Radio Synchronization Using Dual Autocorrelators Against False Locks
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Solution Overview
Problem
Conventional radio receivers, particularly those operating in Bluetooth Low Energy Long Range mode, face issues with false positive synchronization due to interference from other transmitters, leading to lock-up and reduced performance in low signal-to-noise ratio conditions.
Innovation Solution
The implementation of a dual autocorrelator system that exploits the cyclic nature of the preamble, using constructive and destructive interference to enhance co-channel interference rejection, with a demodulator enabled only when the cyclic preamble is confidently detected, and power-saving modes for reduced processing overheads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional autocorrelator is used to detect the preamble, then the receiver can achieve basic synchronization functionality, but false positive detections occur due to interference from other transmitters
Solution Approach 1:
The invention divides the single autocorrelation detection process into two separate autocorrelators: one for constructive interference detection and another for destructive interference detection. This segmentation allows the system to independently analyze both interference conditions and make a more reliable preamble detection decision by comparing both results, thereby reducing false positives caused by co-channel interference.
Solution Approach 2:
The invention converts the harmful effect of co-channel interference into a useful detection mechanism by deliberately exploiting both constructive and destructive interference patterns. By designing the system to detect both types of interference and using their combined information for preamble validation, the system transforms interference from a source of errors into a source of additional verification information that improves detection reliability.
2Reliability
If the receiver operates in low signal-to-noise ratio conditions to extend communication range, then coverage is improved, but false positive detections increase due to noise and interference
Solution Approach 1:
The system implements a feedback mechanism where the outputs of both constructive and destructive autocorrelators are fed into a decision logic that determines whether a valid preamble is present. This feedback loop allows the receiver to continuously monitor correlation results and adjust its detection threshold dynamically, ensuring reliable operation even in low signal-to-noise ratio conditions by requiring consistent positive correlation across both interference conditions.
3Measurement precision
If continuous processing is performed to maintain synchronization accuracy, then detection precision is improved, but power consumption increases
Solution Approach 1:
The invention implements periodic action by enabling the demodulator and performing full autocorrelation processing only when the dual-autocorrelator system confidently detects a valid preamble. Between detection events, the system can operate in a lower-power state with reduced processing overhead. This periodic activation based on detection confidence significantly reduces average power consumption while maintaining high detection precision when needed.
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
Significantly reduces false positive detections, improves synchronization robustness, and enhances performance under interference and low signal conditions, while providing power savings.
Implementation Method 1
The first autocorrelator provides 'constructive' correlation (so-named with reference to constructive interference) because if the preamble is present, then correlating a subset of the samples with a version of those same samples delayed by the period of the cycle (or some integer multiple of the period) should provide high correlation
Implementation Method 2
The second autocorrelator provides 'destructive' correlation (so-named with reference to destructive interference) because if the preamble is present, then correlating a subset of the samples with a version of those same samples delayed by half the period (or any integer-and-a-half periods) should provide low correlation
Data Source
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Figure 4
AI summary
A radio receiver device is configured to determine whether a received digital radio signal includes a predetermined cyclic preamble having a period. An input portion is configured to sample the received digital radio signal and to generate a plurality of samples, which are stored in a buffer. A first autocorrelator (202) is configured to correlate first and second subsets of the plurality of samples to generate a first correlation metric, the second subset having been stored in the buffer earlier than said first subset by an even integer multiple of half of the preamble period. A second autocorrelator (204) is configured to correlate first and third subsets of the plurality of samples to generate a second correlation metric, the third subset having been stored in the buffer earlier than said first subset by an odd integer multiple of half of the preamble period. A processing portion is configured to calculate a difference between the correlation metrics and determine that the radio signal includes the predetermined cyclic preamble when the difference is greater than a threshold value.