Random Access Resource Determination Using QCL Information in NR-U
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Solution Overview
Problem
In New Radio (NR) Unlicensed (NR-U) systems, determining a corresponding Physical Random Access Channel (PRACH) resource for a Synchronization Signal Block (SSB) is challenging due to the Listen Before Talk (LBT) principle, where SSB position indexes differ from Quasi Co-Located (QCL) indexes, leading to inefficient resource utilization and potential waste of PRACH resources.
Innovation Solution
A method to determine random access resources by using either QCL information or position indexes of SSBs, associating SSBs with the same QCL relationship to the same PRACH resource, thereby optimizing resource allocation and avoiding waste.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If SSB position index is used to determine PRACH resource in NR-U system, then synchronization can be obtained, but QCL relationship cannot be correctly determined leading to inefficient resource utilization
Solution Approach 1:
The patent introduces QCL information as an intermediary element that bridges the gap between SSB position index and PRACH resource determination. Instead of directly mapping position index to PRACH resource, the system uses QCL information (obtained through QCL indication information) as an intermediate step to correctly identify the corresponding PRACH resource, thereby resolving the contradiction between accurate SSB identification and efficient resource utilization
2Reliability
If LBT principle is applied for signal transmission in NR-U, then channel access is controlled, but multiple SSB candidate positions result in position index differing from QCL index causing PRACH resource waste
Solution Approach 1:
The patent changes the parameter used for PRACH resource determination from SSB position index to QCL information. By transforming the determination basis from positional information to QCL-based information, the system adapts to the LBT mechanism's impact on SSB positioning, ensuring that PRACH resources are allocated based on actual QCL relationships rather than candidate position indices, thereby eliminating resource waste
3Ease of manufacture
If one-to-one mapping between SSB index and PRACH resource is used, then resource allocation is simple, but multiple SSBs with same QCL relationship cannot share common PRACH resource
Solution Approach 1:
The patent merges multiple SSBs that share the same QCL relationship into a single group that can use a common PRACH resource. Instead of maintaining separate one-to-one mappings for each SSB, the system combines SSBs with identical QCL information, allowing them to share the same PRACH resource configuration. This merging approach maintains allocation simplicity while significantly improving resource utilization efficiency
Data Source
AI summary
The embodiments of the present application relate to a method for determining a random access resource, a terminal device, and a network device. The method includes: determining, by a terminal device, Quasi Co-Located (QCL) information or position information of a target Synchronization Signal Block (SSB); and determining, by the terminal device, a set of target random access resources corresponding to the target SSB based on a correspondence between QCL information or position information of SSBs and sets of random access resources. A random access resource in the set of target random access resources is used for the terminal device to perform a random access process. The position indexes of at least two SSBs with a QCL relationship in the correspondence correspond to a same set of random access resources.