• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2013.10a
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• pp.851-853
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• 2013

Recently, location-based service as the developed continuously, interest in positioning technology is increasing. As the most famous indoor positioning technology, WPS is a positioning technology using WiFi, which can complement the limits of the indoor positioning to have a GPS. In this paper, to provide a system for monitoring the position of the inside of the user based on the position information that using the RSSI signal of the wireless AP based WPS technology, they grip the location information of the mobile nodes in the indoor. If using the method proposed, it is expected to be applied to various services it is possible to apply the WPS, this is because it is possible to estimate in real time the location distribution of mobile nodes in the indoor.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.7B
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• pp.586-594
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• 2012

The drastic growth of mobile communication and spreading of smart phone make the significant attention on Location Based Service. The one of most important things for vitalization of LBS is the accurate estimating position for mobile object. Focusing on AP's probabilistic position estimation, we develop an AP distribution map and new pattern matching algorithm for position estimation. The developed approaches can strengthen the advantages of Radio fingerprint based Wi-Fi Positioning System, especiall on the algorithms and data handling. Compared on the existing approaches of fingerprint pattern matching algorithm, we achieve the comparable higher performance on both of average error of estimation and deviation of errors. Furthermore all fingerprint data have been harvested from the actual measurement of radio fingerprint of Seoul, Kangnam area. This can approve the practical usefulness of proposed methodology.

• Korean Journal of Soil Science and Fertilizer
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• v.33 no.2
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• pp.71-78
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• 2000

Preferential flow has recently been the subject of increasing interest because these phenomena contribute to solute transport in soils. Commonly, preferential flow paths are associated with macropores or highly structured soils. We presented an analysis of the measured breakthrough curves (BTCs) of $Cl^-$ and $Cu^{2+}$ ions to test the occurrence of preferential flow in soils using miscible displacement technique under steady flow conditions. We also analyzed soil water retention curves and from this curves induced cumulative pore size distribution of undisturbed soils, which sampled from Ap1, B1, and C horizons of Songjeong series soils (the fine loamy, mesic family of Typic Hapludults). In this study, miscible displacement experiment on C horizon was excluded, because it is structureless sandy loam with saturated hydraulic conductivity of $5.2cmhr^{-1}$. The saturated hydraulic conductivity of Ap1 horizon was $2.0cmhr^{-1}$, which was about 7 times higher than that of B1 horizon ($0.27cm hr^{-1}$). Cumulative pore size distribution predicted that Ap1 horizon had more macropores (pore diameter larger than $49{\mu}m$, equivalent to -6 kpa of soil matric potential) than B1 horizon. The hydrodynamic dispersion coefficient from chloride BTCs was estimated as $1.3cm^2hr^{-1}$ for B1 and $34cm^2hr^{-1}$ for Ap1 horizon. However the retardation factors of B1 and Ap1 horizon were significantly different, i.e. 1 and 0.6, respectively, which means that there was distinct partition between mobile water and immobile phase in Ap1 horizon. The copper retardation effect of Ap1 horizon was less than that of B1 horizon, even though cation exchange capacity of Ap1 horizon was higher than that of B1 horizon. Thus, breakthrough curves of $Cl^-$ and $Cu^{2+}$ obviously showed the probability that preferential flow would occur in Ap1 horizon.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.9A
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• pp.892-899
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• 2006

In this paper, we propose an automatic switching technology between the ad-hoc and the infrastructure modes without user intervention in the IEEE 802.11b wireless LAN. Also, we design our proposed technology and implemented on the Linux machine. For this operation, the area within an Access Point (AP) coverage is defined as a switching area, and a node without any transmission in this area is assumed to be able to relay frames between the AP and nodes in the shaded area that is outside the coverage and cannot reach the AP. By using the proposed technology, it is possible to provide the seamless Internet access service to nodes at the ad-hoc mode in the shaded area. In this paper, we explains the operation of the detection method of the switching area, presents the flowchart and implementation environment. To prove the operation of our technology, we obtain the results of captured packets transmitted between nodes and throughput results through ftp transmission experiment. Hence, we can see that our proposed scheme can be improve the wireless access service in wireless and mobile networks.

• Journal of KIISE:Information Networking
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• v.28 no.4
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• pp.527-539
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• 2001

The wireless asynchronous transfer mode (ATM) system has the advantage of providing the broadband services with various quality-of-service requirements to the mobile terminal efficiently by utilizing the ATM technology developed for the wired ATM system. The available bit rate (ABR) service among various ATM services utilizes the available bandwidth remaining in the ATM link, which allows the efficient bandwidth usage. During the handoff of the mobile terminal, however, the queue length in the access point (AP) which resides in the boundary of the wired ATM network and the wireless ATM network may increase abruptly. In this paper, we propose a scheme which prevents the buffer-overflow and buffer-underflow in the AP during the handoff of the wireless ABR connection in the wireless ATM system using binary feedback rate-based ABR traffic control. This scheme controls the source's cell generation rate during both handoff period and some time interval after the completion of the handoff procedure. The simulation results show that the proposed scheme prevents the buffer-overflow and buffer-underflow. The proposed scheme can contribute to increasing the throughput of the wireless ABR service during handoff by preventing the buffer overflow and underflow during handoff period.

• Journal of Korean Society for Geospatial Information Science
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• v.22 no.3
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• pp.57-69
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• 2014

As of 2013, Korean population density is 505 persons per $1km^2$ and is ranked 3rd place in the most densely populated countries exception of city-states. It shows clearly the population is concentrated in the city area. To fulfil this urban concentration population demand, the enlargement and complexation of buildings, subway and other underground spaces connection tendency has been intensified, and it is need to construct the indoor spatial information DB as well as the accurate indoor surveying DB to promote people's safety and social welfare. In this study, Sadang station and Incheon National Airport were aimed for the construction of Wi-Fi AP location DB and RadioMap DB by collecting the indoor AP raw datas by using mobile device and those collected results were ran through the process of verification, supplementation, and analyzation. To evaluate the performance of constructed DB, 10 points in Incheon Airport- 3rd flr in block A, and 9 points in Sadang station-B1 were selected and calculated the estimated points and ran evaluation experiment using survey positioning error, which is distance between real position and the estimated position. The result shows that Incheon international airport's average and standard deviation was separately 17.81m, 17.79m and Sadang station's average and standard deviation was separately 22.64m, 23.74m. In Sadang station's case, the areas near the exit has low performance of surveying position due to fewer visible AP points than other areas. As total datas were examined except those position, it was verified that the user's location was mapping close position in surveying positioning by using constructed DB. It means that constructed DB contains correct Wi-Fi AP locations and radio wave patterns in object region, so it is considered that the indoor spatial information service based on constructed DB would be available.

• International Journal of Internet, Broadcasting and Communication
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• v.14 no.3
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• pp.22-29
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• 2022

Recently, with the development of mobile computing power, mobile-based VR and AR services are being developed. Due to network performance and computing power constraints, VR and AR services using large-capacity 3D content have limitations. A study on an efficient 3D content load method for a mobile device is required. The conventional method downloads all 3D content used for AR services at the same time. In this paper, we propose an active 3D content load according to the user's track. The proposed method is a partitioned 3D object load. Edge servers were installed for each area and connected through the MESH network. Partitioned load the required 3D object in the area referring to the user's location. The location is identified through the edge server information of the connected AP. The performance of the proposed method and the conventional method was compared. As a result of the comparison, the proposed method showed a stable Mobile AR Service. The results of this study, it is expected to contribute to the activation of edge server-based AR mobile services.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.9 no.5
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• pp.53-63
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• 2009

This paper is to develop WiMAX CPE(wireless AP) that can provides Wi-Fi terminal with wireless Internet service by connecting to Wibro wireless network. This AP aims to support WiBro in upstream interface basically, and Wi-Fi and 100M Ethernet interface in downstream. So, we has developed the equipment for business that wireless ISP can provide many Internet customers with wireless Internet service by using Wi-Fi terminal in subway, car, ship, and so on, and the equipment for users that a user can purchase and then install in person. For the latter, multiple Wi-Fi terminals that be registered in WiBro service can be connected to Internet simultaneously.

• Journal of KIISE:Information Networking
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• v.36 no.3
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• pp.256-262
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• 2009

In this paper, we propose a mechanism for increasing the handover performance of the IEEE 802.11 link layer. The mechanism reduces the number of scanning channels by referencing an AP map based on GPS. Also, by monitoring the SNRs of the mobile node and neighbor APs, it enables the handover to maintain a higher SNR than a given threshold. The experimental results establish that it has a disconnection ratio of 6.7% and an average SNR of 16.8 dB. It is 4.1% lower disconnection ratio and 26% higher SNR than the mechanism used by MadWifi.

• Journal of Digital Contents Society
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• v.12 no.3
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• pp.347-353
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• 2011

In HIPERLAN/2, the radio channels are assigned by AP(Access Point) that is centrally operated and the MAC protocol is based on TDMA/TDD. Mobile terminal that data transmission is necessary to uplink requests radio resource to AP through RCH channel. The changing number of RCHs in each MAC frame is important because too many RCHs may result in a waste of radio resources and too few RCHs may result in many access collisions and prolong time that connect to AP. Hence the number of RCH should be allocated properly according to traffic. From these point, this paper proposes an scheme that dynamically assigned the number of RCH which is based on the number of success and collision of message in previous MAC frame. To prove efficiency of proposed scheme, lots of simulations are conducted and analyzed.