• The Journal of the Korea institute of electronic communication sciences
• /
• v.14 no.6
• /
• pp.1109-1120
• /
• 2019

In the field of VLBI, If the quality of the connected network between the VLBI station and the correlation center is ensured, the existing inefficiency of repeatedly storing the observation data in each station and the correlation center can be overcome. In other words, the data center can be unified with the correlation center where data analysis is performed, which can improve data processing speed and productivity. In this paper, we design a massive VLBI data system that directly transmits and stores the observation data stream obtained from the VLBI station to the correlation center via the high - speed network KREONET. Based on this system, VLBI test observations confirmed that the observation data was stored perfectly in the recording system of the correlation center without a single packet loss.

• Journal of Communications and Networks
• /
• v.3 no.4
• /
• pp.383-395
• /
• 2001

Recent measurement and simulation studies have revealed that wide area network traffic displays complex statistical characteristics-possibly multifractal scaling-on fine timescales, in addition to the well-known properly of self-similar scaling on coarser timescales. In this paper we investigate the performance and network engineering significance of these fine timescale features using measured TCP anti MPEG2 video traces, queueing simulations and analytical arguments. We demonstrate that the fine timescale features can affect performance substantially at low and intermediate utilizations, while the longer timescale self-similarity is important at intermediate and high utilizations. We relate the fine timescale structure in the measured TCP traces to flow controls, and show that UDP traffic-which is not flow controlled-lacks such fine timescale structure. Likewise we relate the fine timescale structure in video MPEG2 traces to sub-frame encoding. We show that it is possibly to construct a relatively parsimonious multi-fractal cascade model of fine timescale features that matches the queueing performance of both the TCP and video traces. We outline an analytical method ta estimate performance for traffic that is self-similar on coarse timescales and multi-fractal on fine timescales, and show that the engineering problem of setting safe operating points for planning or admission controls can be significantly influenced by fine timescale fluctuations in network traffic. The work reported here can be used to model the relevant characteristics of wide area traffic across a full range of engineering timescales, and can be the basis of more accurate network performance analysis and engineering.

• 한국HCI학회:학술대회논문집
• /
• 2008.02a
• /
• pp.679-682
• /
• 2008

High interest for the wireless network is going on the research to apply the related technologies in one's real life. Among these wireless network technologies, local area wireless network, Binary CDMA(Code Division Multiple Access), is the method transferring the data by using RF band based on 2.4Ghz. Binary CDMA has longer transmission distance than Bluetooth. Also, it is of benefit to an inexpensive price because the circuit is simple as compared with being similar to the performance of the existing CDMA. Though Binary CDMA has these benefits, one problem is a frequency overlap, and anther problem is to generate the sections with the shorter distance. To solve these problems, We propose the clustering method that can cover wide area.

• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.9 no.3
• /
• pp.225-232
• /
• 2009

Increasing the number of the solitude old person maintain a healthy lifestyle, the research for the emergency detection and life monitoring is required. In this paper, the wireless sensor network technology is utilized to design a silver-care service model in the area of emergency silver generation activities. The service model proposed in this paper acquired by using mobile devices to access silver-care service with the network information obtained through video monitoring and sensing. Also, Proposed model, based on wide-area network connected with the best wireless network of the PDA and mobile phones for the solitude old person.

• Journal of KIISE:Computer Systems and Theory
• /
• v.33 no.10
• /
• pp.746-758
• /
• 2006

Many objects existing on wide area environments have the replication characteristics according to how to categorize using their own names or properties. From the clients' requests, the existing naming and trading services have not supported with the binding service for replicated solver object with the same service type. For this reason, we present an integrated model that can support the selection of replicated object and dynamic binding services on wide-area computing environments. This model suggests provides not only location management of replicated objects but also active binding service which enables to select a least-loaded object on the system to keep the balance of load between systems. In this purpose, constructing both the service plan and model for support solver object's binding with replication property on wide area computing environments has been researched. In this paper, we showed the test environment and analyzed the performance evaluation of client/server binding procedures via integrated binding service in federation model and verified our model under the condition to see whether load balance can be applied to our model. For the performance evaluation of suggested wide area integrated binding service federation model, evaluated the integrated binding service of each domain and analyzed the performance evaluation of process for non-replication object's under federation model environment. Also, we analyzed the performance evaluation of the federation model between domains for wide area environment. From the execution results, we showed the federation model provides lowers search-cost on the physical tree structure of network.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.20 no.3
• /
• pp.318-322
• /
• 2014

A kind of field bus called Actuator and Sensor interface bus(AS-i) was designed in this paper. The configuration of AS-i network system used Application Specific Integrated Circuit(ASIC) SAP5S chip and PLC S7-200 station, which included CPU 224 and AS-i master module CP 243-2. We also created an example program for PLC S7-200 to control AS-i network. The fire and smoke detection system was made with AS-i network system that was designed. This system had got more advantages than other system such as number of stations, easy installation, wide working area, etc. And designed system can be used as a partner network for higher level field bus networks.

• Electronics and Telecommunications Trends
• /
• v.34 no.1
• /
• pp.49-60
• /
• 2019

The prosperity of modern society is heavily depending on communication technology. Communication is now expanding its roles from personal convenience to social/industrial functioning. Photonics was first introduced to communication in longdistance transmission area since it provided wide bandwidth cost-effectively. However, nowadays, photonics is not only a harmonious collaborator with electronics, but has its own exclusive playgrounds in various parts of communication. Limit-zero network pursues a network that can provide abundant capacity and efficiency using very limited resources. Photonics is the most promising candidate to accomplish the goal. In this article, we review the current status and predict the future contributions of photonics to limit-zero network.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.13 no.3
• /
• pp.1599-1610
• /
• 2019

Intelligent services have expanded as Internet of Things (IoT) technology has evolved and new requirements emerge to accommodate various services. One new requirement is transmitting data over long distances with low-power. Researchers have developed low power wide area (LPWA) network technology to satisfy the requirement; this can improve IoT network infrastructure and increase the range of services. However, network coverage expansion causes several problems. The traffic load is concentrated at a specific gateway, which causes network congestion and leads to decreased transmission efficiency. Therefore, the approach proposed in this paper attempts to recognize and then avoid congestion through gateway channel hopping. The LPWA network employs multiple channels, so wireless channel hopping is available in a gateway. Devices that are not delay sensitive wait for the gateway to reappear on their wireless channel; delay sensitive devices change the wireless channel along the hopping gateway. Thus, the traffic load and congestion in each wireless channel can be reduced improving transmission efficiency. The proposed approach's performance is evaluated by computer simulation and verified in terms of transmission efficiency.

• Journal of Korean Society of Transportation
• /
• v.8 no.2
• /
• pp.55-66
• /
• 1990

The research deals with the establishment of transportation areas in the metropolitan cities. The purpose is three-fold ; 1) to review the existing literature : 2) to analyze the commuting (work and school) pattern and interregional movement pattern of passengers and freights ; 3) to establish the metropolitan transportation area based on the above analyses. The transportation area is defined by the analysis of trip pattern to the center city of each metropolitan area. The detailed indices for establishment are selected by the rank-size and time-distance analyses. For the operational purpose, the study defines 3 different transportation areas as follows : the first transportation area means the directly effecting region of the center city ; the second means the region with many reverse trips and development potentials ; and the third means the indirectly effecting region. It can be concluded that the first transportation area includes 10 cities and 5 counties in Seoul metropol tan region, Yangdsan-Gun, Kimhae-Gun and Kimhae-Si in Busan, Dalsung-Gun, Chilgok-Gun and Kyungsan-Gun in Daegu, Hwasung-Gun and Raju-Gun in Kwangju, and Daeduk-Gun in Daejun. These results could be expected to have many implications for the establishment of area-wide public transportation network, the metropolitan transportation decision-making bodies and others.

• Journal of Digital Contents Society
• /
• v.9 no.1
• /
• pp.87-99
• /
• 2008

High Altitude Platform network systems utilize Unmanned Aerial Vehicle as routers for ground node communication. For this purpose, geographical clustering of ground nodes must be required. In this paper, we assume mobile ground nodes over wide area and the clusters composed of ground nodes are identified. UAVs can be positioned at the point of centroid of clusters. The number of UAVs are derived from the area size and the number of ground nodes deployed in that area. From the simulation and application of clustering algorithms, we showed visual clustering results with dynamic variance of number of ground nodes.