Semi-Static TCI State Switching for mmWave Latency Reduction
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Solution Overview
Problem
Conventional wireless communication systems face inefficiencies in TCI state switching, leading to increased latency and signaling overhead due to slow switching processes and inadequate handling of beam blockages in mmW frequency ranges.
Innovation Solution
Implementing a method where a base station sends a configuration message to a UE indicating a TCI state switching pattern and period, allowing the UE to perform TCI state switching based on this pattern, rather than waiting for subsequent aggregated TTIs, and using DCI to indicate TCI states for TTIs beyond a threshold, thereby reducing latency and overhead.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional TCI state switching is used, then the system maintains simplicity in configuration, but the switching speed is slow and latency increases
Solution Approach 1:
The base station pre-configures multiple TCI states and their switching patterns before actual data transmission. The UE receives and stores these pre-configured TCI states via RRC signaling, so when beam switching is needed, the UE can immediately activate the pre-prepared TCI state without waiting for new configuration messages, thereby reducing switching latency
Solution Approach 2:
The TCI configuration is divided into multiple independent TCI states, each representing a different beam configuration. The base station can selectively activate specific TCI states based on channel conditions and beam blockage detection, allowing granular control over beam switching and improving response speed
2Reliability
If frequent TCI state updates are performed to handle beam blockages, then reception performance improves, but signaling overhead increases
Solution Approach 1:
Multiple TCI states are pre-configured in advance with different beam directions and characteristics. When beam blockage occurs, the base station can quickly switch to a pre-configured alternative TCI state without needing to negotiate new configurations, reducing signaling overhead while maintaining reliable reception
Solution Approach 2:
The system changes TCI state parameters (such as beam direction, spatial filter settings) based on detected channel conditions and blockage events. By modifying these parameters through pre-configured state switching rather than full reconfiguration, the system maintains reliability while minimizing signaling overhead
3Productivity
If TCI state switching waits for subsequent aggregated TTIs, then configuration stability is maintained, but system latency increases
Solution Approach 1:
The TCI state switching mechanism is made dynamic by allowing switching at sub-TTI granularity within aggregated TTIs. The base station can trigger TCI state changes mid-aggregation based on real-time channel conditions, enabling the system to adapt quickly to beam blockages without waiting for aggregation boundaries, thus improving productivity while controlling switching delay
Data Source
AI summary
Methods, systems, and devices for wireless communications are described. A base station may transmit a configuration indicating a transmission configuration indicator (TCI) state switching pattern and a TCI state switching period to a user equipment (UE). The UE may perform TCI state switching according to the TCI state switching pattern and period, and the UE may receive a downlink transmission according to the TCI state switching pattern. The UE may receive a downlink control information (DCI) including an indication of a TCI state for a subsequent TTI. The UE may receive the downlink signal in accordance with both the TCI state switching pattern and the indication in the DCI. The UE may receive a configuration message indicating a first DCI state, receive a DCI indicating a second TCI state for a subsequent TTI, switch to the second TCI state, and receive a downlink signal using the second TCI state.