Default Beam Selection via TCI States Under Short Scheduling Offsets
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Solution Overview
Problem
Existing wireless communication systems face challenges in determining default beams for downlink signal reception, particularly in scenarios where the scheduling offset is less than a threshold, leading to uncertainties in TCI state determination for PDSCH and aperiodic CSI-RS resources in multi-TRP NCJT transmission.
Innovation Solution
A method and apparatus for determining default TCI states by utilizing the TCI states associated with the PDCCH or the lowest codepoint pointing to two TCI states, based on the configuration of tci-PresentInDCI and tci-PresentInDCI-ForFormat1_2 for CORESETs, to ensure accurate beam determination for PDSCH and CSI-RS reception.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the scheduling offset is less than the threshold timeDurationForQCL, then the UE cannot decode DCI and change TCI state in time, but the system needs to ensure accurate beam determination for PDSCH reception
Solution Approach 1:
The patent applies preliminary action by pre-configuring default TCI states through MAC CE activation before the scheduling offset expires. The UE receives and stores multiple TCI states in advance (up to 8 codepoints), so when the scheduling offset is insufficient for decoding and changing TCI states, the UE can immediately apply the pre-configured default TCI state without waiting for DCI processing. This resolves the contradiction by preparing beam information beforehand, ensuring reliable beam determination even under tight timing constraints.
2Ease of operation
If tci-PresentInDCI is configured for all CORESETs, then the DCI can indicate TCI states for PDSCH reception, but the UE may not have enough time to process and apply the indicated TCI state
Solution Approach 1:
The patent applies partial action by providing TCI state information through two channels: MAC CE activation (providing up to 8 codepoints) and DCI indication (providing 3-bit field with 8 codepoints). When the scheduling offset is sufficient, the DCI can indicate a specific TCI state from the pre-activated set. When the offset is insufficient, the UE falls back to using the pre-configured default TCI state from MAC CE. This layered approach ensures that TCI state indication capability is maintained while accommodating varying processing time constraints.
3Productivity
If multiple TCI states are activated for multi-TRP NCJT transmission, then the system can achieve high throughput and reliable transmission, but the complexity of determining default TCI states increases
Solution Approach 1:
The patent applies segmentation by dividing the TCI state management into distinct layers: MAC CE activation layer (configuring up to 8 codepoints with one or two TCI states each) and DCI indication layer (selecting specific codepoints). For multi-TRP NCJT, specific codepoints (e.g., 000 and 001) are assigned to point to two different TCI states. This segmented structure simplifies the determination of default TCI states by providing clear rules: when scheduling offset is insufficient, use the TCI state from the lowest codepoint that points to two TCI states, eliminating the need for complex real-time decisions.
4Loss of information
If the UE reports capability timeDurationForQCL, then the system knows the processing time required, but the UE still cannot change TCI state when the scheduling offset is less than this threshold
Solution Approach 1:
The patent applies beforehand cushioning by providing redundant TCI state information through MAC CE activation in advance. The UE capability timeDurationForQCL reports the minimum processing time required, and the system uses this information to configure default TCI states via MAC CE before the scheduling offset expires. This creates a cushion of pre-configured beam information that the UE can fall back on when the scheduling offset is insufficient, ensuring QCL determination reliability is maintained even when timing constraints prevent normal DCI-based TCI state changes.
Data Source
AI summary
Methods and apparatuses for determining default beam(s) are disclosed. A method comprises receiving an activation command for the activated BWP of a serving cell, wherein the activation command contains codepoints pointing to TCI state(s), and at least one codepoint points to two TCI states; and determining default TCI state(s) for reception of downlink signal according to the TCI state(s) used for receiving the PDCCH or at least one TCI state pointed to by a codepoint pointing to two TCI states, when a scheduling offset between a reception of the PDCCH carrying DCI and the corresponding downlink signal scheduled or triggered by the DCI is less than a predetermined threshold.