• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.10A
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• pp.1004-1014
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• 2007

In sensor networks, it is crucial to reliably and energy-efficiently deliver sensed information from each source to a sink node. Specifically, in mobile sink (user) applications, due to the sink mobility, a stationary dissemination path may no longer be effective. The path will have to be continuously reconfigured according to the current location of the sink. Moreover, the dynamic optimal path from each source to the sink is required in order to reduce end-to-end delay and additional energy wastage. In this paper, an Adaptive Reversal Optimal path Tree (AROT) protocol is proposed. Information delivery from each source to a mobile sink can be easily achieved along the AROT without additional control overhead, because the AROT proactively performs adaptive sink mobility management. In addition, the dynamic path is optimal in terms of hop counts and the AROT can maintain a robust tree structure by quickly recovering the partitioned tree with minimum packet transmission. Finally, the simulation results demonstrate that the AROT is a considerably energy-efficient and robust protocol.

• Journal of Korea Society of Digital Industry and Information Management
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• v.6 no.4
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• pp.153-160
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• 2010

MANET composed mobile nodes without central concentration control like base station communicate through multi-hop route among nodes. Accordingly, it is hard to maintain stability of network because topology of network change at any time owing to movement of mobile nodes. MANET has security problems because of node mobility and needs intrusion detection system that can detect attack of malicious nodes. Therefore, system is protected from malicious attack of intruder in this environment and it has to correspond to attack immediately. In this paper, we propose intrusion detection system based on rules in order to more accurate intrusion detection. Cluster head perform role of monitor node to raise monitor efficiency of packet. In order to evaluate performance of proposed method, we used jamming attack, selective forwarding attack, repetition attack.

• Journal of Communications and Networks
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• v.5 no.3
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• pp.202-214
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• 2003

The central challenge in the design of ad-hoc networks is the development of dynamic routing protocol that efficiently finds route between mobile nodes. Several routing protocols such as DSR, AODV and DSDV have been proposed in the literature to facilitate communication in such dynamically changing network topology. In this paper, a Node Transition Probability (NTP) based routing algorithm, which determines stable routes using the received power from all other neighboring nodes is proposed. NTP based routing algorithm is designed and implemented using Global Mobile Simulator (GloMoSim), a scalable network simulator. The performance of this routing algorithm is studied for various mobility models and throughput, control overhead, average end-to-end delay, and percentage of packet dropped are compared with the existing routing protocols. This algorithm shows acceptable performance under all mobility conditions. The results show that this algorithm maximizes the bandwidth utilization during heavy traffic with lesser overhead.

• Journal of Korea Society of Digital Industry and Information Management
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• v.7 no.2
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• pp.59-65
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• 2011

All-optical signal processing is expected to offer advantages in speed and power consumption against over electronics signal processing. It has a potential to solve the bottleneck issues of ultra-high speed communication network nodes. All-optical serial-to-parallel and parallel-to-serial data converters would make it possible to easily process the serial data information of a high-speed optical packet without optical-to-electronic-to-optical data conversion. In this paper, we explain the principle of simple and easily expandable all-optical serial-to-parallel and parallel-to-serial data converters based on Mach-Zehnder interferometers. We experimentally demonstrate these data converters at 10Gbit/s serial data rate. They are useful all-optical devices for the all-optical implementations of label decoding, self-routing, control of variable packets, bit-wise logical operation, and data format conversion.

• Proceedings of the KIEE Conference
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• 2002.07d
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• pp.2469-2471
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• 2002

MMI 시스템은 제철 공정에서 발생되는 다양한 데이터를 조업자에게 쉽고 빠르게 전달하기 위해, real time operating system에서 동작하는 제철공정의 주된 제어 프로세스와 인터페이스 한다. 따라서 MMI 시스템은 제철 공정의 주된 제어 프로세스와 ethernet network을 통해 공유 데이터들을 통신하도록 개발되고, MMI 시스템은 M/S window operating system과 DDE(Dynamic Data Exchange) 라이브러리 환경을 기반으로 개발된다. 수 개의 MMI client PC와 1 개의 MMI server로 구성되는 MMI 시스템은 MMI client들 사이의 공유 데이터가 동기화될 수 있도록 최적 packet 양을 도출하고, 신뢰성 높은 데이터 전송을 위한 특별한 데이터 핸들링 방법을 사용한다. MMI 시스템은 GUI(Graphic User Interface)를 사용하여 조업자에게 친숙한 window 화면을 제공하므로, MMI 시스템의 화면 수정, 첨가 및 삭제가 비용 부담없이 용이하게 진행되므로, 기존 제철 공정에서 사용하던 OCP(Operating Control Panel)들이 MMI 시스템으로 대체되고 있다.

• Proceedings of the Korean Information Science Society Conference
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• 2003.10c
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• pp.373-375
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• 2003

애드 혹 네트워크는 기존의 하부 기반구조를 필요로 하지 않고도 이동 노드들 사이의 통신이 가능한 네트워크를 의미한다. 현재 애드 혹 라우팅 프로토콜에 관련하여 IETF MANET에서는 단일 경로를 제공하는 라우팅 프로토콜들이 제안되어 있으나 애드 혹 네트워크의 특성상 노드의 잦은 이동으로 인해 빈번한 경로 실패가 발생함으로 인하여 큰 오버헤드와 지연시간을 가지고 있다. 이러한 문제를 해결하기 위해 다양한 다중경로 설정 메커니즘들이 제안 되었으나 추가적인 제어 메시지와 복잡한 메시지 처리 과정으로 인하여 애드 혹 노드의 제한된 처리 능력과 네트워크 자원을 소모를 가져왔다. 본 연구에서는 대표적인 요구기반(on demand) 방식의 단일경로 라우팅 프로토콜인 AODV와 다중경로 라우팅 프로토콜 AOMDV 의 단점을 보완한 저비용 다중경로 메커니즘을 제안한다.

• Proceedings of the Korean Information Science Society Conference
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• 2002.10e
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• pp.529-531
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• 2002

VoIP기술의 확산과 그에 따른 IP기반의 망을 포함한 packet, Multimedia서비스를 제공하는 서비스가 늘고있다. 그러나 실시한 서비스를 필요로 하는 이 서비스의 경우에는 그에 따르는 경로에 확실한 대역폭의 조건이 요구되고 있다. 하지만 best-effort방식을 사용하는 기존의 망에서는 대역폭의 확실한 보장이 이루지기 힘들다. 하지만 MPLS와 트래픽 엔지니어링 기술의 발전으로 다중경로 패킷 전달 및 동적인 부하 제어가 가능하게 되었다. 곧 차별화된 서비스에 따른 대역폭의 할당이 이루어질 수 있다. 동적인 부하 제어는 네트웍의 상태를 고려하여 경로간의 부하를 조절함으로써 네트웍의 효율성을 높일 수 있으나, 상태 정보의 시간차이에 의해 불안정한 상태에 이르기 쉽다. 본 논문에서는 차별화된 서비스를 하기 위해 부하의 할당을 안정적으로 변화시키면서도 효율적인 부하로 용량에 맞게 흐름을 받아들이고 패킷을 전송하는 기법을 제안한다.

• ETRI Journal
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• v.24 no.2
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• pp.142-152
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• 2002

In this paper, we propose and analyze a new multiple access protocol for a local area optical Internet based on a wavelength division multiplexing technique which uses a passive star coupler. The proposed contention-based reservation protocol can support variable-length as well as fixed-length messages for transporting Internet packets with one reservation of a minislot at the beginning of a packet transmission. The minislot is used to reserve the data channel on the basis of the slotted ALOHA protocol and the control node ensures subsequent message transmission on the same wavelength. Thus, all messages need not be broken down to many fixed-length packets, and consecutive messages are transmitted through the same wavelength. Moreover, the proposed protocol reduces the collision probability of minislots and improves wavelength utilization. We determine the maximum throughput and verify the results with simulation.

• ETRI Journal
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• v.37 no.6
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• pp.1096-1107
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• 2015

This paper presents a dynamic retry adaptation scheme for H.264 HD video, called DRAS.264, which dynamically adjusts the retry limits of frames at the medium access control (MAC) layer according to the impact those frames have on the streamed H.264 HD video. DRAS.264 is further improved with a bandwidth estimation technique, better prediction of packet delays, and expanded results covering multi-slice video. Our study is performed using the Open Evaluation Framework for Video Over Networks as a simulation environment for various congestion scenarios. Results show improvements in average peak signal-to-noise ratios of up to 4.45 dB for DRAS.264 in comparison to the default MAC layer operation. Furthermore, the ability of DRAS.264 to prioritize data of H.264 bitstreams reduces error propagation during video playback, leading to noticeable visual improvements.

• ETRI Journal
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• v.29 no.1
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• pp.116-119
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• 2007

In this letter, we design a collision resolution protocol for optical burst switching ring networks to avoid burst collision. We define the offset time condition for no burst transmission collision and manage the free time list of nodes for no burst reception collision. In order to improve the throughput, we use a fiber delay line, void-filling, and void-compression. This protocol does not require any additional procedures for bandwidth reservation such as centralized assignment of bandwidth, lightpath setup of WDM ring networks, or token capturing for the burst transmission. The simulation results show that the proposed protocol can achieve high throughput while saving 70% of wavelengths when compared to round robin with random selection, round robin with persistent, and round robin with non-persistent with only destination delay.