Sign in Subscribe

NR-RRC Connection Reestablishment Request

Last updated on 


In 5G New Radio (NR), the NR-RRC (Radio Resource Control) Connection Reestablishment Request is a signaling message used to initiate the reestablishment of an RRC connection between the User Equipment (UE) and the base station (gNodeB) after the connection has been temporarily lost or disrupted. This procedure allows the UE to quickly reestablish communication with the network without going through the initial connection setup. Here's a technical explanation of the NR-RRC Connection Reestablishment Request:

1. Purpose of RRC Connection Reestablishment:

  • The primary purpose of RRC Connection Reestablishment is to quickly restore the RRC connection when it has been interrupted due to factors like cell changes (e.g., handover) or radio link failures.
  • Reestablishing the connection minimizes service disruption and maintains the UE's network presence.

2. Triggering Conditions:

  • Several events or conditions can trigger the need for RRC Connection Reestablishment, including:
  • Handover: When the UE moves from one cell to another, it may need to reestablish the connection with the new gNodeB.
  • Radio Link Failure: If there is a significant degradation in the radio link quality, leading to connection failure, reestablishment may be necessary.
  • Interference or Coverage Loss: In scenarios where the UE experiences interference or temporary loss of coverage, it may initiate reestablishment.

3. RRC Reconfiguration:

  • The RRC Connection Reestablishment Request typically includes information about the configuration of the RRC connection that is being reestablished.
  • This includes parameters related to the previous RRC connection, such as security context and mobility-related information.

4. Random Access and Preemption:

  • In some cases, the UE may need to perform a random access procedure as part of the reestablishment process to request resources for signaling.
  • The network may preempt resources for the UE during this process to ensure timely reestablishment.

5. Core Network Re-Establishment:

  • In addition to the RRC connection, the reestablishment process may involve reestablishing the connection with the core network components, such as the Mobility Management Entity (MME) in the 5G core network.
  • This ensures that the UE can continue to access services and network functions seamlessly.

6. Mobility and Handover Considerations:

  • RRC Connection Reestablishment is a critical part of mobility management, especially during handover procedures when the UE moves between cells.
  • It allows the UE to quickly attach to the new cell and continue communication.

7. Security Considerations:

  • Security mechanisms play a crucial role in RRC Connection Reestablishment to ensure the confidentiality and integrity of communication.
  • The security context established during the initial connection may need to be reestablished as well.

8. Resource Allocation and Priority:

  • The network may allocate resources and prioritize the reestablishment request to expedite the process, especially if the UE is involved in critical communication, such as emergency calls.

9. Feedback and Response:

  • Upon receiving the RRC Connection Reestablishment Request, the gNodeB and the core network components validate the request and respond accordingly.
  • If the reestablishment is successful, the UE is granted access to the network.

In summary, the NR-RRC Connection Reestablishment Request is a key procedure in 5G NR that allows the UE to quickly restore its RRC connection with the network after a temporary interruption. It is initiated in response to specific triggering conditions, such as handovers or radio link failures. The reestablishment process includes reconfiguring the RRC connection, possibly performing a random access procedure, and ensuring security and resource allocation. This procedure ensures minimal service disruption and maintains the UE's connectivity to the network.