Receiver Preamble Synchronization Using Coarse and Fine Correlation
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Solution Overview
Problem
Existing receivers face inaccuracies in time synchronization, particularly in multipath and noisy environments, due to their reliance on one-step synchronization methods.
Innovation Solution
A two-step time synchronization approach is introduced, comprising a coarse time synchronization through autocorrelation and a fine time synchronization through crosscorrelation, with independent calculations for each step, and additional steps for frequency synchronization and automatic gain control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If one-step time synchronisation is used, then the device complexity is reduced, but the measurement precision deteriorates
Solution Approach 1:
The synchronisation process is divided into two independent steps: coarse time synchronisation using autocorrelation and fine time synchronisation using crosscorrelation. Each step uses different correlation methods on different groups of preamble symbols, with independent calculations that do not depend on previous results, thereby improving accuracy without excessive complexity increase.
2Ease of operation
If coarse time synchronisation is performed before frequency synchronisation, then the processing sequence is simplified, but the measurement precision deteriorates due to frequency offset
Solution Approach 1:
The system performs coarse time synchronisation using autocorrelation before frequency synchronisation is completed. The autocorrelation method is specifically chosen because it provides more reliable results even in the presence of frequency offset, allowing the system to establish initial time alignment without requiring perfect frequency synchronisation first.
3Ease of manufacture
If crosscorrelation is used for coarse time synchronisation, then the method is simpler, but the reliability deteriorates in presence of frequency offset
Solution Approach 1:
Different correlation methods are applied at different stages of the synchronisation process. Autocorrelation is specifically used for coarse time synchronisation where it provides robustness against frequency offset, while crosscorrelation is used for fine time synchronisation when frequency offset has been compensated. This local optimisation of method selection improves overall reliability.
Data Source
AI summary
Receivers (1) for receiving frequency signals are, to improve their time synchronization accuracy, provided with synchronization stages (20) for performing a coarse time synchronization through autocorrelating samples of a group of preamble symbols (t1,t2,t3) and a fine time synchronization through crosscorrelating samples of a further group of preamble symbols (t10,G1) with predefined samples. The synchronization stages (20) also perform a coarse and a fine frequency synchronization through detecting and accumulating phases of samples of a yet further group of preamble symbols (t8,t9) and of another group of preamble symbols (T1,T2). The synchronization stages (20) have buffering units (21) and controlling units (22) for controlling mixing units (11) and transformating units (12) in processing stages (10). The preamble symbols have ten short preamble symbols (t1-t10), a guard interval preamble symbol (G 1) and two training symbols (T 1,T2).