• Proceedings of the Korea Information Processing Society Conference
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• 2009.04a
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• pp.1112-1115
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• 2009

네트워크 관리자 입장에서 효율적인 네트워크 관리를 위해 응용 프로그램 별 트래픽 분류의 중요성이 커지고 있다. 응용 프로그램 별 트래픽 분류를 위해 signature 기반, machine learning 방법들이 제안되고 있지만 p2p 방식의 Skype 응용프로그램에 대한 적용결과는 그 신뢰성이 떨어지고 있는 것은 사실이다. 본 논문에서는 Skype의 트래픽을 분류하기 위해 각 Client 마다 Skype application install 시 동적으로 변화하는 Port 를 알아내는 방법, UDP 패킷의 특정위치의 특정 signature, TCP signal flow의 특정위치 패킷에 대한 payload 크기 등을 이용한 Skype traffic 분류 방법을 제안한다. 제안된 방법론은 학내 네트워크에 적용하여 그 타당성을 TMA를 통해 검증하였다.

• Journal of the Korea Computer Industry Society
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• v.2 no.11
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• pp.1365-1372
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• 2001

We have suggested three learning rules and implemented an experimental system that automatically restructures hypertext networks according to their user browsing behavior. The system applies link weights to the hypertext networks and updates these weights according to the learning rules. The learning rules are based on how often a particular hyperlink is being traversed and operate on strictly local information of link traversals. Changes in network structure are fed back to users by dynamic link ordering according to descending link weight. This approach is used collaborative filtering and navigation support techniques. The system has been investigation to be able to structure random hypertext networks into valid representations of their user browsing preferences in experiments.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.6
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• pp.1077-1082
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• 2009

Wireless Mesh Network(WMN) is wireless backbone networks technique which has ease of network configuration and cost of advantage. Recently, WNM released a new product, but most of existing research and technology analysis the performance through the simulation. This paper build the wireless mesh network testbed for actual situation. Testbed supports multi-channel multi-interface using bridge, the Wireless Distribution System and dynamic location-based routing protocol. This routing protocol strongly design against wireless interference using metric for link channel change and real distance. Then, the address of mesh clients assigned by the centralized address management server. Mesh clients is designed and implemented to manage network through Simple Network Management Protocol.

• Journal of KIISE:Information Networking
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• v.30 no.6
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• pp.755-763
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• 2003

To improve performance over noisy wireless channels, mobile wireless networks employ forward error correction(FEC) techniques. The performance of static FEC algorithms, however, degrades by poorly matching the overhead of their correction code to the degree of the fluctuating underlying channel error. This paper proposes an adaptive FEC technique called FECA(FEC-level Adaptation), which dynamically tunes FEC strength to the currently estimated channel error rate at the data link layer. FECA is suitable for wireless networks whose error rate is high and slowly changing compared to the round-trip time between two communicating nodes. One such example network would be a sensor network in which the average bit error rate is higher than $10^{-6}$ and the detected error rate at one time lasts a few hundred milliseconds on average. Our experiments show that FECA performs 15% in simulations with theoretically modeled wireless channels and in trace-driven simulations based on the data collected from real sensor networks better than any other static FEC algorithms.

• Journal of KIISE:Software and Applications
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• v.32 no.11
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• pp.1084-1098
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• 2005

In this paper, we propose a migration technique for autonomous mobile agents suitable to dynamic environments. The proposed migration technique dynamically creates the itinerary of agents that considers states of networks and systems. In the migration of the agent, it first sends prefetching message to the next system. The system receives necessary data for migration in advance. Through this, we reduce the amount of the sending data and save the time for creating the instance of the agent. And it improves the execution efficiency by using the checkpoint-based recovery method that does not execute the agent again and recovers the process states even though the errors take place. To show superiority of the proposed technique, we compare the proposed method with the existing methods through various simulations.

• Proceedings of the Korean Information Science Society Conference
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• 2008.06d
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• pp.449-454
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• 2008

최근의 개인 휴대 장치들의 급속한 발전에 힘입어 pervasive computing 환경은 인프라 시스템의 제약에서 벗어나 개인 장치들의 협력에 의해서 상황에 맞는 서비스를 제공 받을 수 있도록 변하고 있다. 하지만 이러한 ad hoc pervasive 환경은 기존의 스마트 스페이스에서 보다 동적인 변화가 더욱 많은 환경이기 때문에 pervasive computing을 위한 기능들 중에서도 자원 관리가 가장 중요한 역할을 해야 한다. Pervasive computing 환경에서 자원 관리는 자원 모니터링(Resource Monitoring), 자원 발견(Resource Discovery), 자원 할당(Resource Allocation), 자원 적응(Resource Adaptation)의 4가지의 주요 기능으로 구분 될 수 있고, 동적인 변화가 많은 환경에서는 무엇보다도 자원 모니터링이 가장 중요시 되어야 한다. 자원 모니터링에서 정보의 수집은 pull이나 push 방식으로 이루어질 수 있는데, pull 방식은 사용자 요구에 맞춰 요구 했을 때의 가장 최신의 정보를 모아 줄 수 있다. 따라서 이는 자원 발견에 가장 적합하지만 언제 정보 수집을 요청할지는 정보 소비자의 입장에서는 알 수 없기 때문에 push 방식이 다른 여러 기능들을 지원하기 위해서 보다 적절하다. 하지만 대부분의 push 방식은 주기적으로 자신의 정보를 광고하는 방식으로 이루어 진다. 하지만 상황 적응(adaptation)입장에서 봤을 때 특정 수준의 민첩성을 요구하기 위해서는 광고주기를 조절 해야 하고, 이때 필요 이상으로 네트워크의 사용량을 늘릴 수 있다. 뿐만 아니라 변화가 많은지 적은지 등의 각 단말의 상황은 무시된 채 모든 단말들이 동일한 주기로 정보를 광고한다. 이러한 문제점을 해결 하기 위해서 본 논문은 자원 정보 제공자의 상황을 고려한 자원 정보 광고 기법을 제안한다.

• The Journal of the Korea institute of electronic communication sciences
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• v.11 no.8
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• pp.735-742
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• 2016

The Low-Rate WPAN is a short range wireless networking technology characterized by low-rate, low-power, low complexity and low-cost. The LR-WPAN controls wireless channel access among network devices based on the contention-based CSMA/CA algorithm. Therefore, frame collisions may take place at any time, leading to the severe degradation of network performance. This paper proposes a new algorithm that changes back-off periods adaptively in the CSMA/CA process depending on network conditions, resulting in the reduction of frame collisions. Throughout extensive simulations, it turns out that varying the back-off periods dynamically shows better performance than maintaining the fixed back-off periods.

• Journal of the Korean Society of Propulsion Engineers
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• v.26 no.4
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• pp.1-9
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• 2022

In the current study, in order to understand the dynamic response characteristics of the system according to the external acoustic forcing, a numerical approach was developed by adding an sign-sweep forcing function to the existing network model. Through this model, the sensitivity of frequency and pressure amplitude changes according to system parameters such as the physical dimensions and boundary conditions of the target combustor was analyzed in a wide frequency range. Analysis results of dynamic response characteristics of the target combustor are shown that the frequency regime with high dynamic pressure response was similar to the instability frequency range measured in the same combustor, and in particular, the response of the system depends greatly on the location of the acoustic forcing source term.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2021.10a
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• pp.220-222
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• 2021

In this paper, we propose a resource allocation scheme based on entropy for tactical wireless networks. In a tactical situation, the sensing nodes that are located randomly provide transmitted data values depending on environmental conditions. Since they share wireless resources, nodes providing valuable data compared to others need to have more resources. The proposed scheme evaluates the value of received data by a sink node. Based on the results, the sink node reallocates resources to sensing nodes. Through various experiments, we verified the proposed scheme is superior to the fixed allocation scheme.

• Journal of KIISE:Information Networking
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• v.34 no.5
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• pp.379-388
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• 2007

With proliferation of computer and wireless network technology, it is common to access Internet through wireless network using mobile device. Ratio of using streaming media out of many applications through Internet is increasing not only in wired network but also in wireless network. Streaming media is much bigger than other contents and requires more network bandwidth and more computing resources. However mobile devices hate relatively poor computing resource and low network bandwidth. If media streaming service is provided for mobile devices without any consideration about network bandwidth and computing power, it is hard for the client to get high qualify service. Since mobile device is supported with very limited energy from the battery, media streaming should be adjusted to varying energy state of mobile device in realtime to ensure complete playback of streaming media. In this paper, we propose DFRC to provide high qualify service to mobile client through wireless network by controlling the number of frames transmitted to client based on computing resource and energy state of mobile device.