• Proceedings of the Korea Information Processing Society Conference
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• 2012.04a
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• pp.191-194
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• 2012

Rendering maps is an essential feature of the user interface component of a location based service (LBS) system. However, a developer may not too much worry about implementing the rendering maps part of his or her system because there are quite a few publicly available libraries that provide all kinds of functions of manipulating maps. Google Maps, Yahoo Map, Naver Map, Daum Map, and so on are example sites that provide those libraries. Rendering drawings is to indoor LBS as rendering maps is to LBS. However, there is no such thing as Google Maps that provides libraries for rendering drawings. This paper introduces a few web services and a library that is useful in developing user interfaces of indoor LBS systems.

• Proceedings of the Korea Information Processing Society Conference
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• 2007.05a
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• pp.1473-1476
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• 2007

유비쿼터스 컴퓨팅과 유비쿼터스 네트워크가 다양하게 발전되고 활용됨에 따라 유비쿼터스 환경에서 LBS(위치 기반서비스) 관련 기술의 중용성도 높아지고 있다. 이런 LBS를 위한 기존의 대표적인 옥내 측위 시스템들을 알아보고, IEEE802.11b 규격의 2.4GHz RF의 RSSI와 거리와의 관계를 기반으로 TDOA를 이용한 방법과 Extended Kalman Filter를 이용한 방법의 측위 시스템을 구현하고 실험을 통한 실측 오차를 비교 분석한다.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.43 no.6 s.312
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• pp.1-9
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• 2006

For the indoor positioning, wireless fingerprinting is most favorable because fingerprinting is most accurate among the techniques for wireless network based indoor positioning which does not require any special equipments dedicated for positioning. The deployment of a fingerprinting method consists of off-line phase and on-line phase. Off-line phase is not a time critical procedure, but on-line phase is indeed a time-critical procedure. If it is too slow then the user's location can be changed while it is calculating and the positioning method would never be accurate. Even so there is no research of improving efficiency of on-line phase of wireless fingerprinting. This paper proposes a decision-tree method for wireless fingerprinting and performs comparative analysis of the fingerprinting techniques including K-NN, Bayesian and our decision-tree.

• Proceedings of the Korea Information Processing Society Conference
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• 2005.11a
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• pp.1343-1346
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• 2005

위치기반서비스 시스템에서 가장 기본이 되는 요소는 사용자의 위치를 정확히 측정하는 것이다. 측위 시스템은 옥외용과 옥내용으로 구분될 수 있고, 옥외용은 GPS 기반 시스템이 가장 일반적이다. 본 논문은 SiRF StarⅡ chipset을 이용하여 전자캠퍼스를 위한 옥외용 측위시스템 구현 사례를 소개한다. 전자캠퍼스의 특징으로 적용 영역이 비교적 협소하다는 것과 따라서 좀 더 정확한 측정 방법이 필요하다는 것을 들 수 있다. 본 논문은 RADAR 방식을 사용하여 오차를 줄일 수 있다는 것과 사용자 추적 방법 구현 사례를 보인다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.6A
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• pp.476-483
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• 2009

Recently much attention has been devoted to femtocell's potential to improve indoor cellular coverage and high speed wireless communications. Femtocell based commercial services have been already launched in some countries and standardization activities are actively on-going, there has been concern however over potential issues of interference between femtocells and the micro/macro networks. With universal frequency reuse, the ensuing cross-tier interference causes unacceptable data rate and outage probability, so an analysis of effect of interference in femtocell embedded networks would be necessary for a stable system design. This paper investigates the effect of interference on system performances of femtocell embedded hierarchical cell structure (HCS) networks considering the characteristics of propagation environments. Various channel parameters are specially considered for indoor environments where most of femtocells are deployed to investigate the effect of interference of femtocell embedded RCS networks. System capacity and coverage are provided with variant distance between macrocell and femtocell, location of the user in femtocell coverage, and characteristic of building structures.

• The Journal of Information Systems
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• v.17 no.1
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• pp.131-153
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• 2008

So many location based service systems, including automobile navigation system logistic management, taxi fleet management, and so on, are being used everywhere. However, these are all outdoors. This paper provides a stepping stone for commercial indoor location based services by developing an integrated system of our indoor positioning and map viewer modules. For the indoor positioning, we propose WLAN (Wireless Local Area Network) based EKF (Extended Kalman Filter) which estimates user's current location and tracts user's trace in the sequence of time. Our map viewer renders a map recorded in an Autocad DXF file and provides functions of map manipulation such as zoom-in, zoom-out, and move. We integrate our indoor positioning and map viewer modules and discuss the experimental results of the integrated system.

• The Journal of Information Systems
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• v.19 no.1
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• pp.1-17
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• 2010

This paper proposes an updating policy of indoor moving object databases (IMODB) for location-based services. our method applies the Ka1man filter on the recently collected measured positions to estimate the moving object's position and velocity at the moment of the most recent measurement, and extrapolate the current position with the estimated position and velocity. If the distance between the extrapolated current position and the measured current position is within the threshold, in other words if they are close then we skip updating the IMODB. When the IMODB needs to know the moving object's position at a certain moment T, it applies the Kalman filter on the series of the measurements received before T and extrapolates the position at T with the estimations obtained by the Kalman filter. In order to verify the efficiency of our updating method, we performed the experiments of applying our method on the series of measured positions obtained by applying the fingerprinting indoor positioning method while we are actually walking through the test bed. In the analysis of the test results, we estimated the communication saving rate of our method and the error increment rate caused by the communication saving.