NTN Cell Selection Using RACH Precompensation Features
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Solution Overview
Problem
In Non-Terrestrial Networks (NTNs), UEs with and without Global Navigation Satellite System (GNSS) capabilities face challenges due to differing residual frequency errors and timing uncertainties during random access, necessitating distinct PRACH formats and configurations that are not currently differentiated by existing systems.
Innovation Solution
The system defines UE classes and features based on random access capabilities, providing tailored RACH configurations for UEs with and without GNSS, ensuring efficient resource allocation and successful random access.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single PRACH configuration is used for all UEs in NTN, then system complexity is reduced, but random access reliability deteriorates due to differing timing uncertainties between GNSS-equipped and non-GNSS UEs
Solution Approach 1:
The patent segments the UE population into distinct classes (GNSS-equipped UEs and non-GNSS UEs) and provides differentiated PRACH configurations for each class. This segmentation allows the system to address the different timing uncertainty characteristics of each UE type, improving random access reliability while managing complexity through structured classification.
Solution Approach 2:
The patent applies local quality by providing tailored PRACH configurations specific to each UE class rather than a uniform configuration. GNSS-equipped UEs receive configurations optimized for their lower timing uncertainty, while non-GNSS UEs receive configurations that account for their higher timing uncertainty, thereby optimizing random access reliability for each local group.
2Adaptability or versatility
If the preamble receiving window is extended to accommodate non-GNSS UEs, then random access accessibility is improved, but resource efficiency deteriorates due to increased idle listening time
Solution Approach 1:
The patent segments the random access resources into different time-frequency configurations for GNSS-equipped and non-GNSS UEs. By providing separate PRACH configurations, the system allows non-GNSS UEs to access the network without forcing GNSS-equipped UEs to wait for extended windows, thereby maintaining resource efficiency while improving accessibility for non-GNSS UEs.
Solution Approach 2:
The patent enables GNSS-equipped UEs to perform preliminary timing compensation using their GNSS timing information before initiating random access. This preliminary action allows them to transmit preambles earlier in the receiving window, reducing the overall window duration needed and minimizing energy loss from extended listening for other UEs.
3Reliability
If differentiated PRACH formats are provided for different UE classes, then random access reliability is improved, but device complexity increases due to multiple configuration sets
Solution Approach 1:
The patent extracts the timing compensation capability as a distinguishing feature for classifying UEs into different groups. By identifying and separating GNSS-equipped UEs from non-GNSS UEs based on this specific capability, the system can apply differentiated PRACH configurations only where necessary, improving reliability while managing device complexity through targeted differentiation rather than universal complexity.
Solution Approach 2:
The patent implements dynamic UE classification where UEs self-identify their GNSS capability and are dynamically assigned to appropriate PRACH configuration groups. This dynamic approach allows the system to adapt configurations in real-time based on UE capabilities, improving random access reliability while avoiding the need for static complex configuration management across all UEs.
Data Source
AI summary
Systems and methods related to cell selection based on random access channel pre-compensation features supported by a wireless device are disclosed. In one embodiment, a method performed by a wireless device comprises obtaining information that indicates one or more random access channel pre-compensation features required for wireless devices to select a cell. The method further comprises making a decision as to whether the wireless device is permitted to select the cell based on the information and one or more random access channel pre-compensation features supported by the wireless device and performing one or more actions in accordance with the decision.