RRC Re-establishment

Technical Explanation

If a UE experiences Radio Link Failure (RLF) or handover failure (T304 expiry), it starts timer T311 and executes cell selection. Upon selecting a suitable cell, it transmits RRCReestablishmentRequest on CCCH. If the target gNodeB can retrieve the UE context, it responds with RRCReestablishment, preserving ongoing PDU sessions.

Key Functions

• Recovers dropped connections following radio link or handover failures
• Searches for healthy cell within window bounded by timer T311
• Restores security context and radio bearers without dropping calls