DFT-s-OFDM Spreading Code Roll-off Selection for PAPR Reduction
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Solution Overview
Problem
Current wireless communication systems face inefficiencies in spectral resource utilization due to peak demand reservations, leading to underutilization, particularly in multiple-access technologies like OFDMA and NOMA, which struggle to optimize Peak-to-Average-Power Ratio (PAPR) and spectral efficiency in 5G and beyond 5G networks.
Innovation Solution
The implementation of discrete Fourier transform spread orthogonal frequency division multiplexing (DFT-s-OFDM) with sparse code spaces and cyclic shifts, along with adaptive pulse shaping, to generate discrete-time spread-OFDM signals that reduce PAPR and enhance spectral efficiency by dynamically selecting spreading code roll-off factors based on power and spectral efficiency criteria.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If spectral resources are reserved to meet peak demand, then system reliability is improved, but spectral efficiency deteriorates due to under-utilization
Solution Approach 1:
The patent implements dynamic resource allocation where the network can flexibly assign spectral resources based on actual demand conditions. The system transitions from static peak-demand reservation to dynamic allocation that adapts to varying traffic conditions, allowing resources to be released during low-demand periods while maintaining availability during peak periods, thus improving both reliability and spectral efficiency
Solution Approach 2:
The patent changes the operational parameters of resource allocation from fixed peak-demand levels to variable levels that adjust based on actual system conditions. By modifying allocation parameters dynamically rather than maintaining constant over-provisioning, the system achieves better spectral efficiency while preserving the reliability needed for peak demand scenarios
2Use of energy by moving object
If spreading code roll-off factors are optimized for power efficiency, then power efficiency is improved, but spectral efficiency deteriorates
Solution Approach 1:
The patent implements dynamic selection of spreading code roll-off factors based on current system conditions and service requirements. Rather than using a fixed roll-off factor, the system adapts the parameter in real-time, selecting optimal values that balance power efficiency and spectral efficiency according to instantaneous traffic patterns, channel conditions, and QoS requirements
Solution Approach 2:
The patent modifies the spreading code roll-off factor parameter dynamically to achieve optimal performance. By changing this parameter based on operational conditions rather than maintaining a fixed value, the system can optimize power efficiency when needed while preserving spectral efficiency during other periods, resolving the trade-off between these two metrics
3Reliability
If PAPR is reduced through signal processing, then device reliability is improved, but processing complexity increases
Solution Approach 1:
The patent applies PAPR reduction techniques at the transmitter before signal transmission, performing necessary signal processing in advance rather than during real-time transmission. By preprocessing the signal to reduce PAPR beforehand, the system improves device reliability while managing processing complexity through advance preparation rather than real-time computation
Solution Approach 2:
The patent introduces intermediate signal processing stages that act as mediators between the data source and the transmission channel. These intermediary processing blocks perform PAPR reduction functions, separating the complexity from the main transmission path and allowing the core transmission system to operate with simpler processing while still achieving the reliability benefits of low PAPR
Data Source
AI summary
Enhanced discrete Fourier transform spread Orthogonal Frequency Division Multiplexing (DFT-s-OFDM) selects spreading code roll-off factors based on available spectrum resources in a wireless network and power efficiency needs of at least one wireless device. Excess spectral resources can be used to increase processing gain and reduce peak-to-average power ratio (PAPR), both of which improve a wireless device's power efficiency. Each layer can employ a portion of the DFT-s-OFDM code space in an OFDM symbol for orthogonal multiple access or non-orthogonal multiple access, allowing multiple layers to share the same OFDM symbol. Both uplink and downlink transmissions can benefit from frequency diversity and low PAPR due to DFT-s-OFDM spreading. Since DFT-s-OFDM codes are cyclic shifts of each other, a DFT-s-OFDM discrete-time signal can be synthesized from cyclic shifts of a kernel discrete-time waveform.