HE-LTF Sequence Layout for Low-PAPR 802.11ax Channel Estimation
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Solution Overview
Problem
The existing wireless local area network (WLAN) systems face high peak-to-average power ratio (PAPR) issues in channel estimation due to the use of conventional LTF sequences, which affect power control efficiency and reduce channel estimation precision, especially in high-density scenarios with increased channel access collisions.
Innovation Solution
A method for generating HE-LTF sequences with optimized subcarrier distributions and phase rotations to reduce PAPR, specifically designed for 802.11ax systems, which involves selecting and concatenating basic HE-LTF sequences with phase rotations to match different RU sizes and locations, ensuring low storage load and easy hardware implementation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If existing LTF generation methods are used in OFDMA mode, then channel estimation can be performed, but peak-to-average power ratio becomes relatively high
Solution Approach 1:
The LTF sequence is segmented into multiple parts corresponding to different resource blocks. Each segment is generated independently with optimized properties, allowing the overall sequence to maintain low PAPR while enabling accurate channel estimation for each resource block assignment.
Solution Approach 2:
Different segments of the LTF sequence are designed with locally optimized properties tailored to specific resource block assignments. This allows each local segment to contribute to low PAPR while collectively providing comprehensive channel estimation coverage across the frequency spectrum.
2Area of stationary object
If LTF sequence is designed for wide bandwidth, then channel estimation coverage is improved, but PAPR increases
Solution Approach 1:
The wide bandwidth LTF sequence is divided into multiple narrower bandwidth segments, each corresponding to specific resource blocks. This segmentation allows each segment to maintain low PAPR properties while collectively covering the entire wide bandwidth for comprehensive channel estimation.
Solution Approach 2:
The LTF sequence design transitions from a single-dimensional wideband approach to a multi-dimensional structure where sequences are organized by resource block assignments and frequency segments, enabling low PAPR in each dimension while achieving wide bandwidth coverage collectively.
Data Source
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AI summary
Embodiments of the present invention provide several long training sequences that are in a wireless local area network and that comply with 802.11ax.