• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.10 no.3
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• pp.111-119
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• 2010

With the rapid progress of wireless technologies today, mobile terminals with multiple access interfaces are emerging. In recent years, WLAN (Wireless Local Area Networks) has become the premier choice for many homes and enterprises. WiMAX (Worldwide Interoperability for Microwave Access) has also emerged as the wireless standard that aims to deliver data over long distances. Therefore, it is important to explore efficient integration methods for delivering multimedia data between heterogeneous wireless networks. In this paper, we developed the simulation models and environments for the mobile multihomed node that has both WiMAX and WLAN interfaces and can move around in both networks by using mobile IP. In order to verify the developed models, we designed and constructed several simulation scenarios, e.g. movement in WiMAX/WLAN, group mobility, MANET, and nested MIP under the various traffic environments such as oneway or bothway UDP packets, FTP traffic, and voice with SIP protocol. The simulation results show that the developed models are useful for mobility studies in various integrated wireless networks.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.45 no.9
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• pp.1-7
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• 2008

The efficient node energy utilization in wireless sensor networks has been studied because sensor nodes operate with limited power based on battery. Since a large number of sensor nodes are densely deployed and collect data by cooperation in wireless sensor network, keeping more sensor nodes alive as possible is important to extend the lifetime of the sensor network. Energy efficiency is an important factor of researches that efficient routing algorithm is needed in wireless sensor network. In this research, I consider some methods to utilize more efficiently the limited power resource of wireless sensor networks. The proposed algorithm is the sink first divides the network into several areas with hop counts and data transmission based on cluster ID. The performance of the proposed algorithm has been examined and evaluated with NS-2 simulator in terms of lifetime, amount of data and overhead.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.11
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• pp.2014-2020
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• 2016

In general, automatic access control management system using smart door-lock must be always exposed to security vulnerability during wireless communication based on Bluetooth. In particular, important information such as a secrete key can be exposed to the attacker when the authentication protocol has been operating in the wireless section. Therefore important information exchanged in the radio section needs to be properly encrypted. In order to analyze security vulnerability for automatic access control management system of public facilities such as subway vent, GNU Radio platform and HackRF device will be considered and experimented. Proposed experimental system to perform software based power analysis attack could be very effectively applied. As a result, important information such as packet type, CRC, length of data, and data value can be easily decoded from wireless packet obtained from HackRF device on GNU Radio platform. Constructed experimental system will be applied to avoid some security problems.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.4
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• pp.677-684
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• 2017

Smart devices are used in a variety of industries, because applications for them are easy to develop and portable. However, industrial equipment can cause security problems for information and accidents when controlling the actuator of the equipment at a remote location. In this paper, we studied methods of solving these problems and the advantages of applying smart control systems to industrial equipment. We propose a manual manipulation method using queries and a smart control access procedure for controlling equipment using a smart device. In addition, we propose a data transmission method employing multiple encryption protocols and a user authentication method using unique information from the smart device and Q & A as the communication data protection and user authentication methods, respectively. In order to evaluate its performance, an operation test of the smart control system and user authentication comparison experiment were performed. In order to understand the advantages of applying the smart control system to the equipment, we conducted a comparative experiment with a teach pendant and evaluated its reaction time in case of error.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.8
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• pp.1631-1636
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• 2015

With the advance of wireless communication technology in terrestrial area, underwater communication is also evolving very fast from a simple point-to-point transmission to an elaborate networked communications. Underwater acoustic channel has quite different features comparing with the terrestrial radio channel in terms of propagation delay, Doppler shift, multipath, and path loss. Thus, existing technologies developed for terrestrial communication might not work properly in underwater channel. Especially medium access control (MAC) protocols which highly depend on propagation phenomenon should be newly designed for underwater network. CSMA/CA has drawn lots of attention as a candidate of underwater MAC protocol, since it is able to resolve a packet collision and the hidden node problem. However, a received signal could be degraded by the interferences from the nodes locating outside the receiver's propagation radius. In this paper, we study the effects of interference on the CSMA/CA based underwater network. We derived the SNR with the interference using the sonar equation and analyzed the degradation of the RTS/CTS effects. These results are compared with the terrestrial results to understand the differences. Finally we summarized the design considerations in CSMA/CA based underwater network.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.9
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• pp.1916-1932
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• 1997

The synchronous stream cipher which require absoulte clock synchronization has the problem of synchronization loss by cycle slip. Synchronization loss makes the state which sender and receiver can't communicate with each other and it may break the receiving system. To lessen the risk, we usually use a continuous resynchronization method which achieve resynchronization at fixed timesteps by inserting synchronization pattern and session key. While we can get resynchronization effectively by continuous resynchroniation, there are some problems. In this paper, we proposed an adaptive resynchronization algorithm for cipher system using HDLC protocol. It is able to solve the problem of the continuous resynchronization. The proposed adaptive algorithm make resynchronization only in the case that the resynchronization is occurred by analyzing the address field of HDLC. It measures the receiving rate of theaddress field in the decision duration. Because it make resynchronization only when the receiving rate is greateer than the threshold value, it is able to solve the problems of continuous resynchronization method. When the proposed adaptive algorithm is applied to the synchronous stream cipher system in packet netork, it has addvance the result in R_e and D_e.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.2A
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• pp.137-146
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• 2005

IP-based design methodology has been popularly employed for SoC design to reduce design complexity and to cope with time-to-market pressure. Interface modules for communication between system buses and IPs are required, since many IPs employ different protocols. Automatic generation of these interface modules would enhance designer's productivity and IP's reusability. This paper proposes an automatic interface generation system based on FSM generated from the protocol description of IPs. The proposed system provides the library modules for the standard buses to reduce the burdens of describing the protocols for data transfer from/to standard buses. Experimental results show that the area of the interface circuits generated by the proposed system had been increased slightly by 4.5% on the average when compared to manual designs. In the experiment, where bus clock is 100 Mhz and slave module clock is 34 Mhz, the latency of the interface had been increased by 7.1% in burst mode to transfer 16 data words. However, occupation of system bus can be reduce by 64.9%. A chip designer can generate an interface that improves the efficiency of system bus, by using this system.

• Journal of Korea Multimedia Society
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• v.6 no.2
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• pp.340-351
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• 2003

We introduce our experiences of the design and implementation of the Page Together system that has expanded hyperlink metaphor to utilize human resources in the web. This system supports that a user connects with others in the web, communicates through video/audio channel, navigates same web pages simultaneously and cooperates some work on Internet. For these functions, it comprises Collaborative Browsing Module (CBM), Multimedia Conferencing Module(MCM) Data Conferencing Module(I)CM) and Multi Protocol Interface(MPI). We adopted three standard protocols, IEC, H.323 and T.120 for each nodule and it allows developers to use them easily. We also defined MPI to synchronize information of session among modules. Each module exchanges information each other in session creating process and session terminating process. After a session is created once, each module works independently as its won protocol. Interferences among modules are reduced as minimizing to exchange information. We also introduce a web site that provides web board service based on the Page Together system. A user may post a notice with a link to himself/herself on our web board. After then, if someone read that notice and has any question about it, he or she can try to connect to the writer as clicking the link in that notice and communicate each other. This service site shows that our system can be applied to diverse internet services such as distance teaming and distance conference.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.41 no.7
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• pp.31-40
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• 2004

In this paper, we analyze mathematically the performance of the gated service scheduling in the Interleaved Polling with Adaptive Cycle Time(IPACT) was proposed to control upstream traffic for Gigabit Ethernet-PONs. In the analysis, we model EPON MAC protocol as a polling system and use mean value analysis. We divide arrival rate λ into three regions and analyze each region accordingly In the first region in which λ value is very small, there are very few ONUs' data to be transmitted. In the second region in which λ has reasonably large value, ONUs have enough data for continuous transmission. In the third region, ONUs' buffers are always saturated with data since λ value is very large. We obtain average packet delay, average Queue size, average cycle time of the gated service. We compare analysis results with simulation to verify the accuracy of the mathematical analysis. Simulation requires much time and effort to evaluate the performance of EPONs. On the other hand, mathematical analysis can be widely used in the design of EPON systems because system designers can obtain various performance results rapidly. We can design appropriate EPON systems for varioustraffic property by adjusting control parameters.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.22 no.1
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• pp.43-56
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• 2012

Wireless sensor networks consist of numerous small-sized nodes equipped with limited computing power and storage as well as energy-limited disposable batteries. In this networks, nodes are deployed in a large given area and communicate with each other in short distances via wireless links. For energy efficient networks, dynamic clustering protocol is an effective technique to achieve prolonged network lifetime, scalability, and load balancing which are known as important requirements. this technique has a characteristic that sensing data which gathered by many nodes are aggregated by cluster head node. In the case of cluster head node is exposed by attacker, there is no guarantee of safe and stable network. Therefore, for secure communications in such a sensor network, it is important to be able to encrypt the messages transmitted by sensor nodes. Especially, cluster based sensor networks that are designed for energy efficient, strongly recommended suitable key management and authentication methods to guarantee optimal stability. To achieve secured network, we propose a key management scheme which is appropriate for hierarchical sensor networks. Proposed scheme is based on polynomial key pool pre-distribution scheme, and sustain a stable network through key authentication process.