HE-SIG-B Phase Scrambling for Lower WLAN Peak Power
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Solution Overview
Problem
Wireless local area network (WLAN) devices face performance degradation due to increased interference and high peak-to-average power ratio (PAPR) in wireless communications, particularly in scenarios with repeated information in the HE-SIG-B field, leading to reduced transmit power and coverage.
Innovation Solution
Scrambling of the HE-SIG-B field is performed using a predetermined scrambling seed value, which can be broadcasted in management frames or conveyed in the SIG-A field, to randomize repeated bits and reduce PAPR, involving phase rotation and scrambling operations within each HE-SIG-B field channel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If repeated information is used in the HE-SIG-B field for robust transmission, then reliability is improved, but peak-to-average power ratio increases causing transmit power reduction
Solution Approach 1:
The patent applies parameter changes by modifying the HE-SIG-B field content through scrambling operations. A scrambling seed value is used to randomize the repeated information bits, transforming the signal characteristics while preserving the information content. This changes the parameter distribution of the transmitted signal, reducing peak power occurrences while maintaining the reliability benefits of repeated information transmission.
2Reliability
If repeated information is used in the HE-SIG-B field for robust transmission, then reliability is improved, but coverage is reduced due to high PAPR
Solution Approach 1:
The patent uses parameter changes through scrambling to modify the signal's power distribution characteristics. By applying a scrambling sequence to the HE-SIG-B field, the signal transitions from having high peak power values to a more uniform power distribution, enabling transmission at higher average power levels that extend coverage area while maintaining the reliability advantages of repeated information.
3Power
If scrambling is applied to HE-SIG-B field to reduce PAPR, then transmit power efficiency is improved, but device complexity increases
Solution Approach 1:
The patent implements preliminary action by performing the scrambling operation on the HE-SIG-B field before transmission. The scrambling seed value is predetermined and available at both transmitter and receiver, allowing the scrambling and unscrambling operations to be executed efficiently using simple XOR operations. This preliminary processing reduces PAPR and improves power efficiency without requiring complex real-time signal processing during transmission.
Data Source
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AI summary
In wireless communications, a high-efficiency (HE) physical layer protocol data unit (PPDU) includes an HE signal-B (SIG-B) field. In order to prevent undesirably large peak-to-average power ratio (PAPR) transmissions caused by repeated information in the HE SIG-B field, the HE SIG-B field may be scrambled. Scrambling of the HE SIG-B field may include scrambling of modulated data tones of each of one or more HE SIG-B field channels of the HE SIG-B field. This scrambling may include applying a phase rotation to the modulated data tones within each of the one or more HE SIG-B field channels. This scrambling (or phase rotation) is performed in addition to a phase rotation applied to each entire HE SIG-B field channel that is commonly referred to as a gamma rotation.