Satellite Link Power Control Using Downlink Beacon
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Solution Overview
Problem
Traditional closed loop power control schemes in satellite communications systems are ineffective in dynamic and high interference environments due to the inability to track rapid changes in signal-to-noise plus interference ratio (SINR) caused by interference from nearby spot beams, leading to fluctuations in end-to-end signal quality.
Innovation Solution
The method adjusts the effective isotropic radiated power (EIRP) of user terminals based on the difference between the message signal power and a target signal power, determined by factors such as frequency gain, path gain, satellite beacon signal power, and gateway calibration data, to maintain balanced signal power spectral densities and mitigate dynamic interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional closed loop power control schemes are used to adjust EIRP at user terminals in response to measured SINR, then power control feedback is provided, but the schemes cannot track dynamic interference because round trip delay through a geo-synchronous satellite is more than 500 mSec, leading to poor performance in dynamic and high interference environments
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing optimal EIRP values in lookup tables at the gateway terminal before interference occurs. When interference is detected, the gateway simply retrieves the pre-computed EIRP value from the lookup table based on current channel conditions, avoiding real-time computation delays and rapid feedback requirements. This eliminates the need for fast closed-loop feedback while maintaining effective power control in dynamic interference environments.
2Productivity
If interference from nearby spot beams operating on the same frequency is present, then bandwidth utilization increases, but end-to-end signal to noise plus interference ratio (SINR) fluctuates by 5 dB or more due to dynamic interference
Solution Approach 1:
The gateway terminal pre-calculates optimal EIRP values for user terminals based on predicted interference conditions from nearby spot beams. These pre-computed values are stored in lookup tables that map channel conditions to recommended power levels. By preparing power control adjustments in advance rather than reacting to SINR fluctuations, the system maintains stable signal quality while utilizing available bandwidth efficiently, even in high interference environments with dynamic spot beam patterns.
Solution Approach 2:
The patent skips the traditional rapid feedback loop by directly implementing open-loop power control using pre-computed EIRP values. Instead of measuring SINR, waiting for feedback, and adjusting power in a slow closed loop, the system rushes through the power control adjustment by having the gateway terminal proactively set EIRP based on pre-analyzed interference conditions, thereby eliminating the feedback delay bottleneck and rapidly adapting to interference changes.
3Ease of operation
If EIRP is adjusted based on measured SINR with round trip delay greater than 500 mSec, then power control feedback is provided, but the adjustment cannot track dynamic interference changes occurring in bursts as short as 10 μSec
Solution Approach 1:
The gateway terminal performs preliminary analysis of interference patterns from nearby spot beams and pre-computes optimal EIRP adjustments before interference bursts occur. These pre-calculated power control values are stored in lookup tables indexed by channel conditions. When transmitting to user terminals, the gateway provides these pre-computed EIRP values, enabling the terminals to adjust their power immediately without waiting for slow feedback loops. This approach maintains operational simplicity while achieving rapid adaptation to dynamic interference changes.
Solution Approach 2:
The patent skips the traditional feedback measurement and adjustment cycle by implementing proactive open-loop power control. The gateway terminal rushes through the power control decision-making process by pre-calculating EIRP values based on predicted interference conditions and directly communicating these to user terminals. This eliminates the need for slow SINR measurement and feedback, enabling the system to track and respond to ultra-short interference bursts (10 μSec) that are far faster than the 500+ mSec feedback loop could handle.
Data Source
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AI summary
A method for determining EIRP of user terminals in a satellite communication system comprises obtaining a frequency gain of a gateway at one or more frequencies, obtaining a path gain of the gateway for one or more signal paths, and obtaining a satellite beacon signal power at a receiver of the gateway. The method also comprises determining a target signal power at the gateway for one or more frequency channels, where the target signal power based at least in part on the frequency gain, the path gain, and the satellite beacon signal power. The method also comprises obtaining a message signal power at the gateway of a message from a user terminal, and determining the EIRP of the user terminal based at least in part on a difference between the target signal power and the message signal power.