Conditional Handover Command Buffering for Wireless Reliability
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Solution Overview
Problem
Current handover procedures in LTE and NR wireless communication systems often fail to ensure robustness, particularly when radio conditions are poor, leading to delayed or failed handover commands due to segmentation or retransmissions, which can result in service interruptions.
Innovation Solution
Implementing conditional handover, where the handover command is associated with specific radio conditions, such as a target cell being X dB stronger than the serving cell, allowing the network to prepare for handover when the radio link is stable and execute it optimally, reducing dependence on unstable radio links.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If handover command is sent during poor radio conditions, then handover execution is delayed or failed, but service interruption increases
Solution Approach 1:
The network prepares the handover command in advance when radio conditions are still good, storing it in the UE's buffer. The actual handover execution is triggered later by a simple condition check (A3 event) rather than waiting for poor conditions, thus ensuring reliable execution without service interruption delays
Solution Approach 2:
The patent prevents the problem of handover failure under poor radio conditions by taking preliminary action - preparing and buffering the handover command before radio degradation occurs. This anticipatory approach counteracts the potential failure mode before it can manifest
2Reliability
If handover command is segmented or retransmitted under poor radio conditions, then handover reliability decreases, but transmission time increases
Solution Approach 1:
The complete handover command is prepared and buffered in advance under good radio conditions, eliminating the need for segmentation or retransmission later. The UE receives the full command when channel quality is high, then executes it immediately when triggered, avoiding time-consuming retransmissions
Solution Approach 2:
The network creates a copy of the handover command and stores it in the UE's buffer. This copied command can be retrieved and executed immediately when the trigger condition is met, without needing to retransmit or re-segment the original message
3Reliability
If conditional handover is implemented with multiple candidate cells, then handover robustness improves, but device complexity increases
Solution Approach 1:
Multiple candidate handover commands are prepared in advance for different target cells, with each command buffered and associated with specific trigger conditions. The UE simply monitors which condition is met and executes the corresponding pre-prepared command, avoiding complex real-time decision-making
Solution Approach 2:
The patent implements dynamic conditional handover where the UE monitors multiple candidate cells and their associated trigger conditions simultaneously. When any condition is satisfied, the corresponding handover is executed dynamically, providing robustness against radio condition variations without requiring complex algorithms
Data Source
AI summary
Methods and apparatuses are disclosed for conditional handover in handover command. In one embodiment, a wireless device (WD) is configured to receive a request to perform a mobility procedure for a wireless device from a source cell supported by a source network node to a target cell supported by the network node, the request including a current configuration for the wireless device in the source cell; upon receiving the request, determine to prepare a conditional reconfiguration for the wireless device; and transmit the conditional reconfiguration and a radio resource control, RRC, reconfiguration for the wireless device, the RRC reconfiguration being associated with the requested mobility procedure from the source cell to the target cell supported by the network node and the conditional reconfiguration being associated with a target candidate cell determined by the network node.