Wireless Communication TCI Configuration for QCL Accuracy in NR-U
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Solution Overview
Problem
In the NR-U system, the uncertainty of SSB transmission positions due to successful LBT in unlicensed frequency bands complicates the indication of QCL reference signals for frame synchronization and downlink channel reception, making it difficult for terminal devices to correctly determine the QCL relationship with downlink channels.
Innovation Solution
The network device configures QCL reference signals using SSB indication information in TCI state configuration, which includes SSB transmission position indices or QCL indices, allowing the terminal device to determine a reference SSB that satisfies the QCL relationship with downlink channels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the network device uses LBT before transmitting SSB in unlicensed frequency band, then the channel access follows fair sharing principle, but the SSB transmission position becomes uncertain
Solution Approach 1:
The network device performs LBT procedure in advance before SSB transmission to secure channel access. By conducting the listening check beforehand and only transmitting when channel is idle, the system ensures fair channel sharing while the pre-determined transmission position (based on successful LBT) provides sufficient predictability for terminal devices to configure QCL parameters
Solution Approach 2:
The patent introduces QCL (Quasi-Co-Location) parameter configuration as an intermediary mechanism. The network device indicates QCL parameters to the terminal device, which then uses these parameters to determine the reference SSB and establish the QCL relationship with downlink channels. This intermediary configuration bridges the gap between uncertain SSB positions and reliable channel reception
2Adaptability or versatility
If the network device transmits SSB at uncertain positions due to LBT, then unlicensed band access is achieved, but the terminal device cannot correctly determine QCL relationship with downlink channels
Solution Approach 1:
The network device provides feedback to the terminal device by indicating QCL parameters through TCI state configuration information. This feedback includes references to specific SSB positions or CSI-RS resources, enabling the terminal device to accurately determine the QCL relationship despite the uncertain SSB transmission positions caused by LBT in unlicensed bands
Solution Approach 2:
The QCL parameter configuration acts as an intermediary that translates the uncertain physical SSB positions into deterministic logical references. The terminal device uses the indicated QCL parameters to identify reference signals and establish quasi-co-location relationships, thereby achieving accurate channel estimation regardless of actual SSB transmission timing
3Productivity
If the terminal device receives downlink channel without accurate QCL reference signal, then communication can proceed, but system performance deteriorates
Solution Approach 1:
The terminal device performs preliminary configuration of QCL parameters based on network device indications before receiving downlink channels. By pre-determining the reference SSB or CSI-RS resource and establishing the QCL relationship in advance, the terminal device ensures reliable frame synchronization and channel estimation, thereby maintaining both communication continuity and high reliability
Data Source
AI summary
A wireless communication method, a terminal device, and a network device are disclosed. The method includes: receiving, by a terminal device, Transmission Configuration Indication (TCI) state configuration information transmitted by a network device, the TCI state configuration information including Synchronization Signal Block (SSB) indication information, the SSB indication information being an SSB transmission position index or an SSB Quasi-Co-Located (QCL) index, and the SSB indication information being used to determine a reference SSB satisfying a QCL relationship with a downlink channel; and receiving, by the terminal device, the downlink channel based on the QCL relationship between the reference SSB and the downlink channel.