Function descriptions (TS 38.331 4.4):
• SI Broadcast: System information (MIB/SIB) transmitted periodically.
• RRC Connection Control: Establishment, maintenance, release.
• Mobility: Handover, cell reselection.
• Measurement Config/Report: Configure and report RRM measurements.
• Security Activation: Integrity and ciphering for SRB/DRB.
• QoS Management: Bearer establishment with QoS parameters.
• UE Capability Handling: Exchange of UE radio capabilities.
• Lower Layer Configuration: PHY/MAC/RLC/PDCP parameters.
• State Management: RRC_IDLE, INACTIVE, CONNECTED transitions.
• Paging: UE notification in IDLE/INACTIVE.
• Beam Management & BWP: Beam sweeping, BWP switching.
• Dual Connectivity / CA: Multi‑connectivity operation.
• NAS Message Transport: Transfer of NAS messages.
• RLF Handling: Detection and recovery from radio link failure.