NTN Uplink Frequency Pre-Compensation for Doppler and Delay Drift
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Solution Overview
Problem
In non-terrestrial network (NTN) communications, the lack of accurate timing and frequency compensation due to propagation delay and Doppler shift leads to phase distortion and demodulation performance degradation, particularly in connected mode, as user equipment (UE) needs to compensate for feeder and service link delays and drift rates to synchronize uplink signals effectively.
Innovation Solution
The proposed solution involves UE obtaining center frequency and reference time, along with feeder and service link delays and drift rates, to perform uplink frequency pre-compensation by calculating the transmit frequency, adjusting sampling rates, and compensating for Doppler shifts and delay drifts, using system information blocks (SIBs) or ephemeris data for precise timing and frequency adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If timing and frequency compensation is performed in NTN communications to account for propagation delay and Doppler shift, then demodulation performance is improved, but the complexity of the system increases due to the need for multiple parameters (UE position, satellite position and velocity, time reference, feeder link delay, service link delay drift rate)
Solution Approach 1:
The patent applies preliminary action by having the network node pre-calculate and signal the uplink frequency offset to the UE before the UE transmits uplink signals. The network node computes the frequency offset based on known parameters (center frequency, reference time, feeder link delay, service link delay drift rate) and provides this compensation value to the UE, allowing the UE to apply the correct frequency offset without performing complex real-time calculations itself.
Solution Approach 2:
The patent uses the network node as an intermediary that centralizes the complex timing and frequency compensation calculations. Instead of each UE independently calculating compensation parameters, the network node acts as a mediator that receives information about the NTN configuration, performs the complex computations, and distributes the resulting frequency offset values to multiple UEs, thereby reducing individual UE complexity while maintaining overall system performance.
2Reliability
If the UE performs uplink frequency pre-compensation using feeder link delay and service link delay drift rate, then phase distortion is reduced, but the loss of information increases due to the need for the UE to obtain and process multiple parameters from system information blocks or ephemeris data
Solution Approach 1:
The patent applies self-service by enabling the network node to autonomously calculate and provide the uplink frequency offset without requiring the UE to independently process and synthesize multiple parameters. The network node retrieves necessary information from system information blocks or ephemeris data, performs the frequency offset calculation, and delivers the result to the UE, thereby reducing the information processing burden on the UE while ensuring accurate phase compensation.
3Measurement precision
If accurate timing compensation is implemented using reference time and service link delay, then synchronization is improved, but the device complexity increases due to the need for continuous tracking of delay drift rates
Solution Approach 1:
The patent applies preliminary action by having the network node pre-calculate the uplink frequency offset incorporating service link delay drift rate effects before the UE transmits. This advance calculation allows the UE to apply a static frequency offset correction without needing to continuously track or recalculate drift rates, thereby maintaining timing synchronization accuracy while reducing the complexity of continuous tracking operations at the UE.
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
This approach enhances demodulation performance by minimizing phase distortion and SINR degradation, ensuring effective communication in NTN environments.
Implementation Method 1
In NTN communications, in order to compensate for propagation delay and Doppler shift in wireless communications over a link, a user equipment (UE) needs to be aware of certain information
Implementation Method 2
In NTN communications, in order to compensate for propagation delay and Doppler shift in wireless communications over a link
Data Source
AI summary
Various solutions for time and frequency in non-terrestrial network (NTN) communications are proposed. An apparatus implemented in a user equipment (UE) obtains a center frequency and a reference time of a non-terrestrial network. The apparatus further obtains a feeder link delay of a feeder link between a network node and a satellite, and a service link delay drift rate of a service link between the apparatus and the satellite. Then, the apparatus performs an uplink frequency pre-compensation through calculating an uplink transmit frequency according to the center frequency, the reference time, the feeder link delay, and the service link delay drift rate.