Adaptive Correlation Threshold for Bandlimited Wireless Signals
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Solution Overview
Problem
Bandpass and channel filtering in wireless technologies used for IoT applications negatively impact signal correlation by attenuating amplitude and reducing peak amplitude swings, leading to inefficient correlation processes.
Innovation Solution
A wireless receiver system with an adaptive threshold circuit that adjusts correlation thresholds based on the synchronization word, using either a lookup table or an evaluation circuit to account for amplitude attenuation caused by filtering, thereby improving correlation accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If bandpass filters are used to isolate channels and filter out noise, then signal-to-noise ratio is improved, but amplitude attenuation occurs and correlation performance deteriorates
Solution Approach 1:
The patent changes the parameter of correlation threshold from a fixed value to an adaptive value that varies based on the sync word pattern. By calculating expected amplitude attenuation for each possible sync word and setting corresponding thresholds, the system compensates for the amplitude reduction caused by bandpass filtering, thereby maintaining correlation accuracy while preserving the noise filtering benefits
Solution Approach 2:
The patent pre-calculates and stores expected amplitude attenuation values for each possible sync word in a lookup table. This copying of pre-computed attenuation characteristics allows the system to quickly retrieve and apply the appropriate compensation threshold without real-time complex calculations, efficiently resolving the contradiction between noise filtering and correlation accuracy
2Device complexity
If fixed correlation threshold is used, then device complexity is reduced, but correlation accuracy deteriorates due to amplitude attenuation from filtering
Solution Approach 1:
The patent performs preliminary calculation of amplitude attenuation for each possible sync word before actual signal processing. These pre-calculated values are stored in a lookup table, allowing the system to simply retrieve the appropriate threshold during operation. This preliminary action maintains high correlation accuracy while avoiding complex real-time calculations during signal processing
Solution Approach 2:
The patent introduces an intermediary lookup table that maps sync words to their corresponding expected amplitude attenuation values. This intermediary structure decouples the complex attenuation calculation from the real-time correlation process, allowing accurate adaptive thresholding with minimal additional circuit complexity during operation
Data Source
AI summary
A wireless receiver including a front end circuit, an adaptive threshold circuit, and a correlator. The front end circuit converts a wireless signal into a series of digital symbols. The adaptive threshold circuit provides an adaptive correlation threshold that is adapted based on a sync word. The correlator correlates the digital symbols with the sync word using the adaptive correlation threshold. The adaptive correlation threshold may be based on amplitude attenuation of the digital symbols that correspond to transitions of the sync word. The adaptive threshold circuit may be a lookup table that stores different threshold values each corresponding to one of multiple different sync words. Alternatively, the adaptive threshold circuit may be implemented as an evaluation circuit that determines the adaptive correlation threshold based on expected amplitude attenuation of the digital symbols that correspond to transitions of the sync word.