• Journal of Communications and Networks
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• v.13 no.5
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• pp.463-471
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• 2011

Cooperative communications using relays in wireless networks have similar effects of multiple-input and multiple-output without the need of multiple antennas at each node. To implement cooperation into a system, efficient protocols are desired. In IEEE 802.11 families such as a/b/g, mobile stations can automatically adjust transmission rates according to channel conditions. However throughput performance degradation is observed by low-rate stations in multi-rate circumstances resulting in so-called performance anomaly. In this paper, we propose active relay-based cooperative medium access control (AR-CMAC) protocol, in which active relays desiring to transmit their own data for cooperation participate in relaying, and it is designed to increase throughput as a solution to performance anomaly. We have analyzed the performance of the simplified AR-CMAC using an embedded Markov chain model to demonstrate the gain of AR-CMAC and to verify it with our simulations. Simulations in an infrastructure network with an IEEE 802.11b/g access point show noticeable improvement than the legacy schemes.

• Proceedings of the Korea Information Processing Society Conference
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• 2018.10a
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• pp.235-237
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• 2018

The Internet has allowed many things to move fast, including sharing of data, files and others within a second. Many domains use applications range from IoT, smart cities, healthcare, and organizations to share the data when necessary. However, there are some challenges faced by existing systems that works on centralized nature. Such challenges are data breach, trustiness issue, unauthorized access and data fraud. Therefore in this work, we focus on using a smart contract which is used by blockchain platform and works on decentralized form. Furthermore, in this work our contract provides an access to the file uploaded onto the decentralized storage such as IPFS. By leveraging smart contract-role based which consist of a contract owner who can manage the users when access the certain resources such as a file and as well as use of decentralized storage to avoid single point of failure and censorship over secure communication channel. We checked the gas cost of the smart contract since most of contracts tends to be a high cost.

• Journal of IKEEE
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• v.26 no.2
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• pp.186-195
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• 2022

In this paper, we propose a new algorithm to improve the accuracy of indoor positioning techniques using Wi-Fi access points as beacon nodes. The proposed algorithm is based on the Weighted Centroid algorithm, a popular method widely used for indoor positioning, however, it improves some disadvantages of the Weighted Centroid method and also for other kinds of indoor positioning methods, by using the received signal strength correction method and genetic algorithm to prevent the signal strength fluctuation phenomenon, which is caused by the complex propagation environment. To validate the performance of the proposed algorithm, we conducted experiments in a complex indoor environment, and collect a list of Wi-Fi signal strength data from several access points around the standing user location. By utilizing this kind of algorithm, we can obtain a high accuracy positioning system, which can be used in any building environment with an available Wi-Fi access point setup as a beacon node.

• Proceedings of the IEEK Conference
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• 1998.06a
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• pp.526-529
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• 1998

This paper describes new sense amplifier with fast sensing delay time of 0.54ns and 32kb CMOS embedded SRAM with 4.67ns access time for a 3-V powr supply. It was achieved using the sense amplifier with multiple point sensing scheme and high speed bit-line scheme. The sense amplifier saves 25% of the power dissipation compared with the conventional one while maintaining a very short sensing delay. The SRAM uses 0.5.mu.m double-polysilicon and triplemetal CMOS process technology. A die size is 1.78mm*2.13mm.

• Journal of Electrical Engineering and information Science
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• v.3 no.3
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• pp.300-305
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• 1998

This paper describes new sense amplifier with fast sensing delay time of 0.54ns and 32kb CMOS embedded SRAM with 4.67 ns access time for a 3-V power supply. It was achieved using the sense amplifier with multiple point sensing scheme and highs peed bit-line scheme. The sense amplifier saves 25% of the power dissipation compared with the conventional one while maintaining a very short sensing delay. The SRAM uses 0.5m double-polysilicon and triple-metal CMOS process technology. A die size is 1.78${\times}$mm2.13mm.

• Journal of KIISE:Computer Systems and Theory
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• v.32 no.9
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• pp.457-464
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• 2005

In this paper a 3D memory system that allows 17 access types at an arbitrary position is introduced. The proposed memory system is based on two main functions: memory module assignment function and address assignment function. Based on them, the memory system supports 17 access types: 13 Lines, 3 Rectangles, and 1 Hexahedron. That is, the memory system allows simultaneous access to multiple data in any access types at an arbitrary position with a constant interval. In order to allow 17 access types the memory system consists of memory module selection circuitry, data routing circuitry for READ/WRITE, and address calculation/routing circuitry In the point of view of a developer and a programmer, the memory system proposed in this paper supports easy hardware extension according to the applications and both of them to deal with it as a logical three-dimensional away In addition, multiple data in various across types can be simultaneously accessed with a constant interval. Therefore, the memory system is suitable for building systems related to ,3D applications (e.g. volume rendering and volume clipping) and a frame buffer for multi-resolution.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.14 no.5
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• pp.3-10
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• 2004

A Wireless Lan has an importance of access control, because we can use wireless Internet via AP(Access Point). Moreover, to use wireless LAN, we will go through authentication process of EAP. DoS(Denial of Service) attack is one of the fatal attack about these AP access and authentication process. That is, if malicious attacker keeps away access of AP or consumes memory of server and calculation ability of CPU and etc. compulsorily in authentication process, legal user can't get any services. In this paper, we presents the way of protection against the each attack that is classified into access control, allocation of resource, attack on authentication protocol. The first thing, attack to access control, is improved by pre-verification and the parameter of security level. The second, attack of allocation of resource, is done by partial stateless protocol. And the weak of protocol is done by time-stamp and parameter of access limitation.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.4B
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• pp.281-290
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• 2002

In this paper, we propose an efficient packet forwarding method for an IP-based wireless Internet access network. Packets are forwarded along with a flow, that is a kind of connection-oriented connection and established before delivering packets. For this purpose, we also propose a flow resolution method and a modified IPv6 header for delivering packet in the wireless Internet access network. In addition, the method to support the mobility of mobile stations is explained, and the implementation issues are discussed. In order to estimate the performance of the proposed method, we analyzed the delay time to deliver packets in the wireless Internet access network. The numerical results show that the proposed method is very efficient, in the view point of delay.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.20 no.4
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• pp.106-114
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• 2012

As Incheon International Airport(IIA) is located in an island 50-km away from Seoul, various travel equipments for access are required. So far two connecting bridges are constructed funded by civilian funds. For the further bridge construction, the reduction of forecast traffic amount and the government subsidy for the civilian funds are big issues. Comparing the access traffics of IIA to those other competing airports, traffic conditions inside the airport are superior to other competing airports from the management point of view, as utilization conditions and equipment capacities are periodically monitored and evaluated to set up comprehensive countermeasures following constructing by stages. However, while the accessability to IIA is very important, as IIA is built on an island the conflicts between near-by developers and traffic facility operators make further bridge construction difficult. As improving the accessibility to an airport is not easy to achieve only by the IIA management's efforts, the central government level authorities should organize a committee with agencies concerned and analyze the characteristics of access traffic periodically to suggest reform measures for each organization concerned to implement appropriate undertakings at apt timing. For the future, central government's level empirical research on the airport accessibility for synthetic and systematic plan set-up is expected.

• Proceedings of the KIEE Conference
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• 2003.11b
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• pp.163-166
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• 2003

In recent years, there has been increased to access multimedia service through the Internet due to rise of the access speed. We suppose the co-existence of the various access networks in adjacent area in the future, such as wireless LAN, Bluetooth, and 3G Cellular So, the size of the cell will be smaller and the number of access point will be increased. In other words, the potable devices need the efficient mobility scheme due to move between cells frequently Currently, the several of the scheme, which is Cellular IP, HAWAII, Mobile IPv4 regional registration, and hierarchical Mobile IPv6, is suggested to support micro-mobility but Mobile IPv4 is standard scheme to support the mobility of the mobile node. MPLS, which forwards the packet through switching instead of routing using IP address, has begun to deploy in the internet backbone to increase the performance of mobility protocol. The integration of both MPLS and Mobile IP improves the scalability of the Mobile IP data forwarding process by leveraging on the features MPLS which are fast switching and high scalability. Moreover it abbreviates IP-in-IP tunneling between HA and FA. In this paper, we suggest efficient mobility scheme through integration of both MPLS and hierarchical Mobile IPv6.