QoS Handling: implement intelligent QoS-to-DRB mapping based on 3GPP TS 23.501

Implement QoS flow multiplexing logic that optimizes DRB usage by classifying
5QI values per 3GPP TS 23.501 Table 5.7.4-1 and applying resource-type-aware
multiplexing limits. The changes are adopted in nr_rrc_add_bearers, which
is the RRC function responsible for adding PDU Sessions and DRBs in RRC.

Key features:
- Classify 5QI by resource type (DC-GBR, GBR, Non-GBR)
- Reuse existing DRBs when QoS characteristics are compatible
- Dedicated DRBs for DC-GBR (5QI 82-90) and high-priority services
- Per-type multiplexing limits: DC-GBR=1, GBR=2, Non-GBR=5
- Aggregate cap: max 5 flows per DRB

Implementation:
- nr_rrc_get_5qi_resource_type():
  Maps 5QI values to resource types using lookup table.
  DC-GBR: 5QI 82-90, GBR: 5QI 1-4,65-67,71-76, Non-GBR: 5QI 5-11,69-70,79-80.
  Unknown 5QIs default to Non-GBR with warning.

- nr_rrc_qos_dedicated_drb():
  Identifies 5QIs requiring isolated DRBs (high priority, low-PER).
  Includes: DC-GBR: 5QI 82-90, 5QI 4,6-10 (video), 5QI 70 (mission-critical),
  5QI 71-73 (live streaming), 5QI 80 (low-latency).

- nr_rrc_count_qos_flows_by_type():
  Counts QoS flows mapped to a specific DRB, grouped by resource type.
  Used to check capacity and enforce multiplexing limits.

- nr_rrc_find_suitable_drb_for_qos():
  Searches existing DRBs in the same PDU session for available capacity.
  Checks resource type compatibility, per-type limits, and aggregate cap.
  Returns DRB ID if suitable, -1 if new DRB needed.
  DC-GBR flows always return -1 (require dedicated DRB).

- nr_rrc_assign_drb_to_qos_flow(), which either reuses a DRB
  selected by nr_rrc_find_suitable_drb_for_qos() or creates a new DRB via
  nr_rrc_add_drb, assigns its ID to the QoS flow

Note: this commit is multi-QoS ready.
Signed-off-by: Guido Casati <guido.casati@openairinterface.org>

common/5g_platform_types.h

@@ -36,6 +36,14 @@ typedef enum {
 
 typedef enum { NON_DYNAMIC, DYNAMIC } fiveQI_t;
 
+/* 5QI (5G QoS Identifier) - 3GPP TS 23.501 §5.7.2.1
+ * Range: 0..255
+ * - Standardized 5QI values: have one-to-one mapping to standardized 5G QoS characteristics (Table 5.7.4-1)
+ * - Pre-configured 5QI values: pre-configured in the AN
+ * - Dynamically assigned 5QI values: require signaling of QoS characteristics as part of QoS profile */
+#define MIN_FIVEQI 0
+#define MAX_FIVEQI 255
+
 /* ARP Priority Level - 3GPP TS 23.501 §5.7.2.2
  * The ARP priority level defines the relative importance of a QoS Flow.
  * Range: 1 to 15, with 1 as the highest priority.

openair2/RRC/NR/rrc_gNB_radio_bearers.h

@@ -57,4 +57,10 @@ bool nr_rrc_remove_drb_by_id(seq_arr_t *drb_ptr, const int drb_id);
 /// @brief Add PDU Sessions and DRBs to UE context list
 void nr_rrc_add_bearers(gNB_RRC_INST *rrc, gNB_RRC_UE_t *UE, int n, pdusession_t *sessions);
 
+/// @brief Find existing DRB that can accept a QoS flow based on resource type and multiplexing limits
+int nr_rrc_find_suitable_drb_for_qos(gNB_RRC_UE_t *UE,
+                                     const int pdusession_id,
+                                     const pdusession_level_qos_parameter_t *qos_params,
+                                     const seq_arr_t *flows);
+
 #endif