• Journal of Korea Multimedia Society
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• v.10 no.9
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• pp.1165-1174
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• 2007

Mobile ad hoc networks suffer from the re-construction of the routing path as a node on the path moves away and/or fails. In this paper we propose a multipath routing scheme, designed for the network based on the directional antennas, in which a new path is quickly recovered by do-touring to an alternative neighbor called braid. Simulations are conducted in random networks with 50 nodes uniformly deployed in a $1,000m{\times}1,000M$ area where, all nodes have a transmission range of 250m and the average node moving speed varies from 0 to 10m/s. The proposed approach under the ideal antenna with K(>1) directional sectors achieves better results compared with the case of K=1, the omnidirectional antenna model, in terms of the metrics: packet delivery ratio and average number of hops for the routing paths. As further study, a scheme to alleviate the heavy amount of latency accompanied by the rout setup is urgently required.

• KIPS Transactions on Computer and Communication Systems
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• v.4 no.12
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• pp.409-414
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• 2015

The energy conservation is the most important subject for long run operation of the sensor nodes with limited power resources. Clustering is one of most energy efficient technique to grouped the sensor nodes into distinct cluster. But, in a cluster based WSN, CHs and gateways bear an extra work load to send the processed data to the sink. The inappropriate cluster formation may cause gateways overloaded and may increase latency in communication. In this paper, we propose a novel load balanced clustering model for improving energy efficiency and giving a guarantee of long network lifetime. We show the result of performance measurement experiments that designs using a branch and bound algorithm and a multi-start local search algorithm to compare with the existing load balanced clustering model.

• Journal of the Institute of Electronics and Information Engineers
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• v.53 no.2
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• pp.10-16
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• 2016

For higher reliability against a link failure of a control network in railway vehicles, a recovery mechanism is needed. We introduce a problem that, when a link failure occurs in a ring-topology control network, a node may experience a significant increase of transmission delay depending on its relative position within the network. We then propose two mechanisms to solve this problem: (1) differentiating and prioritizing node traffic in forwarding; and (2) switching some nodes to a backup bus-topology network. Our simulation study shows that, while the first mechanism achieves a limited gain by only compensating queuing delay, the second one gets a sufficient gain which is impacted by the number of nodes switched to the bus network.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.12 no.3
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• pp.478-484
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• 2008

When a mobile node moves, MIPv6 operates an authentication process for the new connection. These kinds of frequent binding update and authentication processes cause much traffic and delay the service. To solve this problem, PMIPv6 provides a network-based mobility protocol in order to lessen the load on a mobile node. However, when it is moved from a domain to a domain or in a domain, there still lies a need fDr a new address, so MIPv6's demerit still exists. In IPsec, too, a new negotiation should be made when it is moved to WAN(Wide Area Network). This causes load to the mobile node. In this paper suggests MBB(Make Before Break) system to eliminate disconnections or delays resulted from the address change or renegotiation for security. When the mobile node receives a CoA address, IPsec negotiation gets operated. Its identity is authenticated by sending the identifier used for the prior negotiation to CN(Correspondent Node) through the BID message suggested. After that, negotiation Bets simplified that disconnections can be eliminated, and in the IPsec negotiation, the load on the mobile node can be lessened as well; moreover, two addresses are used for the communication simultaneously, so the probability of packet loss can be reduced.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.12 no.2
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• pp.290-298
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• 2008

This paper presents an efficient data storage and reconstruction method in data acquisition and processing of monitoring system. The proposed method extracts minimum data using an interpolation from raw data which are acquired from a target system. They are transferred and saved in a monitoring PC via TCP/IP communication, and then reconstructed as original signals. Therefore, it is possible to design an efficient monitoring system by the improved data communication speed due to the reduced communication packet, and it reduces the storage space. The algorithm for data acquisition and reconstruction is based on Cubic Hermite interpolation. To verify the validity of the proposed scheme, we presents simulation results compared with other interpolation based approaches. Finally, it is applied to a monitoring system for grid-connected photovoltaic power generation system to prove the high-performance of the proposed method.

• The Journal of the Acoustical Society of Korea
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• v.40 no.4
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• pp.370-381
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• 2021

This paper presented an efficient transceiver structure of multiband Frequency Shift Keying (FSK) signals with direct sequence spread spectrum for maintaining covertness and performance. In aspect to covertness, direct sequence spread spectrum method, which multiplying by Pseudo Noise (PN) codes whose rate is much higher than that of data sequence, is employed. In aspect to performance, in order to overcome performance degradation caused by multipath and Doppler spreading, we applied multiband, turbo equalization, and weighting algorithm are applied. Based on the simulation results, by applying 4 number of multiband and number of chips are 8 and 32, experiments were conducted in a lake with a distance of moving from 300 m to 500 m between the transceivers. we confirmed that the performance was improved as the number of bands and chips are increased. Furthermore, the performance of multiband was improved when the proposed weighting algorithm was applied.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.14 no.1
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• pp.35-45
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• 2004

In explosively increasing internet environments, information security is one of the most important consideration. Nowadays, various security solutions are used as such problems countermeasure; IDS, Firewall and VPN. However, basically internet has much vulnerability of protocol itself. Specially, it is possible to establish a covert channel using TCP/IP header fields such as identification, sequence number, acknowledge number, timestamp and so on. In this Paper, we focus cm the covert channels using identification field of IP header and the sequence number field of TCP header. To detect such covert channels, we used Support Vector Machine which has excellent performance in pattern classification problems. Our experiments showed that proposed method could discern the abnormal cases(including covert channels) from normal TCP/IP traffic using Support Vector Machine.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.17 no.6
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• pp.143-148
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• 2007

In the context of mass traffic, firewall system cannot record normal log files against DDoS attack. The loss of log record causes that a firewall system does not know whether a packet is normally filtered or not, and firewall log, which is an essential data for the counter measure of violation accident, cannot be verified as trusted. As a network speed increases, these problems happen more frequently and largely. Accordingly, the method to use simply additional hardware devices is not recommended for the popularization of firewall. This paper is devoted to verify the loss of iptable log that is the mother's womb of most domestic firewall systems and show that the log handling methods for conventional firewall systems are needed to improve.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.17 no.5
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• pp.15-25
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• 2007

According to augmentation about interesting and demanding of privacy over the rest few years, researches that provide anonymity have been conducted in a number of applications. The ad hoc routing with providing anonymity protects privacy of nodes and also restricts collecting network information to malicious one. Until recently, quite a number of anonymous routing protocols have been proposed, many of them, however, do not make allowance for authentication. Thus, they should be able to have vulnerabilities which are not only modifying packet data illegally but also DoS(denial of service) attack. In this paper, we propose routing protocol with providing both anonymity and authentication in the mobile ad hoc network such as MANET, VANET, and more. This scheme supports all of the anonymity properties which should be provided in Ad Hoc network. In addition, based on the group signature, authentication is also provided for nodes and packets during route discovery phase. Finally, route discovery includes key-agreement between source and destination in order to transfer data securely.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.18 no.2
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• pp.65-73
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• 2008

Security layer of the Cdma2000 1x EV-DO is currently completing standard (C.S0024-A v2.0). Accordingly, a hardware security devices, that allows to implementation requirement of the security layer described in standard document, is required to apply security function about data transferred between AT and AN of then Cdma2000 1x EV-DO environment. This paper represents design of hardware device providing EV-DO security with simulation of the security layer protocol via the FPGA platform. The SHA-1 hash algorithm for certification and service of packet data, and the AES, SEED, ARIA algorithms for data encryption are equip in this device. And paper represents implementation of hardware that applies optionally certification and encryption function after executing key-switch using key-switching algorithm.