Satcom Interference Cancellation via Autocorrelation Delay Acquisition
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Solution Overview
Problem
In duplex frequency reuse satellite communications, ambiguity in delay leads to interference cancellation challenges, especially with short periodicities, causing difficulties in selecting the correct correlation peak for interference canceller tracking.
Innovation Solution
A delay/Doppler acquisition process is implemented using autocorrelation on the hub signal to detect periodicity, determine a search range for delay, locate the delay in the hub echo signal, and perform interference cancellation accordingly, ensuring adequate suppression even with ambiguous delays.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If autocorrelation is used to detect delay in hub echo signal, then delay acquisition is achieved, but ambiguity in selecting correlation peak occurs when signal has short periodicity
Solution Approach 1:
The patent segments the delay search space into multiple ranges based on signal periodicity detection. By dividing the full delay range into smaller segments and searching each segment separately, the system avoids the ambiguity of selecting from multiple correlation peaks while maintaining comprehensive coverage of possible delay values
Solution Approach 2:
The patent performs preliminary autocorrelation analysis on the hub signal to detect its periodicity before conducting the main delay acquisition. This preliminary action provides information about the signal structure that guides the subsequent delay search, enabling the system to resolve ambiguity by knowing what to expect in terms of peak patterns
2Productivity
If interference cancellation is performed without resolving delay ambiguity, then processing speed is maintained, but interference suppression performance deteriorates
Solution Approach 1:
The patent implements a partial action approach by performing interference cancellation with the best available delay estimate even when complete ambiguity resolution is not achieved. The system uses the detected periodicity information to identify the most likely correct peak and proceeds with cancellation using that estimate, rather than waiting for complete resolution of all ambiguities
Solution Approach 2:
The patent employs feedback mechanisms where the results of interference cancellation are monitored to validate the selected delay. If the cancellation performance is inadequate, the system can re-evaluate the correlation peaks and adjust the delay selection, creating a feedback loop that improves reliability while maintaining overall processing efficiency
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
This process effectively resolves ambiguity, maintaining interference suppression and allowing for reacquisition when periodicity changes, improving cancellation performance even if an incorrect delay is initially acquired.
Implementation Method 1
an autocorrelation on the hub signal to detect a periodicity in the hub signal
Data Source
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AI summary
A technique for interference cancellation in a satellite communication system involves an autocorrelation on the hub signal to detect a periodicity in the hub signal, determining a search range for a delay in the hub echo signal in accordance with the periodicity, locating the delay in the hub echo signal, and performing the interference cancellation in accordance with the delay. In the case of periodicity, a delay is acquired (either true or false) that provides cancellation (provided that the period does not change). When the period changes, cancellation is discovered to be poor, and another delay (that may be true or false) is acquired that provides good cancellation and so on.