SC-FDM Modulation for Lower-PAPR WLAN Communications
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Solution Overview
Problem
Existing WLAN communication protocols using orthogonal frequency-division multiplexing (OFDM) produce signals with high peak-to-average power ratio (PAPR), leading to reduced effective range and efficiency, especially at higher carrier frequencies.
Innovation Solution
Implementing single-carrier frequency-division multiplexing (SC-FDM) techniques by transforming time-domain symbols into frequency-domain samples using discrete Fourier transform (DFT) and inverse fast Fourier transform (IFFT), with phase rotations and null values to reduce PAPR, and mapping pilot symbols in the time domain for phase tracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If orthogonal frequency-division multiplexing (OFDM) is used for WLAN communication, then data transmission capability is improved, but peak-to-average power ratio (PAPR) increases
Solution Approach 1:
The patent changes the fundamental modulation parameter from OFDM to SC-FDM, transforming the signal structure to achieve lower PAPR while maintaining data transmission capability. This involves using single-carrier modulation with frequency division multiplexing instead of orthogonal frequency-division multiplexing, fundamentally altering how data is modulated and transmitted across the wireless channel.
2Reliability
If power backoff is increased to handle high PAPR, then signal distortion is reduced, but transmission power and effective range are decreased
Solution Approach 1:
By changing the modulation scheme from OFDM to SC-FDM, the patent fundamentally alters the signal characteristics to reduce PAPR. This parameter change allows the system to transmit at higher power levels without excessive backoff, thereby improving effective range while maintaining signal quality through the inherent low-PAPR properties of single-carrier modulation.
3Productivity
If carrier frequency is increased to improve data rate, then bandwidth capacity is improved, but path loss increases
Solution Approach 1:
The patent applies parameter changes by switching to SC-FDM modulation, which reduces PAPR and enables more efficient power amplification. This allows the system to operate at higher carrier frequencies with improved power efficiency, thereby overcoming the increased path loss associated with higher frequencies and maintaining effective transmission range while utilizing the bandwidth capacity benefits of higher carrier frequencies.
Data Source
AI summary
This disclosure provides methods, devices and systems for reducing PAPR in wireless communications. Some implementations more specifically relate to single-carrier frequency-division multiplexing (SC-FDM) techniques that can be used for wireless communications in wireless local area networks (WLANs). In some aspects, a wireless communication device may modulate a physical layer convergence protocol (PLCP) protocol data unit (PPDU) as a series of symbols in the time domain and may transform a subset of the time-domain symbols into a number (Q) of frequency-domain samples based on a Q-point discrete Fourier transform (DFT). The wireless communication device maps the Q frequency-domain samples to a number (N) of orthogonal subcarriers (representing an orthogonal frequency-division multiplexing (OFDM) symbol), where N>Q, and transforms the N subcarriers into N time-domain samples, based on an inverse fast Fourier transform (IFFT), for transmission over a wireless channel.