BPSK Dual Carrier Modulation for Low PAPR WLAN
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Solution Overview
Problem
High peak-to-average power ratio (PAPR) in dual subcarrier modulation (DCM) systems hinders performance in wireless communications, particularly under narrow band interferences and multi-path fading channels, and existing modulation schemes are not robust enough for HE-SIG-B and outdoor scenarios.
Innovation Solution
Implementing a method that uses binary phase shift keying (BPSK) modulation on both lower and upper subcarriers with specific mapping schemes to reduce PAPR, where the second set of modulated symbols is obtained by multiplying the first set by e^(j*π*m), enhancing frequency diversity and robustness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If dual subcarrier modulation (DCM) is used to introduce frequency diversity and improve reliability under narrow band interferences, then reliability is improved, but peak-to-average power ratio (PAPR) increases
Solution Approach 1:
The patent applies asymmetry by using different BPSK modulation schemes for the first and second sets of subcarriers. Specifically, the first BPSK scheme maps encoded bits to lower subcarriers while the second BPSK scheme maps the same encoded bits to upper subcarriers with a phase rotation of e^(j*π*m). This asymmetric modulation approach maintains frequency diversity benefits while reducing PAPR compared to conventional symmetric DCM
Solution Approach 2:
The patent changes the modulation parameters by introducing specific phase rotation factors (e^(j*π*m)) in the second BPSK modulation scheme. This parameter modification allows the system to achieve both frequency diversity and lower PAPR by adjusting the phase relationships between subcarriers rather than using identical modulation schemes
2Reliability
If conventional modulation schemes are used for HE-SIG-B, then device complexity is low, but performance is insufficient under multi-path fading channels and narrow band interferences
Solution Approach 1:
The patent segments the frequency spectrum into lower and upper subcarriers, applying different BPSK modulation schemes to each segment. This segmentation allows the system to achieve frequency diversity and improved performance under multi-path fading while keeping each individual modulation scheme simple and computationally efficient
Data Source
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AI summary
Dual sub-carrier modulation (DCM) is introduced in high efficiency (HE) WLAN. DCM is a solution to deal with narrow band interferences and for range extension. DCM can introduce frequency diversity into OFDM systems by transmitting the same information on two subcarriers separated in frequency. If DCM is applied, then the transmitter modulates the same encoded bits onto two separated subcarriers with the same or different constellation mapping schemes. DCM suffers from a high peak-to-average power ratio (PAPR). In accordance with one novel aspect, a method of transmitting and encoding a HE PPDU frame with binary phase shift keying (BPSK) DCM and lower PAPR is proposed.