Pilot-Based Phase Noise Estimation Beyond Loop Bandwidth
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Solution Overview
Problem
Existing phase noise estimation methods in digital communication systems fail to accurately measure and mitigate higher frequency components of phase noise outside the tracked loop bandwidth, leading to SNR degradation and poor QEF performance.
Innovation Solution
A method for estimating phase noise by measuring symbol phases, deriving total phase error, determining impairment contributions, and adjusting transmit parameters based on phase noise estimation, including increasing symbol rate or changing symbol composition to optimize coherent detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If phase noise is measured using a spectrum analyzer or pure carrier transmission, then measurement precision is improved, but device complexity and ease of operation deteriorate
Solution Approach 1:
The patent uses pilot symbols (known symbols) as a copy or representation of the actual signal structure to estimate phase noise. Instead of requiring a pure carrier or special test equipment, the system extracts phase noise characteristics from these pilot symbols that are already present in the transmitted signal, thereby avoiding additional measurement equipment while maintaining estimation accuracy.
Solution Approach 2:
The system performs self-measurement by using its own transmitted pilot symbols to estimate the phase noise affecting the received signal. The receiver independently calculates phase noise statistics from the received pilot symbols without requiring external measurement equipment or separate test procedures, enabling automated phase noise monitoring in production environments.
2Measurement precision
If phase noise estimation includes higher frequency components outside tracked loop bandwidth, then measurement precision is improved, but calculation complexity increases
Solution Approach 1:
The patent segments the phase noise estimation into two distinct parts: (1) tracking phase noise within the loop bandwidth using conventional phase tracking, and (2) estimating additional phase noise from higher frequency components outside the loop bandwidth by analyzing phase variations of received pilot symbols. This segmentation allows the system to capture total phase noise more accurately while managing computational complexity through modular processing.
Solution Approach 2:
The system performs partial phase noise tracking within the loop bandwidth and supplements it with additional estimation from pilot symbol analysis to capture the excessive or missing high-frequency components. This partial action approach ensures that both in-band and out-of-band phase noise contributions are accounted for without requiring full-spectrum analysis, balancing accuracy with computational feasibility.
3Reliability
If adaptive waveform adjustment is implemented based on phase noise estimation, then reliability is improved, but device complexity increases
Solution Approach 1:
The patent implements dynamic adaptation where the transmitter waveform parameters (such as symbol rate or constellation size) are adjusted in real-time based on the estimated phase noise level. When high phase noise is detected, the system dynamically changes transmission parameters to maintain reliable coherent detection, and reverses these changes when phase noise decreases, enabling flexible response to varying channel conditions.
Solution Approach 2:
The system establishes a feedback loop where phase noise is continuously estimated from received pilot symbols, and this estimation feeds back to control transmitter waveform parameters. The transmitter adjusts its operation based on this feedback information to optimize performance under current phase noise conditions, creating a closed-loop adaptive system that improves reliability through continuous optimization.
Data Source
AI summary
A method is provided for adjusting at least one transmit parameter of a digital transmitter of a communication system by estimating phase noise of a sequence of symbols received in a demodulator of a digital receiver of the communication system. The method includes: measuring a phase for the symbols of the sequence, deriving a total phase error for the sequence from the measured phases, determining a characteristic of the total phase error, deriving, based on a signal quality estimation of the received sequence of symbols, an indication of a contribution to the characteristic from at least one impairment different from phase noise, obtaining a phase noise estimation by subtracting the indication of the contribution from the characteristic of the total phase error, adjusting the at least one transmit parameter depending on the obtained phase noise estimation.