• ETRI Journal
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• 제26권4호
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• pp.321-331
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• 2004

In this paper, we propose a new dynamic bandwidth allocation (DBA) algorithm for multimedia services over Ethernet PONs (passive optical networks). The proposed algorithm is composed of a low-level scheduler in the optical network unit (ONU) and a high-level scheduler in the optical line terminal (OLT). The hierarchical DBA algorithm can provide expansibility and efficient resource allocation in an Ethernet PON system in which the packet scheduler is separated from the queues. In the proposed DBA algorithm, the OLT allocates bandwidth to the ONUs in proportion to the weight associated with their class and queue length, while the ONU preferentially allocates its bandwidth to queues with a static priority order. The proposed algorithm provides an efficient resource utilization by reducing the unused remaining bandwidth caused by the variable length of the packets. We also define the service classes and present control message formats conforming to the multi-point control protocol (MPCP) over an Ethernet PON. In order to evaluate the performance, we designed an Ethernet PON system on the basis of IEEE 802.3ah "Ethernet in the first mile" (EFM) using OPNET and carried out simulations. The results are analyzed in terms of the channel utilization, queuing delay, and ratio of the unused remaining bandwidth.

• 한국지능시스템학회논문지
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• 제14권3호
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• pp.304-309
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• 2004

본 논문에서는 편리한 방식으로 착용할 수 있으며 지능을 지니고 있는 시스템을 구현하고자 한다. 인간을 보조하는 역할을 수행함과 동시에 착용할 수 있는 장점을 지닌 시스템의 구현은 다양한 제어기에 적용될 수 있다. 이동 중인 로봇의 상태를 파악하고 인간을 대신하여 명령을 전달해주는 시스템의 구현이 가능해진 것이다. 본 논문에서는 이동 로봇의 주행 정보를 받아들여 충돌 회피 주행에 필요한 속도와 회전각을 판단하여 명령을 전달하는 시스템을 착용 형태의 장치를 이용하여 구현하였다. 웨어러블 장치의 지능을 구현하기 위해 계층적 퍼지 논리와 신경망의 학습 능력을 결합하였다.

• 정보통신설비학회논문지
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• 제10권4호
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• pp.121-127
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• 2011

Many peer-to-peer (p2p) systems have been studied in distributed, ubiquitous computing environments. Distributed hash table (DHT)-based p2p systems can improve load-balancing even though locality utilization and user mobility are not guaranteed. We propose a mobile locality-based hierarchical p2p overlay network (MLH-Net) to address locality problems without any other services. MLH-Net utilizes mobility features in a mobile environment. MLH-Net is constructed as two layers, an upper layer formed with super-nodes and a lower layer formed with normal-nodes. Because super-nodes can share advertisements, we can guarantee physical locality utilization between a requestor and a target during any discovery process. To overcome a node failure, we propose a simple recovery mechanism. The simulation results demonstrate that MLH-Net can decrease discovery routing hops by 15% compared with JXTA and 66% compared with Chord.

• 한국생물정보학회:학술대회논문집
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• 한국생물정보시스템생물학회 2004년도 The 3rd Annual Conference for The Korean Society for Bioinformatics Association of Asian Societies for Bioinformatics 2004 Symposium
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• pp.39-49
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• 2004

When there is a lack of detailed kinetic information, dFBA(dynamic flux balance analysis) has correctly predicted cellular behavior under given environmental conditions with FBA and different ial equations. However, until now, dFBA has centered on substrate concentration, cell growth, and gene on/off, but a detailed hierarchical structure of a regulatory network has not been taken into account. For this reason, the dFBA has limited the represen tation of interactions between specific regulatory proteins and genes and the whole transcriptional regulation mechanism with environmental change. Moreover, to calculate optimal metabolic flux distribution which maximizes the growth flux and predict the b ehavior of cell system, linear programming package(LINDO) and spreadsheet package(EXCEL) have been used simultaneously. thses two software package have limited in the visual representation of simulation results and it can be difficult for a user to look at the effects of changing inputs to the models. Here, we descirbes the construction of hierarchical regulatory network with defined symbolsand the development of an integrated system that can predict the total control mechanism of regulatory elements (opero ns, genes, effectors, etc.), substrate concentration, growth rate, and optimal flux distribution with time. All programming procedures were accoplished in a visual programming environment (LabVIEW).

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제9권1호
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• pp.1-19
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• 2015

With the recent popularity of smart terminals, the demand for high-data-rate transmission is growing rapidly, which brings a new challenge for the traditional cellular networks. Both device-to-device (D2D) communication and small cells are effective to improve the transmission efficiency of local communication. In this paper, we apply D2D communication into a small cell network system (SNets) and study about the optimization problem of resource allocation for D2D communication. The optimization problem includes system scheduling and resource allocation, which is exponentially complex and the optimal solution is infeasible to achieve. Therefore, in this paper, the optimization problem is decomposed into several smaller problems and a hierarchical scheme is proposed to obtain the solution. The proposed hierarchical scheme consists of three steps: D2D communication groups formation, the estimation of sub-channels needed by each D2D communication group and specific resource allocation. From numerical simulation results, we find that the proposed resource allocation scheme is effective in improving the spectral efficiency and reducing the outage probability of D2D communication.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2007년도 추계종합학술대회
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• pp.58-62
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• 2007

최근 QoS(Quality of Service)의 요구가 증가되고 망내에서 트래픽이 갈수록 증가함에 따라 확장성을 보장하는 계층형 MPLS 네트워크의 연구가 진행되고 있다. 하지만 계층형 MPLS는 망을 이루는 edge,core망 계층의 증가와 각 망 계층내의 노드 증가에 따라 많은 LER과 링크가 발생하게 되고 이는 계층형 MPLS설치의 설치비용이 증가하는 문제가 있다. 따라서 본 연구에서는 계층형MPLS 망 계층간에 MPLS 네트워크를 구성하여 트래픽이 발생했을 경우 각 망 계층간의 LER수와 링크 수에 따른 패킷의 전송시간을 NS를 통해 시뮬레이션 하여 그 성능을 분석한다. 그 결과, 링크의 수가 증가함에 따라 전송속도의 성능이 향상됨을 확인할 수 있었다.

• 한국정보처리학회논문지
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• 제5권5호
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• pp.1257-1263
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• 1998

위성 동보 서비스를 위하여 가입자 정보를 분산 관리하는 계층화 구조로서 가입자 지구국을 그룹 관리하는 부제어국을 설치한 계층 구조로 제안하고 해석하였다. 위성 동보 서비스를 위한 지구국 구성을 가입자국과 부제어국간 그리고 부제어국과 중신국간의 링크에 대한 통신 처리 시간비를 파라미터로 한 폴링 방법에 의한 수신 상태의 응답처리시간을 최소로하는 최적값을 해석하고 이를 3 계층 구성에서 처리할 수 있음을 알 수 있었다. 이러한 3 계층 구성을 하여 사용자국과 부제어국간 억세스 통신 비용의 절감이 요구되는 경우, 지상 공중망을 제어회선으로 사용하고, 통신 비용이 거리 의존성이 있는 경우에는 종래의 2 계층 구성에 비교하여 계층화 비용을 절감할 수 있음을 알 수 있었다.

• 한국통신학회논문지
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• 제32권4A호
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• pp.351-357
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• 2007

Ad Hoc 네트워크를 연구한 많은 논문들은 확장성을 향상시키기 위해서 계층적 네트워크 구조를 사용하였다. 계층적 구조는 여러 개의 클러스터들로 구성되고 각 클러스터는 모든 클러스터들에 대하여 정보를 관리하는 클러스터헤드를 가진다. 클러스터헤드는 정확한 정보를 유지하기 위하여 그들끼리 정보를 교환할 필요가 있으며 이를 위하여 클러스터헤드가 이웃하는 다른 클러스터헤드들에게 정보를 보낼 수 있는 효율적인 메커니즘이 필요하다. 이 문제를 해결하기 위한 알고리즘들은 대부분 클러스터헤드가 재전송할 브릿지들을 선정하거나 혹은 부가적인 메시지를 사용하여 재전송 브릿지를 선정하는 메커니즘을 사용하였다. 여기에 제안하는 DSP(Distributed Self-Pruning)알고리즘은 각 노드가 수신한 메시지를 재전송할 것인지에 대하여 독자적으로 판단을 한다. 두 개의 클러스터기반 라우팅 프로토콜에 제안한 알고리즘을 적용함으로써 알고리즘의 적합성을 검증하였다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1994년도 추계학술대회 논문집
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• pp.670-675
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• 1994

Yhis paper describes a fault diagnosis simulation of the Real-Time Multiple Fault Dignosis System (RTMFDS) for forcasting faults in a system and deciding current machine state from signal information. Comparing with other diagnosis system for single fault,the system developed deals with multiple fault diagnosis,comprising two main parts. One is a remotesignal generating and transimission terminal and the other is a host system for fault diagnosis. Signal generator generate the random fault signal and the image information, and send this information to host. Host consists of various modules and agents such as Signal Processing Module(SPM) for sinal preprocessing, Performence Monotoring Module(PMM) for subsystem performance monitoring, Trigger Module(TM) for multi-triggering subsystem fault diagnosis, Subsystem Fault Diagnosis Agent(SFDA) for receiving trigger signal, formulating subsystem fault D\ulcornerB and initiating diagnosis, Fault Diagnosis Module(FDM) for simulating component fault with Hierarchical Artificial Neural Network (HANN), numerical models and Hofield network,Result Agent(RA) for receiving simulation result and sending to Treatment solver and Graphic Agent(GA). Each agent represents a separate process in UNIX operating system, information exchange and cooperation between agents was doen by IPC(Inter Process Communication : message queue, semaphore, signal, pipe). Numerical models are used to deseribe structure, function and behavior of total system, subsystems and their components. Hierarchical data structure for diagnosing the fault system is implemented by HANN. Signal generation and transmittion was performed on PC. As a host, SUN workstation with X-Windows(Motif)is used for graphic representation.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제2권1호
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• pp.5-21
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• 2008

In order to securely transmit multicast data packets in a mobile environment where frequent join/leave events are a characteristic of the environment, there is a need for a new secure and efficient group key management solution. We propose a secure group key generation/distribution solution providing scalability and reliability. Using this solution, when a mobile node, which is in a multicast session, enters a new domain, the agent of the domain joins the multicast session and coordinates its data packets with the mobile node. The agent encrypts and transmits subsequent data packets to the mobile node, using a local one-time pad key. This key is generated with FI sequences, enabling the mobile node to regenerate the same data packet, based on the information sent by the agent. Our performance analysis demonstrates that the proposed solution can significantly reduce the number of key generations and distributions, when it is applied to the hierarchical mobile IPv6 network.