• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.2
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• pp.334-348
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• 2015

Widespread use of smart devices accompanies increase of use of access point (AP), which enables the connection to the wireless network. If the appropriate security is not served when a user tries to connect the wireless network through an AP, various security problems can arise due to the rogue APs. In this paper, we are going to examine the threat by evil-twin, which is a kind of rogue APs. Most of recent researches for detecting rogue APs utilize the measured time difference, such as round trip time (RTT), between the evil-twin and authorized APs. These methods, however, suffer from the low detection rate in the network congestion. Due to these reasons, in this paper, we suggest a new factor, packet inter-arrival time (PIAT), in order to detect evil-twins. By using both RTT and PIAT as the learning factors for the support vector machine (SVM), we determine the non-linear metric to classify evil-twins and authorized APs. As a result, we can detect evil-twins with the probability of up to 96.5% and at least 89.75% even when the network is congested.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.1B
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• pp.11-17
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• 2003

In this paper, we presented the dynamic random access channel allocation method under the priority based scheduling policy in order to improve the system performance of HIPERLAN/2 standardized by ETSI According to the scheduling policy, AP scheduler primarily allocates the resource to the collision MT This scheduling policy bring about decreasing the transmission delay of collision MT Dynamic RCH(random access channel) allocation method decreases the collision probability by increasing the number of RCH slots in case of low traffic. While it increases the maximum throughput by increasing the number of the data transmission slots in case of high traffic Therefore dynamic allocation method of RCH slots decreases the scheduling delay and increases the throughput When we evaluate the performance of presented method based on standards, we saw that the presented method improve the performance of the MAC protocol in terms of throughput and transmission delay.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.7B
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• pp.586-594
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• 2012

The drastic growth of mobile communication and spreading of smart phone make the significant attention on Location Based Service. The one of most important things for vitalization of LBS is the accurate estimating position for mobile object. Focusing on AP's probabilistic position estimation, we develop an AP distribution map and new pattern matching algorithm for position estimation. The developed approaches can strengthen the advantages of Radio fingerprint based Wi-Fi Positioning System, especiall on the algorithms and data handling. Compared on the existing approaches of fingerprint pattern matching algorithm, we achieve the comparable higher performance on both of average error of estimation and deviation of errors. Furthermore all fingerprint data have been harvested from the actual measurement of radio fingerprint of Seoul, Kangnam area. This can approve the practical usefulness of proposed methodology.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.11 no.2
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• pp.197-203
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• 2011

Ad-hoc networks do not rely on a preexisting infrastructure such as Access Points(AP) in wireless network infrastructure. Instead each node participates in routing by forwarding data for other nodes. It makes required broadcasting to transmit packets to the whole network. In that part, each node tries to transmit data without any information about the other nodes. Therefore it causes duplication of transmission and waste of power. This paper presents adaptive probabilistic broadcasting schemes based on packet reception counts to alleviate the broadcast storm problem for wireless ad hoc networks. In this algorithm, each node calculates efficiency broadcast probability. Simulation results for the proposed flood algorithm are also presented.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.1A
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• pp.58-64
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• 2009

In this paper, we propose an dynamic random channel allocation scheme increasing probability of channel acquisition and reducing delay by limiting the number of minimum RCHs(Random CHannels) as an optimal factor $\beta$. The MAC protocol of HIPERLAN/2 is based on TDMA/TDD and MT(Mobile Terminal) can obtain chance of traffic transmission through channel competition in RCH period. And AP(Access Point) can dynamically schedule the number of RCHs based on the number of the collision in each RCH of the previous frame. Therefore, the proposed scheme increases a probability of channel acquisition and reduces delay by means of guaranteeing the number of minimum RCHs. With a practical Internet traffic, it is concluded that by the proposed scheme the delay reduction of the order of 19% and slightly better throughput are obtained compared to the conventional algorithm.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.8
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• pp.1561-1570
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• 2009

Being different from traditional mobile communication networks or wireless LAN with access points, ad hoc network can provide direct communications between homogeneous stations. Thus, it can be considered as a much advanced network. Somehow, many researches have been done to enhance system performance of ad hoc networks up to now, one of which is cooperative communications. In this paper, a cooperative MAC protocol, called CO-MAC protocol, is proposed and its performance is evaluated with a mathematical approach. Numerical results show that this scheme provides more enhanced system throughput especially when frame transmission error probability is high than DCF scheme, which is the key protocol in IEEE 802.11 standard, and rDCF scheme.

• Journal of the Korean Institute of Intelligent Systems
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• v.22 no.1
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• pp.12-21
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• 2012

IEEE 802.11 MAC protocol standard, DCF(CSMA/CA), is originally designed to ensure the fair channel access between mobile nodes sharing the local wireless channel. It has been, however, revealed that some misbehavior nodes transmit more data than other nodes through artificial means in hot spot area spreaded rapidly. The misbehavior nodes may modify the internal process of their MAC protocol or interrupt the MAC procedure of normal nodes to achieve more data transmission. This problem has been referred to as a selfish node problem and almost literatures has proposed methods of analyzing the MAC procedures of all mobile nodes to detect the selfish nodes. However, these kinds of protocol analysis methods is not effective at detecting all kinds of selfish nodes enough. This paper address this problem of detecting selfish node using Tsallis-Entropy which is a kind of statistical method. Tsallis-Entropy is a criteria which can show how much is the density or deviation of a probability distribution. The proposed algorithm which operates at a AP node of wireless LAN extracts the probability distribution of data interval time for each node, then compares the one with a threshold value to detect the selfish nodes. To evaluate the performance of proposed algorithm, simulation experiments are performed in various wireless LAN environments (congestion level, how selfish node behaviors, threshold level) using ns2. The simulation results show that the proposed algorithm achieves higher successful detection rate.

• Journal of KIISE:Computing Practices and Letters
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• v.11 no.6
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• pp.503-513
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• 2005

With the recognition of the importance of computational approach for protein-protein interaction prediction, many techniques have been developed to computationally predict protein-protein interactions. However, few techniques are actually implemented and announced in service form for general users to readily access and use the techniques. In this paper, we design and implement a protein interaction prediction service system based on the domain combination based protein-protein interaction prediction technique, which is known to show superior accuracy to other conventional computational protein-protein interaction prediction methods. In the prediction accuracy test of the method, high sensitivity($77\%$) and specificity($95\%$) are achieved for test protein pairs containing common domains with teaming sets of proteins in a Yeast. The stability of the method is also manifested through the testing over DIP CORE, HMS-PCI, and TAP data. Performance, openness and flexibility are the major design goals and they are achieved by adopting parallel execution techniques, web Services standards, and layered architecture respectively. In this paper, several representative user interfaces of the system are also introduced with comprehensive usage guides.