• Journal of the Korea Institute of Information and Communication Engineering
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• v.17 no.11
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• pp.2569-2574
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• 2013

In 13.56MHz RFID system of Auto-ID center, STAC protocol is defined as an anti-collision algorithm for multiple tag reading. In STAC protocol, the reader uses the tag number estimation scheme to determine the number of slots for the next reply round. If errors occur in the estimated number of tags, the identification performances will be degraded due to a lot of collision or idle slots. Therefore, in this paper, we propose an ERPB algorithm that the reader cancels the reply round when it experiences a series of collision or idle slots during the current round. The transmission probability control for the tag is also applied to the proposed algorithm. Through simulations, it is demonstrated that the collision rate for the proposed scheme is about 39% lower than STAC protocol. Therefore, the proposed scheme can achieve faster tag identification time compared with STAC protocol due to the low collision rate.

• Journal of the Korea Society of Computer and Information
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• v.16 no.4
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• pp.111-117
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• 2011

In this paper, we propose an QoS aware multi-layer MAC(QAML-MAC) protocol in a wireless sensor networks. Since the proposed protocol is based on the sleep-awake architecture, which save node's energy to prolong the entire network lifetime. For this purpose the QAML-MAC first classifies incoming data according to their transmission urgency and then saves them. The protocol also adapts the cross-layer concept to re-arrange the order of transmission with the same destination. So the delay can be decreased, which can not be obtained with the previous related protocols. And high priority data such as real-time multimedia or critical value in the field monitoring applications can be transmitted quickly, Furthermore the proposed protocol has advantage of decreasing transmitted data collisions using multiple layers of idle listening when there is no high-priority data. So energy consumptions of sensor nodes can be saved and the network lifetime can be prolonged.

• Journal of the Korean Institute of Telematics and Electronics T
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• v.35T no.1
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• pp.67-74
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• 1998

The primary cause of air pollution by vehicles is imperfect combustion of fuel. One of the most usual causes of this imperfect combustion is the misfire in IC engins. The U.S. EPA(Environment Protection Agency) and the CARB(California air Resources Board) have imposed regulations for the detection of misfiring in automotive engines. The OBD-II regulations require that misfire should be monitored by the engine diagnostic system, and that the goal of OBD-II is to alert the driver to the presence of a malfunction of the emission control system. Several solutions to the misfire detection problem have been proposed for the detection of misfires. However, the performance of these methods in the presence of misfire is not altogether clear. This paper presents a precise method and system for internal combustion engine misfire. Present invention based upon measurements of engine roughness as derived from crankshaft angular velocity measurements with special signal processing method. Crankshaft angular velocity signals are processed by WDPT, so that the more reliable misfire detection than the time domain analysis. Experimental work confirms that it is possible to apply the WDFT for the detection of misfires in no-load idle and road testing.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.5B
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• pp.317-326
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• 2012

Recently, many researchers have studied to solve the energy consumption of network equipments since the interest of Green IT has been increased. In this paper, we apply Low Power Idle (LPI) to OBS network to reduce energy consumption of network devices. Many previous researches have focused on maximizing the sleep time of network equipments to increase the energy saving efficiency of LPI. But transition overhead caused by LPI might not only depreciate the performance of energy saving but also increase packet delay. In this paper, Transition Decision (TD) algorithm is proposed to improve energy saving efficiency by reducing the number of unnecessary transition and guarantee the required QoS such as packet delay. To evaluate the performance of proposed algorithm, we model OBS edge router with LPI by OPNET and analyze the performance of the proposed algorithm in views of energy saving, transition count and average packet delay.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.1
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• pp.61-69
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• 2015

Through Virtual Machine technology(VM), VMs can be packed into much fewer number of physical servers than that of VMs. Since even an idle physical server wastes more than 60% of max power consumption, it has been considered as one of energy saving technologies to minimize the number of physical servers by using the knapsack problem solution based on the computing resources. However, this paper shows that this tightly packed consolidation may not achieve the efficient energy saving. Instead, a service pattern-based VM consolidation algorithm is proposed. The proposed algorithm takes the service time of each VM into account, and consolidates VMs to physical servers in the way to minimize energy consumption. The comprehensive simulation results show that the proposed algorithm gains more than 30% power saving.

• Journal of Communications and Networks
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• v.15 no.1
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• pp.77-86
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• 2013

Cognitive radio (CR) has emerged as one of effective methods to enhance the utilization of existing radio spectrum. Main principle of CR is that secondary users (SUs) are allowed to use the spectrum unused by primary users (PUs) without interfering PU's transmissions. In this paper, PUs operate on a slot-by-slot basis and SUs try to exploit the slots unused by PUs. We propose OSA protocols in the single channel and we propose an opportunistic spectrum access (OSA) protocols in the multi-channel cognitive radio networks with one control channel and several licensed channels where a slot is divided into contention phase and transmission phase. A slot is divided into reporting phase, contention phase and transmission phase. The reporting phase plays a role of finding idle channels unused by PUs and the contention phase plays a role of selecting a SU who will send packets in the data transmission phase. One SU is selected by carrier sense multiple access / collision avoidance (CSMA/CA) with request to send / clear to send (RTS/CTS) mechanism on control channel and the SU is allowed to occupy all remaining part of all idle channels during the current slot. For mathematical analysis, first we deal with the single-channel case and we model the proposed OSA media access control (MAC) protocol by three-dimensional discrete time Markov chain (DTMC) whose one-step transition probability matrix has a special structure so as to apply the censored Markov chain method to obtain the steady state distribution.We obtain the throughput and the distribution of access delay. Next we deal with the multi-channel case and obtain the throughput and the distribution of access delay by using results of single-channel case. In numerical results, our mathematical analysis is verified by simulations and we give numerical results on throughput and access delay of the proposed MAC protocol. Finally, we find the maximum allowable number of SUs satisfying the requirements on throughput and access delay.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.3
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• pp.451-458
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• 2015

The deployment density of AP increases as well as the density WLAN stations due to increase of WLAN use and the real performance of WLAN is degraded. To improve the performance, there are many PHY/MAC technologies and OFDMA and full duplex are promising technologies among them. In conventional OFDMA WLAN MAC relate works, there are some limitations in terms of channel utilization and collision probability. Thus, it need to research for effective channel allocation protocol. Full duplex can transmit data on the same time and same frequency resource so it can allocate channel more flexible than half duplex. In this paper, we prose the OFDMA FD-MAC(Full Duplex MAC) protocol that it allocates the sub-channels based on the idle channel information for full duplex pair. In addition, it shows the throughput improvement by performance analysis.

• The Journal of Bigdata
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• v.6 no.1
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• pp.1-12
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• 2021

The rapid growth of mobile-based online shopping and the appearance of untact business initiated by COVID-19 has led to an explosive increase in demand for logistics services such as delivery services. In order to respond to the rapidly growing demand, most logistics and distribution companies are working to improve customer service levels through the establishment of a full-filament center in the city center. However, due to social factors such as high land prices and traffic congestion, it becomes more difficult to establish the logistics facilities in the city center. In this study, it has been proposed the way to choose the candidate locations for the shared distribution centers among the space nearby the tall-gate which can be idle after the smart tolling service is widely extended. In order to evaluate the candidate locations, it has been evaluated the centralities of all candidates using social network analysis (SNA). To understand the result considering the characteristics of centrality, the network structure was regenerated based on the distance and the traveling time, respectively. It is possible to refer the result of evaluation based on the cumulative relative importance to choose the best set of candidates.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.3
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• pp.20-29
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• 2021

In the Industry 4.0 era, artificial intelligence has attracted considerable interest for learning mass data to improve the accuracy of forecasting and classification. On the other hand, the current method of detecting anomalies relies on traditional statistical methods for a limited amount of data, making it difficult to detect accurate anomalies. Therefore, this paper proposes an artificial intelligence-based anomaly detection methodology to improve the prediction accuracy and identify new data patterns. In particular, data were collected and analyzed from the point of view that sensor data collected at vehicle idle could be used to detect abnormalities. To this end, a sensor was designed to determine the appropriate time length of the data entered into the forecast model, compare the results of idling data with the overall driving data utilization, and make optimal predictions through a combination of various sensor data. In addition, the predictive accuracy of artificial intelligence techniques was presented by comparing Convolutional Neural Networks (CNN) and Long Short Term Memory (LSTM) as the predictive methodologies. According to the analysis, using idle data, using 1.5 times of the data for the idling periods, and using CNN over LSTM showed better prediction results.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2022.06a
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• pp.385-386
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• 2022

Currently, global developed countries in shipping and logistics establish smart ports by introducing various digital technologies such as automated terminals and sharing platforms. This means that the importance of efficiency throughout the port by improving resource utilization efficiency and minimizing work idle time is increasing. Therefore, this study proposes a yard truck dispatching method of improving resource utilization efficiency. And we analyze the problems of the existing dispatching rules and develop Y/T dispatching algorithm that comprehensively considers related constraints. In addition, the simulation takes into account the terminal congestion based on the operation data of the Busan New Port, it is conducted using the existing dispatch method and developed Y/T dispatching algorithm. And the operational effects of analysis result are evaluated.