Random Access Preamble Generation for Non-Terrestrial Networks
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Solution Overview
Problem
Conventional random access preamble formats in wireless communication systems, such as LTE, are inadequate for non-terrestrial networks due to their inability to handle large frequency and time offsets, which can lead to incorrect detection and synchronization issues in high-speed and satellite communication scenarios.
Innovation Solution
The method involves generating a long preamble sequence by concatenating or superposing Zadoff-Chu sequences based on multiple roots and cyclic shifts, which are then prepended with a cyclic prefix and guard time, enabling high frequency and time offset estimation with low complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional random access preamble formats are used, then device complexity is reduced, but the ability to handle large frequency and time offsets deteriorates
Solution Approach 1:
The long preamble sequence is segmented into multiple short preamble sequences concatenated in time domain. Each short preamble can be independently processed, allowing the system to handle large frequency and time offsets through sequential correlation operations while maintaining manageable computational complexity at each stage.
Solution Approach 2:
The patent transitions from handling offsets in a single dimension to addressing both frequency and time offsets in multiple dimensions by using multiple roots and cyclic shifts across concatenated sequences. This multi-dimensional approach enables robust offset estimation without requiring overly complex single-structure preambles.
2Measurement precision
If long preamble sequences are used to handle large offsets, then frequency and time offset estimation accuracy is improved, but processing complexity increases
Solution Approach 1:
The long preamble is divided into multiple short preambles that can be processed sequentially through correlation operations. This segmentation maintains high estimation accuracy by preserving the full time duration while reducing per-operation complexity, as each short preamble correlation is computationally lighter than processing the entire long preamble as a single unit.
Solution Approach 2:
The patent uses multiple cyclic shifts and roots beyond what a single sequence would provide, creating redundant measurement opportunities. This partial/excessive action across multiple sequences enhances estimation precision through multiple correlation peaks while distributing the processing load across simpler, repeated operations rather than one complex computation.
3Adaptability or versatility
If multiple roots and cyclic shifts are used, then signature pool capacity is extended, but sequence generation complexity increases
Solution Approach 1:
The patent employs multiple Zadoff-Chu roots and cyclic shifts that serve dual purposes: they expand the signature pool capacity for user differentiation and simultaneously provide frequency offset estimation capability. This multi-functionality allows the same sequence structures to achieve both user identification and synchronization without requiring separate mechanisms, thereby extending signature capacity without proportionally increasing generation complexity.
Solution Approach 2:
The system varies parameters such as root indices and cyclic shift values to generate diverse preambles from a limited set of base Zadoff-Chu sequences. By changing these parameters rather than creating entirely new sequences, the patent extensively expands the signature pool capacity while keeping the underlying generation process relatively simple and reusable across multiple preambles.
4Measurement precision
If conventional preambles are used, then processing speed is maintained, but detection accuracy in high-speed scenarios deteriorates
Solution Approach 1:
The segmented structure of multiple short preambles enables parallel or pipelined processing where correlation operations can be performed sequentially on each segment. This maintains high processing speed by breaking down the computation into smaller, faster operations while achieving superior detection accuracy through the cumulative information from all segments, particularly effective in high-speed scenarios with large Doppler shifts.
Data Source
AI summary
Methods, systems, and devices for generating preamble sequences where several Zadoff-Chu (ZC) sequences are generated based on multiple roots and multiple cyclic shifts per root and combined to generate the preamble sequences. Some embodiments may be used in wireless communication embodiments in which large propagation delays and/or Doppler movement are expected.