• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.7 no.2
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• pp.13-25
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• 2008

In this paper, we propose the Location Awareness System adjusting Ranging Technology for CSS(Chirp Spread Spectrum) which is adopted on 2.45GHz standard in IEEE 802.15.4a and TOA(Time-of-Arrival) algorithm. The conventional methods have adopted RSSI, ultrasonic waves and infrared rays in Zigbee. RSSI measures strength indication of received signal and recognizes the position of nodes in RF boundary. However, this technology has the following problems; lots of error by the change of the channel environment and much power consumption. In this paper, adopting chirp pulse on 2.45GHz standard in IEEE 802.15.4a and SDS-TWR(Symmetrical Double Side-Two Way Ranging) method using the characteristic of Spread Spectrum, a new Location Awareness System is suggested. The distance and the coordinate are measured within ${\pm}\;5cm$ by TOA(Time of Arrival) algorithm and proposed algorithm and the data in error rate is decreased less than 1%. Through these results, the algorithm suggested in this paper is verified for its performance in a computer simulation.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.5B
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• pp.370-376
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• 2012

The CSS(Chirp Spread Spectrum) technology is used for developing various WPAN(Wireless Personal Area Network) application fields in general, and it can be adapted to implement localization systems especially using SDS-TWR(Symmetric Double Sided - Two Way Ranging). But the ranging errors are occurred in many practical applications due to some interferences by some experiments. Thus, the compensation algorithm for localization is required for developing localization applications. The suggested compensation algorithm that is named KF_EDR(Kalman Filter and Equivalent Distance Rate) for localization in order to reduce the ranging errors is suggested in this paper. The KF_EDR compensation algorithm for localization is mainly composed of the AEDR(Algorithm of Equivalent Distance Rate) and the Kalman Filter. It is confirmed that the improved error ratio of the KF_EDR are 10.5% and 4.2% compared with the AEDR algorithm in lobby and stadium. From the results, it is analyzed that the KF_EDR can be widely used for some localization system in ubiquitous society.

• The Journal of Korea Robotics Society
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• v.11 no.3
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• pp.127-132
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• 2016

For a practical mobile robot team such as carrying out a search and rescue mission in a disaster area, the localization have to be guaranteed even in an environment where the network infrastructure is destroyed or a global positioning system (GPS) is unavailable. The proposed architecture supports localizing robots seamlessly by finding their relative locations while moving from a global outdoor environment to a local indoor position. The proposed schemes use a cooperative positioning system (CPS) based on the two-way ranging (TWR) technique. In the proposed TWR-based CPS, each non-localized mobile robot act as tag, and finds its position using bilateral range measurements of all localized mobile robots. The localized mobile robots act as anchors, and support the localization of mobile robots in the GPS-shadow region such as an indoor environment. As a tag localizes its position with anchors, the position error of the anchor propagates to the tag, and the position error of the tag accumulates the position errors of the anchor. To minimize the effect of error propagation, this paper suggests the new scheme of full-mesh based CPS for improving the position accuracy. The proposed schemes assuring localization were validated through experiment results.

• Journal of Engineering Education Research
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• v.13 no.5
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• pp.76-80
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• 2010

In this paper, the Location Compensation Mechanism using equivalent distance rate ($LCM_{edr}$) for localization system based on SDS-TWR (Symmetric Double-Sided Two-Way Ranging) in wireless sensor network is proposed. The performance of the mechanism is experimented in terms of two types of the localization tracking scenarios of indoor and outdoor environments in university campus. From the experimentations, the compensation ratio in the $LCM_{edr}$ is better than that in SDS-TWR about 90% in indoor/outdoor environments in scenario 1 but also is better than that of SDS-TWR about 91.7% in indoor environment and about 100% in outdoor environment in scenario 2 respectively.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.7C
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• pp.608-615
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• 2007

Generally time of arrival (TOA) information via two way communications can be derived by accurate round trip time (RTT) between two devices. However, response time demanded in RTT measurement is long, a serious TOA error is caused by each different clock drift between two devices. In order to solve this problem, we propose the TOA and time difference of arrival (TDOA) estimation scheme with mitigating clock drift effect. To verify the performance of proposed method, we compared the proposed scheme with one way based TDOA acquisition method introduced by IEEE 802.15.4a Task Group and then we could conclude that the proposed method has better performance over other methods.

• The KIPS Transactions:PartC
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• v.16C no.2
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• pp.229-236
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• 2009

UWB signal with high resolution capability can be used to estimate ranging and positioning in wireless personal area networks. The clock frequency differences of nodes have serious affects on asynchronous ranging methods to estimate locations of mobile nodes. The specification of high rate UWB describes successive TWR method with the estimation of a relative clock frequency offset. In this paper, we complete the ranging equations using relative frequency offset and time information, and propose a method to estimate the exact frequency offsets. We evaluate the ranging algorithms with simulation. The results show that the performances of the algorithms using frequency offsets are very close without noise. But, at noise environment, the method of exact frequency offsets shows better performance than that of relative frequency offsets.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.2
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• pp.75-83
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• 2005

NASA/DLR Gravity Recovery and Climate Experiment (GRACE) mission, which consists of two co-orbiting low altitude satellites, is to measure the Earth gravity field with unprecedented accuracy. Its key instruments include inter-satellite ranging systems and three-axis accelerometers. For the preliminary design and requirements analysis, extensive instrument simulation models are developed. These modeling techniques and orbit-gravity field estimation techniques are described.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2012.06a
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• pp.133-133
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• 2012

본 연구에서는 현재의 실내 위치인식시스템에 있어서 오차 발생 문제점을 초전센서를 이용하여 보완하였다. 기존의 CSS기술은 SDS-TWR(Symmetric Double-Sided Two-Way Ranging) 기반의 위치인식시스템을 구현하는 기술로 사용되고 있으나 전파의 반사 및 간섭에 의해 레인징의 오차가 크게 발생하고 수신 감도가 현저하게 떨어지는 현상이 발생한다. 따라서 본 논문에서는 환경적인 제약을 받는 공간에서 CSS을 이용한 SDS-TWR과 초전센서를 사용하여 수신불량과 오차를 줄여 사용자의 위치인식을 가능하도록 하였다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39C no.5
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• pp.407-412
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• 2014

Concerns and demands for the Location Based Services (LBS) using Global Positioning System (GPS) and Wi-Fi are largely increased in the world in the present. In some experimental results, it was noted that many errors are frequently occurred when the distances between an anchor node and a mobile node acre measured in indoor localization environment of Wireless Personal Area Network (WPAN). In this paper, localization compensation algorithm based on maximum measurement value ($LCA_{MMV}$) for moving objects in WPAN is proposed, and the performance of the algorithm is analyzed by experiments on three scenarios for movement of mobile nodes. From the experiments, it was confirmed that the average localization accuracy of suggested algorithm was more increased than Symmetric Double-Sided Two-Way Ranging (SDS-TWR) and triangulation as average 40.9cm, 77.6cm and 6.3cm, respectively on scenario 1-3.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.4B
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• pp.309-316
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• 2012

The compensation algorithm for localization using the least-squires method in NLOS(Non Line of Sight) environment is suggested and the performance of the algorithm is analyzed in this paper. In order to improve the localization correction rate of the moving node, 1) the distance value of the moving node that is moving as an constant speed is measured by SDS-TWR(Symmetric Double-Sided Two-Way Ranging); 2) the location of the moving node is measured using the triangulation scheme; 3) the location of the moving node measured in 2) is compensated using the least-squares method. By the experiments in NLOS environment, it is confirmed that the average localization error rates are measured to ${\pm}1m$, ${\pm}0.2m$ and ${\pm}0.1m$ by the triangulation scheme, the Kalman filter and the least-squires method respectively. As a result, we can see that the localization error rate of the suggested algorithm is higher than that of the triangulation as average 86.0% and the Kalman filter as average 16.0% respectively.