Beam Maintenance via CFRA Resource Configuration
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Solution Overview
Problem
Current beam maintenance solutions in wireless communication systems, particularly for multi-TRP and LTM scenarios, are inadequate, especially during UE mobility, leading to suboptimal beam pair link quality between the terminal device and the target cell due to the lack of efficient timing advance and synchronization mechanisms.
Innovation Solution
Configuring contention-free random access (CFRA) PRACH transmissions with resource configurations indicating synchronization signal and CSI-RS indices, allowing the terminal device to select and maintain optimal beams for subsequent transmissions and receptions before a cell switch command, thereby enhancing beam maintenance and timing advance alignment without dedicated DCI scheduling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If current beam maintenance solutions are used in multi-TRP scenarios, then the system can operate with basic timing advance management, but beam pair link quality deteriorates during UE mobility
Solution Approach 1:
The network device pre-configures multiple CFRA resources (preambles, time slots, frequency resources) associated with different SSB/CSI-RS indices before the UE needs to perform beam maintenance. This allows the UE to have ready-to-use beam resources when mobility occurs, eliminating the need for reactive beam reconfiguration during movement
Solution Approach 2:
The patent enables dynamic beam selection by configuring multiple CFRA resources with different SSB/CSI-RS indices that correspond to different beams. The UE can dynamically select the most appropriate beam resource based on current channel conditions and mobility state, making the beam maintenance system adaptable to changing environments
2Measurement precision
If multiple CFRA resources are configured for beam maintenance, then timing advance alignment is improved, but signaling overhead increases
Solution Approach 1:
The patent segments the beam maintenance function into multiple dedicated CFRA resources, each associated with specific SSB/CSI-RS indices. Instead of using generic random access procedures, the system divides the uplink resources into specific CFRA occasions, time slots, and frequency resources, allowing precise timing advance measurement for each beam without requiring extensive signaling
Solution Approach 2:
The CFRA resources are configured to be self-describing through their association with SSB/CSI-RS indices. The UE can autonomously determine which CFRA resource to use based on the downlink beam quality indicators (SSB/CSI-RS measurements) without requiring additional network signaling to specify the exact resource allocation, reducing signaling overhead while maintaining precise timing advance alignment
Data Source
AI summary
Embodiments of the present disclosure relate to methods and apparatus for beam maintenance in a radio access network, in particular, through random access preamble transmission for beam maintenance. A terminal device receives, from a network device, a resource configuration for contention-free random access. The resource configuration indicates a plurality of CFRA resources each associated with a respective synchronization signal and physical broadcast channel block index or channel state information reference signal index. The plurality of CFRA resources are applicable for timing advance acquiring in a target network device. The terminal device transmits, to the target network device, one or more CFRA physical random access channels based on the resource configuration. In this way, beam maintenance may be performed based on an SSB index or CSI-RS index associated with one of the transmitted CFRA PRACH(s) before a cell switch command or a random access response.