• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.6
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• pp.707-713
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• 2016

In the IEEE 802.11 Wireless LAN environment, the common Access Point (AP) selection of the existing terminal is based on signal strength. However, the signal strength-based AP selection method does not ensure an optimal data rate. Recently, several AP selection methods to solve this problem have been suggested. However, when we select AP, these have a latency problem and don't consider dense environments of AP. In this paper, we confirm the problem of the conventional AP selection about the signal strength and the throughput through the actual measurement, and propose algorithm that selects AP by scoring link speed and wireless round trip time to compensate the problem. Furthermore, the proposed AP selection algorithm through the actual experiment proves the improved performance as compared with the existing methods.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2011.10a
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• pp.85-87
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• 2011

WPS_WS는 무선 AP의 정보를 통해 현재 이동 객체의 위치를 찾는 시스템이다. 실외 및 실내의 AP 신호 세기 특징을 활용하여 현재 위치를 판단하며 이를 위해 AP 정보를 저장하기 위한 Radio Map구축이 선행되어야 한다. 최초 서비스를 위하여 map을 구성하더라도 실외의 경우 AP신호의 가변성에 의해 구축된 DB의 map 정보를 100% 신뢰할 수 없다. 따라서 신호세기의 변동을 감지하여 능동적으로 map 정보를 변경해 줄 필요가 있다. 본 논문은 이동객체가 현재의 위치를 판단하기 위해 수집한 AP의 정보 중 오류 정보들을 저장하여 분석하고 이를 토대로 구축된 MAP을 실시간으로 변경 및 수정하여 AP의 신호 변경에 능동적으로 대처할 수 있는 Radio Map 최적화 모듈에 대하여 제안한다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2022.10a
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• pp.59-61
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• 2022

Among indoor positioning system techniques using wireless APs, fingerprint techniques collect Mac information and reception strength of APs before performing positioning, build a radio map, and compare it with AP information collected during positioning. However, the existing Radio Map construction method has a problem in that signal interference occurs due to collisions of numerous APs depending on the indoor environment, and the signal strength search result is not always constant. Therefore, this paper compares the existing fixed radio map construction method and the variable radio map construction technique that actively analyzes and constructs the measurement area itself according to signal strength.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2014.05a
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• pp.341-343
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• 2014

실내 무선 측위 시스템(IPS : Indoor Positioning System) 중 Wifi 신호를 활용하는 방식의 대부분은 측위를 수행하기 이전에 AP의 mac 정보와 수신세기를 수집 하여 radio map을 구축하고 이후 측위 과정에서 수집되는 AP의 정보와 비교하여 위치를 판단한다. 이 방식은 신호 세기의 변화가 없을 경우 실내에서 매우 높은 정확도로 측위를 수행할 수 있다. 그러나 현실세계에서는 구축된 radio map의 신호에 심각한 영향을 줄 수 있는 여러 가지 상황이 존재한다. 대표적으로 채널 간섭 현상을 둘 수 있다. radio map으로 구축되어 있는 AP의 신호 영역 내에 동일 채널 및 인접 채널을 가지는 AP 및 테더링 기기 등이 신규로 설치될 경우 기존 radio map 신호에 영향을 주어 측위 과정에서 정확도가 떨어지는 문제점이 발생하다. 본 논문에서는 앞서 언급한 문제점을 해결하기 위해 AP의 특성 정보를 다중 그리드 Radio map으로 구성하는 방안을 연구하였다. 이 다중 그리드 Radio map을 통해 측위 단계에서 수집된 AP 신호를 더욱 정확하게 분석하고 신호 변동에 능동적으로 대처할 수 있도록 구성하여 기존의 문제점을 해결할 수 있는 방안에 대하여 제안한다.

• Journal of Satellite, Information and Communications
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• v.9 no.3
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• pp.70-73
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• 2014

In this paper, we measure and analyze strength of Beacon signal in Picocell environment by using the frequency of WiFi of ISM band. It is displaying the value what measured by using a beacon signal measurement smartphone app in using AP area, on Google maps using the PC application. the data measured by using mapped GPS signal and RSSI of beacon signal, and convert this data to Position coordinates for Google map in PC. when use this system, we can understand and analyze changes of radio signal through location where installed AP.

• The Journal of the Korea Contents Association
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• v.10 no.6
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• pp.64-71
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• 2010

When Handoff occurs at wireless network, existing AP search chooses one of various APs according to signal strength information. However, IEEE 802.11 uses Medium Access method with CSMA/CA that competes to obtain a channel by sharing medium. Therefore, network performance is heavily affected by the number of nodes and network congestion aside from signal strength. This scheme presented an additional AP selection indicator and a new handoff algorithm to realize handoff guaranteeing the network performance of mobile node in a process selecting new AP. This indicator is includes a handoff cost function reflecting the network information of mobile node, and the mobile node made handoff guaranteeing the network performance using network information possible by using this. also we classified the nodes into high-speed node and low-speed node. Then, when Handoff occurs, high-speed node was made itself choose AP by signal strength information. We also made the low-speed node choose its AP by using AP network information which is applied area. Hence, we demonstrate through simulation that gets an improvement in performance, even in the wireless network which many users concurrently access to, and it has considerable effects on aspects of resources and network management by distribution of users.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.5
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• pp.3440-3446
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• 2015

One of technologies that make it possible for users to enjoy always-on Internet service using potable devices does be Wifi. However, users frequently feel its connection is not stable or its speed becomes slow. On the other hand, users see multiple available Wifi access points exist often. In this paper, we present a smartphone application, called to WiSMax, that periodically changes its Wifi connection to the best one among available Wifi access points to maximize its speed. Experimental results show that WiSMax presents faster Internet connection than IEEE802.11 as much as about fifteen percent and higher signal strength than IEEE802.11 as much as about five dBm.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.27 no.4
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• pp.505-513
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• 2009

Recently, researches on the construction information for construction of high-tech cities are under performed. RTLS(Real-Time location system) for gathering the dynamic location information of construction resources in construction sites, such as workers, materials and equipments, is one of the developments. Especially, construction resources can be managed efficiently with the dynamic location information and the improvement of safety and the reduction of cost are expected. To introduce the RTLS to the construction sites, the installation location of AP(Access Point) must be simulated using the 3-dimensional visibility analysis considering the propagation distance of AP. In this research, 3-dimensional signal simulation software based on the spatial data using surveying terrestrial LiDAR is developed. The simulated results are compared with the signal strength of field experiments for 4 test sites. As a result, the signal strength from the propagation model is most similar to that of field experiment at the front of the main building and the maul playground of Konkuk University. The visibilities in that sites are higher than other sites. among 4 test sites.

• Proceedings of the Korea Information Processing Society Conference
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• 2011.11a
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• pp.581-583
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• 2011

최근에 급격히 증가한 스마트폰의 사용자들이 이동중에도 안정적인 무선 네트워크를 이용하기 위해서는 핸드오프는 반드시 필요하다. 핸드오프를 위하여 기존에 연결되어 있는 AP(Access Point)와의 연결을 끊고 주변의 AP 를 스캐닝한 후 새로운 AP 로 재연결을 하는 과정을 거치게 된다. 이러한 과정 중에 본 논문에서는 스캐닝 단계에서 발생하는 문제점을 분석하고 이에 대한 개선방안으로 AP 의 신호세기와 스마트폰의 센서를 이용하여 사용자의 이동성을 고려하는 스캐닝 방식을 제안한다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38C no.2
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• pp.181-188
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• 2013

In this paper, we present a system design for location determination inside the ship. Since the GPS signal can not be received in the interior of the large vessel, we use the vessel wireless AP (Access Point) RSSI (received signal strength indication) to accurately measure the position. We convert the RSSI for the 3 AP's into distance through the Friis formula and get the location through triangulation. The signal strength varies irregularly due to noise making it difficult to obtain the exact location. Thus Kalman filter is used to real-time position correction, that is store in a server database.