• Journal of Communications and Networks
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• 제17권4호
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• pp.394-405
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• 2015

This paper considers a wideband cognitive radio network which can simultaneously sense multiple narrowband channels and thus aggregate the detected available channels for transmission and proposes a novel cognitive radio system that exhibits improved sensing throughput and can save power consumption of secondary user (SU) compared to the conventional cognitive radio system studied so far. More specifically, under the proposed cognitive radio system, we study the problem of designing the optimal sensing time and power allocation strategy, in order to maximize the ergodic throughput of the proposed cognitive radio system under two different schemes, namely the wideband sensing-based spectrum sharing scheme and the wideband opportunistic spectrum access scheme. In our analysis, besides the average interference power constraint at primary user, the average transmit power constraint of SU is also considered for the two schemes and then a subgradient algorithm is developed to obtain the optimal sensing time and the corresponding power allocation strategy. Finally, numerical simulations are presented to verify the performance of the two proposed schemes.

• 대한원격탐사학회지
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• 제24권1호
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• pp.79-89
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• 2008

Irregular temporal sampling is a common feature of geophysical and biological time series in remote sensing. This study proposes an on-line system for reconstructing observation image series contaminated by noises resulted from mechanical problems or sensing environmental condition. There is also a high likelihood that during the data acquisition periods the target site corresponding to any given pixel may be covered by fog or cloud, thereby resulting in bad or missing observation. The surface parameters associated with the land are usually dependent on the climate, and many physical processes that are displayed in the image sensed from the land then exhibit temporal variation with seasonal periodicity. A feedback system proposed in this study reconstructs a sequence of images remotely sensed from the land surface having the physical processes with seasonal periodicity. The harmonic model is used to track seasonal variation through time, and a Gibbs random field (GRF) is used to represent the spatial dependency of digital image processes. The experimental results of this simulation study show the potentiality of the proposed system to reconstruct the image series observed by imperfect sensing technology from the environment which are frequently influenced by bad weather. This study provides fundamental information on the elements of the proposed system for right usage in application.

• 인포메이션 디스플레이
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• 제18권3호
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• pp.3-12
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• 2017

In the recent years, significant advances have been made in the development of small form-factor, low power, and low cost 3D-sensing devices based on depth-imaging technologies with real-time performance. This has led to the advent of devices and machines that are able to sense and understand the world, navigate in the environment, and interact naturally with their human users. Human-computer interactions based on touch sensing and speech recognition have already become mainstream, and the rapid developments in 3D sensing is paving the path towards the next level of machine intelligence and interactions. This paper discusses the recent developments in real-time 3D sensing technologies and their emerging system application.

• 대한원격탐사학회지
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• 제2권2호
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• pp.69-77
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• 1986

This study was emphasized on the land use classification by Remote Sensing Technique. Land cover maps about the major urbans, Seoul, Tajeon regions, its of each classified classes were extracted by use of Landsat MSS Data and Digital Image Processing System. From the results of this study, it was proved that land use classification by Remote Sensing technique could be used to obtain fully fruitful Results.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2003년도 Proceedings of ACRS 2003 ISRS
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• pp.298-300
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• 2003

A management information system of the Nanji Islands National Marine Reserve is designed and constructed based on method of integration of remote sensing and geographic information system (GIS). The system consists of two sub-systems, dynamic monitoring information system and general database system. The former is used for storage and manage fundamental geographical data (topographical and bathymetric map), satellite remote sensing data (IKONOS, SPOT, IRS, NOAA and SeaWiFS etc.) and multimedia data. The latter is used for storage and manage resource data (shellfish and alga etc.), environmental data (meteorological and hydrologic) and in situ data. As part of electronic government, this system will be submitted to local government for monitoring, management and decision.

• 대한원격탐사학회지
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• 제19권3호
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• pp.191-200
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• 2003

Remote sensing division of satellite technology research center (SaTReC) , Korea advanced institute of science and technology (KAIST) has developed a ground receiving and processing system for high resolution satellite images. The developed system will be adapted and operated to receive, process and distributes images acquired from of the second Korean Multi-purpose Satellite (KOMPSAT-2), which will be launched in 2004. This project had initiated to develop and Koreanize the state-of-the-art technologies for the ground receiving system for high resolution remote sensing images, which range from direct ingestion of image data to the distribution of products through precise image correction. During four years development from Dec. 1998 until Aug. 2002, the system had been verified in various ways including real operation of custom-made systems such as a prototype system for SPOT and a commercialized system for KOMPSAT-1. Currently the system is under customization for installation at KOMPSAT-2 ground station. In this paper, we present accomplished work and future work.

• 전기학회논문지P
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• 제63권1호
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• pp.34-39
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• 2014

In cognitive radios, secondary users can use the spectrum exclusively allocated to a primary wireless system if the secondary users detect the spectrum in idle states. Because the secondary users can utilize the idle state of the spectrum, the utilization rate of the spectrum can be improved. The idle states can be detected by using secondary users' sensing schemes. However, the wireless channel environment where secondary users perform the spectrum sensing is not very friendly to secondary users because the signal-to-noise ratio of the received primary signal is very low. Hence, cooperative sensing scheme where more than one secondary user take part in the spectrum sensing is generally used in cognitive radios. In this paper, we investigate the cooperative sensing performance for machine-to-machine communication devices operated by batteries with limited energy. In general, the energy consumed for the spectrum sensing increases as the length of the sensing period and the number of cooperative sensing nodes. Accordingly, even though the total amount of the consumed energy is the same, an energy allocation methodology how to distribute the energy to the sensing period and sensing nodes can achieve the optimum sensing performance, which is numerically analyzed.

• 한국정보통신학회논문지
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• 제16권4호
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• pp.872-878
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• 2012

본 논문은 사람 팔의 움직임 감지 시스템을 제안한다. 기존의 모션측정 장비들은 고가이거나 혹은 특수한 장소가 따로 필요하였다. 또한 측정한 데이터들을 필요한 데이터로 변환하는 추가적인 시간도 필요하였다. 본 논문에서는 사람이 입을 수 있으며 가격이 매우 저렴하고 추가적인 데이터 변환이 필요 없는 시스템을 개발 하였다.

• 한국정보통신학회논문지
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• 제13권9호
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• pp.1891-1897
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• 2009

본 논문에서는 CR(cognitive radio) 시스템의 throughput 측면에서 스펙트럼 센싱의 최적화를 다루고 있다. 기존의 논문은 incumbent 사용자의 출현에 의해 다른 채널의 탐색 및 채널전환 등을 고려하지 않은 상태에서 스펙트럼 센싱의 최적화 문제를 다루고 있다. 이에 반해 본 논문에서는 채널탐색 및 채널전환 등을 고려하여 CR 사용자의 throughput를 분석하고 있다. 또한 본 논문에서는 데이터 수신 경로와 분리된 센싱수신기를 갖는 형태의 센싱구조를 제시하고, 데이터 수신 경로를 센싱 수신기로 사용하는 경우와 분리된 센싱 수신기를 갖는 센싱 구조와의 센싱성능을 CR 사용자의 throughput 관점에서 비교하고 있다. 수치해석의 결과로는 incumbent 신호가 출현한 경우 채널이동을 위한 다른 빈 채널의 탐색에서 데이터 통신 경로와 분리된 센싱수신기에 의한 채널탐색을 통하여 throughput 효율이 향상됨을 보여주고 있다.

• 한국위성정보통신학회논문지
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• 제12권4호
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• pp.141-145
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• 2017

스펙트럼 센싱은 인지무선 (cognitive radio) 시스템을 동작시키기 위한 주요한 기법이며 인지무선 시스템을 통해 최근 주목받고 있는 무선에너지하비스팅 시스템에 에너지 하비스팅 효율을 개선할 수 있다. 최근 스펙트럼 센싱을 위한 다양한 기술이 연구되었는데, 그 중에서 가장 널리 쓰이고 있는 에너지 검출 (energy detection) 기술이 있다. 그러나 2차 유저 (secondary user; SU) 가 주파수 페이딩 (frequency fading) 및 쉐도잉 (shadowing)에 의해 영향을 받을 수 있기 때문에, 에너지 검출은 실제 무선 통신에서 숨겨진 단말기 문제 (hidden terminal problem)를 갖는다. 협력 스펙트럼 센싱 (cooperative spectrum sensing)은 SU의 공간적 다양성을 이용하여 이 문제를 해결할 수 있습니다. 그러나 다중 보조를 처리하여 데이터를 증가시키는 문제가 있기 때문에 우리는 적응형 스펙트럼 센싱 알고리즘을 사용하는 시스템 모델을 제안하고 성능을 시뮬레이션 한다. 이 알고리즘은 기본 사용자 (primary user; PU)의 수신 신호의 신호 대 잡음비 (signal to Noise Ratio; SNR)에 따라 단일 에너지 검출과 협동 에너지 사이의 감지 방법을 선택하는 방법을 이용한다. 시뮬레이션 결과를 통해 적응형 스펙트럼 센싱이 인지무선 시스템에서 더 효율적이라는 것을 확인한다.