• Journal of Communications and Networks
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• v.7 no.2
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• pp.207-221
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• 2005

The proliferation of wireless local area networks (WLANs) offering high data rate in hot spot area have spurred the demand for possible WLANs and third-generation (3G) cellular network integration solutions as the initiative step towards 4G systems. This paper provides a novel architecture for seamless location-aware integration of WLANs into 3G cellular networks and also an analysis for the efficient handover techniques. We introduce location as a key context in secure roaming mechanism for context-aware interworking in 4G systems. The fast secure roaming with location-aware authentication is implemented at an entity called location-aware service (LAS) broker that utilizes the concepts of direction of user and pre-warming zone. The location-ware interworking architecture supports seamless roaming services among heterogeneous wireless networks including WLANs, wireless metropolitan area networks (WMANs), and 3G cellular networks. This paper also includes a description of procedures needed to implement efficient mobility and location management. We show how the LAS broker with pre-warming and context transfer can obtain significant lower latency in the vertical handover.

• Journal of Sensor Science and Technology
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• v.16 no.4
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• pp.270-276
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• 2007

A location-aware system, which is capable to detect a user's whereabout in a region and provide real-time location information in outdoor environment is designed and fabricated, specifically using the GPS (global positioning system) as key technology in view of its stability and high precision in outdoor environment. Experiment is conducted to test this application in campus-based environment. Once GPS receiver detects specific location which is tagged with GPS coordinates, the system provides information relevant to that context and user can operate and react accordingly. Besides, this location-aware system is able to provide user with the route in order to get to a desired place by detecting the direction that the user is moving towards from his/her initial location. The mapping data is transferred via wireless LAN to PDA carried by the user as well as to the back-end system on real-time basis. The test result is analyzed and discussed to validate the effectiveness of using GPS in implementing this system and indicates future works that could be made to improve this prototype to be implemented in other applications, such as theme park, tourist attraction spot or recreational park.

• Journal of Sensor Science and Technology
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• v.16 no.4
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• pp.277-285
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• 2007

In this paper, we outline the research issues that we are pursuing towards building of location aware environments for mainly ubiquitous healthcare applications. Such location aware application can provide what is happening in this space. To locate an object, such as patient or elderly person, the active ceiling-mounted reference beacons were placed throughout the building. Reference beacons periodically publish location information on RF and ultrasonic signals to allow application running on mobile or static nodes to study and determine their physical location. Once object-carried passive listener receives the information, it subsequently determines it's location from reference beacons. The cost of the system was reduced while the accuracy in our experiments was fairly good and fine grained between 7 and 12 cm for location awareness in indoor environments by using only the sensor nodes and wireless sensor network technology. Passive architecture used here provides the security of the user privacy while at the server the privacy was secured by providing the authentication using Geopriv approach. This information from sensor nodes is further forwarded to base station where further computation is performed to determine the current position of object.

• Proceedings of the KSRS Conference
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• 2007.10a
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• pp.357-360
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• 2007

An asset tracking using wireless sensor network is concerned with geographical locations of sensor nodes. The limited size of sensor nodes makes them attractable for tracking service, at the same time their size causes power restrictions, limited computation power, and storage restrictions. Due to such constrained capabilities, the wireless sensor network basically assumes the failure of sensor nodes. This causes a set of concerns in designing asset tracking system on wireless sensor network and one of the most critical factors is location uncertainty of sensor nodes. In this paper, we classify the location uncertainty problem in asset tracking system into following cases. First, sensor node isn't read at all because of sensor node failure, leading to misunderstanding that asset is not present. Second, incorrect location is read due to interference of RSSI, providing unreliable location of asset. We implemented and installed our asset tracking system in a real environment and continuously monitored the status of asset and measured error rate of location of sensor nodes. We present experimental results that demonstrate the location uncertainty problem in asset tracking system using wireless sensor network.

• Journal of Korean Society of Transportation
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• v.25 no.1 s.94
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• pp.61-71
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• 2007

This study examines the determinants of location decisions for domestic skippers and identifies them with the aid of the location choice model The authors have used Korea's commodity flow survey collected by the inter-regional shippers as well as socio-economic indicators. The results suggest that the location of shippers depend on agglomeration economies, market size, and logistics activities. Finally. this study suggests the direction of locational Policies to help the Korean government with logistics-related policies.

• Journal of Fashion Business
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• v.9 no.4
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• pp.16-29
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• 2005

The purpose of this study is to evaluate the differences of visual image by variations in the location of the waistline and width of the belt of the basic skirt. The stimuli are 21 samples: 7 variations of the location of the waistline and 3 variations of the width of the belt. The data has been obtained from 43 fashion design majors. The data has analyzed by frequency, factor analysis, anova, scheffe's test and the MCA method. The results of this study are as follows. The visual image by variations of the location of the waistline and width of the belt is composed of 3 factors: attention, function, attraction. The visual image by variations of the width of the belt has partial significant differences. The visual image by variations in the location of the waistline has significant differences in all factors. Function shows the interaction between the location of the waistline and width of the belt. However, attention and attraction don't show the interaction between the location of the waistline and width of the belt ; the location of the waistline tends to be the main effect.

• The Journal of the Korea Contents Association
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• v.15 no.2
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• pp.101-108
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• 2015

Location-sharing based service (LSBS) refers to a service that users share their location information with other users with whom friendship. At this time, the location information is shared through service provider, and then their position information is exposed to the service provider. The exposure of this personal position information to the service provider has raised a privacy problem, and thus privacy preserving mechanisms have been proposed to protect them. In this paper, we examine the types and features of the proposed location-sharing based services so far, and survey the research trend of privacy preserving mechanisms for them. Through the analysis on existing privacy preserving mechanisms, we present design factors for a privacy preserving mechanism for the current LSBS services, and suggest future work.

• ETRI Journal
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• v.37 no.6
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• pp.1087-1095
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• 2015

Mobility management is important in mobile cellular networks. In this study, we considered an enhanced location-based registration (ELR) method. In the ELR method, even when a mobile phone enters a cell to find that the cell is already on its list (of visited cells) and then updates its main counter, it does not remove any cells from the list (memory space permitting), which gives better performance than the location-based registration (LR) method. However, the location registration cost of the ELR method is still high, and there is a lot of room for improvement with regards to this matter. We now propose an improved version of the ELR method; namely, the improved ELR (iELR). In the iELR method, when a mobile phone enters a cell to find that the cell counter value is less than the main counter value, or when a mobile phone enters a cell to register its location, it updates the main counter and the cell counter values as much as possible to reduce the future need for registrations. We show that our proposed iELR method provides better performance than the ELR method.

• ETRI Journal
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• v.33 no.4
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• pp.528-536
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• 2011

In this paper, we analyze the location accuracy of real-time locating systems (RTLSs) in multipath environments in which the RTLSs comply with the ISO/IEC 24730-2 international standard. To analyze the location error of RTLS in multipath environments, we consider a direct path and indirect path, in which time and phase are delayed, and also white Gaussian noise is added. The location error depends strongly on both the noise level and phase difference under a low signal-to-noise ratio (SNR) regime, but only on the noise level under a high SNR regime. The phase difference effect can be minimized by matching it to the time delay difference at a ratio of 180 degrees per 1 chip time delay (Tc). At a relatively high SNR of 10 dB, a location error of less than 3 m is expected at any phase and time delay value of an indirect signal. At a low SNR regime, the location error range increases to 8.1 m at a 0.5 Tc, and to 7.3 m at a 1.5 Tc. However, if the correlation energy is accumulated for an 8-bit period, the location error can be reduced to 3.9 m and 2.5 m, respectively.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.2
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• pp.329-334
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• 2010

Due to the advancement of mobile wireless networks, various LBS's (Location Based Service) with the knowledge of mobile station's current position are emerging. Providing LBS is very essential feature in Mobile WiMAX networks such as WiBro networks for their competitiveness. To this end, WiMAX Forum has established recently the network architecture and protocols for providing LBS and they are included in the Network working group's release 1.5 documents. Though there have been many research efforts on location determination in Wibro networks, none of them addresses the location determination mechanism complying to Forum's recent LBS standards. This paper proposes an enhanced TDOA-RTD combined location determination mechanism, which complies to the Forum's LBS architecture.