Multicarrier Satellite Link Pre-Compensation for Doppler Orthogonality
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In multicarrier communication systems, especially in satellite-based scenarios, Doppler-induced frequency and time offsets cause inter-carrier interference, reducing performance due to the need for tight synchronization and increased complexity, especially when channel conditions vary dynamically.
Innovation Solution
A method that involves predicting and pre-compensating for mobility-related channel offsets by determining targetable subcarriers and allocating resources to ensure orthogonality at the access node, using a channel state tracker to estimate and adjust for frequency and time offsets, thereby optimizing subcarrier allocation and reducing interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If tight time and frequency synchronization is enforced to maintain orthogonality between users' signals, then orthogonality is maintained, but device complexity and processing requirements increase significantly
Solution Approach 1:
The patent applies preliminary action by having transmitters pre-compensate for channel offsets before transmission. The access node estimates channel offsets (Doppler frequency shifts and time offsets) and communicates these estimates to transmitters, which then adjust their signals in advance to counteract the expected channel effects, eliminating the need for tight synchronization during transmission
Solution Approach 2:
The patent implements feedback by having the access node estimate channel offsets from received signals and communicate these estimates back to the transmitters. This feedback loop enables transmitters to adapt their signals based on actual channel conditions, maintaining orthogonality without requiring complex real-time synchronization mechanisms
2Reliability
If feedback channel is used to provide channel offset estimates to transmitters for pre-compensation, then orthogonality is maintained, but receive processing complexity at the access node increases
Solution Approach 1:
The patent extracts the complex processing function from the access node and relocates it to the transmitters. Instead of the access node performing complex real-time offset correction, the access node only estimates offsets and communicates them via feedback, while the transmitters perform the actual pre-compensation processing, simplifying the access node's receive processing requirements
3Object-affected harmful factors
If fixed guard bands and guard intervals are used to provide time and frequency separation, then interference is reduced, but spectral efficiency decreases
Solution Approach 1:
The patent converts the harmful channel offsets (Doppler shifts and time offsets) into beneficial information by having the access node estimate and communicate these offsets to transmitters. Transmitters then use this information to pre-compensate their signals, transforming the channel's adverse effects into opportunities for maintaining orthogonality without requiring guard bands or guard intervals, thereby eliminating waste of spectral resources
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 spectral efficiency by maintaining orthogonality between signals despite Doppler effects, reducing processing complexity and interference, and allowing for dynamic channel resource allocation.
Implementation Method 1
relative movement between the access node and the plurality of terminals generates one or more mobility related channel offsets. The one or more channel offsets comprise one or more mobility related channel offsets
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
Methods and apparatus for communication between terminals and an access node in a multiuser multicarrier communications network are described. The access node may be a satellite access node. Terminals are configured to perform initial estimation and tracking of channel offsets and to estimate channel offsets for future packets to be transmitted by the terminal. In some embodiments the channel offsets comprise mobility related channel offsets due to the relative movement between the access node and the plurality of terminals. Transmissions from the terminals to the access node are pre-compensated for the channel offsets, so that the aggregate signal received by the access node occupies a bandwidth greater or equal to the maximum signal bandwidth of any individual terminal. Terminal transmissions may overlap in frequency and time on the ground, but arrive orthogonally at the access node.