Sign in Subscribe

5G NR RRC Procedure and Its states

Last updated on 


The 5G New Radio (NR) Radio Resource Control (RRC) procedure plays a crucial role in the establishment, maintenance, and release of radio resources in a 5G network. The RRC procedure defines the states and transitions between these states to manage the connection between the User Equipment (UE) and the 5G network. Here, I'll provide a technical explanation of the 5G NR RRC procedure and its states:

5G NR RRC States:

  1. Idle State (RRC_IDLE):
    • Description: In the Idle state, the UE is not connected to the network and is periodically searching for available cells to camp on.
    • Activities: The UE monitors system information broadcasts, performs cell selection, and acquires system information to determine the available cells and their capabilities.
  2. Connected Mode (RRC_CONNECTED):
    • Description: The UE transitions to the Connected state upon initiating a connection request or responding to a paging message.
    • Activities:
      • Cell Selection: The UE selects a suitable cell based on system information.
      • Random Access: The UE performs a random access procedure to establish a connection with the network.
      • RRC Connection Establishment: Establishes an RRC connection with the network.
      • Security Setup: Establishes security procedures for the connection.

5G NR RRC Procedures:

  1. RRC Connection Establishment:
    • Initiation: The UE initiates a connection request by sending a RRC Connection Request message to the network.
    • Acceptance: The network responds with an RRC Connection Setup message.
    • Completion: The UE acknowledges the setup by transmitting an RRC Connection Setup Complete message.
  2. RRC Connection Reconfiguration:
    • Initiation: The network sends an RRC Connection Reconfiguration message to the UE to modify an existing connection.
    • Acceptance: The UE acknowledges the reconfiguration, and both parties update their configuration accordingly.
  3. RRC Connection Release:
    • Initiation: Either the UE or the network initiates the release of the connection.
    • Acceptance: The other party acknowledges the release, and the connection is terminated.
  4. Handover (RRC Intra-NR Handover and RRC Inter-RAT Handover):
    • Initiation: Triggered by network conditions or UE mobility.
    • Execution: The handover command is sent to the UE, and the UE performs necessary configuration changes.
    • Completion: The UE reports the handover completion, and the new connection is established.
  5. Cell Reselection:
    • Initiation: The UE monitors neighboring cells and decides to reselect a more suitable cell.
    • Execution: The UE sends a reselection request to the network.
    • Completion: The network responds with a reselection completion, and the UE moves to the new cell.
  6. UE Inactive:
    • Initiation: The UE may become temporarily inactive due to user inactivity or power-saving measures.
    • Wake-up: The UE becomes active again when needed, sending a request to the network to resume normal operation.

Conclusion:

The 5G NR RRC procedure and its associated states and transitions are essential for managing the connection between the UE and the 5G network efficiently. These procedures ensure that the UE is appropriately connected, configured, and handed over between cells as needed, providing a seamless and optimized user experience in a 5G network.