Sub-channel Phase Rotation for PAPR Reduction in WLAN
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Solution Overview
Problem
Current WLAN communication systems face challenges in achieving high throughput with 80 MHz or greater bandwidth due to crowded spectra, and existing phase rotation techniques are not effective for non-contiguous channel configurations, particularly in reducing peak-to-average-power-ratio (PAPR) issues.
Innovation Solution
The method involves determining a fundamental set of phase rotations, performing cyclic shifts, and multiplying by a complex constant to generate a final set of phase rotations for each sub-channel, allowing for phase rotation adjustments that reduce PAPR in both contiguous and non-contiguous channel configurations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If phase rotation technique from IEEE 802.11n is applied to 40 MHz bandwidth, then PAPR problem is reduced, but the technique cannot be directly applied to 80 MHz or greater bandwidth including non-contiguous channels
Solution Approach 1:
The patent segments the 80 MHz bandwidth into multiple 20 MHz sub-channels and applies phase rotation techniques independently to each sub-channel. This segmentation allows the phase rotation method designed for 40 MHz to be extended to 80 MHz and non-contiguous channel configurations by treating each sub-channel as a separate entity that can be processed individually.
Solution Approach 2:
The patent introduces a new dimension of sub-channel indexing and phase rotation pattern selection that extends the original 40 MHz phase rotation technique. By adding sub-channel specific phase rotation patterns (e.g., different rotation angles or patterns for different sub-channels), the method becomes adaptable to wider bandwidths and non-contiguous configurations without losing the PAPR reduction benefit.
2Productivity
If contiguous 80 MHz bandwidth is used, then throughput is increased, but spectrum availability becomes limited
Solution Approach 1:
The patent creates a universal phase rotation method that works across multiple bandwidth configurations (20 MHz, 40 MHz, 80 MHz) and channel arrangements (contiguous and non-contiguous). This multi-functional approach allows the system to achieve high throughput when 80 MHz contiguous bandwidth is available, while automatically adapting to non-contiguous configurations when spectrum is fragmented, thus resolving the contradiction between throughput and spectrum availability.
3Adaptability or versatility
If non-contiguous transmission is used, then probability of transmitting with wider bandwidth increases, but existing phase rotation techniques are not effective
Solution Approach 1:
The patent applies local quality by allowing different phase rotation patterns to be applied to different sub-channels based on their specific frequency locations and contiguity relationships. Each sub-channel can have locally optimized phase rotation parameters that account for its position in the frequency spectrum, ensuring PAPR reduction effectiveness is maintained even when sub-channels are non-contiguous and have different spectral characteristics.
Data Source
AI summary
A method for determining signal phase rotation of sub-channels within a contiguous transmission bandwidth comprises the steps of: determining a fundamental set of phase rotations; performing a cyclic shift operation for the fundamental set of phase rotations to generate a cyclic-shifted set of phase rotations; multiplying the cyclic-shifted set of phase rotations by a complex constant to generate a final set of phase rotations; and determining the phase rotation of each sub-channel within the contiguous transmission bandwidth according to the final set of phase rotations.