Random Access Preamble Sequence for Satellite Frequency Offset
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Solution Overview
Problem
Satellite communication systems, particularly low earth orbit satellite mobile communication systems, face significant challenges with carrier frequency offset due to crystal oscillator errors and large Doppler frequency offsets, leading to degraded uplink synchronization performance and potential failure of random access preamble sequences.
Innovation Solution
A satellite communication method and device that generates a random access preamble sequence with a cyclic prefix, sequence part, and guard interval, where the sequence part includes subsequences A and B generated using different ZC sequences, providing an anti-frequency offset capability to mitigate frequency offset issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional random access preamble sequence is used in satellite communication systems, then the system can maintain simple sequence structure, but the uplink synchronization performance deteriorates due to large Doppler frequency offsets and crystal oscillator errors
Solution Approach 1:
The random access preamble sequence is segmented into multiple subsequences (at least two subsequences), where each subsequence is generated using a ZC sequence with a different root index. This segmentation allows the system to distribute the frequency offset impact across multiple sequences with different properties, preventing any single sequence from being completely degraded by the frequency offset.
Solution Approach 2:
The invention changes the root index parameter of the ZC sequences used to generate the subsequences. By using at least two different root indexes, the system creates subsequences with different autocorrelation and cross-correlation properties, which provides robustness against frequency offset. The receiver can detect the preamble by identifying which subsequence maintains better correlation properties under the given frequency offset conditions.
2Object-affected harmful factors
If multiple subsequences with different root indexes are used to improve anti-frequency offset capability, then the frequency offset resistance improves, but the sequence structure complexity increases
Solution Approach 1:
The preamble sequence is divided into multiple subsequences, each generated from a ZC sequence with a different root index. This segmentation provides frequency offset resistance because different root indexes produce sequences with different spectral characteristics, making it less likely that all subsequences will be simultaneously degraded by the same frequency offset.
Solution Approach 2:
The multiple subsequences with different root indexes serve multiple functions: they provide frequency offset resistance, enable timing synchronization through correlation detection, and maintain compatibility with existing random access procedures. The receiver can use the same correlation-based detection method for all subsequences, reducing the increase in processing complexity.
3Ease of manufacture
If a single ZC sequence is used for random access preamble, then the sequence generation is simple, but the anti-frequency offset capability is insufficient
Solution Approach 1:
Instead of using a single ZC sequence, the invention segments the preamble into multiple subsequences, each generated from a ZC sequence with a different root index. This maintains the simplicity of ZC sequence generation while improving reliability through diversity. The generation process remains straightforward since ZC sequences are computationally efficient to generate, but the use of multiple root indexes provides the needed frequency offset robustness.
Solution Approach 2:
The invention changes the root index parameter across multiple subsequences rather than changing the fundamental sequence generation method. This allows the system to maintain the simplicity of ZC sequence generation while introducing parameter diversity (different root indexes) that provides anti-frequency offset capability. The receiver can efficiently process these sequences using standard correlation techniques.
Data Source
AI summary
The disclosure provides satellite communication methods and related devices. One example method includes generating a random access preamble sequence which includes a cyclic prefix, a sequence part, and a guard interval. The sequence part includes a subsequence A and a subsequence B, or the sequence part includes a subsequence C, and the subsequence C is a time domain superimposed sequence of a subsequence A and a subsequence B. The subsequence A includes at least one preamble symbol, the subsequence B includes at least one preamble symbol, and the subsequence A and the subsequence B are respectively generated by using ZC sequences of different root indexes, a quantity of subsequences A is m, a quantity of subsequences B is m or m−1, and m is a positive integer. The method further includes outputting the random access preamble sequence.