threshX_HighQ = *freq_cfg[GNB_CONFIG_FREQUENCY_THRESH_X_HIGH_Q_IDX].iptr;
+    p->threshX_LowQ = *freq_cfg[GNB_CONFIG_FREQUENCY_THRESH_X_LOW_Q_IDX].iptr;
+    p->q_OffsetFreq = *freq_cfg[GNB_CONFIG_FREQUENCY_Q_OFFSET_FREQ_IDX].iptr;
+    f.q_RxLevMin = *freq_cfg[GNB_CONFIG_FREQUENCY_Q_RXLEVMIN_IDX].iptr;
+    f.t_ReselectionNR = *freq_cfg[GNB_CONFIG_FREQUENCY_T_RESEL_NR_IDX].uptr;
+
+    /* Add inter-frequency configuration to the list. */
+    add_inter_freq(inter_freqs, &f, gnb_idx);
+
+    LOG_I(GNB_APP,
+          "gNB %d: SIB4 inter-freq ARFCN %d, SCS %d, prio=%d, ThreshX_HighP=%d, ThreshX_LowP=%d, ThreshX_HighQ=%d, "
+          "ThreshX_LowQ=%d, q_OffsetFreq=%d\n",
+          gnb_idx,
+          f.arfcn,
+          f.scs,
+          f.freq_cfg.cellReselectionPriority,
+          f.freq_cfg.threshX_HighP,
+          f.freq_cfg.threshX_LowP,
+          f.freq_cfg.threshX_HighQ,
+          f.freq_cfg.threshX_LowQ,
+          f.freq_cfg.q_OffsetFreq);
+  }
+}
+
+static void set_sib3_offsets(nr_neighbour_cell_t *n, const paramdef_t *cell_params, int n_cell_params)
+{
+  nr_neighbour_cell_neighbor_offset_t *sib3_off = &n->sib3.offset;
+
+  /* SIB3 per-neighbour offsets */
+  sib3_off->q_OffsetCell = *gpd(cell_params, n_cell_params, GNB_CONFIG_STRING_NEIGHBOUR_CELL_Q_OFFSET_CELL)->iptr;
+  sib3_off->q_RxLevMinOffsetCell = *gpd(cell_params, n_cell_params, GNB_CONFIG_STRING_NEIGHBOUR_CELL_Q_RXLEVMIN_OFFSET_CELL)->iptr;
+  sib3_off->q_QualMinOffsetCell = *gpd(cell_params, n_cell_params, GNB_CONFIG_STRING_NEIGHBOUR_CELL_Q_QUALMIN_OFFSET_CELL)->iptr;
+}
+
+static void set_sib4_offsets(nr_neighbour_cell_t *n, const paramdef_t *cell_params, int n_cell_params)
+{
+  nr_neighbour_cell_neighbor_offset_t *sib4_off = &n->sib4.offset;
+
+  /* SIB4 per-neighbour offsets */
+  sib4_off->q_OffsetCell = *gpd(cell_params, n_cell_params, GNB_CONFIG_STRING_NEIGHBOUR_CELL_Q_OFFSET_CELL)->iptr;
+  sib4_off->q_RxLevMinOffsetCell = *gpd(cell_params, n_cell_params, GNB_CONFIG_STRING_NEIGHBOUR_CELL_Q_RXLEVMIN_OFFSET_CELL)->iptr;
+  sib4_off->q_QualMinOffsetCell = *gpd(cell_params, n_cell_params, GNB_CONFIG_STRING_NEIGHBOUR_CELL_Q_QUALMIN_OFFSET_CELL)->iptr;
+}
+
 /** @brief Parse and add neighbour cells for a given cell configuration
  * @param[in,out] cell Neighbour cell configuration to populate
  * @param[in] list Parameter list describing neighbour cells
@@ -2036,6 +2138,11 @@ static void parse_neighbour_cells_list(neighbour_cell_configuration_t *cell,
         .absoluteFrequencySSB = *gpd(cell_params, n_cell_params, GNB_CONFIG_STRING_NEIGHBOUR_CELL_ABS_FREQ_SSB)->i64ptr,
         .tac = *gpd(cell_params, n_cell_params, GNB_CONFIG_STRING_NEIGHBOUR_TRACKING_ARE_CODE)->uptr};
 
+    set_sib3_offsets(&n, cell_params, n_cell_params);
+    set_sib4_offsets(&n, cell_params, n_cell_params);
+    /* SIB4 per-frequency reselection parameters (q_OffsetFreq, thresholds, priority)
+     * are populated in parse_inter_freq_list() per-frequency, not per neighbour here. */
+
     char p[CONFIG_MAXOPTLENGTH]; // plmn path
     snprintf(p, sizeof(p), "%s.%s.[%i].%s", n_path, GNB_CONFIG_STRING_NEIGHBOUR_CELL_LIST, l, GNB_CONFIG_STRING_NEIGHBOUR_PLMN);
     GET_PARAMS(NeighbourPlmn, GNBPLMNPARAMS_DESC, p);
@@ -2087,6 +2194,9 @@ static void fill_neighbour_cell_configuration(const uint8_t gnb_idx, gNB_RRC_INS
   if (nlist.numelt < 1)
     return;
 
+  /* Parse gNB-level inter-frequency configuration once and reuse it for all cells. */
+  parse_inter_freq_list(&rrc->inter_freqs, gnb_idx);
+
   rrc->neighbour_cell_configuration = malloc_or_fail(sizeof(seq_arr_t));
   seq_arr_init(rrc->neighbour_cell_configuration, sizeof(neighbour_cell_configuration_t));
 

openair2/GNB_APP/gnb_paramdef.h

@@ -300,6 +300,11 @@ typedef enum {
 #define GNB_CONFIG_STRING_NEIGHBOUR_CELL_BAND "band"
 #define GNB_CONFIG_STRING_NEIGHBOUR_TRACKING_ARE_CODE "tracking_area_code"
 #define GNB_CONFIG_STRING_NEIGHBOUR_PLMN "plmn"
+/* SIB3 fields (intra-frequency) - per-neighbor */
+#define GNB_CONFIG_STRING_NEIGHBOUR_CELL_Q_OFFSET_CELL "q_OffsetCell"
+#define GNB_CONFIG_STRING_NEIGHBOUR_CELL_Q_RXLEVMIN_OFFSET_CELL "q_RxLevMinOffsetCell"
+#define GNB_CONFIG_STRING_NEIGHBOUR_CELL_Q_QUALMIN_OFFSET_CELL "q_QualMinOffsetCell"
+/* SIB4 per-frequency fields are configured in frequency_list.frequency_config */
 
 // clang-format off
 #define GNBNEIGHBOURCELLPARAMS_DESC { /*   optname     helpstr     paramflags     XXXptr     def     val     type     numelt   */        \
@@ -324,9 +329,82 @@ typedef enum {
   {GNB_CONFIG_STRING_NEIGHBOUR_TRACKING_ARE_CODE,                                                                                        \
     "neighbour cell tracking area (0..16777215)", PARAMFLAG_MANDATORY, .uptr=NULL, .defuintval=0, TYPE_UINT, 0,                          \
     .chkPptr = &(checkedparam_t){.s2 = {config_check_uintrange, {0, 16777215}}}},                                                        \
+  {GNB_CONFIG_STRING_NEIGHBOUR_CELL_Q_OFFSET_CELL,                                                                                       \
+    "Q-OffsetCell for SIB3/SIB4 (Q-OffsetRange, default 0)", 0, .iptr=NULL, .defintval=0, TYPE_INT, 0,                                   \
+    .chkPptr = &(checkedparam_t){.s1 = {config_check_intval,                                                                             \
+    {-24, -22, -20, -18, -16, -14, -12, -10, -8, -6, -5, -4, -3, -2, -1, 0, 1, 2, 3, 4, 5, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24}, 31}}}, \
+  {GNB_CONFIG_STRING_NEIGHBOUR_CELL_Q_RXLEVMIN_OFFSET_CELL,                                                                              \
+    "Q-RxLevMinOffsetCell for SIB3/SIB4 (1..8 or -1=disabled)", 0, .iptr=NULL, .defintval=-1, TYPE_INT, 0,                               \
+    .chkPptr = &(checkedparam_t){.s1 = {config_check_intval, {-1, 1, 2, 3, 4, 5, 6, 7, 8}, 9}}},                                         \
+  {GNB_CONFIG_STRING_NEIGHBOUR_CELL_Q_QUALMIN_OFFSET_CELL,                                                                               \
+    "Q-QualMinOffsetCell for SIB3/SIB4 (1..8 or -1=disabled)", 0, .iptr=NULL, .defintval=-1, TYPE_INT, 0,                                \
+    .chkPptr = &(checkedparam_t){.s1 = {config_check_intval, {-1, 1, 2, 3, 4, 5, 6, 7, 8}, 9}}},                                         \
 }
 // clang-format on
 
+/* Per-frequency neighbour configuration (frequency_list) */
+#define GNB_CONFIG_STRING_FREQUENCY_LIST "frequency_list"
+#define GNB_CONFIG_STRING_FREQUENCY_ABS_FREQ_SSB "absoluteFrequencySSB"
+#define GNB_CONFIG_STRING_FREQUENCY_SCS "subcarrierSpacing"
+#define GNB_CONFIG_STRING_FREQUENCY_BAND "band"
+#define GNB_CONFIG_STRING_FREQUENCY_CONFIG "frequency_config"
+
+#define GNB_CONFIG_STRING_FREQUENCY_CELL_RESEL_PRIO "cellReselectionPriority"
+#define GNB_CONFIG_STRING_FREQUENCY_THRESH_X_HIGH_P "threshX_HighP"
+#define GNB_CONFIG_STRING_FREQUENCY_THRESH_X_LOW_P "threshX_LowP"
+#define GNB_CONFIG_STRING_FREQUENCY_THRESH_X_HIGH_Q "threshX_HighQ"
+#define GNB_CONFIG_STRING_FREQUENCY_THRESH_X_LOW_Q "threshX_LowQ"
+#define GNB_CONFIG_STRING_FREQUENCY_Q_OFFSET_FREQ "q_OffsetFreq"
+#define GNB_CONFIG_STRING_FREQUENCY_Q_RXLEVMIN "q_RxLevMin"
+#define GNB_CONFIG_STRING_FREQUENCY_T_RESEL_NR "t_ReselectionNR"
+
+// clang-format off
+#define GNBFREQUENCYPARAMS_DESC {                                                                  \
+/*   optname                                     helpstr                          paramflags      XXXptr     def val    type      numelt */ \
+  {GNB_CONFIG_STRING_FREQUENCY_ABS_FREQ_SSB, "inter-frequency abs freq ssb",     PARAMFLAG_MANDATORY, .i64ptr=NULL, .defint64val=0, TYPE_INT64, 0}, \
+  {GNB_CONFIG_STRING_FREQUENCY_SCS,          "inter-frequency scs",              PARAMFLAG_MANDATORY, .uptr=NULL,   .defuintval=0,  TYPE_UINT,  0}, \
+  {GNB_CONFIG_STRING_FREQUENCY_BAND,         "inter-frequency band",             PARAMFLAG_MANDATORY, .uptr=NULL,   .defuintval=78, TYPE_UINT,  0}, \
+}
+
+#define GNBFREQUENCYCONFIGPARAMS_DESC {                                                                 \
+  {GNB_CONFIG_STRING_FREQUENCY_CELL_RESEL_PRIO,                                                         \
+    "SIB4 cellReselectionPriority (0..7, -1=disabled)", 0, .iptr=NULL, .defintval=-1, TYPE_INT, 0,      \
+    .chkPptr = &(checkedparam_t){.s2 = {config_check_intrange, {-1, 7}}}},                              \
+  {GNB_CONFIG_STRING_FREQUENCY_THRESH_X_HIGH_P,                                                         \
+    "SIB4 threshX-HighP (0..31)", 0, .iptr=NULL, .defintval=0, TYPE_INT, 0,                             \
+    .chkPptr = &(checkedparam_t){.s2 = {config_check_intrange, {0, 31}}}},                              \
+  {GNB_CONFIG_STRING_FREQUENCY_THRESH_X_LOW_P,                                                          \
+    "SIB4 threshX-LowP (0..31)", 0, .iptr=NULL, .defintval=0, TYPE_INT, 0,                              \
+    .chkPptr = &(checkedparam_t){.s2 = {config_check_intrange, {0, 31}}}},                              \
+  {GNB_CONFIG_STRING_FREQUENCY_THRESH_X_HIGH_Q,                                                         \
+    "SIB4 threshX-HighQ (0..31, -1=disabled)", 0, .iptr=NULL, .defintval=-1, TYPE_INT, 0,               \
+    .chkPptr = &(checkedparam_t){.s2 = {config_check_intrange, {-1, 31}}}},                             \
+  {GNB_CONFIG_STRING_FREQUENCY_THRESH_X_LOW_Q,                                                          \
+    "SIB4 threshX-LowQ (0..31, -1=disabled)", 0, .iptr=NULL, .defintval=-1, TYPE_INT, 0,                \
+    .chkPptr = &(checkedparam_t){.s2 = {config_check_intrange, {-1, 31}}}},                             \
+  {GNB_CONFIG_STRING_FREQUENCY_Q_OFFSET_FREQ,                                                           \
+    "SIB4 q-OffsetFreq (Q-OffsetRange values, default 0)", 0, .iptr=NULL, .defintval=0, TYPE_INT, 0,    \
+    .chkPptr = &(checkedparam_t){.s1 = {config_check_intval, {-24, -22, -20, -18, -16, -14, -12, -10,   \
+    -8, -6, -5, -4, -3, -2, -1, 0, 1, 2, 3, 4, 5, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24}, 31}}},         \
+  {GNB_CONFIG_STRING_FREQUENCY_Q_RXLEVMIN,                                                              \
+    "SIB4 per-carrier Q-RxLevMin (-70..-22, default -22)", 0, .iptr=NULL, .defintval=-22, TYPE_INT, 0,  \
+    .chkPptr = &(checkedparam_t){.s2 = {config_check_intrange, {-70, -22}}}},                           \
+  {GNB_CONFIG_STRING_FREQUENCY_T_RESEL_NR,                                                              \
+    "SIB4 per-carrier t-ReselectionNR (0..7, default 0)", 0, .uptr=NULL, .defuintval=0, TYPE_UINT, 0,   \
+    .chkPptr = &(checkedparam_t){.s2 = {config_check_uintrange, {0, 7}}}},                              \
+}
+// clang-format on
+
+/* Indexes into GNBFREQUENCYCONFIGPARAMS_DESC */
+#define GNB_CONFIG_FREQUENCY_CELL_RESEL_PRIO_IDX 0
+#define GNB_CONFIG_FREQUENCY_THRESH_X_HIGH_P_IDX 1
+#define GNB_CONFIG_FREQUENCY_THRESH_X_LOW_P_IDX 2
+#define GNB_CONFIG_FREQUENCY_THRESH_X_HIGH_Q_IDX 3
+#define GNB_CONFIG_FREQUENCY_THRESH_X_LOW_Q_IDX 4
+#define GNB_CONFIG_FREQUENCY_Q_OFFSET_FREQ_IDX 5
+#define GNB_CONFIG_FREQUENCY_Q_RXLEVMIN_IDX 6
+#define GNB_CONFIG_FREQUENCY_T_RESEL_NR_IDX 7
+
 /* New Measurement Configurations*/
 
 #define GNB_CONFIG_STRING_MEASUREMENT_CONFIGURATION "nr_measurement_configuration"

openair2/RRC/NR/nr_rrc_defs.h

@@ -312,6 +312,72 @@ typedef struct {
   bool is_default_a3_configuration_exists;
 } nr_measurement_configuration_t;
 
+/** @brief Per-neighbor cell-specific offsets (TS 38.331), shared by SIB3 and SIB4
+ * Maps to ASN.1 IntraFreqNeighCellInfo and InterFreqNeighCellInfo
+ * (SIB3.IntraFreqNeighCellList, SIB4.InterFreqCarrierFreqInfo.neighCellList) */
+typedef struct {
+  // q-OffsetCell: (Q-OffsetRange values -24,-22,-20,-18,-16,-14,-12,-10,-8,-6,-5,-4,-3,-2,-1,0,1,2,3,4,5,6,8,10,12,14,16,18,20,22,24 dB)
+  // per-neighbor cell ranking
+  int q_OffsetCell;
+  // q-RxLevMinOffsetCell: Q-OffsetCellSmall (1..8): Per-neighbor RSRP minimum offset
+  int q_RxLevMinOffsetCell;
+  // q-QualMinOffsetCell: Q-OffsetCellSmall (1..8): Per-neighbor RSRQ minimum offset
+  int q_QualMinOffsetCell;
+} nr_neighbour_cell_neighbor_offset_t;
+
+/** @brief SIB3 (intra-frequency) neighbor list parameters (TS 38.331)
+ * Per-neighbor fields for SIB3.IntraFreqNeighCellList.IntraFreqNeighCellInfo.
+ * SIB3 carries intra-freq neighbor offsets for ranking. */
+typedef struct {
+  nr_neighbour_cell_neighbor_offset_t offset;
+} nr_neighbour_cell_sib3_t;
+
+/** @brief SIB4 inter-frequency carrier parameters (TS 38.331)
+ * Per-frequency fields for SIB4.InterFreqCarrierFreqList.InterFreqCarrierFreqInfo.
+ * Stored once per ARFCN; all neighbors on that frequency share this config. */
+typedef struct {
+  // cellReselectionPriority (0..7): Absolute priority of this inter-freq carrier
+  int cellReselectionPriority;
+  // threshX-HighP (0..31): RSRP threshold for reselection to a higher-priority inter-freq
+  int threshX_HighP;
+  // threshX-LowP (0..31): RSRP threshold for reselection to a lower-priority inter-freq
+  int threshX_LowP;
+  // threshX-HighQ (0..31): RSRQ threshold for higher-priority inter-freq reselection
+  int threshX_HighQ;
+  // threshX-LowQ (0..31): RSRQ threshold for lower-priority inter-freq reselection
+  int threshX_LowQ;
+  // q-OffsetFreq (Q-OffsetRange values: -24,-22,-20,-18,-16,-14,-12,-10,-8,-6,-5,-4,-3,-2,-1,0,1,2,3,4,5,6,8,10,12,14,16,18,20,22,24 dB):
+  // Frequency-specific offset in inter-freq cell ranking formula
+  int q_OffsetFreq;
+} nr_neighbour_cell_sib4_freq_t;
+
+/** @brief SIB4 (inter-frequency) parameters per neighbor (TS 38.331)
+ * Combines per-frequency carrier info (InterFreqCarrierFreqInfo) and per-neighbor
+ * offsets (InterFreqNeighCellInfo). */
+typedef struct {
+  // Per-frequency carrier (InterFreqCarrierFreqInfo)
+  nr_neighbour_cell_sib4_freq_t sib4_freq;
+  // Per-neighbor offsets (InterFreqNeighCellInfo)
+  nr_neighbour_cell_neighbor_offset_t offset;
+} nr_neighbour_cell_sib4_t;
+
+/** @brief Per-frequency SIB4 configuration (TS 38.331), keyed by ARFCN
+ * One entry per inter-freq carrier (absoluteFrequencySSB + subcarrierSpacing).
+ * freq_cfg holds InterFreqCarrierFreqInfo parameters. Analogous to one “carrier” slice of SIB4
+ * interFreqCarrierFreqList. */
+typedef struct {
+  // absoluteFrequencySSB (ARFCN)
+  int arfcn;
+  // ssbSubcarrierSpacing
+  int scs;
+  // q-RxLevMin (-70..-22 dBm)
+  int q_RxLevMin;
+  // t-ReselectionNR (0..7)
+  int t_ReselectionNR;
+  // Inter-frequency carrier parameters (InterFreqCarrierFreqInfo)
+  nr_neighbour_cell_sib4_freq_t freq_cfg;
+} nr_inter_freq_cfg_t;
+
 typedef struct {
   uint32_t gNB_ID;
   uint64_t nrcell_id;
@@ -322,6 +388,10 @@ typedef struct {
   plmn_id_t plmn;
   uint32_t tac;
   bool isIntraFrequencyNeighbour;
+  // SIB3 (intra-frequency neighbor cell-specific offsets)
+  nr_neighbour_cell_sib3_t sib3;
+  // SIB4 (inter-frequency neighbor cell-specific parameters)
+  nr_neighbour_cell_sib4_t sib4;
 } nr_neighbour_cell_t;
 
 typedef struct neighbour_cell_configuration_s {
@@ -540,6 +610,9 @@ typedef struct gNB_RRC_INST_s {
 
   nr_mac_rrc_dl_if_t mac_rrc;
   cucp_cuup_if_t cucp_cuup;
+  // Per-frequency SIB4 configurations, indexed by ARFCN
+  seq_arr_t inter_freqs; /* array of nr_inter_freq_cfg_t */
+  // Per-cell neighbour configurations, indexed by cell_id
   seq_arr_t *neighbour_cell_configuration;
   nr_measurement_configuration_t measurementConfiguration;