• Journal of the Institute of Electronics Engineers of Korea CI
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• v.46 no.4
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• pp.31-41
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• 2009

IEEE 802.11e proposed by IEEE 802.11 working group to guarantee QoS has contention based EDCA and contention free based HCCA. HCCA, a centralized polling based mechanism of 802.11e, needs a scheduling algorithm to allocate the network resource efficiently. The existing standard scheduler, however, is inefficient to support for QoS guarantee for real-time service having VBR traffic. To improve these limit, in this paper, we First, we propose priority polling algorithm which additionally considers the size of MSI and TXOP based on EDD algorithm to increase number of QSTAs. We also propose a dual token bucket TXOP allocation algorithm to reduce congestion caused by stations which enters network with considerable delay variance. TSPEC parameters, Maximum Burst Size (MBS) and Peak Data Rate (PR), are applied to design depth and token generation rate of two buckets. Simulation results show that the proposed algorithm has much higher performance compared with reference and SETT-EDD scheduler in terms of throughput and delay.

• Journal of the Korea Society of Computer and Information
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• v.17 no.4
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• pp.99-107
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• 2012

We propose control mechanism of UAV(Unmanned Aerial Vehicle) group for making the communication network to the base station after the target is found. We assume UAVs can communicate to each other by wireless LAN without existing communication infrastructure. UAVs started to fly in linear formation, after finding target, UAVs move to the base station to send the information about the target. At least one UAV stays the position that the target is found. This paper explains the mechanism supporting reliable connectivity during UAV group's flying. We verify the proposed scheme and evaluate the performance through NS-2 simulation. The proposed scheme can be applied to the disaster area and war zone, which the existing communication infrastructure cannot be worked.

• Progress in Medical Physics
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• v.14 no.2
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• pp.124-130
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• 2003

Currently, as a consequence of PACS (Picture Archiving Communication System) implementation many hospitals are replacing conventional film-type interpretations of diagnostic medical images with new digital-format interpretations that can also be saved, and retrieve However, the big limitation in PACS is considered to be the lack of mobility. The purpose of this study is to determine the optimal communication packet size. This was done by considering the terms occurred in the wireless communication. After encoding medical image using JPGE2000 image compression method, This method embodied auto-error correction technique preventing the loss of packets occurred during wireless communication. A PC class server, with capabilities to load, collect data, save images, and connect with other network, was installed. Image data were compressed using JPEG2000 algorithm which supports the capability of high energy density and compression ratio, to communicate through a wireless network. Image data were also transmitted in block units coeded by JPEG2000 to prevent the loss of the packets in a wireless network. When JPGE2000 image data were decoded in a PUA (Personal Digital Assistant), it was instantaneous for a MR (Magnetic Resonance) head image of 256${\times}$256 pixels, while it took approximately 5 seconds to decode a CR (Computed Radiography) chest image of 800${\times}$790 pixels. In the transmission of the image data using a CDMA 1X module (Code-Division Multiple Access 1st Generation), 256 byte/sec was considered a stable transmission rate, but packets were lost in the intervals at the transmission rate of 1Kbyte/sec. However, even with a transmission rate above 1 Kbyte/sec, packets were not lost in wireless LAN. Current PACS are not compatible with wireless networks. because it does not have an interface between wired and wireless. Thus, the mobile JPEG2000 image viewing system was developed in order to complement mobility-a limitation in PACS. Moreover, the weak-connections of the wireless network was enhanced by re-transmitting image data within a limitations The results of this study are expected to play an interface role between the current wired-networks PACS and the mobile devices.

• Journal of KIISE:Software and Applications
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• v.34 no.1
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• pp.79-94
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• 2007

In the ubiquitous computing age which uses a high quantity network, mobile devices such as wearable and hand-held ones with a small tamers and a wireless communication module will be widely used in near future. Thus, a lot of researches about an augmented game on mobile devices have been attempted recently. The existing augmented games used a traditional 'backpack' system and a pattern marker. The 'backpack' system is expensive, cumbersome and inconvenient to use, and because of the pattern marker, it is only possible to play the game in the previously installed palace. In this paper, we propose an augmented game called Flying Cake using a face region to create the virtual object(character) without the pattern marker, which manually indicates an overlapped location of the virtual object in the real world, on a small and mobile PDA instead of the cumbersome hardware. Flying Cake is an augmented shooting game. This game supplies us with two types: 1) a single player which attacks a virtual character on images captured by a camera in an outdoor physical area, 2) dual players which attack the virtual character on images which we received through a wireless LAN. We overlap the virtual character on the face region using a face detection technique, and users play Flying Cake though attacking the virtual character. Flying Cake supplies new pleasure to flayers with a new game paradigm through an interaction between the user in the physical world captured by the PDA camera and the virtual character in a virtual world using the face detection.

• Journal of Digital Convergence
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• v.11 no.3
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• pp.415-426
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• 2013

Smart work has recently introduced as a way to solve problems such as greenhouse gas emissions, low birth rate and aging as well as to improve productivity. Because of development of ICT infrastructure and the proliferation of smart devices, the mobile office has the most commonly used within types of smart work in Korea. But the adoption of the mobile office in small businesses is only half of that of large corporations. The security issue appears to be one of the biggest obstacles to the introduction of smart work in small businesses. Therefore, the purpose of this study is to analyze the information security factors that should be considered when the mobile office is introduced to small businesses. By analyzing the previous studies, the information security factors of the mobile office are classified 5 groups composed of 24 factors. 5 groups are terminals, applications and platforms, networks, servers and users. According to the survey result using AHP, 'User' was drawn to the most important group, and 'Data Encryption', 'Wireless LAN Control' and 'Terminal Recovery When Leaving' were drawn to the important information security factors of the mobile office among 24 factors.