Adaptive CDMA Signal Noise Distribution Shaping
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Solution Overview
Problem
Existing Code Division Multiple Access (CDMA) signal receivers face challenges in managing pulsed interferences and thermal noise, leading to reduced signal-to-noise and interference ratio and degraded tracking performances due to fixed blanking thresholds.
Innovation Solution
A method for noise distribution shaping of data modulated CDMA signals involves separating the signal into channels with adaptive blankers, correlating with phase-shifted replicas to extract symbol signs, and adjusting upper and lower blanking thresholds based on these signs to improve tracking and demodulation performances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If fixed blanking thresholds are used to reduce pulsed interference, then interference rejection is improved, but tracking performance deteriorates due to incorrect threshold offset direction
Solution Approach 1:
The blanking thresholds are made dynamic by adjusting their offset direction based on the detected symbol polarity. The system switches between positive and negative threshold offsets depending on whether the current symbol is positive or negative, allowing the thresholds to adapt to the signal conditions rather than remaining fixed.
Solution Approach 2:
The system uses feedback from the correlation result to determine the symbol polarity, which then controls the threshold offset direction. The correlation output provides information about the current symbol state, which feeds back to adjust the blanking threshold configuration for optimal performance.
2Object-affected harmful factors
If blanking is applied to reduce interference effects, then interference mitigation is improved, but signal-to-noise ratio deteriorates due to unnecessary zeroing of thermal noise samples
Solution Approach 1:
The blanking operation is applied selectively rather than uniformly. By adjusting the threshold offset direction according to symbol polarity, the system creates locally optimized blanking regions that are more effective at rejecting interference while being less aggressive toward thermal noise, thereby preserving signal quality in regions where it is not needed.
Data Source
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AI summary
The present invention provides a method for noise distribution shaping of a data modulated Code Division Multiple Access, CDMA, signal. The method comprises separating the data modulated CDMA signal onto a first and second channel, wherein the first channel comprises an adaptive blanker. The method further comprises correlating the data modulated CDMA signal on the second channel with a replica having the same chip sequence of the CDMA signal. The replica is shifted by a predefined phase. The method comprises extracting from the correlation result a sign of a symbol included in the data. The method comprises modifying the noise distribution of the data modulated CDMA signal on the first channel by applying blanking of the data modulated CDMA signal under control of the adaptive blanker. The adaptive blanker has upper and lower blanking thresholds and the upper and lower blanking thresholds are adjusted based on the symbol. The present invention further provides a device for noise distribution shaping of a data modulated Code Division Multiple Access, CDMA, signal.