Default Beam Identification in Cross-Carrier Scheduling Without CORESET
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Solution Overview
Problem
In wireless communications, especially during cross-carrier scheduling, there is a challenge in identifying a default beam and detecting beam failures when a Control Resource Set (CORESET) is not available, as current methods rely on CORESETs for default beam determination and dynamic updating of beam failure detection sets, which are not feasible in cross-carrier scenarios.
Innovation Solution
A method where a User Equipment (UE) reuses a default beam from a previous cross-carrier scheduled data transmission if a subsequent data transmission occurs within a threshold time window after a downlink grant, and performs beam failure detection by monitoring reference signals indicated by downselected Transmission Configuration Indicator (TCI) states, even without a CORESET association, to trigger appropriate reporting procedures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If cross-carrier scheduling is implemented without CORESET association, then scheduling flexibility is improved, but default beam identification becomes infeasible
Solution Approach 1:
The patent introduces an intermediary mechanism where the downlink grant on the scheduling carrier serves as a mediator to convey beam indication information (TCI states) for the data transmission on the data carrier. This resolves the contradiction by providing a pathway for beam identification without requiring CORESET association, thus maintaining scheduling flexibility while enabling default beam identification through the downlink grant message itself.
Solution Approach 2:
The patent applies preliminary action by configuring downselected TCI states in advance through higher layer signaling (RRC or MAC-CE) before the actual data transmission occurs. This pre-configuration enables the UE to have a ready set of candidate beams available when needed, resolving the beam identification issue without requiring complex real-time determination, thus maintaining both flexibility and simplicity.
2Reliability
If downselected TCI states are used for beam failure detection, then beam failure detection capability is improved, but signaling overhead increases
Solution Approach 1:
The patent makes the downselected TCI states serve multiple functions: they are used for both default beam identification during cross-carrier scheduling and for beam failure detection. By making these states multi-functional, the patent avoids the need for separate signaling for beam failure detection, thus improving reliability while minimizing additional signaling overhead.
Solution Approach 2:
The system uses the already-configured downselected TCI states for beam failure detection without requiring additional dedicated configuration signaling. The UE autonomously utilizes the existing TCI state configuration for both beam identification and beam failure monitoring, eliminating redundant signaling while maintaining detection capability.
Data Source
AI summary
Methods, systems, and devices for wireless communications are described. A base station may transmit a first downlink grant (e.g., a PDCCH transmission) for a first data transmission (e.g., a PDSCH transmission) over a first component carrier; the first data transmission over a second component carrier; and a second downlink grant (e.g., another PDCCH transmission) for a second data transmission (e.g., another PDSCH transmission) over the second component carrier. A user equipment (UE) receives the first data transmission over a first beam and may use the first beam for receiving the second data transmission. Additionally or alternatively, the UE may receive a configuration message indicating a set of TCI states for downlink data transmissions to the UE; identify one or more reference signals monitor for beam failure detection (BFD), identify one or more BFD beams, monitor the identified one or more reference signals; and selectively trigger a beam failure reporting procedure.