• Journal of IKEEE
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• v.17 no.2
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• pp.129-134
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• 2013

For the conventional power metal-oxide semiconductor field-effect transistor (MOSFET) device structure, there exists a tradeoff relationship between specific on-resistance ($R_{ON.SP}$) and breakdown voltage ($V_{BR}$). In order to overcome the tradeoff relationship, a uniform super-junction (SJ) trench metal-oxide semiconductor field-effect transistor (TMOSFET) structure is studied and designed. The structure modeling considering doping concentrations is performed, and the distributions at breakdown voltages and the electric fields in a SJ TMOSFET are analyzed. The simulations are successfully optimized by the using of the SILVACO TCAD 2D device simulator, Atlas. In this paper, the specific on-resistance of the SJ TMOSFET is successfully obtained 0.96 $m{\Omega}{\cdot}cm^2$, which is of lesser value than the required one of 1.2 $m{\Omega}{\cdot}cm^2$ at the class of 100 V and 100 A for BLDC motor.

• Journal of the Korea Society of Computer and Information
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• v.20 no.11
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• pp.39-46
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• 2015

In this paper, we propose a performance-aware workload model for efficient implementation of control systems. When implementing a control algorithm as an embedded computer system, the control code executes periodically. For such systems, its control performance depends on not only the accuracy of the control algorithm itself but also temporal parameters such as control period and sensing to actuation delay. In this regard, this paper studies the relation between control period and delay by measuring and analyzing the control performance of LKAS (Lane Keeping Assist System) with varying period and delay combinations. Through this experimental study, this paper shows that the two timing parameters, i.e.,control period and delay, has a tradeoff relation in terms of control performance.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.1C
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• pp.1-8
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• 2009

Cooperative diversity is a novel technique to improve diversity gains, capacity gains, and energy saving. This technique involves multiple terminals sharing resources in order to build a virtual antenna array in a distributed fashion. In this paper, we propose a multi-user cooperative diversity protocol called Relay-assisted Multiple Access Channel(R-MAC) that allows multiple source terminals to transmit their signals simultaneously and the relay terminal forwards the aggregated signal received from the source terminals to the destination terminal. The proposed protocol converts the distributed antenna channels into an effective MIMO channel by exploiting a relay, increasing both diversity gain and system throughput. We investigate the performance of the proposed protocol in terms of outage probability and diversity-multiplexing tradeoff where we assume block fading channel environment. Our simulation results show that the proposed protocol outperforms direct transmission in the high spectral efficiency regime where the conventional cooperative diversity protocols cannot outperform direct transmission.

• ETRI Journal
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• v.44 no.1
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• pp.105-116
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• 2022

In this study, a novel group-indexed orthogonal frequency division multiplexing index modulation (OFDM-IM) scheme is proposed to achieve a tradeoff between spectral efficiency (SE) and bit-error-rate (BER) performance. In the proposed scheme, the total subcarriers in a group are divided into subgroups, and additional bits are transmitted by subgroup indexing, unlike the conventional OFDM-IM scheme, which uses index bits to select active subcarriers. With the proposed scheme, the additional degree of freedom provided by the number of active subgroups selected provides a tradeoff between spectral efficiency and BER performance. Decoding is performed in steps to reduce computional complexity in the decoder design. Simulaton results show that the number of active subgroups selected influences the proposed scheme's performance in terms of energy efficiency, spectral efficiency, and BER performance.

• The Journal of the Korea institute of electronic communication sciences
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• v.2 no.1
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• pp.19-24
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• 2007

Abstract. In the ubiquitous environment of the next generation, RFID is predicted to occupy an important technical location and also expected to apply to various fields. However, the properties of tags in itself which is the core of RFID have a dysfunction like an invasion of privacy for user. An existing cryptanalytic protection scheme of the information leakage have a difficult problem to apply to RFID tags for privacy protection. We applied Ohkubo et al.'s scheme to the protection of the tag's information efficiently in the RFID system environment using low-cost tags. But, this method has all informations of tagsto identify tag's ID and then performs the process of identification in sequence in the Back-end server. These processes have lots of computations so that it have problems about a scalability. In this paper, we are based on Ohkubo et al.'s scheme to solve problems, and then analyze the parallelism with the Hellman's tradeoff method, divide it into nodesin parallel. In this paper, we are based on Okubo et al.'s scheme to solve problems, and then analyze the parallelism with Hellman's tradeoff method, divide it into the ${\omega}$ node in parallel. as a result, we can reduce the computing complexity of key search to $O(\frac{m^{2/3}n^{2/3}}{\omega})$ seconds from O(mm) seconds. finally we show the results to be enhanced the scalability.

• Journal of Advanced Navigation Technology
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• v.12 no.5
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• pp.437-443
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• 2008

In this paper, we derive the optimum number of users which can maximize the information theoretic sum capacity in multiuser OFDM virtual MIMO uplink system. In which, there are multiple antennas at the base station and a number of users with single transmit antenna. Pilot-assisted channel state estimation is assumed for a block fading channel and time-varying fading channel. We analyze the tradeoff between the multiplexing gain and pilot overhead especially in low SNR regime and conclude that the optimum number of users is min ($N_r$,LT/2 ) in frequency nonselective block fading channel and approximately equal to min ($N_r$, ${\lfloor}{\sqrt{LT+1}}-1{\rfloor}$) in time varying fading channel. assuming the same pilot and signal pwoer.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.7
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• pp.109-114
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• 2013

Power MOSFET (metal-oxide semiconductor field-effect transistor) are widely used in power electronics applications, such as BLDC (Brushless Direct Current) motor and power module, etc. For the conventional power MOSFET device structure, there exists a tradeoff relationship between specific on-state resistance and breakdown voltage. In order to overcome the tradeoff relationship, a non-uniform super-junction (SJ) trench MOSFET (TMOSFET) structure for an optimal design is proposed in this paper. It is required that the specific on-resistance of non-uniform SJ TMOSFET is less than that of uniform SJ TMOSFET under the same breakdown voltage. The idea with a linearly graded doping profile is proposed to achieve a much better electric field distribution in the drift region. The structure modelling of a unit cell, the characteristic analyses for doping density, and potential distribution are simulated by using of the SILVACO TCAD 2D device simulator, Atlas. As a result, the non-uniform SJ TMOSFET shows the better performance than the uniform SJ TMOSFET in the specific on-resistance at the class of 100V.

• Journal of Communications and Networks
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• v.12 no.2
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• pp.103-113
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• 2010

In this paper, a tradeoff between the total energy consumption-per-bit and the end-to-end rate under spatial reuse in wireless multi-hop network is developed and analyzed. The end-to-end rate of the network is the number of information bits transmitted (end-to-end) per channel use by any node in the network that is forwarding the data. In order to increase the bandwidth efficiency, spatial reuse is considered whereby simultaneous relay transmissions are allowed provided there is a minimum separation between such transmitters. The total energy consumption-per-bit includes the energy transmitted and the energy consumed by the receiver to process (demodulate and decoder) the received signal. The total energy consumption-per-bit is normalized by the distance between a source-destination pair in order to be consistent with a direct (single-hop) communication network. Lower bounds on this energy-bandwidth tradeoff are analyzed using convex optimization methods. For a given location of relays, it is shown that the total energy consumption-per-bit is minimized by optimally selecting the end-to-end rate. It is also demonstrated that spatial reuse can improve the bandwidth efficiency for a given total energy consumption-per-bit. However, at the rate that minimizes the total energy consumption-per-bit, spatial reuse does not provide lower energy consumption-per-bit compared to the case without spatial reuse. This is because spatial reuse requires more receiver energy consumption at a given end-to-end rate. Such degraded energy efficiency can be compensated by varying the minimum separation of hops between simultaneous transmitters. In the case of equi-spaced relays, analytical results for the energy-bandwidth tradeoff are provided and it is shown that the minimum energy consumption-per-bit decreases linearly with the end-to-end distance.

• The KIPS Transactions:PartC
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• v.16C no.6
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• pp.791-800
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• 2009

Multicasting is fundamental to many ad hoc network applications requiring collaboration of multiple nodes in a group. A general approach is to construct an overlay tree and to deliver a multicast packet to multiple receivers over the tree. This paper proposes adaptive overlay trees (AOTs) on wireless ad hoc networks of static nodes for delay- and energy-efficient multicast. A tradeoff function is derived, and an algorithm for AOT construction is developed. Note here that the requirements of delay and energy consumption may vary with different classes of applications. By adjusting parameters in the tradeoff function, different AOTs can be adaptively chosen for different classes of applications. An AOT is constructed in O(ke) time where e is the number of wireless links in a network and k is the number of member nodes in a multicast group. The simulation study shows that AOT adaptively provides tradeoffs between the fastest multicast (which is the choice if delay is the most important factor) and the most energy efficient multicast (which is used when energy consumption is the primary concern). In other words, one of AOTs can be appropriately chosen in accordance with the operation requirement.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.6C
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• pp.842-847
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• 2004

We present a new video coding technique to tradeoff frame rate and picture quality for low bit rate video coding. We show a model equation for selecting the optimal frame rate from the motion content of the source video. We can determine DCT quantization parameter (QP) using the frame rate and bit rate. For objective video quality measurement we propose a simple and effective error measure for skipped frames. The proposed method enhances the video quality up to 2 ㏈ over the H.263 TMN5 encoder.