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NR-IRAT Handover From UTRAN Request

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In 5G New Radio (NR), an NR-IRAT (Inter-RAT) Handover From UTRAN (Universal Terrestrial Radio Access Network) Request is a signaling message exchanged during the handover procedure when a User Equipment (UE) is transitioning from a UTRAN network (3G) to a 5G NR network. This procedure allows the UE to smoothly switch from 3G to 5G while maintaining connectivity and service continuity. Here's a technical explanation of the NR-IRAT Handover From UTRAN Request:

1. Purpose of NR-IRAT Handover From UTRAN Request:

  • The primary purpose of this signaling message is to initiate the handover of the UE from a UTRAN (UMTS Terrestrial Radio Access Network) to a 5G NR network.
  • It allows the UE to continue its communication and data services in the 5G NR network seamlessly.

2. Handover Scenario:

  • The handover scenario occurs when a UE, initially connected to a UTRAN, needs to transition to a 5G NR network. This transition can be due to factors such as improved service quality, coverage, or the availability of 5G NR network services.

3. UE's Handover Request:

  • Before the NR-IRAT Handover From UTRAN Request is generated, the UE first detects the presence of the 5G NR network and determines that it should perform an inter-RAT handover.
  • The UE initiates the handover process by sending a handover request message, including the target 5G NR cell information, to the UTRAN network.

4. UTRAN's Response:

  • The UTRAN network, upon receiving the UE's handover request, processes the request and determines if it is valid.
  • If the handover is permitted and the UE's request is accepted, the UTRAN generates the NR-IRAT Handover From UTRAN Request message.

5. Contents of NR-IRAT Handover From UTRAN Request:

  • The NR-IRAT Handover From UTRAN Request message contains essential information, including:
  • Acknowledgment of the handover request.
  • Target 5G NR cell information, including cell identity and radio parameters.
  • Timing and synchronization information to facilitate the handover.
  • Security-related information, ensuring the integrity and authentication of the handover procedure.

6. UE Confirmation and Execution:

  • Upon receiving the NR-IRAT Handover From UTRAN Request, the UE acknowledges the message.
  • The UE then proceeds with the handover process, configuring its radio resources and synchronizing with the target 5G NR cell.

7. Handover Completion:

  • Once the UE successfully transitions to the 5G NR network and establishes a connection with the target NR gNodeB (gNB), the handover procedure is considered complete.
  • The UE can continue its communication with the network via the 5G NR cell.

8. Quality of Service (QoS) Considerations:

  • The NR-IRAT handover process may involve parameters related to Quality of Service (QoS) to ensure that the UE's service continuity is maintained at an appropriate level.

In summary, the NR-IRAT Handover From UTRAN Request is a key message exchanged during the inter-RAT handover procedure in 5G NR. It allows the UE to transition smoothly from a UTRAN (3G) network to a 5G NR network while maintaining connectivity and service continuity. The handover procedure is crucial for enabling a seamless user experience as UEs move between different radio access technologies.