Beam Selection for Conditional Handover Random Access
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Solution Overview
Problem
Existing wireless communication systems face inefficiencies in beam selection for random access during conditional handover (CHO) execution, particularly in allocating CFRA resources without knowing the immediate join time of the user equipment (UE).
Innovation Solution
The system configures user equipment (UE) with conditional handover (CHO) configurations that include random access channel (RACH) configuration information, such as beam quality thresholds, threshold offsets, and associated contention free random access (CFRA) resources, allowing the UE to autonomously select a target cell beam for random access based on these criteria.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the target base station allocates CFRA resources for a subset of beams during preparation phase, then the random access resource allocation is optimized, but the system fails when the UE joins at a different time with different optimal beams
Solution Approach 1:
The target base station pre-allocates CFRA resources for multiple potential beams during the preparation phase, not just a single subset. This preliminary action ensures that when the UE performs handover at any subsequent time, suitable CFRA resources are already available for the currently optimal beam, resolving the contradiction between early optimization and later reliability.
Solution Approach 2:
The system dynamically adapts the CFRA resource allocation based on the UE's actual handover timing and beam conditions. The target base station can update or re-allocate CFRA resources for different beams as the UE approaches and executes handover, making the system flexible rather than static, thus maintaining both efficiency and reliability.
2Speed
If the UE uses latest unfiltered L1-RSRP measurement for beam selection, then the beam selection responds quickly to current conditions, but measurement inaccuracies may lead to suboptimal beam selection
Solution Approach 1:
The UE evaluates multiple beams beyond just the single latest measurement, considering a set of candidate beams with their respective CFRA resources. By having more beam options available through pre-configured CFRA resources, the system can tolerate some measurement variability while still achieving reliable handover, balancing speed and precision.
3Adaptability or versatility
If CFRA resources are allocated for multiple beams, then the system adapts better to different handover timings, but the resource allocation complexity increases
Solution Approach 1:
The CFRA resources are segmented and specifically associated with individual beams or beam groups. Each beam has its designated CFRA resources configured in advance, which simplifies the UE's selection process during handover. The UE can directly map its selected beam to pre-configured resources without complex real-time allocation decisions, reducing operational complexity while maintaining adaptability.
Data Source
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AI summary
Conditional handover (CHO) configurations may include random access channel (RACH) configuration information (e.g., beam quality thresholds, beam quality threshold offsets, one or more beams associated with configured contention free random access (CFRA) resources, one or more beams associated with configured contention based random access (CBRA) resources, or some combination thereof). A user equipment (UE) may, upon detection that a handover condition in a CHO configuration has been satisfied, select a target cell beam for transmission of a random access request based on the RACH configuration information included in the CHO configuration. In various examples, the selected beam may correspond to a highest quality beam with a highest quality beam measurement value above the beam quality threshold, a beam with an earliest configured CFRA resource or an earliest configured CBRA resource (e.g., if a corresponding beam measurement at least falls within the beam quality threshold offset), etc.