PTRS Placement in Pre-DFT Sequences for Phase Noise Tracking
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Solution Overview
Problem
Next-generation wireless communication systems face challenges in phase noise tracking and compensation due to the placement of phase tracking reference signal (PTRS) groups at the end of OFDM symbols, which degrades the receiver's ability to perform phase noise tracking and compensation, affecting overall link performance.
Innovation Solution
The method involves constructing and acquiring pre- and post-DFT sample sequences with strategically placed PTRS groups within the OFDM signal, ensuring the last PTRS group is positioned a certain number of samples before the end of the sequence, and arranging multiple PTRS groups with equal spacing to facilitate accurate phase noise estimation and interpolation, thereby improving phase noise tracking and compensation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the last PTRS group is located at the tail of an OFDM symbol (at the last several samples), then the PTRS provides phase noise tracking information, but it degrades the receiver's capability to perform phase noise tracking and compensation
Solution Approach 1:
The patent extracts the problematic PTRS group from the tail region of the OFDM symbol and relocates it to a safe position before the tail. Specifically, the last PTRS group is positioned at samples M-B to M-1, where B is the timing offset parameter, ensuring it does not overlap with the tail region M-T to M-1. This separation resolves the conflict between providing phase noise tracking information and avoiding degradation of tracking capability.
Solution Approach 2:
The patent performs preliminary positioning of the last PTRS group before the tail region begins. By placing the PTRS group at M-B to M-1 (where B > 0), the system proactively prevents the PTRS from encroaching into the tail region M-T to M-1, thereby avoiding the degradation of phase noise tracking capability before it can occur.
2Measurement precision
If multiple PTRS groups are arranged with equal spacing within the pre-DFT sample sequence, then phase noise interpolation becomes simpler and more accurate, but the positioning constraints become more complex
Solution Approach 1:
The patent applies different positioning strategies to different PTRS groups. While maintaining equal spacing for most PTRS groups to enable simple linear interpolation, the last PTRS group is given special treatment by positioning it at M-B to M-1 to avoid the tail region. This local differentiation resolves the conflict between uniform spacing benefits and positioning constraints.
3Ease of operation
If the PTRS groups are placed uniformly within an OFDM symbol, then intra-symbol phase noise interpolation is simplified with a single linear interpolation filter, but the last PTRS group may fall into the tail region causing tracking degradation
Solution Approach 1:
The patent extracts the last PTRS group from the uniform spacing pattern and relocates it to a specific position M-B to M-1 that guarantees it will not fall into the tail region. This allows the remaining PTRS groups to maintain uniform spacing for simple linear interpolation, while the extracted last group ensures tracking reliability.
Data Source
AI summary
An apparatus for constructing a pre-DFT sample sequence for an OFDM-signal is provided. The apparatus comprises: a processor configured to construct a pre-DFT sample sequence with a pre-defined length such that it comprises data; and a PTRS-group, wherein the last sample of the PTRS-group is placed within the pre-DFT sample sequence at a pre-defined position located B samples before the end of the pre-DFT sample sequence.