A-PPDU LTF Phase Rotation for Lower Wireless PAPR
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Solution Overview
Problem
The generation of a large peak to average power ratio (PAPR) in the downlink transmission of aggregated physical layer protocol data units (A-PPDUs) in wireless local area networks (WLANs) due to the direct sending of long training field (LTF) sequences, particularly in EHT-AP scenarios with non-AP STAs operating on 80 MHz or 160 MHz bandwidths, is a challenge.
Innovation Solution
Adjusting the LTF sequence sending manner by performing phase rotation on segments of HE and EHT LTF sequences using specific phase rotation parameters, including at least one parameter value of -1, to alter the superposition of tones and reduce the total PAPR in A-PPDU transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If LTF sequences are directly sent in A-PPDU downlink transmission, then transmission simplicity is maintained, but peak to average power ratio (PAPR) becomes excessively large
Solution Approach 1:
The patent applies phase rotation parameters to the LTF sequences in A-PPDU transmission. Specifically, different phase rotation parameters (e.g., 1, -1, j, -j) are applied to different LTF sequences or segments, which changes the signal characteristics and reduces the PAPR while maintaining transmission functionality. This parameter modification approach directly addresses the contradiction by transforming the signal without complicating the transmission process.
2Object-generated harmful factors
If phase rotation with multiple parameters is applied to LTF sequences, then PAPR is reduced, but signal processing complexity increases
Solution Approach 1:
The patent segments the A-PPDU transmission into multiple parts, each with its own LTF sequence that can be independently phase-rotated. This segmentation allows the phase rotation operation to be applied in a distributed manner across different segments rather than requiring complex global processing, thereby reducing the overall processing complexity while still achieving PAPR reduction across the entire transmission.
Solution Approach 2:
The patent uses a limited set of discrete phase rotation parameters (1, -1, j, -j) rather than continuous parameter adjustment. This quantization of parameters simplifies the processing requirements while still providing sufficient flexibility to reduce PAPR effectively. The discrete nature of these parameters makes implementation more straightforward compared to continuous parameter optimization.
Data Source
AI summary
A data transmission method and a communication apparatus are disclosed. The method includes: determining an aggregated physical layer protocol data unit (A-PPDU), where the A-PPDU includes at least two PPDUs belonging to different protocols, the A-PPDU includes a first sequence, the first sequence includes N segments of subsequences, any of the N segments of subsequences is obtained by performing phase rotation on a high efficiency-long training field (HE LTF) sequence and/or an extreme high throughput-long training field (EHT LTF) sequence based on a phase rotation parameter corresponding to the HE LTF sequence and/or a phase rotation parameter corresponding to the EHT LTF sequence, N phase rotation parameters corresponding to the N segments of subsequences include at least one phase rotation parameter whose value is −1, and N is a positive integer greater than or equal to 2; and sending the A-PPDU.