• Journal of the Korean GEO-environmental Society
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• v.17 no.4
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• pp.33-37
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• 2016

The hydration process of Controlled Low Strength Material (CLSM) used for backfill is the primary factor to determine the construction period. The objective of this study is to monitor the hydration process of CLSM using the Time Domain Reflectometry (TDR) and to establish the relationship between dielectric constant and compressive strength. The CLSM specimen is composed of cement, flyash, silt, sand, accelerator, and water. The material characteristics of the CLSM including flow, unit weight, compressive strength are investigated. To measure the dielectric constant of the CLSM during the curing time, TDR probe incorporated with a mold and a reflectometer are used. Experimental results show that the dielectric constant remains constant at early stage, and then decreases as the curing time increases. In addition, the dielectric constant is related to the compressive strength in inverse power function. This paper suggests that the TDR technique may be used as a non-destructive testing method in order to estimate the compressive strength of the CLSM mixture under construction.

• The KIPS Transactions:PartC
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• v.16C no.5
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• pp.661-668
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• 2009

The Extended real-time Polling Service (ErtPS) is proposed tosupport QoS of VoIP service with silence suppression which generates variable size data packets in IEEE 802.16e systems. If the silence is suppressed, VoIP should support Comfort Noise Generation (CNG) which generates comfort noise for receiver's auditory sense to notify the status of connection to the user. CNG mode in silent-period generates a data with lower bit rate at long packet transmission intervals in comparison with talk-spurt. Therefore, if the ErtPS, which is designed to support service flows that generate data packets on a periodic basis, is applied to silent-period, resources of the uplink are used inefficiently. In this paper, we proposed the Improved ErtPS algorithm for efficient resource utilization of the silent-period in VoIP traffic supporting CNG. In the proposed algorithm, the base station allocates bandwidth depending on the status of voice at the appropriate interval by havingthe user inform the changes of voice status. The Improved ErtPS utilizes the Cannel Quality Information Channel (CQICH) which is an uplink subchannel for delivering quality information of channel to the base station on a periodic basis in 802.16e systems. We evaluated the performance of proposed algorithm using OPNET simulator. We validated that proposed algorithm improves the bandwidth utilization of the uplink and packet transmission latency

• Journal of KIISE:Computing Practices and Letters
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• v.15 no.9
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• pp.626-636
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• 2009

In Mobile IP-enabled wireless LAN (WLAN), packet flows are corrupted due to the handoff of a mobile node (MN) at the link and network layers, which results in burst packet losses and can cause temporary buffer underflow in a streaming client at the MN. This transient behavior hurts time-sensitive streaming media applications severely. Among many suggestions to address this handoff problem, few studies are concerned with empirical issues regarding the practical validation of handoff options on the time-sensitive streaming media applications. In this paper, targeting seamless streaming over Mobile IP-enabled WLAN, we introduce a seamless media streaming framework that estimates accurate pre-buffering level to compensate the handoff latency. In addition, we propose a link-layer (L2) assisted seamless media streaming system as a preliminary version of this framework. The proposed system is designed to reduce the handoff latency and to overcome the playback disruption from an implementation viewpoint. A packet buffering and forwarding mechanism with L2 trigger is implemented to reduce the handoff latency and to eliminate burst packet losses generated during the handoff. A pre-buffering adjustment is also performed to compensate the handoff latency. The experimental results show that the proposed approach eliminates packet losses during the handoff and thus verify the feasibility of seamless media streaming over Mobile IP-enabled WLAN.

• The KIPS Transactions:PartC
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• v.12C no.5 s.101
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• pp.709-716
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• 2005

QoS is an important requirement of the FTTH (Fiber To The Home) subscriber in access network using E-PON (Ethernet Passive Optical Network). In this research, we describe the structure of the access network and propose a bandwidth guarantee scheme for subscriber and service according to the requirements of the subscriber, service and system. This scheme uses two kinds of the classification table, which are called 'service classification table' and 'subscriber classification table.' Using the classification table, we can identify the flow of the subscriber and service. Also, we compute the number of hash table entry to minimize the loss ratio of flows using the M/G/k/k queueing model. Finally, we apply the DRR scheduling through virtual queueing per subscriber instead of the aggregated class.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.7B
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• pp.642-651
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• 2006

In ad-hoc network, the most of existing packet scheduling schemes provides throughput-based fairness. To provide throughput-based fairness, it basically supposes that the channel capacity is fixed. But, the supposing that the channel capacity is fixed is not appropriate because IEEE 802.11b and 802.11g which are normally used for organizing ad-hoc network can provide various data rate according to channel conditions. So, we define time-based fairness for each flow to consider multi-rate and suggest the MRADPS reaching the defined time-based fairness. Simulation result shows that MRADPS improves the total network throughput in ad-hoc network with providing time-based fairness to each flow.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.7 no.7
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• pp.1498-1508
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• 2003

It is important to integrate an enterprise application for automating of the business process, which is responded by a flow of market environment. There are two categories of method that integrate enterprise applications. One is Synchronous Integration, and the other is Asynchronous Integration. EAI(Enterprise Application Integration) and Web service which of the asynchronous integration is focused in the automating method of the business process. After we construct the application integration for automating of the business process, we have to concern about managing of the business transaction. Many Organizations have proposed the process method of business transaction based on 2-phase commit protocol. But this method can't supply the phase that classify the transaction by transaction weight. In this Paper, we Propose an efficient method of transaction process for business transactions, which is composed by ‘Classify Phase’ that classify transactions. We called this model “3-Phase Commit Method Applied by Classify Phase”, we design this model to manage an resource of enterprise efficiently. The proposed method is compared by the method based on 2-Phase commit that could be a problem of management the resource of enterprise, and the advantage of this method is certified to propose the solution of that problem.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.8
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• pp.1508-1516
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• 2017

Multipath TCP (MPTCP) is a transport layer protocol that supports multipath transmission. If a bufferbloat occurs in one of the subflows of MPTCP, HoL blocking occurs at the receiver due to the difference in packet arrival time among paths. In MPTCP, HoL blocking degrades not only the performance of the path where bufferbloat occurs, but also the performance of other paths. In this paper, we propose a bandwidth measurement based scheduler to solve this problem. Bandwidth measurement based scheduler is designed to measure the bandwidth of each subflow and to perform packet scheduling based on it. In order to verify the proposed scheduler, we implemented the proposed scheduler in the Linux kernel and constructed a testbed in which bufferbloat occurs. Experimental results show that the proposed scheduler has better performance than the legacy MPTCP in bufferbloat environment.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.32 no.6
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• pp.472-476
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• 2019

We have proposed a novel planar lightwave circuit (PLC) optical sensor to monitor the contamination in a flow-cell where water is continuously supplied through a water quality measurement system. We designed a PLC chip with a V-shape waveguide and the simulated its function as a sensor for monitoring contamination in a flow-cell using a numerical the FDTD (finite-difference time-domain) analysis. A novel cross type of waveguide was introduced to make the PLC chip of the V-shaped waveguide. The fabricated PLC was cut into the cross waveguide. A change in the optical propagation loss of the PLC sensor was observed after immersing the PLC sensor into city water. It was determined that the propagation loss of the PLC sensor was 3 dB at a wavelength of $1.55{\mu}m$ in the city water for 15 days.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.18 no.6
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• pp.121-126
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• 2018

IEEE 802.1 TSN TG is developing standards for end-to-end delay bounds and zero packet loss based on Ethernet technology. We focus on packet forwarding techniques. TSN packet forwarding techniques can be classified into Synchronous and Asynchronous framework. Synchronous approach allocates fixed time period for a class, yet is complex for large networks. Asynchronous approach provides delay guarantee by regulator-scheduler pair, yet is unnecessarily complex, too. We propose network components for TSN Asynchronous architecture, which remove the complexity of maintaining flow state for regulation decisions. Despite such a simplicity, the proposed architecture satisfies the TSN's delay requirements provided the limited high priority traffic's maximum packet length.

• Convergence Security Journal
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• v.20 no.5
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• pp.3-10
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• 2020

Recently, the Internet and networks are regarded as essential infrastructures that constitute society, and security threats have been constantly increased. However, the network switch that actually transmits packets in the network can cope with security threats only through firewall or network access control based on fixed rules, so the effective defense for the security threats is extremely limited in the network itself and not actively responding as well. In this paper, we propose an in-network security framework using the high-level data plane programming language, P4 (Programming Protocol-independent Packet Processor), to deal with DDoS attacks and IP spoofing attacks at the network level by monitoring all flows in the network in real time and processing specific security attack packets at the P4 switch. In addition, by allowing the P4 switch to apply the network user's or administrator's policy through the SDN (Software-Defined Network) controller, various security requirements in the network application environment can be reflected.