• Title/Summary/Keyword: LEO satellite

Search Result 305, Processing Time 0.025 seconds

Calculation Scheme of Interference between Low Earth Orbit Satellite System and Terrestrial System (저궤도 위성시스템과 지상시스템의 간섭 계산 기법)

  • Gam, Hye-Mi;Oh, Dae-Sub;Ahn, Do-Seob
    • Journal of Satellite, Information and Communications
    • /
    • v.4 no.2
    • /
    • pp.46-51
    • /
    • 2009
  • This paper addresses the calculation method of the interference produced between the LEO(Low Earth Orbit) satellite constellation and Terrestrial system operating in the same frequency and area. We describes the procedure used in the numerical computation of the statistics of the total interference produced by interference system. The presented results are applied for mutual protection of LEO satellite constellation and FS system during system design phase.

  • PDF

A rerouting-controlled ISL handover protocol for LEO satellite networks

  • Dong, Wei;Wang, Junfeng;Huang, Minhuan;Tang, Jian;Zhou, Hongxia
    • KSII Transactions on Internet and Information Systems (TIIS)
    • /
    • v.6 no.10
    • /
    • pp.2620-2631
    • /
    • 2012
  • In this paper, a rerouting-controlled ISL (Inter-Satellite link) handover protocol for LEO satellite networks (RCIHP) is proposed. Through topological dynamics and periodic characterization of LEO satellite constellation, the protocol firstly derives the ISL related information such as the moments of ISL handovers and the intervals during which ISLs are closed and cannot be used to forward packet. The information, combined with satellite link load status, is then been utilized during packet forwarding process. The protocol makes a forwarding decision on a per packet basis and only routes packets to living and non-congested satellite links. Thus RCIHP avoids periodic rerouting that occurs in traditional routing protocols and makes it totally unnecessary. Simulation studies show that RCIHP has a good performance in terms of packet dropped possibility and end-to-end delay.

Technology Trends in Communication Payload for the Broadband LEO Satellite Constellation (저궤도 군집 통신위성 탑재체 기술 동향)

  • Uhm, M.S.;Chang, D.P.;Lee, B.S.
    • Electronics and Telecommunications Trends
    • /
    • v.37 no.3
    • /
    • pp.41-51
    • /
    • 2022
  • This article presents an overview of the key technologies in the communications payload of broadband LEO satellite communications systems. In recent years, new developments have been realized for LEO satellite communications. SpaceX's Starlink, a technology leader in this field, offers premium services with satellites carrying in-house developed communications payloads. OneWeb, Amazon, Telesat, and Boeing are also developing LEO satellite communications payloads. The communications payload consists of user link antennas, inter-satellite link communications equipment, feeder link antennas, and a digital processor. Highly sophisticated technologies of compact active phased array antennas for generating multiple hopping beams and light laser communication equipment for ultra-high-speed inter-satellite communication will be applied to next- generation payloads.

Adaptive Compensation Method Using the Prediction Algorithm for the Doppler Frequency Shift in the LEO Mobile Satellite Communication System

  • You, Moon-Hee;Lee, Seong-Pal;Han, Young-Yearl
    • ETRI Journal
    • /
    • v.22 no.4
    • /
    • pp.32-39
    • /
    • 2000
  • In low earth orbit (LEO) satellite communication systems, more severe phase distortion due to Doppler shift is frequently detected in the received signal than in cases of geostationary earth orbit (GEO) satellite systems or terrestrial mobile systems. Therefore, an estimation of Doppler shift would be one of the most important factors to enhance performance of LEO satellite communication system. In this paper, a new adaptive Doppler compensation scheme using location information of a user terminal and satellite, as well as a weighting factor for the reduction of prediction error is proposed. The prediction performance of the proposed scheme is simulated in terms of the prediction accuracy and the cumulative density function of the prediction error, with considering the offset variation range of the initial input parameters in LEO satellite system. The simulation results showed that the proposed adaptive compensation algorithm has the better performance accuracy than Ali's method. From the simulation results, it is concluded the adaptive compensation algorithm is the most applicable method that can be applied to LEO satellite systems of a range of altitude between 1,000 km and 2,000 km for the general error tolerance level, M = 250 Hz.

  • PDF

RTT-Enabled Doppler Positioning in LEO-PNT Systems (저궤도 위성 항법 시스템에서의 왕복시간 및 도플러 천이 기반 위치 측위 기법 설계)

  • Duhui Yang;Jeongwan Kang;Minsoo Jeong;Sunwoo Kim
    • Journal of Positioning, Navigation, and Timing
    • /
    • v.13 no.3
    • /
    • pp.301-307
    • /
    • 2024
  • In this paper, we propose a round trip time (RTT)-enabled Doppler-based positioning method considering the low earth orbit (LEO) satellite visibility restriction. Doppler-based positioning typically requires visibility to at least eight satellites, which is often unfeasible due to the limited coverage of LEO satellites, as beamforming technique is applied to current LEO satellites. To solve this problem, we utilize the RTT measurements, assuming that a communication link exists between the user equipment (UE) and LEO satellites. We employ the Newton-Raphson method to estimate the UE position with RTT and Doppler measurements. We analyze the positioning performance of the considered framework via simulation, demonstrating its performance in 3D positioning errors under varying satellite numbers and measurement errors.

A Study on S-Band Phased Array Antenna System for Receiving LEO Satellite Telemetry Signals (저궤도 위성 원격측정데이터 신호 수신을 위한 S-대역 위상배열안테나 시스템 연구)

  • Lee, Dong-Hyo;Seo, Jung-Won;Lee, Myoung-Sin;Chung, Daewon;Lee, Dongkook;Pyo, Seongmin
    • Journal of IKEEE
    • /
    • v.26 no.2
    • /
    • pp.211-218
    • /
    • 2022
  • This paper presents a S-band phased array antenna system for receiving LEO satellite telemetry signals. The proposed antenna, which is performed to be beam-tiled along the elevation direction, consists of 16 sub-array assemblies, 16 active circuit modules, a perpendicular feed network and a control/power unit. In order to precisely track an LEO satellite, the developed antenna is placed with its elevation axis along the projected trajectory of the satellite on the earth. The center of antenna aperture is facing to the maximum elevation angle in the LEO trajectory. The beam-tilted angles for tracking LEO satellite are obtained by calculating accurately satellite points. Satellite tracking measurements are carried out in the range of ±30° with the respect to the maximum elevation angle. The S/N ratio of 16.5 dB and the Eb/No of 13.3 dB at the maximum elevation angle are obtained from the measurements. The measured result agrees well with the pre-analyzed system margin.

Development of Energy Balance Analysis Program for LEO Satellite Design (저궤도 인공위성 설계를 위한 에너지 균형 분석 프로그램 개발)

  • Lee, Sang-Kon;Ra, Sung-Woong
    • Journal of the Korean Society for Aeronautical & Space Sciences
    • /
    • v.35 no.9
    • /
    • pp.850-857
    • /
    • 2007
  • The design and analysis of satellite electrical power subsystem is an important driver for the mass, size, and capability of the satellite. In particular, satellite energy balance analysis is critical in determining the capabilities and limitations of the power subsystem and the success of satellite operations. This paper introduces a new energy balance analysis program for LEO satellite development and shows an example of test results using other LEO satellite design data. The test results show that the proposed energy balance program can be used the optimal sizing of satellite electrical power subsystem and the analytical prediction of the on-orbit energy balance during satellite mission operations.

Stabilization Converter Design and Modeling of LEO Satellite Power Systems (저궤도 위성의 전력 시스템 안정화를 위한 모델링 및 제어)

  • Yun, Seok-Teak;Won, Young-Jin;Lee, Jin-Ho
    • Journal of Satellite, Information and Communications
    • /
    • v.5 no.2
    • /
    • pp.29-33
    • /
    • 2010
  • Satellites industry has been developing with the commercial and military needs. Because power system of satellite is very important to survival operation and hard to test, increasing reliability is very critical. Due to LEO small satellites are very sensitive to power system, effective stabilization control is important. Therefore, this paper introduce methods for general modeling of power converting system which it can be used design of controller and analysis of external disturbance influences. In conclusion, a modeling of LEO small satellites power converting system and a possible guide line to design reliable controller which optimizing power converters of LEO small satellite are generated.

A Study on Modelling and Attitude Control Techniques of LEO Satellite (저궤도 위성체의 모델링 및 자세제어 기법에 관한 연구)

  • Lho, Young-Hwan
    • Journal of the Institute of Electronics Engineers of Korea SC
    • /
    • v.46 no.6
    • /
    • pp.9-13
    • /
    • 2009
  • In the three axis control of Low Earth Orbit (LEO) satellite by using reaction wheel and gyro, a reaction wheel produces the control torque by the wheel speed or momentum, and a gyro carries out measuring of the attitude angle and the attitude angular velocity. In this paper, the dynamic modelling of LEO is consisted of the one from the rotational motion of the satellite with basic rigid body model and a flexible model, in addition to the reaction wheel model. A robust controller $(H_\infty)$ is designed to stabilize the rigid body and the flexible body of satellite, which can be perturbed due to disturbance, etc. The result obtained by $H_\infty$ controller is compared with that of the PI (Proportional and Integration) controller, which has been traditionally using for the stabilizing LEO satellite.

Performance Enhancement of Spread Spectrum LEO Satellite communication System Using Constant Modulus Antenna Array

  • Lee, Byung-Seub
    • Journal of Satellite, Information and Communications
    • /
    • v.12 no.2
    • /
    • pp.65-70
    • /
    • 2017
  • The structure of MMSE receiver front-ended by CMA(Constant Modulus Array) array working in CDMA forward link which is applicable to LEO spread spectrum satellite communication system is proposed. By using the despreaded pilot signal of forward link as a reference signal, the CMA array can capture multi-path signals securely even in severely faded LEO satellite channel. The remaining MAI (Multiple Access Interference) is cancelled by the cascaded MMSE receiver. Besides theoretical development, through relevant computer simulation, it is proved that the proposed system shows much better BER performance than any other possible candidate systems. As a spatio-temporal receiver mounted on a mobile vehicle, the proposed system also reduces implemental cost and complexity by adopting the simplest algorithm for its spatial and temporal domain processing.