Jaegeol Yim

Extended Kalman Filter for wireless LAN based indoor positioning

A WLAN (Wireless Local Area Network) based Extended Kalman Filter (EKF) method for indoor positioning is introduced in this paper. WLAN based indoor positioning is more economical than other methods because it does not require any special equipment dedicated to positioning. The most popular technique used for indoor positioning is the fingerprinting method, but the EKF method is easier to deploy because, unlike fingerprinting, it does not require a time consuming off-line phase. This paper also provides experimental comparisons of our EKF method with other indoor positioning methods.

Erratum to “New Optical Methods for Liveness Detection on Fingers”

This paper is devoted to new optical methods, which are supposed to be used for liveness detection on fingers. First we describe the basics about fake finger use in fingerprint recognition process and the possibilities of liveness detection. Then we continue with introducing three new liveness detection methods, which we developed and tested in the scope of our research activities--the first one is based on measurement of the pulse, the second one on variations of optical characteristics caused by pressure change, and the last one is based on reaction of skin to illumination with different wavelengths. The last part deals with the influence of skin diseases on fingerprint recognition, especially on liveness detection.

Protecting cultural heritage tourism sites with the ubiquitous sensor network

Cultural heritage tourism resources are vulnerable to natural and human disasters: once damaged or destroyed, it is hard to restore them to their original condition. This study examines an online and real-time early fire detection system, using advanced information technology and a ubiquitous sensor network to protect cultural heritage tourism resources. It notes the danger of accidental and deliberate fires being started by cultural site visitors, as well as natural fires from lightning strike or nearby forest fires. The system architecture, sensor and network design, and software design of the fire detection system are presented, based on experimental work at the Bulguksa temple in South Korea, a UNESCO World Heritage Site. Lessons learned from building and operating the Ubiquitous(U)-Bulguksa system are presented to provide guidelines for applying ubiquitous sensor networks to protect other cultural heritage tourism resources.

New optical methods for liveness detection on fingers.

This paper is devoted to new optical methods, which are supposed to be used for liveness detection on fingers. First we describe the basics about fake finger use in fingerprint recognition process and the possibilities of liveness detection. Then we continue with introducing three new liveness detection methods, which we developed and tested in the scope of our research activities—the first one is based on measurement of the pulse, the second one on variations of optical characteristics caused by pressure change, and the last one is based on reaction of skin to illumination with different wavelengths. The last part deals with the influence of skin diseases on fingerprint recognition, especially on liveness detection.

Utilizing Map Information for WLAN-Based Kalman Filter Indoor Tracking

Extended Kalman filter (EKF), which has long been used in the field of GPS positioning, has recently been used for indoor positioning, introduced extended Kalman filter (EKF) indoor positioning method based on Bluetooth signal strength. However, the error range of the EKF is so large when it was applied in WLAN tracking that we modified it to use K-NN method for the measurement of the EKF. Furthermore, this paper proposes an idea of improving accuracy of EKF tracking by adjusting parameter values referring to map information. Experimental results comparing our method with other previous methods are discussed.

A Performance Comparison of Positioning Methods Considering Measurement Noise

This paper proposes three positioning algorithms using TOA measurements: 1) The well-known linearization method using Taylor series, 2) a modified Savarese method considering measurement noise, which does not need linearization, and 3) a modified Bancroft method where TOA measurements instead of pseudorange measurements are considered. Furthermore, through an error analysis, for Savarese method, divergence of altitude is anticipated if the transmitters are located at the same height. To prevent height divergence, the Savarese method is modified again for receivers which assumed moving on the even plane. Error analysis also shows the relationship between Bancroft and Savarese method. From the analysis it is expected that the performance of Savarese method is worse than Bancroft method because of error amplification during difference operation. Experiments using real TOA measurement from the time difference of ultra sound and RF validate the proposed methods and show that analysis is correct.

Timed net with choice probability and its minimum cycle time—The case of location-based service

Abstract For performance analysis of computer systems, the minimum cycle time method has been widely used. The minimum cycle time method is a mathematical technique with which we can find the minimum duration time needed to fire all the transitions at least once and coming back to the initial marking in a timed net. A timed net is a modified version of a Petri net, where a transition is associated with a delay time. In the real world, an event A is usually in the conflict relation with another event B, i.e. if event A is selected to occur then event B cannot occur. When events A and B are in conflict, they are usually associated with probability of choices. However, a timed net is not equipped with any facility of specifying probabilities of event choices. Therefore, the minimum cycle time method applied on a timed net is apt to overlook probabilities of event choices and yield a wrong result. We are proposing ‘Timed net with Choice Probability’, where a transition can be associated with both delay time and a probability of choice. We also introduce an algorithm for minimum cycle time analysis for ‘Timed net with Choice Probability’. As an example of application, we are performing an analysis of a location-based service system using ‘Timed net with Choice Probability’.

Implementation of a Preliminary Natural User Interface for Video on Demand Systems

Video on Demand (VOD) is so popular that most of Internet traffic is for VOD service. If the user interface of VOD system can recognize user’s gesture then even a disabled person can easily controll the system to enjoy the service. Kinect is an example device that recognizes user’s gesture and voice and is widely used for games. Therefore, this paper proposes a Kinect based VOD user interface, describes our implementation of VOD system with the user interface, and discusses our experimental tests of the VOD system.

Museum Guide, a Mobile App

As science and technology are advancing, computers become so small and powerful that they are now embedded into mobile telephones. Not only a computer but also so many sensors are installed in a smartphone. Making use of those devices, they have developed so many apps running on smartphones. Museum guide we are introducing in this paper is one of those apps. To the best of our knowledge, Museum Guide is the first indoor-location-based, context-aware, and video-on-demand app.

Strategy of Positioning for LBS on U-Campus

Location-based service is one of the most popular buzzwords in the field of U-city. Positioning a user is an essential ingredient of a location-based system on a U-city. For the outdoor positioning, GPS based practical solutions have been introduced. However, GPS measurement error is too big to be used for U-campus services because the size of a campus is relatively smaller than a city. We propose Relative-Interpolation Method in order to improve the correctness of outdoor positioning. Besides, indoor positioning is necessary for U-campus while GPS signal is not available inside buildings. For the indoor positioning, Cricket, Active Badge, and so on have been introduced. These methods require special equipments dedicated for positioning. Our method does not require such equipments because it determines the users position based on the receiver signal strength indicators (RSSI) from access points (AP) which are already installed for WLAN. The algorithm we are using for indoor positioning is a kind of finger prints method. However our algorithm builds a decision treeinstead of a look-up table in the off-linephase. Therefore, our method is faster than existing indoor positioning methods in the real-timephase. We have integrated our indoor and outdoor positioning methods and implemented a prototype of our indoor-outdoor positioning method on a laptop. Our experimental results are discussed in this paper.