LTF Sequence Construction for Wideband WLAN Channel Estimation
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Solution Overview
Problem
The existing IEEE 802.11 standards are limited to a maximum bandwidth of 320 MHz, and there is a need for improved channel estimation in next-generation wireless local area networks (WLANs) to support higher bandwidths, particularly in reducing peak-to-average power ratio (PAPR) and channel estimation errors.
Innovation Solution
A communication method and apparatus that generates and receives LTF sequences in a 2x mode, based on a basic LTF sequence corresponding to a basic subchannel, to support bandwidths greater than 320 MHz, reducing PAPR and channel estimation errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the bandwidth of PPDU is increased beyond 320 MHz to support next-generation WLAN requirements, then the wireless transmission capacity and throughput are improved, but the peak-to-average power ratio (PAPR) of the LTF signal increases and channel estimation accuracy deteriorates
Solution Approach 1:
The patent divides the large-bandwidth LTF sequence into multiple basic LTF sequences corresponding to different basic subchannels. Each basic LTF sequence is designed for a specific subchannel bandwidth (e.g., 80 MHz), and these segmented sequences are then combined through frequency-domain multiplication with subchannel unit matrices to form the complete large-bandwidth LTF sequence. This segmentation approach allows the system to handle bandwidths beyond 320 MHz while maintaining controlled PAPR and accurate channel estimation.
Solution Approach 2:
The patent applies different LTF sequence designs to different subchannels based on their specific characteristics. By designing basic LTF sequences optimized for individual subchannels and then combining them, the system ensures that each local segment (subchannel) maintains optimal signal quality and estimation accuracy, which collectively improves overall system performance in large-bandwidth scenarios.
2Productivity
If the bandwidth of PPDU is increased beyond 320 MHz, then the throughput performance is improved, but the peak-to-average power ratio (PAPR) of the LTF signal increases causing signal distortion
Solution Approach 1:
The patent segments the large-bandwidth LTF sequence into multiple basic LTF sequences, each optimized for a specific subchannel. This segmentation prevents the PAPR from becoming excessively high across the entire bandwidth, as each basic sequence maintains controlled peak power characteristics. The segmented sequences are then combined through frequency-domain operations to achieve the desired large bandwidth while maintaining acceptable PAPR levels.
Solution Approach 2:
The patent changes the structural parameters of the LTF sequence by introducing subchannel unit matrices and modifying the sequence construction approach. Instead of using a single monolithic LTF sequence for the entire bandwidth, the system uses multiple basic sequences with specific mathematical relationships (frequency-domain multiplication), which alters the power distribution characteristics and reduces peak-to-average ratio.
Data Source
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AI summary
Disclosed are a communication method and apparatus, applied to the field of communication technologies. They are applicable to wireless local area network systems supporting IEEE 802.11 series protocols such as a next-generation Wi-Fi protocol of 802.11ax, for example, 802.11be, Wi-Fi 7 or EHT, and a next generation of 802.11be, Wi-Fi 8, UHR, Wi-Fi AI, or millimeter wave (MMW); and also applicable to WPAN systems, sensing systems, and the like supporting UWB. A first communication apparatus generates a PPDU, and sends the PPDU. A second communication apparatus receives the PPDU, and performs channel estimation based on an LTF sequence. The PPDU includes an LTF carrying the LTF sequence. The LTF sequence corresponds to a bandwidth of the PPDU. The LTF sequence is determined based on a basic LTF sequence. The LTF sequence is a sequence in a 2x mode. The LTF sequence can effectively reduce a channel estimation error.