Reference Signal Transmission for Phase Noise Estimation
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Solution Overview
Problem
In high-frequency wireless communications, phase noise caused by the random jitter of local oscillators leads to inaccurate channel state information (CSI) estimation due to varying phase errors across OFDM symbols, especially when using existing SRS and CSI-RS methods that rely on frequency hopping and code division, which fail to provide a common reference for phase noise estimation.
Innovation Solution
A method involving the transmission of a first reference signal (e.g., SRS) and a second reference signal (PT-RS) where the PT-RS is mapped to the same frequency-domain location across multiple symbols, allowing for relative phase error calculation and improved CSI estimation by ensuring phase tracking accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If frequency hopping and code division are used for reference signal transmission, then spectrum resources are efficiently utilized, but phase noise estimation accuracy deteriorates due to lack of common reference across symbols
Solution Approach 1:
The patent introduces a phase tracking reference signal (PT-RS) as an intermediary element that remains at the same frequency-domain location across multiple symbols. This PT-RS serves as a common reference point that mediates between the frequency-hopping SRS/CSI-RS signals and the phase noise, enabling accurate phase error estimation without sacrificing spectrum resource efficiency
Solution Approach 2:
The patent segments the reference signal functionality into two distinct parts: (1) frequency-hopping SRS/CSI-RS for channel sounding and coverage, and (2) stationary PT-RS for phase tracking. This segmentation allows each component to optimize its specific function while working together to solve the overall problem
2Reliability
If reference signals are mapped to different frequency locations across symbols, then frequency diversity is achieved, but phase error varies making CSI estimation inaccurate
Solution Approach 1:
The PT-RS acts as a stationary intermediary reference that remains at the same frequency location across symbols, providing a consistent phase reference point. This allows the system to maintain frequency diversity through SRS/CSI-RS hopping while using the PT-RS to measure and compensate for phase errors
Solution Approach 2:
The patent implements a feedback mechanism where the receiver measures phase errors using the stationary PT-RS and feeds back this information to correct the CSI estimation. The phase error measured from PT-RS is used to compensate for phase variations in the frequency-hopping reference signals
3Measurement precision
If multiple reference signals are transmitted for channel estimation, then channel state information quality improves, but device complexity increases due to additional signaling overhead
Solution Approach 1:
The patent segments reference signal functions into specialized components: SRS/CSI-RS for channel sounding and PT-RS for phase tracking. This segmentation improves CSI quality by giving each signal type a dedicated function, while the modular design allows for efficient resource allocation that manages complexity
Data Source
AI summary
Embodiments of the present invention disclose a reference signal transmission method, including: sending, by a terminal, a first reference signal and a second reference signal; and correspondingly, receiving, by a network device, the first reference signal and the second reference signal, where the first reference signal is mapped to a plurality of symbols and is used for estimation of channel state information, the second reference signal is mapped to at least two of the plurality of symbols and is used for phase tracking, and a subcarrier to which the second reference signal is mapped on one of the at least two symbols has a same frequency-domain location as a subcarrier to which the second reference signal is mapped on the rest of the at least two symbols. With the foregoing solution, accuracy of channel state information estimation can be improved.