Sparse Non-Sparse Spreading for PAPR Reduction
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Solution Overview
Problem
Existing multiple access schemes face challenges in achieving low Peak to Average Power Ratio (PAPR) and robust collision handling while maintaining good multi-user detection performance, particularly due to interference caused by DFT de-spreading in non-orthogonal multiple access (NoMA) systems.
Innovation Solution
The method employs a combination of sparse and non-sparse spreading techniques, where input symbols are divided into sets and subjected to time-domain sparse spreading followed by non-sparse spreading, using complementary sparsity patterns to reduce PAPR and control interference, enabling efficient multi-user detection and supporting a larger number of users through frequency hopping and signature space extension.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If DFT de-spreading is applied at the receiver to enable multi-user detection, then multi-user detection capability is improved, but interference from partially overlapping sparsity patterns contaminates all symbols and degrades detection performance
Solution Approach 1:
The patent segments the spreading process into two distinct stages: sparse spreading (for collision control and user separation) and non-sparse spreading (for maintaining signal integrity). This segmentation allows the system to benefit from both sparse and non-sparse spreading characteristics without the interference problems that arise when using only sparse spreading with DFT de-spreading.
Solution Approach 2:
Non-sparse spreading acts as an intermediary between sparse spreading and DFT de-spreading. By applying non-sparse spreading after sparse spreading, the patent creates a transition layer that preserves the collision-control benefits of sparse patterns while eliminating the interference contamination issue that plagues direct DFT de-spreading of partially overlapping patterns.
2Reliability
If sparse symbol mapping with DFT de-spreading is used to control collision, then collision handling capability is improved, but Peak to Average Power Ratio (PAPR) increases
Solution Approach 1:
The patent merges sparse spreading and non-sparse spreading into a unified transmission scheme. The sparse spreading component handles collision control through pattern-based user separation, while the non-sparse spreading component reduces PAPR by distributing signal energy more uniformly across time-frequency resources. This combination achieves both collision handling and PAPR reduction simultaneously.
Solution Approach 2:
The patent creates a composite spreading signal that combines the properties of sparse and non-sparse spreading patterns. This composite approach leverages the collision-control advantages of sparse patterns while incorporating the PAPR-reduction benefits of non-sparse patterns, resulting in a hybrid signal structure that achieves both objectives.
3Object-affected harmful factors
If entirely non-overlapping sparsity patterns are used to avoid interference, then interference control is improved, but the system becomes orthogonal and loses multiple access capability
Solution Approach 1:
The patent introduces dynamic control over the degree of overlap between sparsity patterns. Rather than using fixed non-overlapping patterns, the system dynamically adjusts pattern overlap levels and applies non-sparse spreading to manage the resulting interference. This dynamic approach allows the system to operate in between purely orthogonal and fully non-orthogonal modes, maintaining multiple access capability while controlling interference through adaptive pattern selection and non-sparse spreading application.
Data Source
AI summary
A transmission method, and corresponding transmitter are provided that use a combination of sparse symbol mapping with non-sparse spreading. This can be used for a low-PAPR multiple access scheme where good performance is achieved by sparse domain multi-user detection. The provided method uses per-frequency block time-domain non-sparse spreading across sparse blocks which provides PAPR reduction. Sparsity patterns are partitioned into groups that allows PAPR reduction. The method may be used to support the transmission of a single-carrier signal, e.g. DFT-spread signal, to provide PAPR reduction. More generally the provided method can use any low-PAPR waveform, for example any single-carrier waveform or any single-subcarrier waveform.