• The Journal of the Korea institute of electronic communication sciences
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• v.15 no.1
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• pp.205-210
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• 2020

Children should be provided with the right to be protected by adults, related organizations, or countries because they lack power, situation recognition ability, and situation judgment ability compared to adults. Also, children's accidents and accidents caused by neglect of management occur every year. Currently, there are about 3 to 20 children managed by one teacher in a daycare center, and it is very difficult for teachers to care for all children as many children have to be managed. Especially, when outdoor activities are conducted in open space, children's activities are expanded compared to the in-house, and children who do not follow the control of the in-house teacher may occur, so there is a limit to the control and management of children depending on the viewpoint of teachers. In this study, we designed and implemented IoT terminal and system to provide safety to children and to provide convenience to guardians and teachers by systemizing the location or interval between children and in-service teachers using portable devices that can communicate with each other. It is hoped that this will contribute to the safety of infants.

• Journal of KIISE:Computing Practices and Letters
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• v.14 no.4
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• pp.436-440
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• 2008

In IEEE 802.15.4 beacon-enabled mode, performance decreases as the number of devices competing in the contention access period(CAP) increases. In this letter, we propose partitioned contention access mechanism(PCAM) to compensate performance degradation. In PCAM, the PAN coordinator divides CAP into two sub-periods and activity of devices is delimited in their assigned sub-periods. Since PCAM reduces the number of devices which compete at the same time by half, collision probability between transmitted frames can be reduced. In addition, devices can save their power consumption because PCAM shorten the duration that devices stay in active state into half. We perform simulations to compare the performance of PCAM with that of the IEEE 802.15.4 standard. From the result, PCAM yields better performance than IEEE 802.15.4 standard.

• Journal of Satellite, Information and Communications
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• v.2 no.2
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• pp.41-47
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• 2007

The first geostationary satellite made by Korea, COMS, has the three different payload ; Meteorological sensor, Oceanographic sensor and Ka-band communication payload. There are Meteorological & Ocean Data Communication Subsystem(MODCS) and Telemetry, Command and Ranging Subsystem(TC&R) as other RF radiation sources. MODCS transmits and receives Meteo and Ocean measurement data from/to earth using L-band and TC&R using S-band. The Ka-band communication payload will provide high-speed multimedia services and communication services for natural disaster such as prediction, prevention, and recovery services in the government communications network.Ka-band beacon is for the earth antenna pointing and the experiment of rain fading. This paper gives the analysis results about the mutual radiation effect on Ka-band communication payload, Ka-band beacon, MODCS and TC&R. Up/Down link power and coupling factor including the geometrical position and distance of antenna, filter rejection and degradation factor due to the different polarization are considered. The results show MODCS and TC&R are compatible for Ka-band communication payload and Ka-band beacon does not interfere with MODCS and TC&R normal operation.

• Journal of KIISE:Computing Practices and Letters
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• v.16 no.11
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• pp.1081-1085
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• 2010

In the wireless sensor networks, power consumption and interference among the nodes can be reduced by using the transmission power control. Because link quality is changed by spatial and temporal effect, link failures are frequently occurred. In order to adapt to link quality variation, existing transmission power control schemes broadcast beacon messages periodically to neighbor nodes and control the transmission power dynamically. However, it can effect on the time and energy overhead according to period of transmission power control. In this paper, the dynamic method of transmission power control by the link quality variation and variable period are proposed. When a link quality is unstable, the control duty cycle is reduced and the link quality is agilely maintained. In contrast, when link quality is stable, the control period is increased and control overhead is decreased.

• Journal of Korea Multimedia Society
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• v.23 no.9
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• pp.1164-1170
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• 2020

In this paper, we consider the wireless-powered backscatter communication which consists of a power beacon, a source, a relay, and a destination. For the proposed wireless-powered backscatter communication, the source transmits its signals to both the relay and the destination via a backscattering channel and the relay which has a rechargeable battery performs an energy harvesting as well as an information forwarding based on the time switching relay (TSR) protocol. Based on the decode-and-forward (DF) relay transmission, we investigate performances of the proposed system in terms of outage probability and transmission rate in which the exact performance analysis of outage probability is given. Finally, some numerical examples are given to verify our provided analytical results for different system conditions.

• Proceedings of the KIEE Conference
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• 2007.04a
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• pp.423-425
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• 2007

In this paper, Medium Access Control(MAC) protocol designed for Wireless Body area Sensor Network(Bio-MAC) is proposed, Because in WBSN, the number of node is limited and each node has different characteristics. Also, reliability in transmitting vital data sensed at each node and periodic transmission should be considered so that general MAC protocol cannot satisfy such requirements of biomedical sensors in WBSN. Bio-MAC aims at optimal MAC protocol in WBSN. For this, Bio-MAC used Pattern -SuperFrame, which modified IEE E 802.15.4-based SuperFrame structurely. Bio-MAC based on TDMA uses Medium Access-priority and Pattern eXchange -Beacon method for dynamic slot allocation by considering critical sensing data or power consumption level of sensor no de etc. Also, because of the least delay time. Bio-MAC is suitable in the periodic transmission of vital signal data. The simulation results demonstrate that a efficient performance in WBSN can be achieved through the proposed Bio-MAC.

• Proceedings of the Korea Information Processing Society Conference
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• 2005.11a
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• pp.643-646
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• 2005

지그비(zigbee) 장비는 센서 네트워크 장비 중에서도 규모가 큰 축에 속하고 배터리로 동작하기 때문에 전력 소비가 큰 문제점으로 부각되고 있다. 지그비에서 비콘(beacon)을 사용하는 네트워크를 구성하면, 센서 장치들은 데이터 전송 빈도가 낮을 때도 중앙 데이터 처리기(coordinator)가 전송하는 비콘 패킷을 매번 받아야 하기 때문에 그에 따른 전력소모가 상당히 높다. 이러한 지그비 네트워크의 중앙 데이터 처리기와 주변 센서 장치(device)에 비콘 수신 주기를 동적으로 설정할 수 있는 프로토콜을 추가 함으로써 기존의 데이터 응답 속도를 유지하면서 전력 소모도 줄이는 방안을 제시하고자 한다.

• Proceedings of the Korean Society of Computer Information Conference
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• 2017.07a
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• pp.326-327
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• 2017

저전력 블루투스가 공개 된 이후 저전력 블루투스 비콘을 이용한 서비스들이 출시되고 있다. 비콘 기반 서비스는 사용자의 스마트폰이 블루투스 기능을 활성화해두었을 때, 일정한 주기의 블루투스 스캐닝을 통해 이용할 수 있다. 블루투스 비콘이 밀집된 실내 공간의 경우, 동일한 비콘이 중복 탐지되거나 사용자가 사용하지 않을 먼 거리의 비콘까지 탐지하게 되므로 스마트폰에서 불필요한 에너지 소모가 발생한다. 이러한 문제를 해결하고자 본 연구에서는 실내 구획화를 통해 동일 영역 내에서 비콘이 중복으로 탐지되는 것을 방지하는 방법과, 사용자 이동성에 따른 동적 스캐닝 주기 최적화를 통해 밀집된 실내 공간에서도 누락되는 비콘 신호를 최소로 하는 기법을 제안한다. 이러한 사용자 이동성에 기반한 스캐닝 주기 최적화 방법은 스마트폰의 전력소모량을 감소시킨다.

• Bulletin of the Korean Space Science Society
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• 2004.10b
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• pp.247-250
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• 2004

Tracking systems for launch vehicle consist mainly of radar transponder (beacon), RF switch or power divider, antennas as onboard system, and single or multiple radars as ground one. In this paper, tracking systems, which are applicable to KSLV (Korea Space Launch Vehicle)-l, are introduced and the electrical performances for developed prototypes are presented. We have also performed RF link analysis for both uplink and downlink, and estimated that the maximum distance to be able to track KSLV-l stably is dependent on uplink characteristic in our system.

• Proceedings of the Korea Information Processing Society Conference
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• 2016.04a
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• pp.897-899
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• 2016

In recent years, BLE technology has received extensive attention and has been applied to all aspects of life. The existing BLE device has two methods, one is the connection method, and the other is a non-connection method. The representative profile of the connection method is the proximity file. The most typical example of Non-connection method BLE device is a beacon. However, they are both independent and have their own shortcomings. Connection method device can provide service for only one user, others can't use. Security performance of Non-connection method BLE device is poor and the device can't be controlled by the user. In this paper, a combination-mode BLE device profile design scheme is presented, which combines with the previous two methods, and solves the defaults. And We define a dual purpose advertising package that can be used in a normal environment as well as in a disaster environment. Finally, a unidirectional Control idea is proposed. Through performance evaluation, we found that the device has strong stability and low power consumption.