• ETRI Journal
• /
• v.26 no.4
• /
• pp.371-374
• /
• 2004

We propose and demonstrate a fabrication method of chirped fiber gratings by a thermal diffusion process. The method could suggest a direction for a simple and cost-effective implementation of chirped fiber grating-based devices.

• Proceedings of the Korea Society for Simulation Conference
• /
• 1994.10a
• /
• pp.12-12
• /
• 1994

Simulation output knowledge analysis is one of problem-solving and/or knowledge adquistion process by investgating the system behavior under study through simulation . This paper describes an approach to simulation outputknowldege analysis using fuzzy neural network model. A fuzzy neral network model is designed with fuzzy setsand membership functions for variables of simulation model. The relationship between input parameters and output performances of simulation model is captured as system behavior knowlege in a fuzzy neural networkmodel by training examples form simulation exepreiments. Backpropagation learning algorithms is used to encode the knowledge. The knowledge is utilized to solve problem through simulation such as system performance prodiction and goal-directed analysis. For explicit knowledge acquisition, production rules are extracted from the implicit neural network knowledge. These rules may assit in explaining the simulation results and providing knowledge base for an expert system. This approach thus enablesboth symbolic and numeric reasoning to solve problem througth simulation . We applied this approach to the design problem of broadband communication network.

• ETRI Journal
• /
• v.39 no.1
• /
• pp.51-61
• /
• 2017

This paper demonstrates a systematic approach for the design of broadband, high efficiency, high power, Class-AB RF amplifiers with high gain flatness. It is usually difficult to simultaneously achieve a high gain flatness and high efficiency in a broadband RF power amplifier, especially in a high power design. As a result, the use of a computer-aided simulation is most often the best way to achieve these goals; however, an appropriate initial value and a systematic approach are necessary for the simulation results to rapidly converge. These objectives can be accomplished with a minimum of trial and error through the following techniques. First, signal gain variations are reduced over a wide bandwidth using a proper pre-matching network. Then, the source and load impedances are satisfactorily obtained from small-signal and load-pull simulations, respectively. Finally, two high-order Chebyshev low-pass filters are employed to provide optimum input and output impedance matching networks over a bandwidth of 100 MHz-500 MHz. By using an EM simulation for the substrate, the simulation results were observed to be in close agreement with the measured results.

• ETRI Journal
• /
• v.26 no.1
• /
• pp.27-37
• /
• 2004

The architecture in a differentiated services (DiffServ) network is based on a simple model that applies a per-class service in the core node of the network. However, because the network behavior is simple, the network structure and provisioning is complicated. If a service provider wants dynamic provisioning or a better bandwidth guarantee, the differentiated services network must use a signaling protocol with QoS parameters or an admission control method. Unfortunately, these methods increase the complexity. To overcome the problems with complexity, we investigated scalable dynamic provisioning for admission control in DiffServ networks. We propose a new scalable $qDPM^2$ mechanism based on a centralized bandwidth broker and distributed measurement-based admission control and movable boundary bandwidth management to support heterogeneous QoS requirements in DiffServ networks.

• Journal of Multimedia Information System
• /
• v.1 no.1
• /
• pp.67-75
• /
• 2014

Nowadays as video services grow rapidly, it is important for the service providers to provide customized services. Video ranking plays a key role for the service providers to attract the subscribers. In this paper we propose a weekly video ranking mechanism based on the quantified user engagement. The traditional QoE ranking mechanism is relatively subjective and usually is accomplished by grading, while QoS is relatively objective and is accomplished by analyzing the quality metrics. The goal of this paper is to establish a ranking mechanism which combines the both advantages of QoS and QoE according to the third-party data collection platform. We use data mining method to classify and analyze the collected data. In order to apply into the actual situation, we first group the videos and then use the regression tree and the decision tree (CART) to narrow down the number of them to a reasonable scale. After that we introduce the analytic hierarchy process (AHP) model and use Elo rating system to improve the fairness of our system. Questionnaire results verify that the proposed solution not only simplifies the computation but also increases the credibility of the system.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.10 no.5
• /
• pp.2375-2393
• /
• 2016

Key agreement is paramount in secure wireless communications. A promising approach to address key agreement schemes is to extract secure keys from channel characteristics. However, because channels lack randomness, it is difficult for wireless networks with stationary communicating terminals to generate robust keys. In this paper, we propose a Robust Secure Key Agreement (RSKA) scheme from Received Signal Strength (RSS) in stationary wireless networks. In order to mitigate the asymmetry in RSS measurements for communicating parties, the sender and receiver normalize RSS measurements and quantize them into q-bit sequences. They then reshape bit sequences into new l-bit sequences. These bit sequences work as key sources. Rather than extracting the key from the key sources directly, the sender randomly generates a bit sequence as a key and hides it in a promise. This is created from a polynomial constructed on the sender's key source and key. The receiver recovers the key by reconstructing a polynomial from its key source and the promise. Our analysis shows that the shared key generated by our proposed RSKA scheme has features of high randomness and a high bit rate compared to traditional RSS-based key agreement schemes.

• ETRI Journal
• /
• v.28 no.3
• /
• pp.329-336
• /
• 2006

This paper investigates the problem of protecting multicast sessions in mesh wavelength-division multiplexing (WDM) networks against single link failures, for example, a fiber cut in optical networks. First, we study the two characteristics of multicast sessions in mesh WDM networks with sparse light splitter configuration. Traditionally, a multicast tree does not contain any circles, and the first characteristic is that a multicast tree has better performance if it contains some circles. Note that a multicast tree has several branches. If a path is added between the leave nodes on different branches, the segment between them on the multicast tree is protected. Based the two characteristics, the survivable multicast sessions routing problem is formulated into an Integer Linear Programming (ILP). Then, a heuristic algorithm, named the adaptive shared segment protection (ASSP) algorithm, is proposed for multicast sessions. The ASSP algorithm need not previously identify the segments for a multicast tree. The segments are determined during the algorithm process. Comparisons are made between the ASSP and two other reported schemes, link disjoint trees (LDT) and shared disjoint paths (SDP), in terms of blocking probability and resource cost on CERNET and USNET topologies. Simulations show that the ASSP algorithm has better performance than other existing schemes.

• Journal of the Korea Society of Computer and Information
• /
• v.23 no.9
• /
• pp.51-56
• /
• 2018

Currently, many households raise their companion animals for personal reasons. In this environment, the companion animal is left alone in the home, the owner of the companion animal is increasingly curious about the behavior pattern of the companion animal left alone, and there are many devices that can solve this question. In this paper, we have designed and implemented a Bluetooth-based slave device (beacon in this paper) and a router capable of connecting to a broadband network that can observe behavior patterns of companion animals by using advanced ICT technology. The Bluetooth router designed and implemented in this paper installs a beacon in the home, receives the beacon signal from the device and the beacon installed by the companion animal, and transmits the moving line of the companion animal to the owner of the companion animal through the broadband network, so that it can be confirmed in real time through the app for the provided smart phone.

• Korean Management Science Review
• /
• v.11 no.3
• /
• pp.103-128
• /
• 1994

Due to the trend of evolution toward a broadband communication network with fiber-optics, the design and operation of fiber-optic network have been received a great deal of research attention recently. Furthermore, even a single fiber link failure in the network may result in severe service loss. Thus, the network survivability becomes an importantissue in planning and designing the network. This survey is on modelling of various fiber-optic subscriber loop network(FSLN) design problems, which are essential ones for providing broadband communication services and B-ISDN services. Models are classified and investigated as either conventional decomposition-iteration approach or integrated design method. To build survivable networks, SHR models are also suggested by ring control schemes. The result of this study will be effectively applied to build a design model for FSLN in the practical applications.

• ETRI Journal
• /
• v.26 no.1
• /
• pp.13-20
• /
• 2004

We propose a new optical code division multiple access (OCDMA) scheme for reducing multiple access interference (MAI) and enhancing performance for optical subscriber access networks using modified pseudorandom noise (PN)-coded fiber Bragg gratings with bipolar OCDMA decoders. Through the bipolar OCDMA decoder and the modified PN codes, MAI among users is effectively depressed. As the data are encoded either by a unipolar signature sequence of the modified PN code or its complement according to whether the data bit is 1 or 0, the bit error ratio (BER) can be more improved with the same signal to interference plus noise ratio over the conventional on-off shift keying-based OCDMA system. We prove by numerical analysis that the BER of the proposed bipolar OCDMA system is better than the conventional unipolar OCDMA system. We also analyze the spectral power distortion effects of the broadband light source.