DFT-s-OFDM Spectrum Extension for PAPR-Limited Uplink Coverage
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Solution Overview
Problem
Conventional DFT-s-OFDM signals suffer from unsatisfactory peak-to-average power ratio (PAPR), particularly in coverage-limited scenarios, limiting uplink coverage in wireless systems.
Innovation Solution
A communication device that repeats and cyclically shifts Fourier coefficients based on modulation symbol constellations and FDSS windows to optimize PAPR, using a FDSS window of size Nsc and a shift parameter L to map coefficients onto subcarriers, thereby reducing PAPR.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If DFT-s-OFDM is used to reduce PAPR compared to standard OFDM, then PAPR is improved, but PAPR remains unsatisfactory in deep-indoor coverage-limited scenarios
Solution Approach 1:
The patent applies parameter changes by modifying the spectral characteristics of DFT-s-OFDM signals through frequency domain spectrum shaping (FDSS) windows and spectrum extension techniques. By changing the spectral distribution parameters and applying specific window functions, the signal's PAPR is further reduced while maintaining coverage performance, directly resolving the contradiction between PAPR reduction and coverage reliability.
2Use of energy by moving object
If π/2-BPSK modulation is used to achieve lower PAPR, then PAPR is reduced and RF amplifier power efficiency is improved, but data rate is limited
Solution Approach 1:
The patent employs dynamics by enabling adaptive modulation and flexible switching between different modulation schemes (π/2-BPSK, QPSK, and higher-order modulations). The system dynamically selects the optimal modulation order based on channel conditions and coverage requirements, allowing it to achieve low PAPR when needed while maintaining high data rates when possible, thus resolving the contradiction between PAPR reduction and data rate.
3Use of energy by moving object
If frequency domain spectrum shaping (FDSS) is applied to reduce PAPR, then additional PAPR reduction is achieved, but self-interference increases
Solution Approach 1:
The patent applies local quality by using frequency-domain window functions that selectively shape the spectral distribution of different portions of the signal. The FDSS windows are designed to apply different weighting factors to specific frequency regions, locally optimizing the spectral characteristics to reduce PAPR while minimizing the introduction of self-interference, thus resolving the contradiction between PAPR reduction and self-interference.
4Reliability
If spectrum extension with FDSS is implemented to achieve lower PAPR for high-order modulation, then coverage is improved, but device complexity increases
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing optimal FDSS window functions and spectrum extension parameters for different modulation schemes and channel conditions. These pre-computed parameters are then directly applied during transmission without requiring complex real-time calculations, thereby achieving improved coverage through spectrum extension while minimizing the increase in device complexity through the use of pre-prepared optimization data.
Data Source
AI summary
Embodiments of the invention relate to DFT-s-OFDM signal with spectral extension. A communication device is provided that obtains Ndata Fourier coefficients based on Ndata data symbols, and repeats Ne Fourier coefficients of the Ndata Fourier coefficients to obtain Nsc Fourier coefficients, wherein Ne is determined based on at least one of a modulation symbol constellation of the Ndata data symbols, and a frequency domain spectrum shaping (FDSS) window of the communication device. The Nsc Fourier coefficients are multiplied with an FDSS window of size Nsc to obtain Nsc frequency shaped Fourier coefficients which are mapped onto Nsc subcarriers to obtain a discrete Fourier transform spread orthogonal frequency division multiplexing (DFT-s-OFDM) signal, which is transmitted.