• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.05a
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• pp.121-126
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• 2002

We proposed the design of SVC adaptive fuzzy logic controller(AFLC) using Tabu search and neural network. We tuned the gains of input-output variables of fuzzy logic controller(FLC) and weights of neural network using Tabu search. Neural network was used for adaptively tuning the output gain of FLC. The weights of neural network was learned from the back propagation algorithm in real-time. To evaluate the usefulness of AFLC, we applied the proposed method to single-machine infinite system. AFLC showed the better control performance than PD controller and GAFLC[8] for. three-phase fault in nominal load which had used when tuning AFLC. To show the robustness of AFLC, we applied the proposed method to disturbances such as three-phase fault in heavy and light load. AFLC showed the better robustness than PD controller and GAFLC[8].

• Journal of Communications and Networks
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• v.12 no.2
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• pp.114-121
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• 2010

In this paper, an auctioning strategy is proposed for cellular networks that ensures net energy savings. The pricing scheme, in conjunction with a two dimensional bid structure, incentivizes cooperation at the terminal nodes for better interference management at receivers and for cooperative relaying. It is shown that, for the proposed auctioning strategy, network operators are guaranteed revenue gains, mobile nodes' dominant strategy is to bid their true valuation of their energy resources, and overall effective energy gains occur under the assumption of a reserve price for bidding. Simulation results show that significant energy savings can be achieved by employing this auctioning mechanism for a 3G cellular set-up.

• Proceedings of the KIEE Conference
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• 1994.11a
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• pp.356-358
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• 1994

In this paper, to alleviate the effect of approximation error and discontinuous variation of the controller parameters, the variable structure control scheme using neural networks is presented. In the proposed method, the variable structure control rules for each local linear models are designed to reject the effect of linearization error caused by linearization of the nonlinear system. And neural network infer approximate controller gains from combination of local linear control gains. The proposed control methods can be used to control nonlinear systems and it has robust characteristic against system parameter variations and external disturbances.

• Journal of Convergence for Information Technology
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• v.10 no.11
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• pp.9-15
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• 2020

Wireless sensor nodes adopting the advanced preamble detection function, Message-In-Mesage (MIM), maximize the concurrent transmission opportunities due to the capture effect, result in improving the system performance significantly compared to the legacy IEEE 802.15.4 based sensor devices. In this paper, we propose an MIM capture probability model to analyze the performance gains by applying the MIM function to the wireless sensor nodes. We implemented the IEEE 802.15.4 and MIM by Python and performed extensive simulations to verify the performance gains through MIM capture effects. The evaluation results show that the MIM sensors achieve 34% system throughput gains and 31% transmission delay gains over the legacy IEEE 802.15.4-based sensors, which confirm that it was consistent with the analysis result of the proposed MIM capture probability model.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.6
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• pp.628-636
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• 2014

This paper describes the design and analysis of five-element planar array antenna of an anti-jamming satellite navigation system. We propose a design of multi-layer patch antenna for Global Positioning System(GPS) $L_1/L_2$ dual bands. The proposed antenna has two ports feeding network with a hybrid chip coupler for a broad bandwidth with Right-Handed Circular Polarization(RHCP). The measurement results show the bore-sight gains of 1.10 dBic($L_1$) and 0.37 dBic($L_2$) for the center element. The bore-sight gains of an edge element are 0.99 dBic($L_1$) and -0.57 dBic($L_2$). At a fixed elevation angle of $30^{\circ}$, antennas show average gains of -2.08 dBic ($L_1$) and -5.33 dBic($L_2$) for the center element, and average gains of -0.40 dBic($L_1$) and -2.09 dBic($L_2$) for the edge elements. The results demonstrate that the proposed array antenna is suitable for anti-jamming applications.

• International Journal of Computer Science & Network Security
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• v.22 no.12
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• pp.212-216
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• 2022

Space based constellation network is a kind of ad hoc network in which users are self-organized without center node. In space based constellation network, users are allowed to enter or leave the network at any given time. Thus, the number of active users is an unknown and time-varying parameter, and the performance of the network depends on how accurately this parameter is estimated. The so-called problem of active user identification, which consists of determining the number and identities of users transmitting in space based constellation network is discussed and a novel active user identification method is proposed in this paper. Active user identification code generated by transmitter address code and receiver address code is used to spread spectrum. Subspace-based method is used to process received signal and judgment model is established to identify active users according to the processing results. The proposed method is simulated under AWGN channel, Rician channel and Rayleigh channel respectively. Numerical results indicate that the proposed method obtains at least 1.16dB E_b/N₀ gains compared with reference methods when miss alarm rate reaches 10^-3.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.12 no.9
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• pp.4205-4227
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• 2018

Network Coding (NC) is an approach recently investigated for increasing the network throughput and thus enhancing the performance of wireless mesh networks. The benefits of NC can further be improved when routing decisions are made with the awareness of coding capabilities and opportunities. Typically, the goal of such routing is to find and exploit routes with new coding opportunities and thus further increase the network throughput. As shown in this paper, in case of proactive routing the coding awareness along with the information of the measured traffic coding success can also be efficiently used to support the congestion avoidance and enable more encoded packets, thus indirectly further increasing the network throughput. To this end, a new proactive routing procedure called Congestion-Avoidance Network Coding-Aware Routing (CANCAR) is proposed. It detects the currently most highly-loaded node and prevents it from saturation by diverting some of the least coded traffic flows to alternative routes, thus achieving even higher coding gain by the remaining well-coded traffic flows on the node. The simulation results confirm that the proposed proactive routing procedure combined with the well-known COPE NC avoids network congestion and provides higher coding gains, thus achieving significantly higher throughput and enabling higher traffic loads both in a representative regular network topology as well as in two synthetically generated random network topologies.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.6 no.10
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• pp.2548-2566
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• 2012

This paper derives two main end-to-end performance metrics, namely the spatial capacity density and the average end-to-end delay of the multi-hop wireless ad hoc networks with multi-antenna communications. Based on the closed-form expressions of these performance metrics, three hopping strategies, i.e., the closest neighbor, the furthest neighbor and the randomly selected neighbor hopping strategies have been investigated. This formulation provides insights into the relations among node density, diversity gains, number of hops and some other network design parameters which jointly determine network performances, and a method of choosing the best hopping strategy which can be formulated from a network design perspective.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2005.11a
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• pp.375-380
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• 2005

In this paper, We studied an antenna for the wireless home network service. From the structural modification of patch and ground plane, we made a reverse heart shape radiated pattern of antenna which is suited to wireless home network service. As a result, bandwidth between maximum gains is 110 degree, and the difference of downward direction gain from maximum gain have become -3.6dB. Installing the antenna on the ceiling, horizontal plane of the inner home will be formed the uniform electromagnetic environment. Accordingly, stable reception level acquisition and outdoor radiated suppression could be possible.

• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.119.3-119
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• 2001

When building a network-based real-time control system, a network-induced delay time should be surly considered for real time schedulability to be guaranteed. The network delay time on end-to-end communication has been analyzed theoretically and modeled mathematically from many previous works. There also exist any other delay element not considered before. In this paper, the remote feedback control system using the CAN protocol is proposed to control three axes´ manipulator arm and the application layer of CAN is modeled to analyze the delay elements defined by three types of time delay: Software delay time, Controller delay time, and Access delay time, in details. The analyzed results are used as an important component to determine PID gains of the proposed system. The effect of the delay time on the control performance is evaluated by com paring the response characteristics of the control system through simulation.