Time and Frequency Synchronization for Low Power Communication
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Solution Overview
Problem
Existing synchronization techniques for digital data communication systems, particularly those using non-coherent and differentially coherent modulation techniques, face challenges in low complexity and low power configurations, and are not well-suited for short duration training sequences, leading to suboptimal performance in systems like BLE and other resource-constrained environments.
Innovation Solution
The proposed solution involves independent time and frequency synchronization methods using second-order differentials and cross-correlation for time synchronization, and constant bias or phase rotation for frequency synchronization, allowing for parallel or partially parallel implementation with low complexity circuitry such as shifters and adders, suitable for low power and low cost systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If existing synchronization techniques are used in low complexity and low power configurations, then device complexity and power consumption are reduced, but synchronization performance deteriorates
Solution Approach 1:
The patent divides the synchronization process into two independent segments: time synchronization (symbol boundary estimation) and frequency synchronization (CFO estimation). Each segment has its own dedicated circuitry and processing path, allowing them to operate independently without interfering with each other. This segmentation enables low-complexity implementation of each function while maintaining overall synchronization performance.
Solution Approach 2:
The patent performs time synchronization (symbol boundary estimation) before frequency synchronization (CFO estimation). By establishing accurate symbol boundaries first, the system prepares the received signal in advance for the subsequent frequency synchronization process, ensuring that the CFO estimation is performed on properly timed samples, thereby maintaining high synchronization performance in low-complexity configurations.
2Duration of action of moving object
If existing synchronization techniques are used for short duration training sequences, then training sequence duration is reduced, but synchronization accuracy deteriorates
Solution Approach 1:
The patent extracts and eliminates the dependency between time and frequency synchronization operations. By removing the coupling where frequency synchronization depended on time synchronization results, the system can achieve accurate synchronization even with short training sequences. Each synchronization function operates independently with its own optimization, preventing error propagation and maintaining accuracy despite reduced training duration.
Solution Approach 2:
The patent changes the processing parameters specifically optimized for short training sequences. The time synchronization uses second-order differentials and cross-correlation with parameters tailored for short sequences, while frequency synchronization uses constant bias or phase rotation methods also optimized for short durations. This parameter optimization enables accurate synchronization with minimal training overhead.
3Device complexity
If sequential synchronization operations are performed, then device complexity is reduced, but error propagation increases
Solution Approach 1:
The patent segments the synchronization system into independent time and frequency synchronization modules with separate processing paths. Although the modules operate sequentially in time, they are structurally independent with dedicated circuitry for each function. This segmentation prevents error propagation because each module processes its own signal characteristics independently without relying on the results or intermediate states of the other module.
4Reliability
If high performance synchronization is achieved, then synchronization accuracy is improved, but computational complexity and power consumption increase
Solution Approach 1:
The patent replaces complex computational algorithms with simpler mathematical operations. Instead of using computationally intensive methods like Fourier transforms or complex correlation algorithms, the system uses second-order differentials, cross-correlation with simple comparisons, constant bias detection, and phase rotation measurements. These substitutions maintain high synchronization accuracy while dramatically reducing computational complexity and power consumption for implementation in resource-constrained devices.
Data Source
AI summary
Systems and methods which provide training sequence or preamble-based synchronization with respect to non-coherent modulated signals and/or differentially coherent modulated signals are described. Embodiments provide for time synchronization using a technique for mitigating the effect of carrier frequency offset (CFO) with respect to the received signal. Embodiments of the present invention provide for frequency synchronization using a technique for estimating CFO using a constant bias induced with respect to the received signal by CFO. Additionally or alternatively, embodiments of the present invention provide for frequency synchronization using a technique for estimating CFO using phase rotation caused by CFO. The time synchronization and frequency synchronization of embodiments may be performed independently, without requiring the results of one synchronization operation for performing the other synchronization operation.