Phase Rotation for PAPR Reduction in 320 MHz WLAN Preambles
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Solution Overview
Problem
Existing WLAN systems face challenges in efficiently transmitting PPDU through broadband, particularly in optimizing PAPR for L-STF and L-LTF while considering limited preamble puncturing.
Innovation Solution
A method and apparatus for setting a phase rotation value applied to a legacy preamble to optimize PAPR in L-STF or L-LTF, specifically designed for the next generation WLAN system (IEEE 802.11be) with broadband transmission of 240 MHz or 320 MHz.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a legacy preamble is transmitted through broadband (240 MHz or 320 MHz) without phase rotation optimization, then the transmission structure is simple, but the PAPR is high which limits transmission power and range
Solution Approach 1:
The patent applies phase rotation parameter changes to the legacy preamble sequences. Specifically, it introduces a phase rotation value (e.g., multiplying by -1 or j) applied to specific fields (L-STF, L-LTF, or L-SIG) within the legacy preamble. This parameter modification reduces the PAPR of the broadband signal while maintaining backward compatibility with legacy devices that can still decode the rotated preamble using standard procedures.
2Power
If preamble puncturing is applied to reduce PAPR, then transmission power can be increased, but the preamble structure becomes more complex and compatibility is reduced
Solution Approach 1:
Instead of applying uniform puncturing across the entire preamble, the patent applies phase rotation selectively to specific local regions or fields within the legacy preamble (such as L-STF, L-LTF, or L-SIG). This localized parameter modification reduces PAPR in critical sections while preserving the overall preamble structure that legacy devices rely upon, thereby maintaining compatibility while achieving power optimization.
3Length of stationary object
If phase rotation is applied to optimize PAPR, then transmission range is increased, but the signaling complexity increases
Solution Approach 1:
The phase rotation scheme is designed to be self-service in nature. The receiving device, whether legacy or next-generation, can autonomously determine the phase rotation value based on predefined rules or indicators in the signal structure. Next-generation devices can detect the rotation and compensate accordingly, while legacy devices simply process the rotated signal as-is. This self-service mechanism extends transmission range without requiring complex centralized control or additional signaling overhead.
Data Source
AI summary
Presented are a method and a device for receiving a PPDU in a wireless LAN system. Particularly, a receiving STA receives a PPDU from a transmitting STA through a broadband, and decodes the PPDU. The PPDU includes a legacy preamble and first and second signal fields. The legacy preamble and the first and second signal fields are generated on the basis of a first phase rotation value. The first phase rotation value is acquired on the basis of a first preamble puncturing pattern of the broadband. The first preamble puncturing pattern includes the pattern in which 40 MHz or 80 MHz band is punctured in the broadband, when the broadband is a 320 MHz band. The first phase rotation value is [1 −1 −1 −1 1 −1 −1 −1 −1 1 1 1 −1 1 1 1].