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NR-RRC Connection Reconfiguration Reject

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In 5G New Radio (NR), an NR-RRC Connection Reconfiguration Reject is a message sent by the network (gNB or gNodeB) to a user equipment (UE) when it rejects a request for reconfiguration of the RRC (Radio Resource Control) connection. The RRC connection reconfiguration is a procedure that involves modifying various radio resources and parameters for the UE. The NR-RRC Connection Reconfiguration Reject message indicates that the requested changes cannot be applied, and it may include specific reasons for the rejection. Here's a technical explanation of the NR-RRC Connection Reconfiguration Reject message:

RRC Connection Reconfiguration:

  • The RRC connection reconfiguration procedure is initiated by the network when it needs to modify the configuration of the UE's RRC connection.
  • This procedure can involve changes in communication parameters, mobility management, security, and other aspects of the connection.

UE Request and RRC Reconfiguration Message:

  • The UE may request an RRC connection reconfiguration in various scenarios, such as handovers between cells, changes in network configurations, or updates to security-related parameters.
  • In response to the UE's request or network-initiated changes, the gNB generates an NR-RRC Connection Reconfiguration message. This message contains specific information about the requested or required changes.

Rejection Scenarios:

  • The NR-RRC Connection Reconfiguration Reject message is sent by the gNB to the UE when the network cannot apply the requested changes or when there is a specific issue preventing the reconfiguration.

Common rejection scenarios include:

  • Insufficient resources: The gNB may not have the necessary resources (e.g., spectrum, time slots, or power) to accommodate the requested changes.
  • Invalid configuration: The requested changes may violate network policies, configuration rules, or operational constraints.
  • Authentication or security issues: If the UE's identity or security credentials are not valid, the network may reject the reconfiguration request.

Message Content:

The NR-RRC Connection Reconfiguration Reject message typically includes the following information:

  • A rejection cause code or cause value: This code indicates the specific reason for the rejection. Common cause codes are defined in the 3GPP specifications.
  • Optionally, additional information or parameters related to the rejection cause.

UE Response:

  • Upon receiving the NR-RRC Connection Reconfiguration Reject message, the UE processes the message and takes appropriate actions based on the rejection cause.
  • The UE may attempt to address the issue and initiate a new reconfiguration request if necessary.

Error Handling:

  • Error handling and recovery mechanisms may be triggered at both the UE and network sides to resolve issues leading to the rejection.
  • The network may provide guidance or recommendations to the UE on how to proceed.

Log and Monitoring:

  • The rejection and the associated cause code are often logged for network management and troubleshooting purposes.
  • Network operators and administrators can use this information to diagnose and resolve issues in the network.

In summary, the NR-RRC Connection Reconfiguration Reject message is used in 5G NR networks to indicate the rejection of a request to modify the RRC connection configuration. The rejection can occur for various reasons, including resource constraints, invalid configurations, or security concerns. The message provides specific cause information to help diagnose and address the issue, allowing for efficient network management and communication.