TCI State Switching with Quasi Co-Located Reference Signals
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Solution Overview
Problem
In current NR technology, the TCI state update solution is not feasible after a terminal device has accessed a cell, leading to failures in data scheduling due to assumptions about the quasi co-location relationship between reference signals and SSBs, which can differ from the actual transmit beams.
Innovation Solution
A method for updating the TCI state by configuring a second TCI state that is quasi co-located with the first TCI state before changes, ensuring accurate data transmission and reception by maintaining the reference signal consistency during BWP switching and other TCI state changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the terminal device assumes the reference signal pointed by TCI state is the SSB determined during initial cell access, then the terminal device can maintain a simple assumption before TCI state activation, but this assumption becomes invalid after cell access because the transmit beam for SSB may differ from the actual scheduling beam or the SSB measurement duration is excessively long
Solution Approach 1:
The patent applies preliminary action by configuring a default TCI state in advance (before actual data transmission) that points to a reference signal. This default configuration is established through RRC signaling prior to MAC CE activation, ensuring that when the terminal needs to receive data before TCI state activation or after cell re-access, it already has a pre-configured reference signal to use, avoiding the need to rely on potentially invalid SSB assumptions
Solution Approach 2:
The patent introduces an intermediary mechanism by using a default TCI state configuration that serves as a bridge between the initial cell access phase and the activated TCI state phase. This default configuration acts as a temporary mediator that provides valid reference signal information when the original SSB-based assumption is no longer valid, enabling continuous data transmission without interruption
2Stability of the object's composition
If the terminal device uses the current TCI state update solution after cell access, then the terminal device can attempt to maintain beam consistency, but data scheduling fails because the assumed reference signal does not match the actual transmit beam
Solution Approach 1:
The patent implements feedback by having the network device monitor whether the terminal device successfully received and is using the correct TCI state configuration. Through HARQ acknowledgments and uplink transmission quality, the network can determine if the default TCI state reference signal aligns with the actual transmit beam, and adjust subsequent TCI state activations accordingly to ensure beam consistency
Solution Approach 2:
The patent applies parameter changes by dynamically modifying the TCI state configuration parameters (specifically the reference signal indicator) based on the current transmission conditions. When the default TCI state proves insufficient or when beam conditions change, the network updates the TCI state parameters through MAC CE activation to match the actual transmit beam, ensuring reliable data scheduling
Data Source
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AI summary
This application discloses a state configuration method and a device, to update a TCI state, and ensure correct sending and receiving of data. Embodiments of this application provide a state configuration method, including: determining, by a terminal device, that a transmission configuration indicator TCI state configured by a network device changes; obtaining, by the terminal device, a first TCI state configured by the network device before the TCI state changes; configuring, by the terminal device, a second TCI state to be the same as the first TCI state; and when the second TCI state is the same as the first TCI state, a reference signal pointed by using the second TCI state and a reference signal pointed by using the first TCI state are quasi co-located; and after the TCI state changes and before a third TCI state configured by the network device is activated, sending and receiving, by the terminal device, data by using the second TCI state.