• Journal of the Korean Institute of Telematics and Electronics A
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• v.30A no.4
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• pp.28-39
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• 1993

In the international BISDN used satellite, the laser that has large BW has to be used as a carrier for transmitting a lot of visual, vocal, and data information. Interoptical satellite communication has now developed in theoretical and practical aspects. But the optical communication, between satellite and earth station, is hindered by atmospheric absorption, scattering, and turbulence. In this paper, it was supposed that 1Gbps information was transmitted by binary FSK and 50mW AlGaAs semiconductor laser was used as a optical source in the satellite communication link between geosynchronous orbit satellite and earth station. We analyzed the BER and the entire diameter of the noncoherently combined optical heterodyne receiver as el evation angle, and determined the number of the optical heterodyne rece ivers, which is necessary for the BER of the receiver to be less than 10$^{-9}$ by computer simulation under the clear weather condition. It is shown that the BER and the number of the optical heterodyne receivers decrease as the elevation angle increases. In the region used the same number of the optical heterodyne receivers, it is shown that the entire diameter of the receiver increases but the BER decreases as the elevation angle increases.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2010.05a
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• pp.233-236
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• 2010

This paper describes the packet traffic management of the Ubiquitous Healthcare System. In this system, ECG signal and accelerometer signal is transmitted from a wearable health shirt (WHS) to the base station. However, with the increment of users in this system, traffic over-load issue occurs. The main aim of this paper is to reduce the traffic over-load issue between sensor nodes by only transmitting the required signals to the base station when irregular activities are observed. In order to achieve this, in-network processing is adapted where the process of observation is conducted inside the sensor node of WHS. Results shows that irregular activities such as fall can be detected on real-time inside the sensor node and thus resolves traffic over-load issue.

• Journal of Bio-Environment Control
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• v.19 no.1
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• pp.6-11
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• 2010

This experiment was conducted to investigate the effect of greenhouse orientation on the greenhouse environment and the growth and yield of tomato cv 'Momotaro-Yoku' in forcing culture. The photosynthetic phpton flux density (PPFD) of a.m was higher in north-south orientation than that in east-west orientation and it was opposed in the p.m. Mean PPFD of a day was higher in east-west orientation than that in north-south orientation because the light transmitting area became larger in east-west orientation with decrease of incidence angle. The PPFD at 60 cm point above ground of all furrows was poor due to shadows near plants and it was higher in north-south orientation than that in east-west orientation. The air temperature in the greenhouse was higher in east-west orientation than that in north-south orientation but there was no significant difference since mid February as solar altitude goes up. The soil temperature was some higher in east-west orientation than that in north-south orientation and there was not significant difference among ridges. In east-west orientation, as ripening was promoted, high early yield of tomato were obtained. So total yield was greater about 8% in east-west orientation than that in north-south orientation. Therefore, it was considered that east-west orientation is more advantageous than north-south orientation for forcing culture of tomato.

• Aerospace Engineering and Technology
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• v.13 no.2
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• pp.142-149
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• 2014

After launch of Low Earth Orbit(LEO) satellite, Initial Activation Checkout(IAC) and Calibration and Validation(Cal & Val) procedure are performed prior to enter normal operation phase. During normal operation phase, most of the time is allocated for mission operation except following up measures to anomaly and orbit maintenance. Since mission operation capability is key indicator for success of LEO satellite program and consistent with promotion purpose of LEO satellite program, reliability should be ensured by conducting through test. In order to ensure reliability by examining the role of LEO satellite and ground station during ground test phase, realistic test scenario that is similar to actual operation conditions should be created, and test that aims to verify full mission cycle should be performed by transmitting created command and receiving image and telemetry data. This paper describes the test design and result. Consideration items for test design are described in detail and result of designed test items are summarized.

• The Journal of the Korea Contents Association
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• v.14 no.4
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• pp.58-66
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• 2014

It is one of the representation technique very common to be used, such as visual communication, a variety of cultural content, anthropomorphic, is dependent on the anthropomorphic approach most content for children in particular. In addition, personification can see a variety of cases in the field of culture and art of many other operations, including literature and poetry. By analyzing the case of reverse personification and anthropomorphic when transmitting content and image of the language that was meant, of anthropomorphic elements, which can be reverse action and an equal effect between those non-human and human it is possible to confirm that. Therefore, in this paper, we redefine the concept and elements of anthropomorphic, it defines the concept of anthropomorphic station on the basis of this, and were analyzed for the case. In addition, among the cases of good quality that communicate with anthropomorphic approach the station, the character analysis short animation of "The Employment employment", be used as academic materials of anthropomorphic approach the station of visual culture content areas of future possible.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38B no.8
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• pp.679-686
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• 2013

Power efficiency becomes more important in wireless LANs as the mobile stations send more data with limited batteries. It has been known that the IEEE 802.11 PSM is not efficient in high load networks: AP cannot deliver buffered packets to a PS station immediately and it can lead the station to stay in active state quite long and result in energy waste. Moreover, it is inefficient that only one data frame is retrieved by a PS-POLL frame. In this paper, we propose a time slotted scheme to enhance the PSM, in which a mobile station can reserve time slots to receive data frames. Our mechanism can reduce collisions by reservation and decrease the channel occupancy by transmitting multiple data frames via one PS-POLL. The analytic model and simulation results show that proposed scheme reduces power consumption significantly and enhances the performance of PSM.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.46 no.10
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• pp.856-867
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• 2018

This paper presents the applicability of MIMO joint decoding to dual-contact satellite systems in which two LEO satellites using X-band frequency band are transmitting each image data to two ground station antennas, simultaneously. When two satellites are closely positioned within the looking angle of the two antennas, each satellite interferes with each other by the relative antenna gain corresponding to an offset angle and this might cause the performance degradation without interference mitigation. To mitigate the performance degradation, SM MIMO techniques for joint decoding are applied. Especially, the relative antenna gain of ground station depending on the angle difference between two satellites in ground station antenna plays an important role in modelling the dual-contact satellite systems. The condition number of MIMO channel including the antenna gain calculated from the mathematical gain pattern model was primarily analyzed. Simulation results showed that the SM MIMO techniques using detection schemes such as ZF-SIC, MMSE-SIC, and ML can be applicable to dual-contact satellite systems.

• Journal of Digital Contents Society
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• v.9 no.4
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• pp.601-606
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• 2008

U-Healthcare is one of the major applications in ubiquitous sensor network. U-Healthcare has potential to become a critical service for the people who immediately require emergency ambulatory attention. This paper describes about the real time pulse monitoring and reporting system, consisting of two components: thus, the one is a reliable bio-sensor that continuously monitors the pulse information of the subject, and the other is the automatic transfer system that transmits pulse information to both his/her family and hospital care system through the Base Station. In the hospital, this bio-information can be used to treat the patient accordingly. I designed the pulse information monitored by a bio-sensor module that transfers the pulse information to both the Base Station and the central monitoring system through transmitting protocols such as Zigbee and TCP/IP, as well as designed the architecture of information packets for the corresponding protocols. Furthermore, the central monitoring system automatically parses the pulse information of the subject into the web database server, which can continuously provides the real time information and status of the subject via an internet browser to the clients who are family members of the subject and the authenticated medical care personnel as well.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.7B
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• pp.719-726
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• 2002

In WRC-2000, Resolution 734 was adopted to study the use of high altitude platform station(HAPS) operating in the bands above 30GHz. Therefore, frequency sharing feasibility between a new HAPS systems and an existing terrestrial fixed-service(FS) system should be analyzed primarily. In this paper, interference effects from the HAPS system into the radio-relay station are analyzed in terms of two cases; one is the interference distribution from the power-flux density(PFD) of HAPS airships, and the other the interference power from the ground stations. In conclusion, the new PFD criteria different from the exiting satellite system should be required, and the coordinated distance between the HAPS nadir and the radio-relay station should be 60km ∼ 253km for P$\sub$HG/ = -50dBW/MHz of transmitting power spectral density to share the new HAPS system into the existing FS system.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2013.10a
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• pp.1033-1036
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• 2013

A study about collision resolution is needed because huge file, video and multimedia information are transmitted to wireless LAN. CSMA/CR protocol guarantees fairness, but doesn't consider QoS. To practicalize CSMA/CR protocol in saturation fully-connected single hop network environments, this paper proposes method of collision compensation. previous CSMA/CR protocol chooses CR Slot only considering fairness, but this paper chooses front CR Slot for compensation of collision to station experiencing collisions. The station transmits jam signal and has channel priority of transmission. So transmitting efficiency and successful transmission probability rise. This proposed simple method can offer benefit to station experiencing collisions without additional hardware cost.