Adaptive Data Rate Selection for Satellite Links
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Solution Overview
Problem
Existing satellite communication links waste power due to excess link margin during normal conditions, as they are designed to handle occasional degradations, leading to inefficient use of power and bandwidth.
Innovation Solution
The system adjusts the data rate over the air to minimize wasted power by varying the link margin, using feedback from terminals to determine the optimal data rate for transmission and reception, while maintaining constant transmitter power, allowing multiple data rates and changing modulation symbol rates to optimize packet data rate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If satellite communication links are designed with excess link margin to overcome occasional link degradations, then reliability is improved, but power efficiency deteriorates due to wasted power during normal link conditions
Solution Approach 1:
The patent applies dynamics by making the data rate adjustable and adaptive rather than fixed. The system dynamically changes the data rate based on current link conditions, allowing the link margin to be optimized for each transmission. This resolves the contradiction by enabling the system to maintain reliability when needed while improving power efficiency during normal conditions through lower data rates.
Solution Approach 2:
The patent changes the data rate parameter based on link conditions and terminal mobility. By adjusting this key parameter, the system can operate at lower data rates during stable conditions (improving power efficiency) and switch to higher data rates when reliability is compromised (maintaining link reliability). This parameter adaptation directly resolves the contradiction between reliability and power efficiency.
2Reliability
If satellite communication links are designed with excess link margin, then link reliability under degradation is improved, but bandwidth efficiency deteriorates during normal conditions
Solution Approach 1:
The system dynamically adjusts the data rate based on terminal mobility and link conditions. During normal conditions with stable links, it operates at lower data rates to maximize bandwidth efficiency. When link degradation occurs, it dynamically increases the data rate to maintain reliability, thus resolving the contradiction between reliability under degradation and bandwidth efficiency during normal operation.
Solution Approach 2:
The patent changes the data rate parameter adaptively based on measured link quality and terminal movement. This parameter change allows the system to optimize bandwidth efficiency during good conditions while ensuring reliability when degradation occurs, directly addressing the contradiction between these two performance metrics.
3Loss of energy
If constant transmitter power is used, then power efficiency is improved by avoiding excess power transmission, but adaptability to varying link conditions deteriorates
Solution Approach 1:
The patent changes the data rate parameter while maintaining constant transmitter power. This allows the system to adapt to varying link conditions by adjusting the modulation and coding scheme rather than changing power levels. The receiver adapts to different data rates, enabling the system to maintain power efficiency while achieving adaptability to different link conditions through parameter flexibility.
Solution Approach 2:
The system applies local quality by allowing different data rates for different terminals based on their specific link conditions and mobility characteristics. Each terminal receives optimized data rate treatment locally, enabling adaptability to individual conditions while the overall system maintains constant power transmission, thus resolving the contradiction between power efficiency and adaptability.
Data Source
AI summary
A method an apparatus for selecting a forward link and return link data rate for a constant power, variable data rate two-way, mobile satellite communications link. The forward link and return link signal strength (in the form of carrier power to noise power spectral density ratio) is measured, cataloged, and the values are used for the data rate selection. In addition, a ping can be sent by the network operation center to the mobile unit and the response to the ping is used for updating the information of both forward link and return link signal strength, so the chance of wrong data rate selection can be reduced. Multiple re-transmission attempts combined with gradually increased re-transmission margin ensures the proper data rate decision can be eventually achieved even with occasionally inaccurate signal strength information.