80 MHz Preamble Sequence Generation via Phase Rotation
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Solution Overview
Problem
The IEEE 802.11ac standard faces challenges in designing preamble sequences for wireless local area network devices due to the potential for excessively high peak-to-average power ratio (PAPR), which can lead to distortion in RF circuits and decreased packet detection probability, especially with increased channel bandwidths like 80 MHz.
Innovation Solution
A method is introduced to generate an 80 MHz preamble sequence by dividing the channel into four sub-channels, where a 20 MHz preamble sequence from the IEEE 802.11a standard is used as a base, and replicas are created with specific phase rotations for the other sub-channels, optimizing the phase rotation angles to minimize PAPR and arrange them to form an 80 MHz preamble sequence compatible with the IEEE 802.11ac standard.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the channel bandwidth is increased to 80 MHz for higher data rate, then the data rate and throughput are enhanced, but the peak-to-average power ratio (PAPR) becomes excessively high causing distortion in RF circuits
Solution Approach 1:
The patent divides the 80 MHz channel into four 20 MHz sub-channels and generates preamble sequences for each sub-channel independently. By segmenting the wide bandwidth channel into narrower sub-channels, the system can apply appropriate preamble sequences to each segment that control the overall PAPR while maintaining high data rate capability.
Solution Approach 2:
The patent applies different phase rotation angles to the preamble sequences of different sub-channels. By changing the phase rotation parameter across sub-channels, the system optimizes the PAPR distribution while maintaining compatibility with existing IEEE 802.11a/g/n devices and achieving high throughput.
2Reliability
If phase rotation is applied to reduce PAPR, then packet detection probability is improved, but compatibility with legacy IEEE 802.11a/g/n devices may be affected
Solution Approach 1:
The patent segments the 80 MHz preamble into four 20 MHz sub-channel preambles, where the first sub-channel uses the standard IEEE 802.11a/g/n preamble sequence while other sub-channels use phase-rotated versions. This segmentation allows legacy devices to correctly interpret the first sub-channel while new devices can utilize the phase-rotated versions for PAPR reduction.
Solution Approach 2:
Different phase rotation angles are applied to different sub-channels based on their specific requirements. The first sub-channel maintains standard quality for compatibility, while other sub-channels apply phase rotation to optimize PAPR. This local differentiation allows simultaneous support for both legacy and advanced device requirements.
3Device complexity
If the same preamble sequence is used for all sub-channels, then device complexity is reduced, but PAPR remains excessively high
Solution Approach 1:
The patent changes the phase rotation parameter of the preamble sequence for different sub-channels. By adjusting this single parameter across sub-channels, the system effectively reduces PAPR without requiring completely different preamble sequences, thus limiting the increase in device complexity.
Solution Approach 2:
The patent creates copies of the base preamble sequence for each sub-channel and applies phase rotation to these copies. This copying approach allows the system to maintain a simple base preamble structure while generating varied sequences for different sub-channels, balancing complexity and PAPR reduction.
Data Source
AI summary
A method of generating preamble sequence is disclosed. A channel used by a wireless device may be divided into four sub-channels, and the method includes forming a preamble sequence of a first sub-channel, making three replicas of the preamble sequence of the first sub-channel, each replica with a phase rotation of a first angle, a second angle, and a third angle respectively, for forming each preamble sequence of a second sub-channel, a third sub-channel, and a fourth sub-channel, and arranging the preamble sequences of the first, the second, the third, and the fourth sub-channels to form a preamble sequence of the channel.