Satellite Bandwidth Efficiency via Overlapping Signal Combining
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Solution Overview
Problem
Satellite communication systems face limitations in bandwidth efficiency due to mutual interference between neighboring spot beams, which constrains the choice of bandwidth and requires methods that either require access to original source signals for signal extraction or transmit over non-overlapping frequencies, limiting spectral efficiency.
Innovation Solution
Combining two or more source signals into overlapping frequencies for uplink or downlink transmission in satellite communications, using digital signal processors to generate a combined source signal and information signal that specifies the modulation method, allowing for signal extraction without access to original source signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If frequency spectrum is reused between neighboring spot beams, then bandwidth efficiency is improved, but mutual interference between spot beams increases
Solution Approach 1:
The patent applies interference cancellation techniques to convert the harmful mutual interference between spot beams into a beneficial signal processing task. By receiving the combined signal containing interference, generating an estimate of the interfering signal, and subtracting it from the received signal, the system recovers the desired signal while improving bandwidth efficiency through frequency reuse.
2Productivity
If source signals are combined into overlapping frequencies, then spectral efficiency is improved, but signal extraction becomes more difficult
Solution Approach 1:
The patent applies preliminary actions by generating an estimate of the interfering signal before subtracting it from the received signal. This preliminary estimation step, which uses knowledge of the combined signal structure and modulation methods, prepares the signal processing in advance to enable successful separation and extraction of the desired signal from the overlapping frequency combinations.
3Reliability
If traditional non-overlapping frequency transmission is used, then signal quality is maintained, but bandwidth efficiency is limited
Solution Approach 1:
The patent applies merging by combining multiple source signals into a single combined signal that occupies overlapping frequency spectra. Instead of transmitting signals on separate non-overlapping frequencies, the system merges multiple signals into one transmitted signal, then uses interference cancellation at the receiver to separate them, thereby improving bandwidth efficiency while maintaining signal quality.
Data Source
AI summary
Methods and systems are provided for increasing bandwidth efficiency in satellite communications. In some embodiments, a satellite communications method is provided that comprises receiving, at a satellite and from a plurality of user ground terminals, a plurality of source signals, wherein each of the source signals are modulated according to at least one source modulation method, and further receiving, at a satellite and from a plurality of user ground terminals, a plurality of information signals corresponding to the plurality of source signals. The method further includes combining, at the satellite, the plurality of source signals into a combined source signal with an overlapping bandwidth, wherein each of the source signals are further modulated according to at least one predetermined modulation method before they are combined, and transmitting, by a downlink transmission from the satellite to a gateway ground station, the combined source signal.