Dual Sub-Carrier Modulation Phase Rotation PAPR Reduction
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Solution Overview
Problem
High peak to average power ratio (PAPR) in OFDM systems leads to signal distortion, inter-carrier interference, and bit error rate degradation due to the non-linearity of power amplifiers, especially in wideband multi-carrier systems using a large number of subcarriers.
Innovation Solution
The system employs dual sub-carrier modulation with symbol repetition and phase rotation methods, new interleaving parameters, and data-aided carrier frequency offset estimation to reduce PAPR, specifically applying these techniques in high efficiency (HE) wireless network transmissions compliant with IEEE 802.11 specifications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a large number of subcarriers are used in wideband multi-carrier systems, then data transmission capacity is improved, but peak to average power ratio increases causing signal distortion and inter-carrier interference
Solution Approach 1:
The patent applies phase rotation to selected subcarriers in the second half of the frequency spectrum, changing the phase parameter of modulated symbols to reduce peak power values. This modifies the signal parameters to achieve lower PAPR while maintaining the same data transmission capacity through the same number of subcarriers.
Solution Approach 2:
The patent divides the frequency spectrum into two halves and applies different operations to each: the first half uses standard modulation while the second half uses modulation combined with phase rotation. This segmentation allows selective PAPR reduction on specific subcarriers without affecting the overall data transmission capacity.
2Use of energy by moving object
If power amplifiers operate at high power levels to maintain efficiency, then energy consumption is improved, but non-linearity increases causing bit error rate degradation
Solution Approach 1:
The patent applies phase rotation in advance to the modulated symbols before transmission, pre-compensating for the non-linear effects that will occur in the power amplifier. This preliminary action reduces the peak power values that would otherwise cause non-linear distortion, thereby maintaining both power amplifier efficiency and bit error rate performance.
3Device complexity
If conventional OFDM modulation is used without modification, then system complexity is kept low, but out-of-band radiation increases causing interference to adjacent channels
Solution Approach 1:
The patent applies phase rotation selectively to only half of the subcarriers (the second half of the frequency spectrum) rather than all subcarriers. This localized application reduces out-of-band radiation in the most critical frequency regions while minimizing the increase in system complexity by avoiding unnecessary processing of all subcarriers.
Data Source
AI summary
A system includes a modulator, a repetition module, and a phase rotation module. The modulator is configured to (i) modulate data using a first modulation scheme and dual sub-carrier modulation, and (ii) generate modulated symbols for transmission on a plurality of subcarriers. The dual sub-carrier modulation modulates the same information on a pair of subcarriers. The repetition module is configured to repeat the modulated symbols from a first half of the plurality of subcarriers to a second half of the plurality of subcarriers. The phase rotation module is configured to rotate phase of the modulated symbols on selected subcarriers of the second half of the plurality of subcarriers. The selected subcarriers of the second half of the plurality of subcarriers include at least one half of the second half of the plurality of subcarriers.