PPDU Phase Rotation for PAPR Reduction in High Bandwidth OFDM
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Solution Overview
Problem
The high peak to average power ratio (PAPR) in orthogonal frequency division multiplexing (OFDM) systems, particularly exacerbated by higher bandwidths, leads to increased costs and reduced efficiency of high power amplifiers due to in-band distortion and out-of-band dispersion, necessitating a reduction in PAPR to maintain system performance.
Innovation Solution
The method involves generating a physical layer protocol data unit (PPDU) with a bandwidth greater than 160 MHz and rotating some or all fields within the PPDU using a rotation factor sequence, which includes multiple rotation factors corresponding to different bandwidths, thereby reducing the PAPR across various bandwidths such as 200, 240, 280, and 320 MHz.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If higher bandwidth is used to increase information transmission rate, then information transmission rate is improved, but PAPR increases causing in-band distortion and out-of-band dispersion
Solution Approach 1:
The patent applies phase rotation to subcarriers by multiplying them with rotation factors (e.g., e^jθ or e^j2θ) to change the phase parameters of the OFDM signal. This parameter transformation redistributes the signal energy in the time domain, reducing peak values while maintaining the frequency domain structure and information transmission rate across the high bandwidth channel.
2Reliability
If high power amplifier with large linear dynamic range is used to handle high peak signal, then signal quality is maintained, but cost and device complexity increase
Solution Approach 1:
The patent applies preliminary phase rotation to the OFDM subcarriers before transmission to preemptively reduce the peak signal values. By pre-transforming the signal to have lower peak-to-average power ratio, the system prevents the need for expensive high-power amplifiers with large linear dynamic ranges, thereby reducing device complexity and cost while maintaining signal quality.
3Loss of energy
If PAPR reduction is achieved through signal processing, then amplifier efficiency is improved, but signal distortion may increase
Solution Approach 1:
The patent changes the phase parameters of subcarriers through multiplication with complex rotation factors, which transforms the time-domain signal to have reduced peak values. This parameter transformation achieves PAPR reduction that improves amplifier efficiency while maintaining signal integrity, as the rotation is a unitary transformation that preserves signal energy and avoids introducing additional distortion.
Data Source
AI summary
Embodiments of this application provide information transmission methods and apparatuses. One method includes: generating, by a first communications device, a physical layer protocol data unit (PPDU) with a bandwidth of X MHz, wherein X>160, some or all fields in the PPDU are rotated in the bandwidth of X MHz by using a rotation factor sequence, the bandwidth of X MHz comprises n bandwidths ofY MHz, the rotation factor sequence comprises n rotation factors, and each of the n bandwidths corresponds to one rotation factor; and sending, by the first communications device, the PPDU to a second communications device.