RAR Reception QCL Selection Across Serving and Non-Serving Cells
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Solution Overview
Problem
In mobile communication systems, when a random access procedure is initiated by a PDCCH order related to a different cell from the serving cell, the existing quasi co-location (QCL) properties for PDCCH/PDSCH reception are not suitable for receiving the RAR from the serving cell, leading to potential RAR reception failure and increased latency.
Innovation Solution
The method involves receiving PDCCH and PDSCH based on quasi co-location (QCL) properties derived from a CORESET related to a Type 1-PDCCH Common Search Space set, with DMRS ports quasi-co-located for PDCCH and PDSCH, even if the physical cell IDs are different, allowing for improved RAR reception by configuring synchronization signals and RACH based on additional PCI.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing QCL properties related to PDCCH order are applied for RAR reception from serving cell, then QCL properties match the PDCCH order cell, but RAR reception fails when RAR is received from serving cell instead of second cell
Solution Approach 1:
The patent applies different QCL properties based on the local context of RAR reception. When RAR is received from the serving cell, QCL properties related to the serving cell are used; when RAR is received from the second cell, QCL properties related to the second cell are used. This local adaptation resolves the contradiction between reliability (matching QCL to the actual receiving cell) and adaptability (handling both serving cell and second cell scenarios).
Solution Approach 2:
The patent introduces dynamic selection of QCL properties based on the actual RAR reception source. The UE determines whether to apply QCL properties from the PDCCH order or from the serving cell based on whether RAR is received from the second cell or serving cell. This dynamic adaptation ensures reliable RAR reception while maintaining versatility across different cell scenarios.
2Adaptability or versatility
If PDCCH order triggers random access for second cell, then random access can be initiated for candidate cell, but ambiguity arises about which cell's QCL properties to use for RAR reception
Solution Approach 1:
Instead of determining QCL properties before knowing the RAR reception source (which causes ambiguity), the patent inverts the logic: first receive the RAR, then determine which QCL properties to apply based on the actual reception source. This inversion eliminates the detection difficulty by making QCL property selection dependent on observed rather than predicted information.
Solution Approach 2:
The patent introduces an intermediary determination step that mediates between the PDCCH order (which may reference the second cell) and the actual RAR reception (which may come from the serving cell). This intermediary logic resolves the ambiguity by selecting QCL properties based on the actual RAR source rather than the PDCCH order reference.
3Device complexity
If QCL properties are strictly tied to PDCCH order cell, then QCL configuration is simple, but RAR reception from serving cell fails due to mismatched QCL properties
Solution Approach 1:
The patent segments the QCL configuration into two distinct sets: one related to the PDCCH order (second cell) and another related to the serving cell. This segmentation allows the system to maintain simple configuration for each segment while enabling reliable RAR reception by selecting the appropriate segment based on the reception source. The segmentation resolves the contradiction by organizing complexity into manageable, context-specific segments.
Data Source
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AI summary
A method according to an embodiment of the present disclosure comprises receiving a PDCCH order, transmitting a PRACH, receiving a PDCCH related to a RAR, and receiving a PDSCHd to the RAR. Based on a CORESET related to the PDCCH order being related to a second physical cell ID different from a first physical cell ID: the PDCCH and the PDSCH are received based on QCL properties. The QCL properties are based on a CORESET related to a Type 1-PDCCH CSS set.