• Journal of Satellite, Information and Communications
• /
• v.9 no.1
• /
• pp.51-56
• /
• 2014

High-availability seamless redundancy (HSR) is a protocol for fault-tolerant Ethernet (FTE) networks. It provides two frame copies and each copy is forwarded on a separate physical path, which provides zero fail-over time. Therefore, the HSR is becoming a potential candidate for various real-time FTE applications. However, the generation and circulation of unnecessary frames due to the duplication of every sending frame is inherent drawback of HSR. Such drawback degrades the performance of the network and may deplete its resources. In this paper, we present a new algorithm called port locking (PL) based on the media access control (MAC) address to solve the abovementioned problem in popular connected-rings network. Our approach makes the network gradually learn the locations of the source and the destination nodes without relying on network control frames. It then prunes all the rings that do not contain the destination node by locking corresponding rings' entrance ports. With the PL algorithm, the traffic can be significantly reduced and therefore the network performance will be greatly enhanced specially in a large scale connected-rings network. Analytical results are provided to validate the PL algorithm.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.47 no.7
• /
• pp.109-117
• /
• 2010

Building a large-scale testbed for Future Internet is very important to evaluate a new protocol and new network architecture designed by clean-slate approach. In Korea, new Future Internet testbed project, called FIRST (Future Internet Research for Sustainable Testbed), has been started since Mar. 2009 to design and test new protocols. This project is working together with ETRI and 5 universities. The FIRST@PC is to implement a virtualized hardware-accelerated PC-node by extending the functions of NetFPGA card and build a Future Internet testbed on the KOREN and KREONET for evaluating newly designed protocols and interesting applications. In this paper, we first briefly introduce FIRST@PC project and explain a 'MAC in IP Capsulator' user-space program using raw-socket in Linux to interconnect OpenFlow enabled switch sites on the KOREN and KREONET. After that, we address test results for TCP throughput performance for varying packet size. The test results show that the software based capsulator can support a reasonable bandwidth performance for most of applications.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
• /
• v.9 no.1
• /
• pp.49-57
• /
• 2016

Recently, marine accidents such as the sinking accident Mongol freighter ship and the sinking accident of Sewol ferry in Jindo continuously happen. In order to decrease the number of these marine accidents, Korean ships are obliged to follow the AIS(Automatic Identification System) system. The AIS protocol includes all information for sailing ships. However, the standard AIS protocol does not provide any security function, In addition, it is possible to hijack the standard AIS protocol in case of using a satellite communication device called FUNcuve Dongle Pro+. Therefore, this paper analyzes weak points of the security in the standard AIS protocol. Furthermore, this paper ensures reliability by marking the MAC Address of sender and receiver for secure communication and suggests the protocol that can securely send data, using the VPN Tunnelling method. Therefore, the suggested AIS protocol provides the secure communication to the AIS protocol and protect the messages in the AIS protocol, which can serve safe voyages by decreasing the marine accidents.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.18 no.9
• /
• pp.2109-2116
• /
• 2014

This paper presents the implementation and design of the advanced WI-FI systems with beam-forming antenna that radiate their power to the direction of user equipment to improve the overall throughput, contrast to the general WI-FI systems equipped with omni-antenna. The system consists of patch array antenna, DSP, FPGA, and Qualcomm's commercial chip. The beam-forming system on the FPGA utilizes the packet information from Qualcomm's commercial chip to control the phase shifters and attenuators of the patch array antenna. The PCI express interface has been used to maximize the communication speed between DSP and FPGA. The directions of arrival of users are managed using the database, and each user is distinguished by the MAC address given from the packet information. When the system wants to transmit a packet to one user, it forms beams to the direction of arrival of the corresponding user stored in the database to maximize the throughput. Directions of arrival of users are estimated using the received preamble in the packet to make its SINR as high as possible. The proposed beam-forming system was implemented using an FPGA and Qualcommm's commercial chip together. The implemented system showed considerable throughput improvement over the existing general AP system with omni-directional antenna in the multi-user communication environment.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.27 no.4
• /
• pp.1-10
• /
• 2023

In the seismic design of structures, seismic forces are calculated based on structural models and analysis. In order to accurately address the dynamic characteristics of the actual structure in the structural model, calibration based on actual measurements is required. In this study, a 4-story frame test specimen was manufactured to simulate frame building, accelerometers were attached at each floor, and 1-axis shaking table test was performed. The natural period of the specimen was similar to that of the actual 4 story frame building, and the columns were designed to behave with double-curvature having the infinite stiffness of the horizontal members. To investigate the effects seismic waves characteristics, historical and artificial excitations with various frequencies and acceleration magnitudes were applied. The natural frequencies, damping ratios, and mode shapes were obtained using frequency response functions obtained from dynamic response signals, and the mode vector deviations according to the input seismic waves were verified using the Mode assurance criterion (MAC). In addition, the damping ratios obtained from the vibration tests were applied to the structural model, and the method with refined dynamic characteristics was validated by comparing the analysis results with the experimental data.

• Journal of Korean Society for Atmospheric Environment
• /
• v.33 no.3
• /
• pp.205-216
• /
• 2017

Carbonaceous aerosols such as the equivalent black carbon (eBC), the elemental carbon (EC) and the organic carbon (OC) were monitored at the Seoul Olympic Park site ($37.521^{\circ}N$, $127.124^{\circ}E$) during the KORUS-AQ 2016 campaign using a Multi Angle Absorption Photometer (MAAP) and an OCEC Analyzer. Averaged mass concentrations of eBC, EC and OC were presented as $2.46{\pm}1.52{\mu}g/m^3$, $1.01{\pm}0.60{\mu}g/m^3$ and $4.85{\pm}2.60{\mu}g/m^3$, respectively. OC/EC ratio and mass absorption cross-section (MAC) of light absorbing aerosols were calculated as 2.32 and $14.8m^2/g$, respectively. Diesel OC concentrations were estimated from a source profile of diesel vehicles as well. eBC mass concentrations measured from May $26^{th}$ to May $27^{th}$, 2016 showed 40% higher than averaged eBC mass concentrations during campaign period. $PM_{2.5}$ concentrations measured in this period were also higher than average $PM_{2.5}$ concentrations. High eBC concentrations were observed from May $29^{th}$ to May $31^{st}$, 2016 and from June $9^{th}$ to June $11^{th}$, 2016, possibly due to morning rush hour and the effect of temperature inversion at night. Diurnal variations of eBC, EC and Diesel OC showed a typical pattern of metropolitan area. In the weekend, however, diurnal variations of eBC, EC and Diesel OC mass concentrations were different from those measured in the weekday. It is expected that this study can help to understand the relationship between carbonaceous aerosols in a metropolitan area.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.39B no.1
• /
• pp.17-28
• /
• 2014

The increase of smartphone users have made mobile carriers offload increasingly congested traffic of 3/4G by providing Wi-Fi hot-spots in the public places such as coffee shops and subway stations. In the traditional authentication in WLAN, the users should convince the service providers that they are valid customers before they use WLAN services. Since the authentication protocol is designed for service providers. Even with the mutual authentication based on the IEEE 802.1X, which is supported by IEEE 802.11 standard, it is difficult to be convinced of that the service providers really have installed the WLAN APs, which users are confronted with. An attacker can install rogue APs that masquerade as legitimate APs by copying the SSID, MAC address, etc. in order to obtain users' private information. In this paper, we introduce a method of authenticating legitimate APs for smartphone users. And we show our proposal can be well utilized for the current Wi-Fi hot-spots as a security plug-in and prove it through our experiments.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.43 no.11 s.353
• /
• pp.25-34
• /
• 2006

In this paper, we propose the new Cellular Ethernet System that supports faster handovers than IP layer handover scheme for WiBro Networks and analyze the performance of the proposed scheme. In WiBro Networks, it is very important for service providers that supports fast handovers for mobile users who want superior service. But in case of Mobile IPv6, which supports IP layer handovers, there exists very long latency for detecting movement and duplicated IP address. And besides, handovers in wired area must be carried out after completing handovers in wireless area. So, Mobile IPv6 cannot provide superior service to mobile users. To remedy these problems, we here propose the new Cellular Ethernet System that consists of MAC layer bridges for WiBro Networks and analyze the performance of Cellular Ethernet System handover scheme and show that it has better performance than Mobile IPv6.

• Journal of the Institute of Electronics Engineers of Korea CI
• /
• v.47 no.2
• /
• pp.39-47
• /
• 2010

In Wireless Sensor Network, transmission errors are frequently occurred due to the node failure, battery discharge, and interference by objects. Although Directed Diffusion has been considered as a prominent Data-centric routing algorithm, it revealed some weaknesses at this kind of unexpected network errors. In order to address the problem, we proposed a radio-aware routing algorithm for improving reliability of Directed Diffusion in Wireless Sensor Networks. The proposed algorithm is aware of the network status based on the radio information of MAC and PHY layers using a cross-layer approach. The link quality and the node failure information from the acquired network status were used to decide an alternative path to provide a reliable data transmission in error-prone sensor networks. The proposed algorithm showed its effectiveness of the data delivery rate and data ratio with several simulations consisting of various error rates and the number of nodes.

• International Journal of Knowledge Content Development & Technology
• /
• v.11 no.1
• /
• pp.65-84
• /
• 2021

Our understanding of how barriers to access systematically varies with the compositional and contextual characteristics of users is incomplete. Using a public university library in Ghana, this study assessed the heterogeneous barriers or constraints students encounter in accessing electronic resources based on their demographic and contextual attributes. A descriptive survey design was adopted and structured questionnaires were administered randomly to 558 students in the four constituent colleges of the University of Cape Coast, Ghana. Data were collected and analysed using SPSS and descriptive statistics were generated. The results revealed that students faced six key challenges in accessing electronic information resources in the library namely delays in download of information, poor internet connectivity, and limited accessibility of university portal, inadequate computers in the library, poor lighting and limited ancillary services (on the spot printing facilities), with differences based on gender, academic level, and college affiliation. Only 24% males and 26% females had no challenges or problems with delays in download of electronic information. About three-fourth of all users had poor internet connectivity and complained about inadequate computers associated with accessing electronic resources. 40% percent of undergraduate students in the Colleges of Education Studies, Agriculture and Natural Sciences, and Humanities and Legal Studies each encountered four to six simultaneous challenges. Irrespective of gender, first year undergraduate students in all the four colleges were the least likely to report multiple challenges. This suggests the need for targeted and context-specific interventions to address the identified challenges.