Uplink Timing Advance Selection for Multi-TRP PUSCH
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Solution Overview
Problem
In mobile communication systems where a unified TCI framework is not utilized, the ambiguity in determining the Timing Advance Group (TAG) for uplink transmission between multiple Transmission Reception Points (TRPs) leads to unclear uplink timing configurations, particularly in non-ideal backhaul environments with significant propagation delays.
Innovation Solution
A method for determining uplink timing based on Sounding Reference Signal (SRS) resources, Physical Uplink Control Channel (PUCCH) resources, or SRS resource indicator fields in DCI format 0_0, allowing for the identification of TAGs for uplink transmission, even in environments without a unified TCI state configuration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If two TAGs are configured within one serving cell to support TRP-specific timing advance, then the reliability of multi-TRP communication is improved, but the device complexity and difficulty of determining which TAG to use for uplink transmission increases
Solution Approach 1:
The patent introduces an intermediary mechanism (spatial relation info, SRS resource indicators, or PUCCH resource associations) that mediates between the UE and the multiple TAGs. Instead of directly managing two TAGs, the system uses these intermediary elements to indicate which TAG should be applied for each uplink transmission, thereby reducing the complexity of TAG determination while maintaining reliability
Solution Approach 2:
The patent changes the parameter representation from direct TAG ID management to using indirect indicators such as spatial relation info indices, SRS resource indicators, or PUCCH resource associations. This parameter transformation allows the UE to determine the appropriate TAG through lookup tables or pre-configured associations, significantly simplifying the determination process while supporting multiple TAGs for different TRPs
2Adaptability or versatility
If a unified TCI framework is not utilized and two TAGs are managed in Rel-15/16, then backward compatibility is maintained, but the ambiguity in determining which TAG to use for uplink transmission occurs
Solution Approach 1:
The patent applies preliminary action by pre-configuring associations between spatial relation info, SRS resources, PUCCH resources, and TAG IDs before uplink transmission occurs. These associations are established through RRC signaling or MAC CE commands in advance, so when the UE needs to transmit uplink data, the appropriate TAG is already determined through the pre-established relationships, eliminating ambiguity while maintaining backward compatibility with Rel-15/16
3Measurement precision
If multiple TAGs are configured to compensate for timing differences between TRPs, then the propagation delay compensation is improved, but the implementation complexity for supporting uplink transmission with two TAGs increases
Solution Approach 1:
The patent segments the TAG determination process into distinct, manageable components: (1) configuration of spatial relation info and SRS resources with associated TAG IDs, (2) indication through DCI or pre-configuration, and (3) lookup/determination based on SRS resource indicators or PUCCH resource associations. This segmentation allows each component to be implemented and tested independently, reducing overall implementation complexity while maintaining precise timing advance compensation for multiple TRPs
Data Source
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AI summary
A method performed by a user equipment (UE) according to an embodiment of the present disclosure includes receiving configuration information related to a serving cell, receiving downlink control information (DCI) for scheduling of a physical uplink shared channel (PUSCH), and transmitting the PUSCH based on an uplink timing which is related to one of a first timing advance group (TAG) and a second TAG. A TAG related to the uplink timing is determined based on a sounding reference signal (SRS) resource.