• Journal of the Institute of Electronics Engineers of Korea TC
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• v.44 no.10
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• pp.64-75
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• 2007

Service discovery protocols is software components to find specific services or resources on network. The SLP defined by IETF protocol is a framework for automatic service discovery on IP based networks. Automatic service discovery is an important component on ubiquitous computing environment. This paper proposes a service discovery architecture named as SLPA(Service Location Protocol based on AMAAM). AMAAM(Mobility Agent Advertisement Mechanism) is an aggregation-based Mobile IP implementation in MANET. In SLPA, the role of the directory agent is assigned to the mobility agent in AMAAM. The mobility agent periodically beacons an advertisement message which contains both the advertisement of the directory agent in SLP and the advertisement of the mobility agent in Mobile IP. For evaluating the functional correctness of SLPA and the overhead of maintaining a service directory of SLPA. We simulate SLPA using ns-2 and analyze the overhead of control overheads for the aggregation. Through the simulation experiments we show the functional correctness of the proposed architecture and analyze the performance results.

• Journal of Industrial Convergence
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• v.17 no.4
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• pp.125-129
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• 2019

With the growing number of people using bicycle, the number of bicycle accidents also has been increasing. It is said that bicycle accident can be reduced up to 11%~44% when riding a bicycle if LED light is used. The headlight of the bicycle makes exposure effect to the opposite side of bike rider while taillight makes exposure effect to the rear bike rider for improving safety. Bicycle safety device capable of displaying a change of direction by LED is implemented in this study in response to control button signal. This signal makes LED light which is installed in pedal and wheel of bicycle as a module type emitting or flickering during the fixed hour. Bicycle auxiliary device in pedal which is able to improve safety using LED when bikers are riding a bike at night is developed in this study. Bicycle safety device applying wireless communication technology will be expected alternative technology in the future to solve a social problem such as energy, environment, and safety.

• Journal of the Korea Society of Computer and Information
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• v.16 no.2
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• pp.121-129
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• 2011

With advances in wireless networks and advent of powerful mobile devices such as smart phones, the demand for mobile IPTV services has been increasing. It is essential to minimize the energy consumption of mobile devices because their battery capacity is limited. In this paper, we therefore propose a new streaming structure in P2P-based mobile IPTV systems to minimize the energy consumption of mobile peers using agent peers. Agent peers can decrease the energy consumption of mobile peers significantly by performing streaming functionality and exchanging control messages for joining and leaving overlay networks in place of corresponding mobile peers. Finally, by simulation experiments using an energy model, we show that our proposed streaming structure can increase the lifetime of mobile peers using agent peers.

• Journal of the Korea Society of Computer and Information
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• v.16 no.4
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• pp.101-110
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• 2011

A smart grid networks delivers electricity from suppliers to consumers using digital technology with two-way communications to control appliances at consumers' homes to save energy, reduce cost and increase reliability and transparency. Security is critically important for smart grid networks that are usually used for the electric power network and IT environments that are opened to attacks, such as, eavesdroping, replay attacks of abnormal messages, forgery of the messages to name a few. ZigBee has emerged as a strong contender for smart grid networks. ZigBee is used for low data rate and low power wireless network applications. To deploy smart grid networks, the collected information requires protection from an adversary over the network in many cases. The security mechanism should be provided for collecting the information over the network. However, the ZigBee protocol has some security weaknesses. In this paper, these weaknesses are discussed and a method to improve security aspect of the ZigBee protocol is presented along with a comparison of the message complexity of the proposed security protocol with that of the current ZigBee protocol.

• Proceedings of the KSR Conference
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• 2005.05a
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• pp.776-781
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• 2005

In this paper, using received channel information, we analyze performance in MIMO multiuser system in low-to-medium mobile speed by selecting each user's constellations, powers, and transmit antennas. Given a target of symbol error, we determine each user's constellations, powers, selected tranprobability smit antennas such that the required signal-to-noise(SNR) is minimized for MMSE, V-BLAST receiver according to each user's information and channel estimation information. When we do power control with antenna selection technique through uplink channels of MIMO system in low-to-medium mobile speed, we analyze system performance with wireless channel information from Base-Station(BS) to Users. By simulation, it has been shown that the proposed antenna selection scheme for transmitting data offer better performance improvement than all transmit antennas for transmitting data.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.14 no.5
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• pp.209-214
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• 2014

IMS(IP Multi-Media Subsystem) is in the limelight as the Integrated wire and wireless Systems because of a sudden increase of smart mobile devices and growth of multimedia additional services such as IPTV. The structure of IMS is designed as a session control layer to provide various multimedia summative service using SIP based on IP communication network in order to carry out set-up, change and release by NGN of course, the existing voice services. But now It is broadly substituting in the IPTV, wire phone company and it is substituted in internet platform base on the soft-switch in currently. Especially, in currently, 4G LTE in a mobile communication company is rapidly growing in market. Therefore, in this study, we had designed and developed to the main prosser that can admit to 1000 user over and SIP gateway which can link the IMS Core that can link SIP Device which adopt the standard protocol on the SIP and to provide variable multimedia services.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.17 no.5
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• pp.151-155
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• 2017

With the rapid growth of the up-to-date wireless network and Internet technologies, huge and various types of things around us are connected to the Internet and build the hyper-connected society, and lots of smart applications using these technologies are actively developed recently. IoT connects human, things, space, and data with various types of networks to construct the hyper-connected network that can create, collect, share and appling realtime information. Furthermore, most of the smart applications are concentrated on the service that can collect and store realtime contexts using various sensors and cloud technology, and provide intelligence by making inferences and decisions from them nowadays. In this paper, we design a smart application that can accurately control and process the current state of the specific context in realtime by using the state-of-the-art ICT techniques such as various sensors and cloud technologies on the IoT based mobile computing environment.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.46 no.12
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• pp.117-124
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• 2009

In this paper, we have developed communication modules for ubiquitous transportation sensor network (u-TSN). The developed module can be used for intelligent transportation services. The developed systems are based on IEEE 802.11a and IEEE 802.11g technologies for vehicle and infrastructure systems, respectively. We have found that the throughput for the developed systems is at maximum around 15 Mbps. It is reduced to 10 Mbps at a long distance and high speed condition. The performance is enough to support traffic control services in dense traffic condition.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.48 no.4
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• pp.37-46
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• 2011

Time synchronization plays an important role in mobile communication systems, particularly, when an accurate time-division mechanism among the communication entities is required. We present a new time synchronization algorithm for a wireless mobile ad-hoc network assuming that communication link is managed by a time-slot reservation-based medium access control protocol. The central idea is to reduce time synchronization packet collisions by exploiting the advantages found in reference broadcasting. In addition, we adopt a sophisticated clock updating scheme to ensure the time synchronization convergence. To verify the performance of our algorithm, a set of network simulations has been performed under various mobile ad-hoc network scenarios using the OPNET. The results obtained from the simulations show that the proposed method outperforms the conventional TSF method in terms of synchronization accuracy and convergence time.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.45 no.6
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• pp.18-26
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• 2008

In this paper, dynamic GTS scheduling method based on IEEE 802.15.4 is proposed for wireless control system considering reliability and real-time property. The proposed methods can guarantee a transmission of real-time periodic and sporadic data within the limited time frame in factory environment. The superframe of IEEE 802.15.4 is used for the dynamic transmission method of real-time mixed traffic (periodic data, sporadic data, and non real-time message). By separating CFP and CAP properly, the periodic, sporadic, and non real-time messages are transmitted effectively and guarantee real-time transmission within a deadline. The simulation results show the improvement of real-time performance of periodic and sporadic data at the same time.