Hierarchical Modulation Scheme for Capacity Enhancement in the Satellite

통신위성우주산업연구회 통신위성우주산업연구회 2006 Joint Conference on Satellite Communications Vol.2006 No.-

이동통신을 비롯하여 많은 무선통신 시스템에서 사용자들의 멀티미디어 정보에 대한 수요가 증가함에 따라 채널의 용량을 늘리기 위한 여러 가지 방법들이 시도되고 있다. 그러나 현실적으로 여러 가지 제약에 의하여 사용할 수 있는 채널의 숫자와 용량이 제한되어 있다. 이러한 상황을 해결하여 좀 더 크고 많은 채널을 얻기 위한 여러 가지 방법들이 소개되었고 현재에도 연구되고 있다. 이 논문에서는 위성DMB 시스템을 기반으로 하여 제시된 여러 가지 방법 중 계층변조 방식을 이용하여 채널의 용량 및 그에 따른 성능을 분석하도록 한다. 특정 환경에서 사용자 수 증가에 의한 성능분석 및 계층변조 방식과 기존의 방법을 비교 분석하도록 한다. Future communication systems are to be designed to support and serve multimedia and multiple data transmission. Nowadays, requirement of mobile subscribers for the various information such as movie, GPS(Global Positioning System) information, news - is increasing significantly. However, due to practical reasons, the capacity and number of capable channels are limited. To solve this problem, a large number of methods and schemes have been proposed and are under research. In this paper, we demonstrate how satellite DMB (Digital Multimedia Broadcasting) system works with hierarchical modulation scheme. By using hierarchical modulation, we can analyze the capacity. Meanwhile, system performance is evaluated and compared to conventional 0MB system without using hierarchical modulation.

Thermal Control Design for GEO Communication Satellite

통신위성우주산업연구회 통신위성우주산업연구회 2006 Joint Conference on Satellite Communications Vol.2006 No.-

통신해양기상위성은 항공우주연구원(KARI)이 개발하고 있는 통신, 해양 및 기상 관측 목적을 갖고 있는 정지궤도 위성이다. 남쪽 패널에는 Ka 밴드 통신 탑재체가, 북쪽 패널은 해양 및 기상 탑재체 관련 전자장비들이 부착되어 있다. 통신 탑재체의 열제어를 위해, 수동형 하드웨어와 함께 히터가 사용된다. 발열량이 많은 통신 장비들은 외장형 히트 파이프 위에 장착되며, 다층박막절연재(MLI)를 사용하여 위성의 다른 부분과 열적으로 분리시킨다. 위성의 외부 표면은 열의 방출 및 차단을 위해 방열판 및 다층박막 절연재등이 사용된다. 또한 부품의 작동온도에 따라 몇개의 영역으로 나누어 열제어를 수행하는 방법을 사용한다. 임무말 하지, 동지, 임무초 춘추분에 대하여 열제어계 검증을 위한 열해석이 수행되었다. 본 논문은 통신해양기상위성의 열제어의 기본적인 개념 및 그에 대한 열해석을 다루고 있다. COMS (Communication, Ocean and Meteorogical Satellite) is a geostationary satellite and has been developing by KARI for communication and ocean and meteorogicial observations. Ka-band components are installed on South wall, while other equipment for sensors are installed on the opposite side, North wall. A conventional thermal control design is baselined, using well established techniques and space proven hardware in a passive design, supplemented by heater to compensate environmental and unit dissipation variations. High dissipating communication units are located on external (surface) heat pipe and are covered by MLI (Multi Layer Insulation) to decouple them from the rest of the spacecraft. External spacecraft walls are covered by MLI or OSR (Optical Solar Reflector) for insulation from space and for rejection internal heat to space. The Ka-band payload section of south wall is divided several areas based on unit operating temperature in order to optimize radiator area and maximize heat rejection capability. Thermal analysis is carried out for validation of thermal control design. This paper presents principles of thermal control design and results of thermal analysis for COMS.

Integrated Ray Tracing Model for In-Orbit Optical Performance Simulation for GOCI

Ham, Sun-Jeong,Lee, Jae-Min,Kim, Seong-Hui,Youn, Heong-Sik,Kang, Gm-Sil,Myung, Hwan-Chun,Kim, Sug-Whan 통신위성우주산업연구회 2006 Joint Conference on Satellite Communications Vol.2006 No.-

GOCI (Geostationary Ocean Color Imager) is one of the three COMS payloads that KARl is currently developing and scheduled to be in operation from around 2008. Its primary objective is to monitor the Korean coastal water environmental condition. We report the current progress in development of the integrated optical model as one of the key analysis tools for the GOCI in-orbit performance verification. The model includes the Sun as the emitting light source. The curved Earth surface section of 2500 km x 2500 km including the Korean peninsular is defined as a Lambertian scattering surface consisted of land and sea surfaces. From its geostationary orbit, the GOCI optical system observes the reflected light from the surfaces with varying reflectance representing the changes in its environmental conditions. The optical ray tracing technique was used to demonstrate the GOCI in-orbit performances such as red tide detection. The computational concept, simulation results and its implications to the on-going development of GOCI are presented.

Empirical study on mobile satellite link using portable GPS receiver

Abidin, Wan Azilan W. Z.,Fujisaki, Kiyotaka,Tateiba, Mitsuo 통신위성우주산업연구회 2006 Joint Conference on Satellite Communications Vol.2006 No.-

In order to give a high quality mobile satellite (MS) services, it is of vital importance to tackle the issue of signal degradation due to factors such as multipath fading and shadowing effect. The advancement of the Global Positioning System(GPS) technology nowadays allows the commercially available, portable GPS receivers to be manipulated in the study of the MS link quality evaluation system. Apart from being low in cost, these receivers are simple to manage which will greatly reduce the time and cost of doing research. In this paper, the measurement methodology utilizing a portable GPS receiver used to extract important MS propagation parameters is explained and discussed. It describes in detail how the experiment was set up and how the measurement was conducted. We presented results obtained from the empirical data and made comparison between various MS environmental conditions that show the feasibility of using GPS in this research. The outcome of this research work will be used as part of a MS link evaluation system going to be developed based on raw propagation data obtained from portable the GPS receivers.

A Preliminary Performance Analysis of the Meteorological and Ocean Data Communication Subsystem in COMS

Kim, Joong-Pyo,Yang, Koon-Ho 통신위성우주산업연구회 2006 Joint Conference on Satellite Communications Vol.2006 No.-

기상, 해양 및 Ka-대역 통신 탑재체를 탑재하고 정지궤도에서 기상 및 해양 감시 임무 및 통신 서비스를 수행하는 통신해양기상위성은 기상 및 해양 탑재체에서 관측된 각각의 원시 데이터의 지상국 전송및 지상국에서 처리된 기상 데이터의 최종 사용자국에게 중계 전송을 기상해양데이터통신 서브시스템이있다. 기상해양데이터통신 서브시스템은 기상 및 해양 탑재체에서 수집된 원시 데이터를 받아 CCSDS권고안에 준하여 포맷하고 증폭기를 거쳐 지상국에 전송하는 SD 채널과 지상국에서 처리된 기상 데이터를 CGMS 권고안에 따라 LRIT/HRIT 포맷팅된 신호를 최종 사용자국에 중계하는 기능을 제공하는MPDR 채널로 구성된다. 본 논문은 관측 데이터 전송 및 중계를 위해 구성된 기상해양데이터통신 서브시스템을 소개하고 서브시스템 예비 성능 해석을 통해 주요 요구 성능 파라미터의 만족 여부를 확인하는데 있다. The COMS (Communication, Ocean, and Meteorological Satellite) performing meteorological and ocean monitoring and providing communication service with meteorological, ocean and Ka-band payload in the geostationary orbit includes MODCS (Meteorological and Ocean Data Communication Subsystem) which provides transmitting the raw data collected by meteorological payload called MI (Meteorological Imager) and ocean payload named GOCI (Geostationary Ocean Color Imager) to the ground station and relaying the meteorological data processed on the ground to the end-user stations. MODCS comprises of two channels: SD channel which formats the raw data according to CCSDS recommendation, amplifies and transmits its signal to the ground station; MPDR channel which relays to the end-user stations the ground-processed meteorological data in the data format of LRIT/HRIT recommended by CGMS. This paper introduces the architecture of MODCS for transmitting and relaying the observed data, and investigates that the key performance parameters have the required margin through the preliminary performance analyses.

Level Crossing Rate and Average Fade Duration Analysis in Ku-band Satellite Link

Franklin, Fondjo Fotou,Fujisaki, Kiyotaka,Tateiba, Mitsuo 통신위성우주산업연구회 2006 Joint Conference on Satellite Communications Vol.2006 No.-

The level crossing rate (LRC) analysis of a random process brings out useful information about the underlying process. Combined with the average fade duration of the fading channel, it find diverse applications in the evaluation and design of efficient communication system. The statistics of fading time intervals is of great importance because it is closely related to the statistics of error bursts, the outage probability and fading rate. Analyses verified the conservation law and showed that for 3 stations the obtained LCR variation is conserved. In addition, we presented the effect of the sampling period on the LCR.

Ka-band Antenna Subsystem Pointing Variation Analysis

Lee, Yong-Deuk,Chol, Jang-Sup,Park, Jae-Woo,Lee, Seong-Pal 통신위성우주산업연구회 2006 Joint Conference on Satellite Communications Vol.2006 No.-

한국전자통신연구원은 2008 년 말에 발사될 예정인 통신해양기상위성에 탑재될 Ka 대역 안테나서브시스템을 개발하고 있다. Ka 대역 통신용 안테나 서브시스템은 위성체의 동,서 판넬에 각각 하나씩 구성되어 있다. 이를 추진하기 위하여 한국전자통신연구원은 현재 대한항공(주)과 공동으로 통신위성 안테나 서브시스템을 설계하고 있다. 본 논문은 이득 변화 등과 같은 안테나 서브시스템 성능 규격을 검증하기 위하여 Ka 대역 반사판 포인팅 에러 분석에 대하여 기술한다. 수행된 분석은 열변형에 의한 반사판 표면 변형 데이터 이며 이를Ticra로 빔패턴의 변화를 확인하였다. ETRI has been developing the Ka-band Antenna subsystem for COMS(Communications, Ocean, and Meteorological Satellite) which will be launched at the end of 2008. The antenna subsystem employs the two parts: East Panel and West panel of spacecraft. ETRI in cooperation with domestic companies are under design phase for the antenna subsystem development. This paper focuses on the Ka-band reflector pointing error analysis to verify the antenna subsystem performance specification, especially EOC gain variation etc. The analysis performed is that induced by reflector surface deformation as a result of thermo elastic distortion. Beam pattern variations are verified by the use of TICRA

Development of a low-profile wideband antenna system for mobile satellite communication

Yoshida, Tomihiko,Honma, Naoki,Sueyoshi, Tadahiro,Tsuchida, Toshihiro 통신위성우주산업연구회 2006 Joint Conference on Satellite Communications Vol.2006 No.-

Auto-tracking antennas are a key component of broadband mobile satellite communications. In particular, low-profile antennas are required for high-speed trains to reduce wind noise. We present an auto-tracking receiving antenna system with an ultra-low-profile (90-mm height) configuration. The antenna has high G/T, wideband capacity, and highly accurate tracking performance. We tested the antenna on an experimental microbus. Results demonstrate the antenna can be used for mobile satellite communications. This paper describes the configuration and performance of the antenna system.

Low-Cost Responsive Space Exploitation by HAUSAT Small Satellite

Moon, Byung-Young,Lee, Byung-Hoon,Chang, Young-Keun 통신위성우주산업연구회 2006 Joint Conference on Satellite Communications Vol.2006 No.-

본 논문에서는 한국항공대학교 우주시스템연구실에서 개발되고 있는 25kg 급의 나노위성 HAUSAT-2(Hankuk Aviation University SATllite-2) 초소형위성의 설계 및 제작과 이 과정에서 적용된 우주기반기술을 소개하였다. 이러한 초소형 위성은 우주기술을 개발하고 검증하기 위한 도구로서 활용될 수 있다. HAUSAT-2는 국내에서는 처음으로 개발되는 우주용 별 센서와 GPS 수신기의 우주검증을 위한 플랫폼으로 활용될 것이며, plug-and-play 타입의 버스 전장 유닛(BEU), 모멘텀 휠을 이용한 3 축 자세제어, 몸체부착형 태양전지패널의 에너지평형해석 및 디지털 최대전력추적기와 같은 새로운 개념의 초소형위성을 위한 기술이 적용되었다. 이와 같은 초소형위성 개발을 수행하면서 획득된 엔지니어링 기법 및 부품기술은 저가의 효율적인 초소형위성을 이용한 '신속대응 우주(responsive space)'를 구현하기 위한 기초인프라로 활용될 수 있다. This paper addresses the development and design of the 25kg class nano-satellite HAUSAT-2 (Hankuk Aviation University SATellite-2), being developed by SSRL (Space System Research Lab.) of Hankuk Aviation University. This is the second satellite system development program executed at the university level in Korea. Ultra-small satellite can be utilized as a space technology test bed. HAUSAT-2 is intended to be a verification platform for the Korea's first space-borne star tracker and a GPS receiver. New technologies for ultra-small satellite, such as plug-and-play type Bus Electronics Unit (BEU), attitude control method, and energy balance analysis of body-mounted solar panels, were implemented on HAUSAT-2. Engineering skills and technologies obtained by the process of programs such as these will be an enabler for the 'responsive space' that will leverage the low cost, high efficiency ultra-small satellites.

Interference Cancellation Technique based on Discovery of Spreading Codes of Interference Signals and Maximum Correlation Detection for DS-CDMA System

Hettiarachchi, Ranga,Yokoyama, Mitsuo,Uehara, Hideyuki 통신위성우주산업연구회 2006 Joint Conference on Satellite Communications Vol.2006 No.-

In this paper, we propose a new interference cancellation technique of DS-CDMA for improving communication quality and increasing the number of simultaneous communication users for satellite communications. The DS-CDMA transmitter multiplies each user's signal by a distinct code. The detector receives a signal composed of the sum of all user's signals, which overlap in time and frequency. In a conventional DS-CDMA system, a user’s signal is detected by correlating the entire received signal with that user's code. However, multiple access interference (MAI) is a factor which limits the capacity and performance of the DS-CDMA system. Therefore, this paper proposes a new interference cancellation technique for DS-CDMA based on discovery of spreading codes of interference signals and maximum correlation detection.