• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2003.10a
• /
• pp.527-531
• /
• 2003

Previous researches on scalability problem of distributed virtual environment (DVE) have been mainly focused on spatial partitioning of area of interest (AOI). Congestion phenomena by avatar groups in AOI have been neglected relatively. However, AOI congestion is highly related to scalability of DVT because it exhausts system resources such as network bandwidth and rendering time, and could be a bar to perform collaboration among participants. In this paper, this will be defined as the problem that must be solved for the realization of the scalable DVE, and a model will be proposed to measure and control congestion situation in AOI. The purposes of the proposed model are to prevent high density of participants in AOI, and to protect stable collaboration in DVE. For evaluation of the performance it is compared with a previous method by defining the resource cost model which is dynamically activated to AOI congestion.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.21 no.5
• /
• pp.899-905
• /
• 2017

This paper presents a reference-less dual loop clock and data recovery (CDR) circuit that supports a data rate of 2.496 Gb/s for the mobile industry processor interface (MIPI) M-PHY. An adaptive loop bandwidth scheme is used to implement the fast lock time maintaining a low time jitter. To this scheme, the proposed CDR consists of two loops for a frequency locked loop and a phase locked loop. The proposed 2.496 Gb/s reference-less dual loop CDR is designed using a 65 nm CMOS process with 1.2 V supply voltage. The simulated peak-to-peak jitter of output clock is 9.26 ps for the input data of 2.496 Gb/s pseudo-random binary sequence (PRBS) 15. The active area and power consumption of the implemented CDR are $470{\times}400{\mu}m^2$ and 6.49 mW, respectively.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.16 no.5
• /
• pp.434-444
• /
• 1991

An improved 2-D quadrature polar separable (QPS) filter and its applications to texture processing are discussed in thie paper. The frequency response of the filter consists of two independent parts. The first is a radial weighting function based on the prolate spheridal sequence(PSS). The second is the same orientational function of the angle as in the Knutsson filter. The new filter is suboptimal in the energy loss because we let the polar angle function approximate the radial weighting function as in the 2-D Cartesian filter composed of two PSS's. It is easy to control as it depends only upon the design specification of the bandwidth, the drectional agnle, and the central freqneucy. Also the filter is circularly more symmetric in the frequency domain than the Knutsson filter. In order to estimate the orientation and the frequency component of loca textures in the frequency domain, some applications of the new filter, such as the generation of synthetic textures, the estimation of texture orientations, and texture segementations, are discussed.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.37C no.11
• /
• pp.1036-1044
• /
• 2012

Thanks to progressive development of IT technology, the number of intelligent devices communicating each other through an In-Vehicle Network(IVN) has been steadily increasing. It is expected that the required network bandwidth and network nodes for vehicle control in 2015 will be increased by two times and one and half times as compared to in 2010, respectively. As a result, many researchers in automotive industry has showed a significant interest on industrial Ethernets, such as EtherCAT and TTEthernet. This paper addresses an analysis on transmission delay and fault recovery performance with an EtherCAT network which is being considered as an IVN. A mathematical model based on the analysis is verified through a set of experiments using an experimental network setup.

• Journal of the Korean Institute of Intelligent Systems
• /
• v.19 no.4
• /
• pp.451-456
• /
• 2009

In this paper, a virtual force is generated and fed back to the operator to make the teleoperation more reliable, which reflects the relationship between a slave robot and an uncertain remote environment as a form of an impedance. In general, for the teleoperation, the teleoperated mobile robot takes pictures of the remote environment and sends the visual information back to the operator over the Internet. Because of the limitations of communication bandwidth and narrow view-angles of camera, it is not possible to watch certain regions, for examples, the shadow and curved areas. To overcome this problem, a virtual force is generated according to both the distance between the obstacle and the robot and the approaching velocity of the obstacle w.r.t the collision vector based on the ultrasonic sensor data. This virtual force is transferred back to the master (two degrees of freedom joystick) over the Internet to enable a human operator to estimate the position of obstacle at the remote site. By holding this master, in spite of limited visual information, the operator can feel the spatial sense against the remote environment. It is demonstrated by experiments that this collision vector based haptic reflection improves the performance of teleoperated mobile robot significantly.

• Journal of the Society of Disaster Information
• /
• v.12 no.2
• /
• pp.167-175
• /
• 2016

Korea has faced with the problem of the whole national disaster safety due to the Sewol-ho and it reminded people and government of the importance of national safety. It is needed to establish the national unified network especially focused on the disaster site and also improved in the fields of law, system and organization related to the management of disaster. To do this, PS-LTE technology must to be adopted to the network and 700MHz is the most efficient bandwidth for the network. At the same time, we have to improve the management system for the response of disaster including standard procedure and the platform of disaster response system. In order to establish realistic and efficient emergency communications network, it is effective to build own network and use leased networks together. And the cost is estimated about 5.2 trillion won.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.29 no.9A
• /
• pp.1067-1074
• /
• 2004

In the wireless mobile networks, it IS important to provide the quality-of-service (QoS) guarantees as they are increasingly expected to support the multimedia applications Although the QoS provisioning problem arises in the wire-line networks as well, the mobility of hosts and the scarcity of bandwidth make QoS provisioning a challenging task in wireless mobile networks. The resource allocation to multimedia applications of varying QoS reqUlrement 15 a complex issue. In this paper, we propose a new adaptive resource allocation scheme based on the concept of the resource reservation and the renegotiation in order to guarantee the QoS of the real-tune traffic. The proposed scheme is aimed at improving the perfonnance in terms of the new call blocking rate, the bandoff dropping rate, and the bandwIdth utilization.

• Korean Journal of Optics and Photonics
• /
• v.11 no.2
• /
• pp.108-113
• /
• 2000

This paper presents a simple but novel gain deviation detector scheme which can be used for general gain-clamping systems. By using the difference of ASEJprobe powers extracted from the edges of gain-flattened bandwidth, gain deviation of EDFA can be exactly detected regardless of the operating condition of a constructed EDFA. To prove the vahd1ty of the suggested scheme, we Implemented gain clamping systems on a single EDFA and cascaded EDFA's link and achieved sufficient gam-clamping performance without the elaborate measurement for tlIe determination of control parameters. eters.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2012.02a
• /
• pp.196-196
• /
• 2012

Graphene, two-dimensional one-atom-thick planar sheet of carbon atoms densely packed in a honeycomb crystal lattice, has grabbled appreciable attention due to its extraordinary mechanical, thermal, electrical, and optical properties. Based on the graphene's high carrier mobility, high frequency graphene field effect transistors have been developed. Graphene is useful for photonic components as well as for the applications in electronic devices. Graphene's unique optical properties allowed us to develop ultra wide-bandwidth optical modulator, photo-detector, and broadband polarizer. Graphene can support SPP-like surface wave because it is considered as a two-dimensional metal-like systems. The SPPs are associated with the coupling between collective oscillation of free electrons in the metal and electromagnetic waves. The charged free carriers in the graphene contribute to support the surface waves at the graphene-dielectric interface by coupling to the electromagnetic wave. In addition, graphene can control the surface waves because its charge carrier density is tunable by means of a chemical doping method, varying the Fermi level by applying gate bias voltage, and/or applying magnetic field. As an extended application of graphene in photonics, we investigated the characteristics of the graphene-based plasmonic waveguide for optical signal transmission. The graphene strips embedded in a dielectric are served as a high-frequency optical signal guiding medium. The TM polarization wave is transmitted 6 mm-long graphene waveguide with the averaged extinction ratio of 19 dB at the telecom wavelength of $1.31{\mu}m$. 2.5 Gbps data transmission was successfully accomplished with the graphene waveguide. Based on these experimental results, we concluded that the graphene-based plasmonic waveguide can be exploited further for development of next-generation integrated photonic circuits on a chip.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.14 no.10
• /
• pp.3989-4006
• /
• 2020

The intelligent agriculture monitoring is based on the perception and analysis of environmental data, which enables the monitoring of the production environment and the control of environmental regulation equipment. As the scale of the application continues to expand, a large amount of data will be generated from the perception layer and uploaded to the cloud service, which will bring challenges of insufficient bandwidth and processing capacity. A fog-based offline and real-time hybrid data analysis architecture was proposed in this paper, which combines offline and real-time analysis to enable real-time data processing on resource-constrained IoT devices. Furthermore, we propose a data process-ing algorithm based on the incremental principal component analysis, which can achieve data dimensionality reduction and update of principal components. We also introduce the concept of Squared Prediction Error (SPE) value and realize the abnormal detection of data through the combination of SPE value and data fusion algorithm. To ensure the accuracy and effectiveness of the algorithm, we design a regular-SPE hybrid model update strategy, which enables the principal component to be updated on demand when data anomalies are found. In addition, this strategy can significantly reduce resource consumption growth due to the data analysis architectures. Practical datasets-based simulations have confirmed that the proposed algorithm can perform data fusion and exception processing in real-time on resource-constrained devices; Our model update strategy can reduce the overall system resource consumption while ensuring the accuracy of the algorithm.