Phase Rotation for PPDU Legacy Preamble PAPR Reduction
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Solution Overview
Problem
Next-generation WLAN systems face challenges in optimizing Peak to Average Power Ratio (PAPR) during PPDU transmission in 160, 240, and 320 MHz bands, affecting spectrum efficiency and throughput, especially in dense environments with high user loads and interference.
Innovation Solution
A method and device for setting phase rotation values applied to legacy preambles in PPDU transmissions, using specific phase rotation values for L-STF and L-LTF fields, derived from existing 802.11ax phase rotation values, to minimize PAPR across different frequency bands, optimizing subcarrier allocation and throughput.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a PPDU is transmitted through a 160, 240, or 320 MHz band without optimized phase rotation, then the transmission bandwidth is increased, but the PAPR deteriorates
Solution Approach 1:
The patent applies different phase rotation values to different subcarriers within the legacy preamble. Specifically, it uses a first phase rotation value for subcarriers in the first 80 MHz band and a second phase rotation value for subcarriers in the second 80 MHz band. This local differentiation optimizes PAPR performance in each band while maintaining the overall wide bandwidth transmission capability.
2Device complexity
If a single phase rotation value is applied to the entire legacy preamble, then the device complexity is reduced, but the PAPR optimization is insufficient
Solution Approach 1:
The patent segments the legacy preamble into different parts based on frequency bands. It divides the 160/240/320 MHz band into multiple 80 MHz sub-bands and applies different phase rotation values to each segment. This segmentation allows independent optimization of PAPR for each band while keeping the overall system manageable.
Solution Approach 2:
The patent introduces dynamic phase rotation adjustment by selecting different phase rotation values (first or second) for different 80 MHz bands based on transmission conditions. This dynamic approach enables adaptive PAPR optimization without requiring complex reconfiguration of the entire system.
3Reliability
If phase rotation values are optimized for each 80 MHz band, then the PAPR is minimized, but the calculation complexity increases
Solution Approach 1:
The patent changes the phase rotation parameter values systematically for different frequency bands. It defines specific phase rotation values (e.g., 0, π/2, -π/2, π) for different 80 MHz bands, allowing the system to achieve PAPR optimization through parameter adjustment rather than complex computational methods.
Data Source
AI summary
A method and a device for transmitting a PPDU in a WLAN system are proposed. Specifically, a transmission device generates a PPDU and transmits the PPDU to a reception device through a 320 MHz band. The PPDU includes a legacy preamble and an EHT field, and the legacy preamble includes an L-STF and an L-LTF. The legacy preamble is generated by applying a first phase rotation value or a second phase rotation value. The first phase rotation value is obtained based on a third phase rotation value and a fourth phase rotation value. The third phase rotation value is a phase rotation value obtained by repeating a phase rotation value defined when the PPDU is transmitted in an 80 MHz band four times. The fourth phase rotation value is a phase rotation value defined for each 80 MHz band in the 320 MHz band based on an optimal PAPR of the L-STF.