NTN Random Access Preambles for Uplink Timing Uncertainty
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Solution Overview
Problem
Existing NR/LTE-based mobile communication systems face challenges in initial access performance when GNSS and ephemeris information are unavailable, particularly in non-terrestrial networks with large cell sizes, leading to uplink timing uncertainty and interference.
Innovation Solution
A method involving the generation and transmission of primary and secondary random access preambles with specific configurations, including repetition patterns and timing adjustments, to improve initial access performance with minimal impact on existing specifications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single random access preamble configuration is used in NTN with large cells, then device complexity is reduced, but initial access performance deteriorates due to uplink timing uncertainty and interference
Solution Approach 1:
The patent segments the random access preamble into two distinct types: first random access preamble and second random access preamble. Each preamble type has specific configuration parameters (first configuration and second configuration respectively) that are selected based on terminal capabilities and network conditions. This segmentation allows the system to handle different timing scenarios in large cell NTN environments without requiring all possible configurations to be always active, thus improving initial access performance while controlling complexity.
Solution Approach 2:
The patent implements dynamic selection between first and second random access preamble configurations based on terminal capabilities and network conditions. The network can dynamically determine which preamble type to use based on real-time factors such as terminal support for advanced timing adjustment mechanisms. This dynamic approach allows the system to adapt to changing conditions in large cell NTN environments, optimizing initial access performance without requiring static complex configurations.
2Reliability
If multiple random access preambles with different configurations are used, then initial access performance is improved, but device complexity increases
Solution Approach 1:
The patent divides the random access preamble configurations into two distinct segments (first and second preambles with different configurations) rather than using a single complex configuration or multiple equally complex configurations. This segmented approach with two well-defined types simplifies the overall system complexity compared to managing many more preamble variants, while still providing the necessary performance improvement for large cell NTN scenarios.
Solution Approach 2:
The patent changes key parameters of the random access preamble configurations to create distinct first and second preamble types. These parameter changes include timing adjustment mechanisms, configuration selection criteria, and transmission parameters that are optimized for different NTN scenarios. By carefully selecting and limiting the parameter changes to two distinct configurations, the patent achieves improved initial access performance without the excessive complexity that would result from implementing numerous different preamble types.
3Measurement precision
If GNSS and ephemeris information are used for timing, then uplink timing accuracy is improved, but adaptability deteriorates in environments where this information is unavailable
Solution Approach 1:
The patent introduces network-based timing mechanisms as an intermediary to replace or supplement GNSS-based timing in environments where GNSS information is unavailable. The network can provide timing information and configuration parameters for random access preambles without requiring the terminal to have accurate GNSS data. This intermediary approach allows the system to maintain uplink timing accuracy in GNSS-denied NTN environments while preserving adaptability across different operational scenarios.
Solution Approach 2:
The patent designs the random access preamble system to serve multiple functions across different environments. The first and second preamble configurations can be used in various scenarios including GNSS-available and GNSS-unavailable conditions, making the system universally applicable. The network can select appropriate preamble types based on whether the terminal has GNSS information, allowing the same basic mechanism to adapt to both GNSS-enabled and GNSS-denied environments without requiring separate systems.
Data Source
AI summary
The present disclosure provides a random access method. A method according to an embodiment of the present disclosure, performed by a terminal using an asynchronous grant-free non-orthogonal multiple access scheme, may comprise the steps of: acquiring random access preamble generation information from a base station; generating a primary random access preamble on the basis of the random access preamble generation information; and transmitting the generated primary random access preamble to the base station.