HE-LTF Sequence Segmentation for Lower PAPR in 802.11ax OFDMA
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Solution Overview
Problem
The existing WiFi systems face high peak-to-average power ratio (PAPR) issues when using the 80-MHz or 160-MHz LTF sequences in the 802.11ac standard for channel estimation in the OFDMA mode of the next-generation WiFi standard (802.11ax), leading to reduced power control efficiency and channel estimation precision.
Innovation Solution
A method for generating and sending HE-LTF sequences based on bandwidth, RU size, and location, using specific sequence segments for channel estimation, with optimized phase rotations to reduce PAPR.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the existing 80-MHz or 160-MHz LTF sequences from 802.11ac standard are used in OFDMA mode, then channel estimation can be performed, but the peak-to-average power ratio (PAPR) becomes relatively high
Solution Approach 1:
The patent segments the LTF sequence into multiple parts corresponding to different resource blocks (RBs) in the OFDMA system. Instead of using a single full-bandwidth LTF sequence, the method divides the sequence into smaller segments that can be selectively applied to different users' allocated RBs, thereby reducing the PAPR while maintaining channel estimation capability.
Solution Approach 2:
The patent applies local quality by using different LTF sequence segments for different resource blocks allocated to different users. Each user receives an LTF sequence segment that is optimized for their specific RB allocation, rather than using a uniform full-bandwidth sequence. This localized approach reduces the PAPR for each user while maintaining adequate channel estimation precision for their allocated resources.
2Loss of information
If full-bandwidth LTF sequences are used for channel estimation in OFDMA, then comprehensive channel information can be obtained, but power control efficiency deteriorates due to high PAPR
Solution Approach 1:
The patent extracts only the necessary portions of the LTF sequence that correspond to each user's allocated resource blocks. Instead of transmitting full-bandwidth LTF sequences that contain information for all possible RBs, the method extracts and transmits only the relevant segments for each user's specific allocation, reducing the energy required for transmission while maintaining complete channel information for the allocated RBs.
Solution Approach 2:
The patent applies partial action by transmitting LTF sequence segments that cover only the necessary bandwidth for each user's RB allocation rather than the full system bandwidth. This partial transmission approach reduces the energy consumption and improves power control efficiency while still providing complete channel estimation information for the user's allocated resources.
Data Source
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.