Narrowband Random Access Preambles for NTN Doppler Control
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Solution Overview
Problem
In non-terrestrial networks with high altitude platforms or satellites, signal strength is low, round-trip delay is long, and large Doppler shifts occur due to node movement, leading to inefficiencies and inter-carrier interference in wireless communications.
Innovation Solution
Designing narrowband random access preambles with specific parameters for non-terrestrial networks, including different starting subcarriers, frequency hopping patterns, and repetition units to reduce inter-carrier interference and support uplink synchronization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If random access preambles are transmitted using adjacent available frequency resources in NTN, then frequency resource utilization is improved, but inter-carrier interference increases due to large Doppler shifts
Solution Approach 1:
The patent applies local quality by configuring different random access preamble parameters for different frequency resources in NTN. Specifically, certain frequency resources are configured with preambles that have parameters optimized for NTN conditions (larger cyclic prefix, different subcarrier spacing), while other resources use different parameters. This allows adjacent frequency resources to be utilized efficiently while preventing ICI by ensuring that preambles on resources susceptible to Doppler shifts have appropriate local characteristics.
Solution Approach 2:
The patent changes physical parameters of random access preambles specifically for NTN operations. Key parameter changes include: increasing cyclic prefix length to accommodate larger delay spreads, adjusting subcarrier spacing to handle Doppler frequency shifts, and modifying preamble formats. These parameter changes enable preambles to maintain orthogonality and reduce ICI even when transmitted on adjacent frequency resources in the challenging NTN environment.
2Device complexity
If standard terrestrial random access preambles are used in NTN, then device complexity is reduced, but communication reliability deteriorates due to large Doppler shifts and long propagation delays
Solution Approach 1:
The patent implements universality by creating a unified random access preamble framework that can operate in both terrestrial and NTN environments. The base preamble structure remains compatible with existing terrestrial systems, but NTN-specific parameters can be activated when needed. This allows the same preamble mechanism to serve multiple functions: standard terrestrial operations and NTN operations with large Doppler shifts, without requiring entirely separate systems.
Solution Approach 2:
The patent introduces dynamics by making random access preamble parameters adaptable to different network conditions. The system can dynamically select between terrestrial and NTN optimized preamble configurations based on the operating environment. Parameters such as cyclic prefix length, subcarrier spacing, and frequency offset compensation are made dynamic rather than fixed, allowing the system to adjust to varying Doppler shifts and propagation delays in real-time.
3Ease of operation
If frequency resources are allocated without considering Doppler shift effects, then resource allocation simplicity is improved, but measurement precision deteriorates due to inter-carrier interference
Solution Approach 1:
The patent applies preliminary action by pre-configuring frequency resources with appropriate preamble parameters before random access transmissions occur. The network预先 identifies which frequency resources are suitable for NTN operations and configures them with appropriate parameters (larger cyclic prefix, specific subcarrier spacing) in advance. This preliminary configuration prevents ICI issues before they occur, maintaining measurement precision while keeping resource allocation simple, as devices simply follow the pre-configured parameters without complex real-time calculations.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enhances communication efficiency and reliability in non-terrestrial networks by reducing inter-carrier interference and supporting higher mobility and reduced latency for user equipment.
Implementation Method 1
communications in such situations may experience relatively large amounts of Doppler shift due to relatively fast movement of nodes relative to one another
Data Source
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AI summary
Methods, systems, and devices for wireless communications are described in which random access preambles may be designed to provide for relatively low inter-carrier interference (ICI) of adjacent available frequency resources in a non-terrestrial network (NTN). Random access preambles for NTN random access requests may be selected from a first set of random access preambles that are different from a second set of random access preambles for terrestrial random access requests. The first set of random access preambles may be a subset of the second set of random access preambles. The first set of random access preambles may be provided for contention-based random access (CBRA) and contention-free random access (CFRA) preambles may be configured by a base station from random access preambles that correspond to or are different from the second set of random access preambles.