• The Journal of the Korea institute of electronic communication sciences
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• v.2 no.2
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• pp.75-82
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• 2007

Wireless Sensor Network(WSN) is composed of a large number of sensor nodes and accomplish a common task such as environment monitoring or asset tracking. This paper proposed a congestion control mechanism applying the ECN mechanism and the cross layer design to cope with temporal congestion in WSN. We experimented with the proposed congestion control mechanism using ns-2 simulator and measured the throughput of sink node. Simulation results show that the suggested mechanism can improve the performance of packet throughput by dealing with the congestion of network efficiently.

• Journal of KIISE
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• v.43 no.11
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• pp.1223-1232
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• 2016

A virtual network technology can provide a network reflecting the requirements of various services. The virtual network can distribute resources of the physical network to each virtual slice. An efficient resource distribution technique is needed to reflect the requirements of various services. Existing bandwidth distribution techniques can only control downlink traffic without taking traffic conditions on the network into account. Downlink and uplink share the same resources in a wireless network. The existing bandwidth distribution techniques assumed that all stations generate saturated traffic. Therefore, the existing bandwidth distribution technique cannot make traffic isolation in a virtual wireless network. In this paper, we proposed a traffic-based bandwidth control techniques to solve these problems. We applied Software-Defined Networking(SDN) to the virtual wireless network, monitored the traffic at each station, and searched for stations that generated unsaturated traffic. We also controlled both uplink and downlink traffics dynamically based on monitoring information. Our system can be implemented with legasy 802.11 clients and SDN-enabled APs. After the actual test bed configuration, it was compared to existing techniques. As a result, the distribution performance of the proposed technique was improved by 14% in maximum.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.30 no.9
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• pp.602-608
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• 2017

Due to recent industry 4.0, manufacturing has changed a lot. In particular, it is necessary to control the controller and controller of the control system, to communicate various production information and measurement information, and to produce a database in accordance with the flexible production for a small quantity of various items, and to manage the trend of major parts of production facilities. In this paper, we developed a multiple wireless communication controller for small scale control system for smart factory by applying XBee and microcomputer. This controller is cheap and easy to build multi-radio communication environment of 1: N and can control and monitor control system. In addition, we tested multiple wireless communication controllers by using signal processing device and C++, and constructed network, control, and database for mechanism module, and confirmed effectiveness for industrial application.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.9 no.6
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• pp.617-623
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• 2016

Recently, IoT technology has been applied to the control of appliances in the home, and information about temperature, humidity, etc. is collected and the application of the system to control the indoor environment automatically is increasing. Currently, the network configuration of IoT devices is mainly used to connect IoT devices to the Internet through wireless gateways. Since such a method is dependent on a gateway, there are limitations in providing various services. Therefore, this paper proposes an independent method of gateway by using IoT network without using gateway by applying long distance wireless communication technology. IoT devices using the proposed long distance wireless internet technology can connect to a remote server and provide mobility that can not be supported by existing methods, thereby providing more various services. The performance evaluation of the proposed network configuration method is compared with the delay time and the amount of data generated in the existing network method constituted by the gateway and the proposed network configuration method respectively. Experimental results show that the proposed method decreases the delay time and the amount of data generated by the gateway.

• Journal of the Optical Society of Korea
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• v.13 no.1
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• pp.98-106
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• 2009

This paper proposes an optical wireless transfer agent method which realizes the continuous and swift data transfer of optical wireless terminals in optical wireless networks. The unguided wireless channel generally shows frequent link disconnections and propagation delays due to weak wireless links. Specially speaking, optical wireless channels have more vulnerable links and roaming propagation delays relative to the weakness of the previous RF channels due to their low signal connectivity and small geographic coverage. Conventional optical wireless network protocols did not consider any fault models about physical link faults. Consequently, they have shown data transfer inefficiency for both data link control and physical wireless link control. To overcome these optical wireless environmental problems, this paper suggests a new wireless access point (or base station) agent system, which provides wireless or mobile clients with previous link layer protocols compensated.

• The KIPS Transactions:PartC
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• v.16C no.2
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• pp.237-244
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• 2009

The congestion in wireless sensor network increases the ratio of data loss and causes the delay of data. The existing congestion protocols for wireless sensor network reduces the amount of transmission by control the sampling frequency of the sensor nodes related to the congestion when the congestion has occurred and was detected. However, the control method of sampling frequency is not applicable on the situation which is sensitive to the temporal data loss. In the paper, we propose a new congestion control, ACT - Adaptive Congestion conTrol. The ACT monitors the network traffic with the queue usage and detects the congestion based on the multi level threshold of queue usage. Given network congestion, the ACT increases the efficiency of network by adaptive flow control method which adjusts the frequency of packet transmission and guarantees the fairness of packet transmission between nodes. Furthermore, ACT increases the quality of data by using the variable compression method. Through experiment, we show that ACT increases the network efficiency and guarantees the fairness to sensor nodes compared with existing method.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.9 no.6
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• pp.195-200
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• 2009

In this paper, we verified the reliability through local examination by introducing a wired network that is operated at the local waterworks to wireless LAN based Wi-Fi network. The adopted wireless network compared to the existing wired network through saving cost and reducing breakdown points have been proven to be effective qualitatively and quantitatively. This study proved that wireless networks could be introduced for the advancement of operations management of existing metropolitan water supply and the local waterworks that are operating currently.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.7
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• pp.3470-3493
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• 2019

IEEE 802.11s-based infrastructure Wireless Mesh Networks (iWMNs) are envisaged as a promising solution to provide ubiquitous wireless Internet access. The limited network capacity is a problem mainly caused by the medium contention between mesh users and the mesh access points (MAPs), which gets worst when the mesh clients employ the Transmission Control Protocol (TCP). To mitigate this problem, we use wireless network coding (WNC) in the MAPs. The aim of this proposal is to take advantage of the network topology around the MAPs, to alleviate the contention and maximize the use of the network capacity. We evaluate WNC when is used in MAPs. We model the formation of coding opportunities and, using computer simulations, we evaluate the formation of such coding opportunities. The results show that as the users density grows, the coding opportunities increase up to 70%; however, at the same time, the coding delay increments significantly. In order to reduce such delay, we propose to adaptively adjust the time that a packet can wait to catch a coding opportunity in an MAP. We assess the performance of moving-average estimation methods to forecast this adaptive sojourn time. We show that using moving-average estimation methods can significantly decrease the coding delay since they consider the traffic density conditions.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.42 no.5
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• pp.1102-1109
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• 2017

In Train Control Network(TCN), to support advanced services beyond control applications, it was revised to support high speed ethernet as IEC 61375-2-5(ETB) and IEC 61375-3-4(ECN). And Train Topology Discovery Protocol(TTDP) was included by which train-consist can be automatically configured. Meanwhile, to adopt wireless LAN as an next onboard network, TTDP need to be modified to reflect the characteristics of WLAN. This paper proposed a TTDP for WLAN using transmission power control and the number of HELLO-ACK handshake. And it determined whether the TTDP executed using the two WLAN interfaces having different bandwidths is correct or not. The proposed TTDP can allow to reduce interference from other nodes. For evaluation of performance of TTDP, NS-2 was used. The evaluation result shows the high reliability of the TTDP in wireless environment.

• Journal of the Korea Society of Computer and Information
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• v.25 no.12
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• pp.109-117
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• 2020

In this paper, we analyze LADN(Local Area Data Network) that provides high throughput, low latency and service localization for 5G wireless networks and propose an enhanced control protocol design for LADN in 5G wireless networks. The concept of LADN is newly introduced in 3GPP 5G communication system and the LADN is a data network to which the UE(User Equipment) can connect with a specific LADN session only when the UE is located in a certain service area. If the LADN information between the UE and core network is not identical, the LADN session cannot be properly established. The proposed approach promplty synchronizes the LADN information between the UE and core network by using the specific registration procedure and appropriately establishes the LADN session, when the establishment of the LADN session is failed. Consequently, the proposed enhanced control protocol design(ECP) can prevent unnecessary signalling overhead and communication delay for LADN in 5G wireless networks.