Satellite Downlink PAPR Reduction via Dynamic OFDM-DFTS Switching
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Solution Overview
Problem
In LTE-based satellite mobile communication systems, high peak to average power ratio (PAPR) in multi-carrier transmission leads to performance degradation due to non-linearity of the power amplifier, which is not effectively addressed by existing technologies, especially when trying to maintain compatibility with terrestrial networks and reuse existing LTE chipsets.
Innovation Solution
A downlink transmission method that switches between orthogonal frequency division multiplexing (OFDM) and discrete Fourier transform spread (DFTS)-OFDM schemes within specific frame sections, using DFTS-OFDM for sections unavailable for terrestrial mobile communication to reduce PAPR, and utilizing a multimedia broadcast multicast service single frequency network (MBSFN) subframe structure to optimize satellite communication while maintaining compatibility with LTE.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If OFDM is used for downlink transmission in satellite mobile communication systems, then frequency domain resource allocation flexibility is improved, but performance degradation occurs due to high PAPR causing non-linearity in power amplifier
Solution Approach 1:
The system dynamically switches between OFDM and DFTS-OFDM transmission schemes based on the satellite frame structure. DFTS-OFDM is used in sections where terrestrial compatibility is not required (to reduce PAPR and improve reliability), while OFDM is used in sections requiring frequency domain flexibility for terrestrial compatibility. This dynamic adaptation resolves the contradiction by allowing both schemes to coexist in different time/frequency resources.
Solution Approach 2:
The satellite downlink frame is segmented into multiple sections with different transmission schemes. Some sections use OFDM for terrestrial compatibility while other sections use DFTS-OFDM for low PAPR performance. This segmentation allows the system to optimize different parts of the transmission for different requirements, resolving the contradiction between flexibility and reliability.
2Reliability
If single carrier transmission is used to reduce PAPR, then power amplifier efficiency is improved, but frequency domain resource allocation flexibility is reduced
Solution Approach 1:
The system dynamically selects between single carrier (DFTS-OFDM) and multi-carrier (OFDM) transmission modes based on the specific frame section and service requirements. This dynamic mode selection allows the system to achieve high power amplifier efficiency when using DFTS-OFDM while maintaining frequency domain flexibility when switching to OFDM, thus resolving the contradiction.
Solution Approach 2:
The satellite base station is designed to support both single carrier and multi-carrier transmission schemes within the same downlink frame structure. This multi-functionality allows the system to universally support both transmission types, enabling flexibility in resource allocation while maintaining power amplifier efficiency through selective use of DFTS-OFDM.
3Ease of manufacture
If LTE-based terrestrial terminal chipset is reused for satellite communication, then economic efficiency is improved, but performance degradation occurs due to high PAPR sensitivity
Solution Approach 1:
The satellite downlink frame is segmented such that certain sections use DFTS-OFDM transmission which is compatible with existing LTE terminals. This allows reuse of terrestrial chipsets (improving economic efficiency) while the low PAPR characteristic of DFTS-OFDM in specific sections mitigates performance degradation, thus resolving the contradiction.
Solution Approach 2:
The system changes transmission parameters by switching between OFDM and DFTS-OFDM schemes in different frame sections. This parameter change allows existing LTE terminals to process signals with reduced PAPR in DFTS-OFDM sections, improving their performance and reliability while maintaining compatibility and economic efficiency through chipset reuse.
Data Source
AI summary
Provided is a communication method for downlink transmission with a low peak to average power ratio (PAPR) and compatibility with long-term evolution (LTE)-based downlink transmission in an LTE-based mobile communication system in which the performance degradation may occur due to a high PAPR in multi-carrier transmission caused by non-linearity of a power amplifier in a base station including a satellite, to have the effects of supporting a terminal that reuses an existing terrestrial LTE chipset and a terminal that enables downlink reception with a low PAPR with no collision between the terminals, and of implementing an integrated satellite/terrestrial mobile communication system with a minimum change of an existing mobile communication system to ensure economic efficiency.