Sub-Symbol Phase Tracking via DFT-Precoded PTRS
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Solution Overview
Problem
Wireless communication systems face challenges in accurately tracking phase errors, particularly at sub-symbol resolution, due to factors like phase noise, carrier frequency offset, and Doppler effects, which impact the performance of higher-order modulation techniques and resource utilization.
Innovation Solution
A method involving a discrete Fourier transform (DFT) is used to precode symbols, which are then frequency division multiplexed with other symbols and transmitted. The receiving device estimates phase errors based on the DFT-precoded symbols by comparing their time domain representations with reference symbols, allowing for sub-symbol phase tracking and correction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional phase tracking methods are used, then phase error tracking is performed, but sub-symbol resolution phase error estimation is insufficient
Solution Approach 1:
The patent segments the phase tracking process into distinct stages: inserting phase tracking reference signals (PTRS) at specific time-frequency positions, performing DFT on received signals, comparing with reference symbols, and applying corrections. This segmentation enables sub-symbol resolution by focusing measurement precision on specific segmented portions of the signal rather than attempting to track the entire symbol uniformly.
Solution Approach 2:
The patent introduces phase tracking reference signals (PTRS) as intermediary elements between the transmitted signal and the phase error estimation process. These PTRS serve as known reference points that mediate the comparison between received and expected signals, enabling precise sub-symbol phase error measurement without directly processing the entire data signal.
2Productivity
If higher-order modulation techniques are used, then data transmission capacity increases, but susceptibility to phase noise and frequency offset increases
Solution Approach 1:
The patent implements a feedback mechanism where phase error is estimated by comparing received PTRS with reference symbols, corrections are generated based on this estimation, and these corrections are applied to compensate for phase noise and frequency offset. This closed-loop feedback enables higher-order modulation to be used reliably by continuously correcting phase errors that would otherwise degrade performance.
Solution Approach 2:
The patent performs preliminary phase error estimation and correction using PTRS before full data signal processing. By预先 (in advance) identifying and correcting phase errors using the reference signals, the system prepares the received signal to be more robust against phase noise, enabling reliable higher-order modulation without being overwhelmed by harmful phase variations.
3Measurement precision
If phase error correction is applied, then signal accuracy improves, but computational complexity increases
Solution Approach 1:
The patent extracts only the necessary phase error information from the received signal by focusing processing on specific PTRS positions rather than analyzing the entire signal. This extraction approach achieves accurate phase error measurement while minimizing computational complexity by avoiding unnecessary processing of all signal components.
Solution Approach 2:
The patent applies partial action by performing phase error correction only at the PTRS positions and then extrapolating or interpolating these corrections to the data signal, rather than processing every sample point. This partial processing achieves sufficient signal accuracy while significantly reducing computational complexity compared to full-signal processing.
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AI summary
Methods, systems, and devices for wireless communications are described for phase error estimation and correction with sub-symbol resolution. A transmitting device may precode symbols (e.g., phase tracking reference signal (PT-RS) symbols) using a discrete Fourier transform (DFT). The transmitting device may map the DFT-precoded symbols to sets of adjacent subcarriers of a wireless signal, and may map other symbols to other subcarriers of the wireless signal. A receiving device may receive the wireless signal and may compare time domain representations of the DFT-precoded symbols with time domain representations of known reference symbols. The receiving device may estimate a phase error with sub-symbol resolution in the time domain based at least in part on the comparison, and may apply a phase correction in either the time or frequency domain to the other symbols.