Add RRC.ConnMean metric

Implement RRC.ConnMean (3GPP TS 28.552 §5.1.1.4.1): mean number of UEs in
RRC-CONNECTED state over the granularity period, computed as a time-average
of periodic samples.

- ran_func_kpm.c: append RRC.ConnMean to kpm_node_meas_cu[] and
  kpm_node_meas_gnb[].
- ran_func_kpm_subs.h: add rrc_conn_count_sum and rrc_conn_count_samples to
  e2_node_level_stats_t for per-report start/end snapshots.
- ran_func_kpm_subs.c: add fill_RRC_ConnMean(); snapshots the live RRC
  counters into node_stats[1], computes the mean as Δsum/Δsamples over the
  granularity window, returns a real-valued record (noLabel); extend
  cp_node_level_stats() to copy the two new fields; add dispatch entry to
  lst_measure[].
- nr_rrc_defs.h: add rrc_conn_count_sum and rrc_conn_count_samples to
  gNB_RRC_INST.
- rrc_gNB.c: add nr_rrc_sample_conn_count(); it samples the connected-UE
  count and accumulates it into the cumulative counters, invoked from the
  existing stats timer in the RRC task loop. It is always compiled: counting
  is harmless when the E2 agent is disabled, and it leaves the timer setup
  and write_rrc_stats() untouched.

Advertised by CU and monolithic gNB node types.
Signed-off-by: Noemi Giustini <giustini.n@northeastern.edu>

openair2/E2AP/RAN_FUNCTION/O-RAN/ran_func_kpm.c

@@ -447,6 +447,7 @@ static const char* kpm_node_meas_du[] = {
 
 static const char* kpm_node_meas_cu[] = {
   "MR.NRScSSSINR",
+  "RRC.ConnMean",
   NULL,
 };
 
@@ -455,6 +456,7 @@ static const char* kpm_node_meas_gnb[] = {
   "CARR.PUSCHMCSDist",
   "L1M.SS-RSRP",
   "MR.NRScSSSINR",
+  "RRC.ConnMean",
   NULL,
 };
 

openair2/E2AP/RAN_FUNCTION/O-RAN/ran_func_kpm_subs.c

@@ -15,6 +15,8 @@ e2_node_level_stats_t cp_node_level_stats(const e2_node_level_stats_t *src)
     .mac_stats.dl.used_prb_aggregate = src->mac_stats.dl.used_prb_aggregate,
     .mac_stats.ul.total_prb_aggregate = src->mac_stats.ul.total_prb_aggregate,
     .mac_stats.ul.used_prb_aggregate = src->mac_stats.ul.used_prb_aggregate,
+    .rrc_conn_count_sum = src->rrc_conn_count_sum,
+    .rrc_conn_count_samples = src->rrc_conn_count_samples,
   };
 
   return dst;
@@ -160,6 +162,35 @@ static meas_record_lst_t fill_MR_NRScSSSINR(const label_info_lst_t label,
   return meas_record;
 }
 
+/* RRC.ConnMean — 3GPP TS 28.552 - section 5.1.1.4.1 */
+static meas_record_lst_t fill_RRC_ConnMean(__attribute__((unused)) const label_info_lst_t label,
+                                           __attribute__((unused)) uint32_t gran_period_ms,
+                                           __attribute__((unused)) cudu_ue_info_pair_t ue_info,
+                                           __attribute__((unused)) const size_t ue_idx,
+                                           e2_node_level_stats_t* node_stats)
+{
+  meas_record_lst_t meas_record = {.value = INTEGER_MEAS_VALUE};
+
+  node_stats[1].rrc_conn_count_sum     = RC.nrrrc[0]->rrc_conn_count_sum;
+  node_stats[1].rrc_conn_count_samples = RC.nrrrc[0]->rrc_conn_count_samples;
+
+  const uint64_t d_sum     = node_stats[1].rrc_conn_count_sum     - node_stats[0].rrc_conn_count_sum;
+  const uint64_t d_samples = node_stats[1].rrc_conn_count_samples - node_stats[0].rrc_conn_count_samples;
+
+  if (d_samples > 0) {
+    meas_record.int_val = (long)((d_sum + d_samples / 2) / d_samples);
+    node_stats[0].rrc_conn_count_sum     = node_stats[1].rrc_conn_count_sum;
+    node_stats[0].rrc_conn_count_samples = node_stats[1].rrc_conn_count_samples;
+  } else if (node_stats[1].rrc_conn_count_samples > 0) {
+    meas_record.int_val = (long)((node_stats[1].rrc_conn_count_sum + node_stats[1].rrc_conn_count_samples / 2)
+                                 / node_stats[1].rrc_conn_count_samples);
+  } else {
+    meas_record.int_val = 0;
+  }
+
+  return meas_record;
+}
+
 #if defined (NGRAN_GNB_DU)
 static uldlcounter_t last_rlc_pdu_total_bytes[MAX_MOBILES_PER_GNB] = {0};
 static uldlcounter_t last_total_prbs[MAX_MOBILES_PER_GNB] = {0};
@@ -359,6 +390,7 @@ static kv_measure_t lst_measure[] = {
   {.key = "DRB.PdcpSduVolumeUL", .value = fill_DRB_PdcpSduVolumeUL },
   {.key = "L1M.SS-RSRP",         .value = fill_L1M_SS_RSRP },
   {.key = "MR.NRScSSSINR",       .value = fill_MR_NRScSSSINR },
+  {.key = "RRC.ConnMean",        .value = fill_RRC_ConnMean },
 #if defined (NGRAN_GNB_DU)
   {.key = "DRB.RlcSduDelayDl", .value =  fill_DRB_RlcSduDelayDl }, 
   {.key = "DRB.UEThpDl", .value =  fill_DRB_UEThpDl }, 

openair2/E2AP/RAN_FUNCTION/O-RAN/ran_func_kpm_subs.h

@@ -19,6 +19,9 @@ typedef struct {
 
 typedef struct {
   dlul_mac_stats_t mac_stats;
+
+  uint64_t rrc_conn_count_sum;
+  uint64_t rrc_conn_count_samples;
 } e2_node_level_stats_t;
 
 e2_node_level_stats_t cp_node_level_stats(const e2_node_level_stats_t *src);

openair2/E2AP/README.md

@@ -105,6 +105,7 @@ From 3GPP TS 28.552, we support the following list:
   * `CARR.PUSCHMCSDist`
   * `L1M.SS-RSRP`
   * `MR.NRScSSSINR`
+  * `RRC.ConnMean`
 
 From `O-RAN.WG3.E2SM-KPM-version` specification, we implemented:
   * REPORT Service Style 4 ("Common condition-based, UE-level" - section 7.4.5) - fetch above measurements per each UE based on the common S-NSSAI `(1, 0xffffff)` condition

openair2/RRC/NR/nr_rrc_defs.h

@@ -652,6 +652,9 @@ typedef struct gNB_RRC_INST_s {
   /// cell-wide NR serving-cell SS-SINR distribution, see 28.552 5.1.1.32
   /// 0-127 SS-SINR report level (TS 38.133)
   uint32_t ss_sinr_cell_dist[NR_KPM_SS_SINR_NB_LEVELS];
+
+  uint64_t rrc_conn_count_sum;
+  uint64_t rrc_conn_count_samples;
 } gNB_RRC_INST;
 
 /** Forward declaration for UE log macros */

openair2/RRC/NR/rrc_gNB.c

@@ -3514,6 +3514,18 @@ static bool write_rrc_stats(const gNB_RRC_INST *rrc)
   return true;
 }
 
+static void nr_rrc_sample_conn_count(gNB_RRC_INST *rrc)
+{
+  if (rrc == NULL)
+    return;
+  uint32_t count = 0;
+  rrc_gNB_ue_context_t *ue_context_p = NULL;
+  RB_FOREACH(ue_context_p, rrc_nr_ue_tree_s, &rrc->rrc_ue_head)
+    count++;
+  rrc->rrc_conn_count_sum += count;
+  rrc->rrc_conn_count_samples += 1;
+}
+
 void *rrc_gnb_task(void *args_p)
 {
   UNUSED(args_p);
@@ -3553,6 +3565,7 @@ void *rrc_gnb_task(void *args_p)
 
       case TIMER_HAS_EXPIRED:
         if (TIMER_HAS_EXPIRED(msg_p).timer_id == stats_timer_id) {
+          nr_rrc_sample_conn_count(RC.nrrrc[0]);
           if (!write_rrc_stats(RC.nrrrc[0]))
             timer_remove(stats_timer_id);
         } else {