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확률기하학을 이용한 LoRa 기반의 저궤도 위성네트워크 가시성과 연결성 분석
정수엽,유준규,이준세 한국통신학회 2024 韓國通信學會論文誌 Vol.49 No.1
Various applications through Low-Earth Orbit (LEO) satellite networks are considered in next-generation communication. Especially, IoT services using the broad coverage of low-orbit satellite networks have been widely considered in many areas. Long Range (LoRa) is an essential technique to compensate for the Doppler effect due to the fast mobility of LEO satellites or to support low-power communication for IoT services. This paper analyzes the visibility and connectivity of the network viewed from the user's perspective on the ground when the LoRa technique is applied to LEO satellite networks. We assume that the spreading factor, an essential physical layer parameter for LoRa-based communication, is determined based on the distance from the user. Then, we present analyses of the network environment experienced by the user using stochastic geometry. The main results provide intuitions on the interrelationship between network parameters and performances. Finally, we present some numerical results which verify that our analyses are consistent with the simulations.
위성통신시스템의 주파수 효율 향상을 위한 동일위성채널 전송 기술 연구
정수엽,유준규,오덕길 한국통신학회 2018 정보와 통신 Vol.35 No.6
위성통신분야에서 연구되어온 주파수 효율 향상 기법들 중, 동일위성채널 전송 기술은 양방향 위성통신채널의 하향링크 주파수 대역을 순방향과 역방향 링크에서 공유함으로써 이론적으로 두 배의 주파수 효율 향상을 이끌어 낼 수 있는 효과적인 방법이다. 본고에서는 동일위성채널 전송 기술이 실제 적용되기 위해 필요한 비선형 보상 기법 및 자기간섭 제거 기술에 대해 자세히 설명하고 있으며, 그 밖에 해외 기술동향에 대해 살펴본다.
Performance analysis of DSSS- and CSS-based physical layer for IoT transmission over LEO satellites
정수엽,임경래,정동현,김판수,유준규,강준혁 한국전자통신연구원 2022 ETRI Journal Vol.44 No.4
To determine a suitable waveform for Internet of Things (IoT) transmission over low-Earth orbit (LEO) satellites, this paper reports the results of a performance comparison between chirp spread spectrum (CSS)-based LoRa and direct sequence spread spectrum (DSSS)-based Ingenu. The performance of both waveforms was measured in terms of the packet error rate, throughput, and packet loss rate, considering the Doppler effect caused by the high speed of LEO satellites and the interference among multiple terminals. Simulation results indicate that the DSSS scheme is more suitable than the CSS scheme for high-traffic IoT services because of its robustness against interference among multiple terminals. However, the CSS scheme is more suitable than the DSSS scheme for highmobility IoT services because of its robustness against the Doppler effect. We discuss various solutions, such as the preprocessing of Doppler effect and avoidance of packet collision, to enhance the performance of the DSSS and CSS schemes. The simulation results of the proposed solution show that the enhanced DSSS scheme can be a proper waveform in IoT transmission over LEO satellites for both the high-traffic and high-mobility services.
정수엽,류준규,오덕길,유희정 한국전자통신연구원 2017 ETRI Journal Vol.39 No.6
For efficient spectral utilization of satellite channels, a shared band transmission technique is introduced in this paper. A satellite transmits multiple received signals from a gateway and terminal in the common frequency band by superimposing the signals. To improve the power efficiency as well as the spectral efficiency, a travelling wave tube amplifier in the satellite should operate near the saturation level. This causes a nonlinear distortion of the superimposed transmit signal. Without mitigating this nonlinear effect, the self-interference cannot be properly cancelled and the desired signal cannot be demodulated. Therefore, an adaptive compensation scheme for nonlinearity is herein proposed with the proper operation scenario. It is shown through simulations that the proposed shared band transmission approach with nonlinear compensation and self-interference cancellation can achieve an acceptable system performance in nonlinear satellite channels.