• Journal of the Korean Institute of Telematics and Electronics B
• /
• v.32B no.11
• /
• pp.1365-1373
• /
• 1995

In this paper, we address the issues related to storage and retrieval of continuous media (CM)data we face in designing multimedia on-demand (MOD) storage servers. To support the two orthogonal factors of MOD server design, i.e., storage and retrieval of CM data, this paper discusses the techniques of disk layout, disk striping and real-time disk scheduling, which are integrated as a combined solution to the high- performance MOD storage subsystem. The proposed clustered striping technique enables either a multiple-disk or a parallel system to guarantee a continuous retrieval of CM data at the bandwidth required to support user playback rate by avoiding the formation of I/O bottlenecks.

• IEMEK Journal of Embedded Systems and Applications
• /
• v.5 no.1
• /
• pp.7-17
• /
• 2010

ITS(Intelligent Transport System) as things are used for Broadcast service using TDMB/TPEG/NAVI rather than personal seamless service. It is attaching weight to Traffic information gathering, Charging, Settlement service. This research is applied to improve DCCP(Datagram Congestion Control Protocol) which has function as protecting data and preserving message boundary. The improving method is like that we solve data trust in UDP because Connection and Transmission overhead in UDP is less than in TCP. We fix the data loss which is generated from unordered delivery section of IP base wireless service by using DCCP protocol. We guarantee of connection with OBE(On-Board Equipment) and reliance about transmission of data by complement to mapping table and multi-hoping. Finally, We evaluate the performance about transmission of IP based data. We constructed a test-bed near research center for this test.

• Journal of the Korea Society of Computer and Information
• /
• v.21 no.1
• /
• pp.49-57
• /
• 2016

In this paper we propose the resource allocation scheme for the overlaid macro-femtocell networks, which considers the type of handovers such as the inter-macrocell, macrocell-to-femtocell, femtocell-to-macrocell, or inter-femtocell in order to guarantee Quality of Service (QoS) and expand the accommodation capacity. Our proposed scheme takes into account the movement of mobile terminals, the QoS degradation, or the load control which trigger handovers in the overlaid networks, before it allocates resources dynamically. Moreover it considers QoS requirements of realtime or non-realtime mobile multimedia services such as video communication, Video on Demand (VoD) and dataa services. Simulation results show that our scheme provides better performances than the conventional one with respect to the outage probability, data transmission throughput and handover failure rate.

• Journal of Information Processing Systems
• /
• v.8 no.4
• /
• pp.589-602
• /
• 2012

With the increasing demand for real time applications in the Wireless Senor Network (WSN), real time critical events anticipate an efficient quality-of-service (QoS) based routing for data delivery from the network infrastructure. Designing such QoS based routing protocol to meet the reliability and delay guarantee of critical events while preserving the energy efficiency is a challenging task. Considerable research has been focused on developing robust energy efficient QoS based routing protocols. In this paper, we present the state of the research by summarizing the work on QoS based routing protocols that has already been published and by highlighting the QoS issues that are being addressed. The performance comparison of QoS based routing protocols such as SAR, MMSPEED, MCMP, MCBR, and EQSR has also been analyzed using ns-2 for various parameters.

• Journal of the Korea Society of Computer and Information
• /
• v.6 no.3
• /
• pp.72-77
• /
• 2001

The method of connection admission control is presented by using the equations related with traffic classes for real-time connection admission control. without assuming the cell arrival processes in the multi-level structure of ATM traffic control. The equations related with traffic classes are obtained by 3 or 4 of first order inequalities from the admissible ranges of connection considering the expected total instantaneous demand to guarantee the required quality of services of each class.

• Journal of Applied Reliability
• /
• v.15 no.4
• /
• pp.241-247
• /
• 2015

Purpose : The demand for higher fuel economy vehicles has helped develop fuel-efficient vehicles such as a CVVL called continuous variable valve lift. Existing CVVL has been applying DC type motor to control intake valve, but recently some car parts manufacturers have been developing a BLDC type CVVL motor for improvements of endurance performance. The purpose of this study is to find the potential failure mechanism of the CVVL BLDC moto in early stage of development based on the design properties and design the accelerated life test model. Methods : CVVL BLDC is consist of brushs, coil, magnetic, PCB, bearing and so on. Each component has a latent failure mechanism caused by temperature, humidity, vibration. By analysis result of the failure mechanism, thermal fatigue is the most important factor of a durability of CVVL BLDC motor. So, we designed a new accelerated life test model for guarantee of the CVVL BLDC motor. Results : A crack occurred on via hole in test using the conditions we designed, so we did change the design to avoid this failure. The via hole dimension is changed a little larger, as a result we achieve improvements in reliability of the CVVL BLDC motor. By applying various kinds and extreme level of stresses, we can find the operating limits of products. Conclusion : In thesis, We analyzed the failure mechanism of CVVL BLDC and designed an accelerated life test method to give a guarantee for reliability. Based on the test results, we could improve the reliability of developments by change of design.

• Journal of the Korea Institute of Information Security & Cryptology
• /
• v.23 no.2
• /
• pp.279-286
• /
• 2013

The recent power shortages due to surge in demand for electricity highlights the importance of smart grid technologies for efficient use of power. The experimental content for vulnerability against availability of smart meter, an essential component in smart grid networks, has been reported. Designing availability protection mechanism to boost the realization possibilities of the secure smart grid is essential. In this paper, we propose a mechanism to detect the availability infringement attack for smart meter and also to find anomaly nodes through analyzing smart grid structure and traffic patterns. The proposed detection mechanism uses approximate entropy technique to decrease the detection load and increase the detection rate with few samples and utilizes the signal information(CIR or RSSI, etc.) that the anomaly node can not be changed to find the anomaly nodes. Finally simulation results of proposed method show that the detection performance and the feasibility.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.22 no.9
• /
• pp.1250-1256
• /
• 2018

Recently, wireless networks are becoming an important infrastructure for the critical large-scale applications such as cyber-physical systems and next generation industrial automations. However, the fundamental performance uncertainty of wireless networks may incur the serious instability problem of the overall systems. This paper proposes the proactive network optimizer to guarantee the application demands without any real-time link monitoring information of the networks. In particularly, the proposed proactive optimizer is the cross-layer approach to jointly optimize the routing path and traffic distribution in order to guarantee the performance demand within a maximum k number of link faults. Through the simulations, the proposed proactive network optimizer provides better robustness than the traditional existing reactive networks. Furthermore, the proactive network does not expose to the major weakness of the reactive networks such as the performance degradation due to the erroneous link monitoring information and the network reconfiguration cost.

• Korean Journal of Construction Engineering and Management
• /
• v.10 no.2
• /
• pp.121-131
• /
• 2009

This study will estimate the fair return on private participants' investments on BTO type PPI (Private Public Infrastructure) projects using the data from past BTO projects in Korea. In the past, the real returns of $6%\sim9%$ were provided to private participants. The results of this study show that those returns were too high compared with the estimated fair returns, especially for projects with the minimum revenue guarantee (MRG) by the government. Moreover, the excess portion of the return over the fair return becomes even larger when there is a demand forecast bias. In reality, most of the BTO projects have far lower actual revenues than the initial forecasted revenue in concession agreements. This phenomenon implies that BTO projects have a tendency of overly forecasting revenues. If so, the value of the minimum revenue guarantee becomes larger, and therefore, the fair return to private participants should decrease. It is hoped that this study helps future BTO projects' concession agreements between the government and private participants to become more fair from the perspectives of risk and return profiles.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.28 no.8B
• /
• pp.707-715
• /
• 2003

In this paper, we propose a new MAC(Medium Access Control) protocol using Movable-boundary, which tries to guarantee Qos for multimedia traffic in the slotted CDMA system. In this scheme, the traffic scheduler assigns channel resource according to the packet priority per service class and adapts the Movable-boundary concept in which the minimum resource is assigned to each traffic class; the remaining resource if it is available can be assigned dynamically according to the temporal demand of other traffic classes. For performance analysis, we performed computer simulations to obtain throughput and packet loss rate and compared the results with Fixed-boundary system. We observed that the error rate of voice traffic could be maintained below a prescribed value while bursty traffic such as video source shares the same channel. In comparison with Fixed-boundary scheme, our protocol exhibits better throughput and packet loss rate performance.