Conditional Handover SN Release Delay in MR-DC
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Solution Overview
Problem
Current conditional reconfiguration approaches in multi-connectivity scenarios, particularly in New Radio (NR) systems, face challenges due to fast fading at higher frequencies and fail to adequately manage the multiplicity of radio network nodes or cells, leading to race conditions and unintended Secondary Node (SN) Releases in Multi-Radio Dual Connectivity (MR-DC) operations.
Innovation Solution
The proposed solution involves methods for network nodes to manage conditional handovers by delaying SN release messages, setting longer supervision timers, and reserving resources to prevent unintended SN Releases, allowing for optimized resource allocation and ensuring that SN changes or keep operations are executed only when conditions are met, thereby improving robustness and reducing race conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the network transmits a conditional reconfiguration to a wireless device and specifies a condition that is to trigger the wireless device to execute that conditional reconfiguration, then the reconfiguration proves robust to link deterioration, but the wireless device may take longer to access a candidate target MN, or may not even attempt to access it
Solution Approach 1:
The network transmits the conditional reconfiguration message in advance, preparing the wireless device with pre-configured parameters and conditions before handover is actually needed. This preliminary configuration allows the device to quickly execute the handover when conditions are met, without requiring real-time negotiation, thus resolving the contradiction between robustness and access time.
2Adaptability or versatility
If the target MN receiving a handover request decides to release MR-DC or continue the MR-DC operation, then the network can adapt to different scenarios, but this leads to race conditions and unintended SN Releases from the candidate target SN
Solution Approach 1:
The patent introduces dynamic state management for the conditional reconfiguration, where the target MN can transition between different states (pending, executed, cancelled) based on whether the handover conditions are met. This dynamic approach allows the system to adapt to different scenarios while maintaining reliability by preventing race conditions through proper state tracking and timing mechanisms.
Solution Approach 2:
The network implements feedback mechanisms where the target MN informs the source MN about the handover execution status. This feedback loop allows the source MN to understand whether the conditional reconfiguration was executed or not, preventing unintended SN releases and resolving the race condition problem while maintaining adaptability.
3Ease of operation
If legacy procedures define that the source MN releases the SN when the target MN transmits the Handover Request Acknowledge message, then the procedure is simplified, but in the CHO case, that is not the desired behavior as the equivalent changes at the UE are only performed when the conditions are fulfilled
Solution Approach 1:
The source MN delays the SN release action until it receives confirmation that the conditional handover has been executed by the UE. This preliminary delay ensures that the SN is not released prematurely before the UE actually needs it, while still maintaining procedural simplicity through a clear trigger-based mechanism.
Solution Approach 2:
The system uses feedback from the target MN to the source MN about handover execution status to trigger the SN release at the correct time. This feedback mechanism maintains ease of operation by providing a clear trigger event while ensuring reliability by releasing the SN only when the UE has actually executed the conditional reconfiguration.
Data Source
AI summary
Techniques for conditional reconfiguration in a multi-connectivity scenario. In an example method, a first network node, configured to operate as a master node, MN, for multi-connectivity operation of a wireless device along with a second network node operating as a secondary node, SN, for the wireless device, determines (810) to configure the wireless device with a conditional reconfiguration and transmits (820) a handover request message to a third network node, the handover request message including an indication that the handover request message is for conditional handover. The first network node receives (830) an acknowledgment of the handover request message and, in response, delays (840) transmission of a release message to the second network node until the first network node receives an indication that the conditional handover is executed.