• The Journal of Korean Institute of Communications and Information Sciences
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• v.39C no.12
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• pp.1289-1297
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• 2014

In this paper, we use the ECMA-392 standard, the first cognitive radio networks to meet the demand for IT services in the ship. We propose a ECMA-392 cooperative MAC protocol to ensure QoS to support multimedia services in the ship area in a multi-hop wireless bridge using ECMA-392 networks. Because the proposed protocol transmits directly or relay transmission by selecting efficient routes based on the information of the ECMA-392 devices, it provides communication to ensure QoS of the device. The simulation results show that the proposed cooperative MAC protocol improves a throughput of devices compared to the existing method.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.4
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• pp.774-784
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• 2009

A wireless sensor network consisting of a large number of nodes with limited battery power should minimize energy consumption at each node to prolong the network lifetime. To improve the sensitivity of wireless sensor networks, an efficient scheduling algorithm and energy management technology for minimizing the energy consumption at each node is desired. ill this paper, we propose energy-aware routing mechanism for maximum lifetime and to optimize the solution quality for sensor network maintenance and to relay node from its adjacent cluster heads according to the node"s residual energy and its distance to the base station. Proposed protocol may minimize the energy consumption at each node, thus prolong the lifetime of the system regardless of where the sink is located outside or inside the cluster. Simulation results of proposed scheme show that our mechanism balances the energy consumption well among all sensor nodes and achieves an obvious improvement on the network lifetime. To verify propriety using NS-2, proposed scheme constructs sensor networks adapt to current model and evaluate consumption of total energy, energy consumption of cluster head, average energy dissipation over varying network areas with HEED and LEACH-C.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2015.05a
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• pp.113-115
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• 2015

In this paper, we proposed an algorithm based on movement prediction using rate of change of the attribute information of nodes what is called WRC(Weighted Rate Control) in delay tolerant networks(DTNs). Existing DTN routing algorithms based on movement prediction communicate by selecting relay nodes increasing connectivity with destination node. Thus, because the mobile nodes are in flux, the prediction algorithms that do not reflect the newest attribute information of node decrease reliability. In this paper, proposed algorithm approximate speed and direction of attribute information of node and analysis rate of change of attribute information of node. Then, it predict movement path of node using proposed weight. As the result, proposed algorithm show that network overhead and transmission delay time decreased by predicting movement path of node.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.6A
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• pp.506-514
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• 2009

To minimize energy consumption, most of MAC Protocols in WSNs exploit low duty cycling. Among those, RMAC [4] allows a node to transmit a data packet for multiple hops in a single duty cycle, which is made possible by exploiting a control frame named Pioneer (PION) in setting up the path. In this paper, we present a MAC Protocol called Hop Extended MAC (HE-MAC) that transmits the data packet for more multiple hops in a single duty cycle. It employs an EXP (Explorer) frame to set up the multiple hop transmission, which contains the information of the maximum hop that a packet can be transmitted. With the use of the information in EXP and an internal state of Ready to Receive (RTR), HEMAC extends the relay of the packet beyond the termination of the data period by two more hops compared to RMAC. Along with our proposed adaptive sleeping method, it also reduces power consumption and handles heavy traffic efficiently without experiencing packet inversion observed in RMAC. We analytically obtain the packet delivery latency in HE-MAC and evaluate the performance through ns-2 simulations. Compared to RMAC, HE-MAC achieves 14% less power consumption and 20% less packet delay on average for a random topology of 300 nodes.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.44 no.3
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• pp.37-42
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• 2007

This paper reconsiders established power conservation models for ubiquitous sensor networks that use relay nodes instead of direct communication and proposes novel network power consumption model with consideration of the channel level and radio chip level simultaneously. We estimate the effect of minimum hop-count policy in terms of network power consumption through simulation of various situations for low power RF module CC2420. It is observed that maximum RF power and minimum hop-count results in lower energy consumption relatively. Also, in total network energy consumption, which is included re-transmission, minimum hop count policy presents decrease by 33.1% of energy consumption in compare with the conventional model.

• Journal of IKEEE
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• v.23 no.4
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• pp.1116-1121
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• 2019

Networking services based on the flying drones may cause many handover events because the coverage radius is narrower than that of the existing infrastructure, such as cellular networks. Therefore, it copes with frequent handover by pre-caching data to target network provider before handover using a content store. As a result of the simulation, it can be confirmed that the delay is lowered. This is because the data that was requested before the handover is delivered to the target drones, and the car that has completed the handover receives the data through the target drones. On the other hand, if the proposed method is not used, it can be confirmed that the delay is increased. This is because it can not cope with the path change due to the handover and re-sends the packet requesting the data.

• Journal of Korea Multimedia Society
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• v.9 no.11
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• pp.1474-1482
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• 2006

Recently, it is advanced about the variable research of IPv6 and the wireless sensor network. However, the existed researches are not enough about the internetworking technology between the wireless sensor network and the Internet based on IPv6 for supporting ubiquitous service. Accordingly, this paper proposes two internetworking models for connecting the wireless sensor network and Internet based on IPv6. The relay router in the first model and the sink node of the wireless sensor network in the second mode] were used as a gateway. Then we analyze and compare with two internetworking models. Additionally we construct the test-bed connected between the wireless sensor network and KOREN(KOrea advanced REsearch Network) based on IPv6 using the first model. And we verified the operation of the test-bed by experiments.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.42 no.5
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• pp.999-1008
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• 2017

In this paper, we propose a pipeline network coding (PNC) scheme for efficient data transmission in wireless networks, a data authentication scheme for verifying the integrity of data, and a node authentication scheme for a virtual source. PNC is a technique that improves the overall network performance by relaying data such that the relay node performing network coding transmits to the sender instead. However, network coding is vulnerable to a pollution attack, which is an attack by a malicious attacker to inject modified data into the network. To prevent this, hash-based message authentication code (HMAC) is used. For this purpose, in order to generate a tag used for data authentication, a key must be distributed to the nodes performing authentication. We applied a hash chain to minimize the overhead of key distribution. A null vector is used as the authentication scheme for the virtual source. Finally, we analyze the safety and complexity of the proposed scheme and show he performance through simulation.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.4 no.4
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• pp.491-508
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• 2010

In peer-to-peer (P2P) on-demand streaming networks, the alleviation of server load depends on reciprocal stream sharing among peers. In general, on-demand video services enable clients to watch videos from beginning to end. As long as clients are able to buffer the initial part of the video they are watching, on-demand service can provide access to the video to the next clients who request to watch it. Therefore, the key challenge is how to keep the initial part of a video in a peer's buffer for as long as possible, and thus maximize the availability of a video for stream relay. In addition, to address the issues of delivering data on lossy network and providing scalable quality of services for clients, the adoption of multiple description coding (MDC) has been proven as a feasible resolution by much research work. In this paper, we propose a novel caching scheme for P2P on-demand streaming, called Dynamic Buffering. The proposed Dynamic Buffering relies on the feature of MDC to gradually reduce the number of cached descriptions held in a client's buffers, once the buffer is full. Preserving as many initial parts of descriptions in the buffer as possible, instead of losing them all at one time, effectively extends peers’ service time. In addition, this study proposes a description distribution balancing scheme to further improve the use of resources. Simulation experiments show that Dynamic Buffering can make efficient use of cache space, reduce server bandwidth consumption, and increase the number of peers being served.

• Journal of Digital Convergence
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• v.14 no.1
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• pp.171-179
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• 2016

The energy consumption problem in wireless sensor networks is investigated. The problem is to expend as little energy as possible receiving and transmitting data, because of constrained battery. In this paper, in order to extend the lifetime of the network, we proposed a location-based clustering algorithm for wireless sensor network with skewed-topology. The proposed algorithm is to deploy multiple child nodes at the sink to avoid bottleneck near the sink and to save energy. Proposed algorithm can reduce control traffic overhead by creating a dynamic cluster. We have evaluated the performance of our clustering algorithm through an analysis and a simulation. We compare our algorithm's performance to the best known centralized algorithm, and demonstrate that it achieves a good performance in terms of the life time.