• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.6A
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• pp.568-576
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• 2011

In this paper, a channel assignment technique to mitigate interferences due to ISI(Inter Symbol Interference) and ICI(Inter Carrier Interference) caused by TDoA(Time Difference of Arrival) among distributed MRs(Mesh Routers) in OFDMA(Orthogonal Frequency Division Multiple Access)-based WMN(Wireless Mesh Network) is proposed. The SINR(Signal to Interference and Noise Ratio) associated with the channel assignment for each MR is defined to minimize the effect of ISI and ICI due to TDoA in WMN, which is then used to propose an channel assignment technique considering fairness constraint. It is verified by computer simulation that the proposed channel assignment technique can improve the performance of BER(Bit Error Rate) in WMNs with compared to the conventional technique.

• Journal of Communications and Networks
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• v.10 no.3
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• pp.239-252
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• 2008

For orthogonal frequency division multiplexing (OFDM), cyclic prefix (CP) should be longer than the length of channel impulse response, resulting in a loss of bandwidth efficiency. In this paper, we describe a new technique to restore the cyclicity of the received signal when the CP is not sufficient for OFDM systems. The proposed technique efficiently restores the cyclicity of the current received symbol by adding the weighted next received symbol to the current received symbol. Iterative CP reconstruction (CPR) procedure, based on the residual intersymbol interference cancellation (RISIC) algorithm, is analyzed and compared to the RISIC. In addition, we apply the CPR method to Alamouti space-time block coded (STBC) OFDM system. It is shown that in the STBC OFDM, tail cancellation as well as cyclic reconstruction of the CPR procedure should be repeated. The computational complexities of the RISIC, the proposed CPR, the RISIC with STBC, and the proposed CPR with STBC are analyzed and their performances are evaluated in multipath fading environments. We also propose an iterative channel estimation (CE) method for OFDM with insufficient CP. Further, we discuss the CE method for the STBC OFDM system with the CPR. It is shown that the CPR technique with the proposed CE method minimizes the loss of bandwidth efficiency due to the use of CP, without sacrificing the diversity gain of the STBC OFDM system.

• KIPS Transactions on Computer and Communication Systems
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• v.5 no.1
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• pp.17-26
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• 2016

IoT means things space networks that form the intelligent relationship such as sensing, networking, information processing about human being, things and service without explicit mutual cooperation of human being. Lately many IoT groups such as AllSeen Alliance, OIC launched a platform for IoT. Self-adaptive is aimed at implementation without the need for decisions of human being during the operation, so that the machine can respond to changes in its own determination. There is a need to apply the concept of self-adaptive to existing IoT and IoT platform. So In this paper, We look for trends of existing IoT, IoT platform and comparisons by applying a self-adaptive concept to IoT, IoT platform. In addition as an example of this paper, we suggest lacking self-adaptive elements to OIC.

• Journal of Convergence Society for SMB
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• v.6 no.2
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• pp.37-43
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• 2016

Due to the remarkable improvement of ICT, with the popularization of mobile devices and every sector of society connected by networks, an era, in which peer to peer, peer to thing, thing to thing can be connected to one another everywhere, has begun. As all the electronic devices are connected to Internet, they have become more intellectualized and automated, making convergence and process of information through the connection of the devices possible to provide a lot better services. However, those devices communicate mutually to send information and they are exposed to various security threats. Therefore, this study analyzes ZigBee, CoAP, MQTT, XMPP, which are communication-related technology of IoT, draws security threats they have, and suggests requirements that components of IoT should have. Plus, it examines real cases about security threats in IoT, and suggests a countermeasure so as to contribute to establishment of a basis for IoT to be used much more safely in the future.

• KSCI Review
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• v.14 no.2
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• pp.235-244
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• 2006

This paper attacked the unknown DoS which mixed a DoS attack, Worm and the Trojan horse which used IP Source Address Spoofing and Smurf through the SYN Flooding way that UDP, ICMP, Echo, TCP Syn packet operated. the applications that used TCP/UDP in VoIP service networks. Define necessity of a Dynamic Update Engine for a prevention, and measure Miss traffic at RT statistics of inbound and outbound parts in case of designs of an engine at IPS regarding an Self-learning module and a statistical attack spread. and design a logic engine module. Three engines judge attack grades (Attack Suspicious, Normal), and keep the most suitable filtering engine state through AND or OR algorithms at Footprint Lookup modules. A Real-Time Dynamic Engine and Filter updated protected VoIP service from DoS attacks, and strengthened Ubiquitous Security anger, and were turned out to be.

• KSCI Review
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• v.14 no.2
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• pp.215-224
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• 2006

Regarding a spam attack and the interception that a spinoff is largest among Vulnerability of VoIP at these papers study. Write scenario of a spam attack regarding VoIP Vulnerability, and execute Call spam. Instant Messaging spam, Presence spam attack. A spam attack is succeeded in laboratories, and prove. and confirm damage fact of a user in proposals of a spam interception way of VoIP service, 1) INVITE Request Flood Attack 2) Black/White list, 3) Traceback, 4) Black Hole-Sink Hole, 5) Content Filtering, 6) Consent based Communication, 7) Call act pattern investigation, 8) Reputation System Propose, and prove. Test each interception plan proposed in VoIP networks, and confirm security level of a spam interception. Information protection of VoIP service is enlarged at WiBro, BcN. and to realize Ubiquitous Security through result of research of this paper contribute, and may make.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.20 no.3
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• pp.15-23
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• 2020

As the IoT industry expands, various application services based on location information of devices are released. In order to transmit the location information, various wireless communication technologies such as Bluetooth and Wi-Fi are used. However, these technologies have limited coverage, and cellular networks with relatively wide coverage have the disadvantage of paying for use. In this paper, we implemented our own location information system using LoRa, a low power long distance wireless communication technology. As a result, no cost is incurred and it has relatively wider coverage than other wireless communication technologies using LoRa technology. The implementation system enables LoRa communication based on IPv6 using CoAP and 6LoWPAN, and enables multiple devices to interwork with the existing Internet environment.

• Journal of Digital Convergence
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• v.12 no.12
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• pp.345-350
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• 2014

According to the necessity of smart working with various mobile devices, and the increasing services based on the converged infrastructures such as Cloud, Wearable Computing, Next Generation Wired/Wireless Mobile Networks, the network reliability has been one of the most important things. However, the research related to the network reliability is still insufficient. To solve these problems, we propose the ISNTC (Intelligent Safe Network Technology based on Cloud), which uses the safe network technique based on SDN, to be adopted to the smart working environments. The proposed ISNTC guarantees secure data forwarding through the synchronized transmission path and timing. We have verified the throughput which outperformed the existing techniques through the computer simulations using OPnet.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.47 no.2
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• pp.1-10
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• 2010

Mapping virtual process topology to physical processor topology is one of the most important design issues in parallel programming. However, the mapping problem is complicated due to the topology irregularity and routing complexity. This paper proposes a new process mapping scheme called adjacency-based mapping (AM) for irregular cluster systems assuming that the two-dimensional mesh process topology is specified as an interprocess communication pattern. The cluster systems have been studied and developed for many years since they provide high interconnection flexibility, scalability, and expandability which are not attainable in traditional regular networks. The proposed AM tries to map neighboring processes in virtual process topology to adjacent processors in physical processor topology. Simulation study shows that the proposed AM results in better mapping quality and shorter interprocess latency compared to the conventional approaches.

• Biotechnology and Bioprocess Engineering:BBE
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• v.8 no.4
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• pp.233-239
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• 2003

For the quantitative analysis of an unknown sample a calibration curve should be obtained, as analytical instruments give relative, rather than absolute measurements. Therefore, researchers should make standard samples with various known concentrations, measure each standard and the unknown sample, and then determine the concentration of the unknown by comparing the measured value to those of the standards. These procedures are tedious and time-consuming. Therefore, we developed a polymer based microfluidic device from polydimethylsiloxane, which integrates serial dilution and capillary electrophoresis functions in a single device. The integrated microchip can provide a one-step analytical tool, and thus replace the complex experimental procedures. Two plastic syringes, one containing a buffer solution and the other a standard solution, were connected to two inlet holes on a microchip, and pushed by a hydrodynamic force. The standard sample is serially diluted to various concentrations through the microfluidic networks. The diluted samples are sequentially introduced through microchannels by electro-osmotic force, and their laser-induced fluorescence signals measured by capillary electrophoresis. We demonstrate the integrated microchip performance by measuring the fluorescence signals of fluorescein at various concentrations. The calibration curve obtained from the electropherograms showed the expected linearity.