Frequency Change Activation Signal for Satellite Doppler Shift
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Solution Overview
Problem
IoT terminals installed in remote areas face demodulation issues due to high-speed low earth orbit satellites causing in-frame Doppler shifts in downlink signals, preventing activation even with high reception levels.
Innovation Solution
A wireless communication system that includes a mobile relay station applying frequency changes to activation signals based on the altitude and position of the satellite, allowing terminal stations to demodulate and decode the signals effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the low earth orbit satellite moves at high speed, then the satellite can cover large areas quickly, but in-frame Doppler shift occurs in the downlink signal causing demodulation failure
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the frequency of the activation signal to compensate for the Doppler shift. The frequency change application unit modifies the signal frequency based on the satellite's position and velocity, transforming the harmful Doppler effect into a manageable parameter adjustment that enables reliable demodulation despite high satellite speed
Solution Approach 2:
The system implements dynamics by making the activation signal frequency adaptive rather than fixed. The frequency changes continuously according to the satellite's real-time position and velocity conditions, allowing the system to track and compensate for Doppler variations throughout the satellite's passage, thereby maintaining demodulation reliability
2Use of energy by moving object
If the IoT terminal waits for the satellite to pass overhead to transmit data, then power consumption is reduced, but the terminal cannot be activated when Doppler shift exceeds the allowable range
Solution Approach 1:
The patent applies preliminary action by transmitting the activation signal before the satellite reaches its peak overhead position. By sending the activation signal in advance and applying frequency compensation, the system ensures terminals can be activated during the approach phase when Doppler shift is manageable, rather than waiting for the peak position where Doppler shift becomes excessive
Solution Approach 2:
The frequency change application unit dynamically adjusts the activation signal frequency based on the satellite's current position and velocity parameters. This parameter change enables the terminal to successfully demodulate the activation signal even when the satellite is not at peak overhead position, allowing activation during the approach phase while maintaining low power consumption
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
Enables the activation of communication devices on the ground even when Doppler shifts occur, ensuring reliable communication with moving wireless communication devices.
Implementation Method 1
an in-frame Doppler shift occurs in the downlink signal transmitted from the low earth orbit satellite
Data Source
AI summary
There is provided a wireless communication device in a wireless communication system including one or more communication devices installed on the ground and a moving wireless communication device, the wireless communication device including: an activation signal generation unit that generates an activation signal for activating the one or more communication devices; a distribution unit that distributes the activation signal generated by the activation signal generation unit; one or more frequency change application units that apply a frequency change to the activation signal distributed by the distribution unit; and a transmission unit that transmits an activation signal to which a frequency change is applied to the one or more frequency change application units.