Adaptive Noise Distribution Shaping for CDMA Receivers
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Solution Overview
Problem
Existing noise blanking techniques for CDMA signals, such as those used in GNSS receivers, often reduce the Signal-to-Noise and Interference Ratio (SNIR) due to fixed thresholds that fail to distinguish between thermal noise and pulsed interferences, leading to unwanted signal suppression.
Innovation Solution
Adapting blanking thresholds or signal samples based on the amplitude of the received CDMA signal, using an offset value calculated from the estimated power and scaling factors, to modify the noise distribution and improve SNIR by applying a set of adaptive blanking thresholds or offsetting the signal samples.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If fixed blanking thresholds are used to suppress pulsed interferences, then interference rejection is improved, but Signal-to-Noise and Interference Ratio (SNIR) deteriorates due to unwanted suppression of thermal noise portions
Solution Approach 1:
The patent applies dynamics by making the blanking thresholds adaptive rather than fixed. The thresholds dynamically adjust based on the estimated signal amplitude, allowing the system to differentiate between genuine pulsed interferences and thermal noise portions. This resolves the contradiction by enabling interference rejection only when necessary, preserving SNIR in normal conditions.
Solution Approach 2:
The patent changes the parameter of blanking thresholds from fixed values to amplitude-dependent values. By calculating thresholds as a function of the estimated signal amplitude (using scaling factors and offset values), the system adapts its behavior to current signal conditions, improving both interference rejection and SNIR preservation.
2Reliability
If blanking thresholds are lowered to preserve signal portions, then SNIR is improved, but susceptibility to pulsed interferences increases
Solution Approach 1:
The system dynamically adjusts thresholds based on real-time signal amplitude estimation. When signal amplitude is low, thresholds are lowered to preserve SNIR; when signal amplitude indicates potential interference, thresholds are raised to reject pulsed interferences. This dynamic adaptation resolves the contradiction between SNIR preservation and interference susceptibility.
Solution Approach 2:
The patent implements feedback by continuously estimating signal amplitude and using this information to adjust blanking thresholds. The estimated power and amplitude feed back into the threshold calculation, creating a closed-loop system that automatically optimizes the balance between SNIR and interference rejection based on current conditions.
3Reliability
If adaptive blanking thresholds are implemented, then SNIR is improved by reducing unwanted noise suppression, but device complexity increases
Solution Approach 1:
The system performs self-service by using the received signal itself to determine the appropriate blanking thresholds. The signal's own amplitude and power characteristics are used to adapt the thresholds, eliminating the need for external control systems or complex adaptive algorithms. This reduces implementation complexity while maintaining SNIR improvement.
Solution Approach 2:
The patent simplifies complexity by changing only the threshold parameters based on signal amplitude, rather than redesigning the entire blanking system. This parameter-based adaptation approach maintains simplicity while achieving SNIR improvement, avoiding the need for complex machine learning or adaptive filtering systems.
4Object-affected harmful factors
If blanking is applied continuously to suppress interferences, then interference rejection is improved, but loss of useful signal information increases
Solution Approach 1:
The patent applies partial action by using blanking selectively rather than continuously. The adaptive thresholds ensure that blanking is applied only when and where necessary to suppress actual interferences, avoiding excessive blanking that would remove useful signal information. This resolves the contradiction by optimizing the balance between interference suppression and information preservation.
Data Source
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AI summary
The invention relates to noise distribution shaping for signals, particularly for the application in receivers for CDMA signals. An embodiment of the invention provides a method for noise distribution shaping for signals comprising the acts of generating a blanking control signal by comparing a received signal with at least one blanking threshold (S10), adapting the at least one blanking threshold or the received signal according to an offset value depending on the amplitude of the received signal (S12, S14), and modifying the noise distribution of the received signal by applying blanking of the received signal under control of the blanking control signal (S16).