Adaptive Satellite Transmodulation Using a Universal Constellation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In satellite communication systems, the lower signal quality from satellites to user equipment compared to gateway systems limits spectral efficiency due to the need for matching modulation schemes, which may not support the optimal throughput required by user equipment.
Innovation Solution
Implementing a forward-link transmodulation system that uses a higher-order modulation for the feeder link from a gateway to a satellite, which is then demodulated and remodulated into lower-order modulation schemes for user links, utilizing a universal constellation to adapt to varying signal-to-noise ratios (SINR) without frequent constellation changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the same modulation scheme is used for both feeder link and user link in bent-pipe satellite transmission, then the system maintains simple architecture and operation, but spectral efficiency is limited because the modulation must be lowered to match the weaker satellite-to-UE signal conditions
Solution Approach 1:
The transmission link is segmented into two independent sections: feeder link (gateway to satellite) and user link (satellite to UE). Each section can use different modulation schemes optimized for its specific signal conditions, allowing high-order modulation on the strong feeder link and lower-order modulation on the weaker user link, thereby resolving the contradiction between system simplicity and spectral efficiency
Solution Approach 2:
The system dynamically adapts modulation schemes for different link sections based on real-time signal conditions. The satellite performs transmodulation to convert between different modulation orders, enabling flexible adjustment of spectral efficiency without requiring complex reconfiguration of the entire system architecture
2Productivity
If higher-order modulation is used on the feeder link to increase throughput, then spectral efficiency improves, but the satellite must perform complex demodulation and remodulation operations increasing processing complexity and power consumption
Solution Approach 1:
The satellite changes the modulation parameter (modulation order) between incoming and outgoing signals. By receiving high-order modulation on the feeder link and transmitting lower-order modulation on user links, the satellite adapts signal characteristics to match different channel conditions while maintaining efficient throughput
3Reliability
If lower-order modulation is used for user links to ensure reliable reception, then signal reliability improves, but the overall system throughput is reduced because the feeder link cannot transmit at its full capacity
Solution Approach 1:
The transmission system is divided into independent link sections that can be optimized separately. The feeder link uses high-order modulation for maximum throughput while user links use lower-order modulation for reliable reception, with transmodulation at the satellite bridging the two sections to resolve the contradiction between reliability and throughput
Solution Approach 2:
Different modulation quality levels are applied to different parts of the transmission system. High-order modulation provides high throughput on the strong feeder link, while lower-order modulation ensures reliable reception on weaker user links, allowing each section to have the appropriate signal characteristics for its specific requirements
Data Source
AI summary
Methods, systems, and apparatus for transmodulation in multi-beam satellite communication systems. In some implementations, a gateway receives bitstreams for transmission on different forward links from a satellite to terminals. The gateway is configured to modulate data for transmission on a feeder link for transmissions from the gateway to a satellite, including using a same symbol constellation to modulate data to provide different numbers of bits per symbol. The gateway can be configured to select symbols for transmission from among different subsets of the symbols in the symbol constellation to achieve different numbers of bits per symbol. The gateway can also be configured to select symbols for transmission from among one of the subsets determined based at least in part on a measure of signal strength for the feeder link.