Satellite Synchronization Signal Detection Under Doppler and VLSNR
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In non-terrestrial 5G networks, the detection of synchronization signals by user terminals is challenging due to unfavorable link conditions, including very low signal-to-noise ratios (VLSNR) and significant frequency shifts caused by satellite motion, especially in Low Earth Orbit scenarios, which complicates the cell search procedure.
Innovation Solution
A method for user terminals to receive and process synchronization transmissions using a combination of correlation techniques and frequency correction to detect and decode synchronization signals, including PSS, SSS, and PBCH, despite unknown frequency and time offsets, by employing three-dimensional correlation and coherent combining of signal instances to enhance detection quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If satellite is placed in Low Earth Orbit to minimize latency, then response time is improved, but signal-to-noise ratio deteriorates to very low levels due to larger distance and rain fades
Solution Approach 1:
The patent applies preliminary action by performing frequency offset compensation and signal combining operations before final signal detection and decoding. The receiver pre-processes multiple received signal instances by compensating for frequency offsets caused by satellite motion and combining them coherently, thereby improving signal-to-noise ratio before the actual detection stage, which enables reliable communication despite the VLSNR conditions imposed by LEO satellite distances
2Speed
If satellite moves at high speed (about 25,000KPH) to maintain orbit, then orbital positioning is achieved, but frequency shift increases to exceed 300kHz causing detection difficulty
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the frequency offset compensation parameter based on the satellite's velocity and orbital position. The receiver estimates the Doppler frequency shift caused by the satellite's high-speed motion (exceeding 300kHz) and applies compensating frequency shifts to the received signal, thereby transforming the signal parameters back to the expected frequency range for reliable synchronization signal detection
Solution Approach 2:
The patent implements feedback by using the detected synchronization signal and channel state information to continuously update and refine the frequency offset compensation. The receiver monitors the received signal quality and adjusts the frequency compensation parameters in real-time based on feedback from the detection process, enabling adaptive tracking of the satellite's motion-induced frequency variations
3Adaptability or versatility
If rain fades affect Ku-band or Ka-band signals, then signal attenuation increases, but these frequency bands remain necessary for satellite communication licensing
Solution Approach 1:
The patent applies merging by combining multiple received signal instances or diversity branches (such as multiple antennas or repeated transmissions) to combat rain fade effects. By coherently combining the signals after frequency offset compensation, the receiver achieves signal-to-noise ratio improvement that overcomes the attenuation caused by rain fades in licensed Ku-band or Ka-band frequencies
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
The method effectively enables initial connectivity in non-terrestrial networks by overcoming VLSNR and frequency offsets, allowing accurate extraction of network identifiers and essential parameters for network access, thereby improving synchronization and reducing detection errors.
Implementation Method 1
significant frequency shifts caused by satellite motion, especially in Low Earth Orbit scenarios
Implementation Method 2
frequency correction to detect and decode synchronization signals, including PSS, SSS, and PBCH, despite unknown frequency and time offsets
Data Source
Figure 1~2
Figure 3
Figure 4
AI summary
Methods are described for synchronization in a non-terrestrial network. A satellite communication terminal may receive, over its satellite link, synchronization transmissions containing one or more synchronization signals. The synchronization transmission may be received with an unknown frequency offset and/or at very low signal-to-noise ratio, and/or the synchronization signals may be formatted in any of several predefined patterns, making detection and/or demodulation of the one or more synchronization signals a challenge. According to the methods described herein, detection of at least one synchronization signal may include about simultaneous correlation in 3 dimensions of multiple instances of the at least one synchronization signal. The correlation result may then be used for generating a fine-resolution frequency correction, once applied demodulation of one or more additional synchronization signals and extraction of network access information becomes possible.