Low PAPR Waveform for Millimeter Wave SCMA
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Solution Overview
Problem
Millimeter wave (mmW) transmissions face challenges due to high peak-to-average power ratio (PAPR) in OFDM signals, leading to increased complexity and cost in analog/digital converters and radiofrequency power amplifiers, as well as signal distortion, which is exacerbated in uplink transmissions by mobile devices' cost, size, and power constraints.
Innovation Solution
The use of sparse code multiple access (SCMA) combined with pulsed shaped subcarrier based frequency-division multiplexing reduces PAPR by allowing non-orthogonal multiplexing of code layers, resource overloading, sparsity, and multi-dimensional codewords, enabling low-density non-zero values in coding sequences and localized pulse shapes to minimize receiver complexity and synchronization requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If OFDM signal is used for mmW transmission, then data transmission capability is improved, but PAPR increases leading to higher complexity and cost of ADC/DAC and PA
Solution Approach 1:
The patent changes the fundamental parameters of the signal structure by transitioning from conventional OFDM to SC-FDMA with DFT spreading. This parameter change in the signal processing domain transforms the high-PAPR OFDM signal into a low-PAPR single-carrier signal, thereby reducing the complexity requirements for power amplifiers and converters while maintaining data transmission capability
Solution Approach 2:
The patent introduces a new dimension of processing by applying DFT spreading across multiple subcarriers before modulation. This dimensional transformation in the frequency domain creates a single-carrier equivalent signal that maintains the parallel processing benefits of OFDM while achieving low PAPR characteristics
2Productivity
If OFDM signal is used for mmW transmission, then data transmission capability is improved, but signal distortion increases due to power amplifier nonlinearity
Solution Approach 1:
By changing the signal structure from multi-carrier OFDM to single-carrier SC-FDMA through DFT spreading, the patent reduces the peak power variations that cause power amplifier nonlinearity. This parameter change in signal characteristics directly reduces signal distortion while maintaining data transmission capability
Solution Approach 2:
The patent converts the inherent limitation of single-carrier signals (lower spectral efficiency) into a benefit by using DFT spreading to achieve both low PAPR and high data transmission capability. The single-carrier structure that normally limits performance is transformed into an advantage by reducing distortion in the power amplifier
3Device complexity
If SC-FDMA is used for uplink transmission, then PAPR is reduced compared to OFDMA, but constant PAPR cannot be provided for all modulation levels
Solution Approach 1:
The patent applies local quality by designing specific codebooks with optimized properties for different modulation levels. Each codebook is locally optimized to provide constant PAPR characteristics, allowing the system to adapt to different modulation requirements while maintaining low PAPR performance
Solution Approach 2:
The patent creates a universal solution by developing codebooks that work across multiple modulation levels (QPSK, 16-QAM, 64-QAM, etc.). The codebook design provides constant PAPR for all modulation types, making the system universally applicable regardless of the modulation scheme used
Data Source
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AI summary
Methods and systems for signal transmission in millimeter wave (mmW) range. A set of sequences is used to encode a data signal for one layer in a group of layers. Each sequence in the set of sequences has a length equal to the number of resources shared among the group of layers. At least a portion of the sequences have a low density of non-zero values, and the non-zero values are assigned to a subset of the shared resources. Each sequence assigns a non-zero value to at most one resource of the subset of shared resources, and all non-zero values assigned by all sequences have equal power amplitudes.