mmWave OTFS Pilot Patterns for Channel Estimation Under PA Nonlinearity
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Solution Overview
Problem
Existing channel estimation methods for mmWave OTFS systems fail to account for the nonlinear behavior of power amplifiers, leading to inter-symbol interference (ISI) and inaccurate channel parameter estimation in high mobility scenarios.
Innovation Solution
A pilot pattern and channel estimation method are developed for mmWave OTFS systems that consider the nonlinear behavior of power amplifiers, involving selective placement of pilot and guard signals within a grid defined by the communication channel's maximum delay and Doppler index, and utilize multiplicative distortion correction to remove ISI.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing channel estimation methods are used for mmWave OTFS systems, then the system can operate in high mobility scenarios, but the nonlinear behavior of power amplifiers causes inter-symbol interference and inaccurate channel parameter estimation
Solution Approach 1:
The patent applies preliminary action by designing a specialized pilot pattern and guard structure before transmission to preemptively handle the nonlinear distortion. The pilot signal is placed at specific grid positions with guard regions configured to anticipate and mitigate the inter-symbol interference that will be generated by the power amplifier's nonlinear behavior, enabling accurate channel estimation despite the anticipated distortion
Solution Approach 2:
The patent applies local quality by configuring different regions of the pilot signal with different properties. Specifically, the pilot pattern places pilot signal elements at selected grid positions defined by maximum delay and Doppler index, with zero-valued guard regions surrounding them. This local differentiation allows the receiver to distinguish between distorted pilot components and guard regions, enabling accurate channel parameter estimation while isolating the harmful nonlinear effects to specific localized areas
2Measurement precision
If pilot signal elements are placed throughout the grid, then channel estimation can be performed, but nonlinear distortion distorts the pilot and induces inter-symbol interference that destroys the guard region
Solution Approach 1:
The patent applies the taking out principle by extracting the pilot signal elements from continuous coverage and placing them only at specific selected grid positions. This selective placement removes the pilot signal from regions where it would be most vulnerable to nonlinear distortion, while maintaining enough pilot elements to enable channel estimation. The guard regions are similarly extracted and positioned to surround only the essential pilot elements
Solution Approach 2:
The patent applies local quality by creating distinct regions with different functions: pilot signal elements at selected grid positions for channel estimation, and zero-valued guard regions surrounding them to protect against distortion. This local differentiation ensures that the guard regions maintain their protective function even in the presence of nonlinear distortion, while the pilot elements provide sufficient information for accurate channel parameter estimation
3Device complexity
If conventional pilot patterns are used, then the system structure remains simple, but the multiplicative distortion depends on pilot magnitude and power amplifier parameters which complicates receiver processing
Solution Approach 1:
The patent applies parameter changes by modifying the pilot pattern configuration parameters - specifically placing pilot signal elements at selected grid positions defined by maximum delay and Doppler index, with specific guard region positioning. This parameter optimization ensures that the multiplicative distortion, while still present, follows a predictable pattern that the receiver can compensate for using known power amplifier characteristics, thereby maintaining ease of operation despite the nonlinear effects
Data Source
AI summary
The present invention provides a new pilot pattern and channel estimation method involving such pilot for mmWave OTFS systems in high mobility scenarios with non-ideal power amplifier, which is applicable in the fifth generation (5G) and beyond networks. The pilot pattern for communication signal in wireless communications involving mmWave systems with non-ideal power amplifier comprises signal including a pilot signal element, information-bearing symbol and zero as guard, wherein, position of pilot and guard are arranged to combat the effect of inter symbol interference (ISI) from nonlinear impairment of the power amplifier for accurate channel estimation.