• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2006.05a
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• pp.397-401
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• 2006

In this paper, we proposed a high precision location estimation algorithm using an enhanced decision scheme for RTLS and analyzed its performance in point of an average estimation error distance at 2D coordinates searching area, $300m\times300m$ and LOS propagation environments. Also the performance was compared with that of conventional TDOA algorithm according to the number of available reader and received sub-blink. From the results, we confirmed that the proposed location estimation algorithm using an enhanced decision scheme was able to improve an estimation accuracy even in boundary region of searching area. Moreover, effectively reduced an error distance in entire searching area so that increased the stability of location estimation in RTLS. Therefore, we verified that the proposed algorithm provided a more higher estimation accuracy and stability than conventional TDOA.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.10
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• pp.2523-2529
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• 2014

Location estimation service can be provided outdoors using various location estimation system based on GPS. However, location estimation system is based on existing indoor resources as GPS cannot be used because of insufficient visible satellites and weak signals. The fingerprinting technique that uses WLAN signal, in particular, is good to use indoors because it uses RSSI provided by AP to estimate location. However, its accuracy may vary depending on how accurate data the offline stage used where the fingerprinting map is built. The study sampled various data at the stage that builds the fingerprinting map and suggested a location estimation system that enhances its precision by saving the data of high frequency among them to improve this problem. The suggested location estimation system based on majority sampling data estimates location by filtering RSSI data of the highest frequency at the client and server to be saved at a map, building the map and measuring a similar distance. As a result of the test, the location estimation precision stood at minimum 87.5 % and maximum 90.4% with the margin of error at minimum 0.25 to 2.72m.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• v.9 no.2
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• pp.459-462
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• 2005

In this paper, we investigate the high precision location estimation algorithm in 2.45GHz band RTLS with multiple tags. The location is estimated in LOS environments, 300m ${\times}$ 300m area, and 2D coordinates adopting a TDOA scheme which is not necessitate the transmission time of tags. We evaluate the average estimation error in distance assuming that tags are randomly distributed and the readers(3${\sim}$8) are uniformly(equal space) placed in test area. In results, average estimation error is 3.12m and 1.47m at reader numbers of 4 and 8, respectively. Minimum estimation error is obtained when the accumulated receiving signal from a tag is 3 or 4 regardless of available reader numbers. The error is less than 3m, satisfies the specification of RTLS.

• Journal of Advanced Navigation Technology
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• v.16 no.2
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• pp.297-306
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• 2012

In this paper, we propose a Time Delay Traceback Scheme for the TDOA location estimation performance enhancement in NLOS environment and analyze the performance in various conditions. We place multiple readers in a square($300m{\times}300m$) searching area for reuse of received signal. Also, we use more active NLOS reader detection methode for NLOS error mitigation. when NLOS time delay 70 m, the number of the NLOS reader is 3 and the received sub-blinks number 3, proposed time delay trace-back scheme improve the RMSE about 16 m. From these results, we confirm that the proposed time delay traceback scheme is well-suited for the high precision location estimation to offer the location based service.

• International Journal of Advanced Culture Technology
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• v.9 no.4
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• pp.302-306
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• 2021

Indoor localization is one of the basic elements of Location-Based Service, such as indoor navigation, location-based precision marketing, spatial recognition of robotics, augmented reality, and mixed reality. We propose a Voxel Labeling-based visual positioning system using object simultaneous localization and mapping (SLAM). Our method is a method of determining a location through single image 3D cuboid object detection and object SLAM for indoor navigation, then mapping to create an indoor map, addressing it with voxels, and matching with a defined space. First, high-quality cuboids are created from sampling 2D bounding boxes and vanishing points for single image object detection. And after jointly optimizing the poses of cameras, objects, and points, it is a Visual Positioning System (VPS) through matching with the pose information of the object in the voxel database. Our method provided the spatial information needed to the user with improved location accuracy and direction estimation.

• Journal of Korean Society of Transportation
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• v.20 no.4
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• pp.83-93
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• 2002

To improve the performance of estimation, the research that uses additional information addition to traffic count and target OD with additional survey cost have been studied. The purpose of this paper is to improve the performance of OD estimation by reducing the feasible solutions with cost-efficiently additional information addition to traffic counts and target OD. For this purpose, we Propose the OD estimation method with sample link use proportion as additional information. That is, we obtain the relationship between OD trip and link flow from sample link use proportion that is high reliable information with roadside survey, not from the traffic assignment of target OD. Therefore, this paper proposes OD estimation algorithm in which the conservation of link flow rule under the path-based non-equilibrium traffic assignment concept. Numerical result with test network shows that it is possible to improve the performance of OD estimation where the precision of additional data is low, since sample link use Proportion represented the information showing the relationship between OD trip and link flow. And this method shows the robust performance of estimation where traffic count or OD trip be changed, since this method did not largely affected by the error of target OD and the one of traffic count. In addition to, we also propose that we must set the level of data precision by considering the level of other information precision, because "precision problem between information" is generated when we use additional information like sample link use proportion etc. And we Propose that the method using traffic count as basic information must obtain the link flow to certain level in order to high the applicability of additional information. Finally, we propose that additional information on link have a optimal counting location problem. Expecially by Precision of information side it is possible that optimal survey location problem of sample link use proportion have a much impact on the performance of OD estimation rather than optimal counting location problem of link flow.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.8
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• pp.1779-1788
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• 2012

Recently, demands of application services in consideration of interior environment according to the stream of times, Ubiquitous. In case of interior location-based service, WLAN is now mostly used. But it is largely affected by environmental changes. To solve this problem, lots of studies on UWB are underway. The reason why studies on UWB are much made lies in that it is not much affected by environment changes owing to radio wave characteristics. So this study suggests the location correction algorithm which derives values with less influence of environment and high accuracy and corrects with more accurate location information using Ubisense system based on UWB technologies. The location correction algorithm suggested is one made after constructing environment database and use it to estimate more accurate location from the location measuring system in a high position.

• Journal of Advanced Navigation Technology
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• v.10 no.2
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• pp.95-102
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• 2006

In this paper, we model a traffic of multiple tags operated in 2.45GHz band RTLS environment and analyze the multi-tag interference. Also, we propose a high precision location estimation algorithm of RTLS and then analyze its performance. From the results, the BER performance of RTLS degrades as the number of multi-tags increase in Gaussian noise and fading(m=15) environment. To meet the BER specification of RTLS, $10^{-5}$, we have to limit the multi-tag number to below 40. We also estimate the tag's location in $250m{\times}250m$ searching-area with enhanced TDOA scheme. It is confirmed that the 3m radius within accuracy of RTLS specification is satisfied, if the number of sub-blink receives more than 2 when available reader is 3 to 8.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.18 no.5
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• pp.1317-1340
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• 2024

With the rapid development of information technology, people's demands on precise indoor positioning are increasing. Wireless sensor network, as the most commonly used indoor positioning sensor, performs a vital part for precise indoor positioning. However, in indoor positioning, obstacles and other uncontrollable factors make the localization precision not very accurate. Ultra-wide band (UWB) can achieve high precision centimeter-level positioning capability. Inertial navigation system (INS), which is a totally independent system of guidance, has high positioning accuracy. The combination of UWB and INS can not only decrease the impact of non-line-of-sight (NLOS) on localization, but also solve the accumulated error problem of inertial navigation system. In the paper, a fused UWB and INS positioning method is presented. The UWB data is firstly clustered using the Fuzzy C-means (FCM). And the Z hypothesis testing is proposed to determine whether there is a NLOS distance on a link where a beacon node is located. If there is, then the beacon node is removed, and conversely used to localize the mobile node using Least Squares localization. When the number of remaining beacon nodes is less than three, a robust extended Kalman filter with M-estimation would be utilized for localizing mobile nodes. The UWB is merged with the INS data by using the extended Kalman filter to acquire the final location estimate. Simulation and experimental results indicate that the proposed method has superior localization precision in comparison with the current algorithms.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.39 no.6
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• pp.10-10
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• 2002

This paper introduces the high-resolution channel estimation technique which are used to estimate the first arrival multipath delay component. The proposed technique yields the precise estimate of the first time arrival which is directly related to the performance of TDOA-based position location. The proposed technique utilizes the transformed auto-correlation function of received common pilot signal in frequency domain, its samples compose the hermitian Toeplitz matrix at sequel. Then the time delay components could be estimated with precision by the analysis of eigen-structure of corresponding matrix. In this paper, obeying the modified CODIT model, the performance of the PR-IPDL(Pseudo Random-Idle Period Downlink) and TA-IPDL(Time Aligned-Idle Period Downlink considered as 3GPP position location technique will be exploited systematically through the computer simulations with applying the proposed technique.