Hyuncheol Park

Korea Advanced Institute of Science and Technology, Sŏul, Seoul, South Korea

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Publications (105)50.12 Total impact

  • Gibum Kim · Jinwoo Kim · Hyuncheol Park

    No preview · Article · Jul 2015
  • Haelyong Kim · Gibum Kim · Wan Choi · Hyuncheol Park
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    ABSTRACT: Coordinated beamforming (CBF) provides improved sum rate with less overhead and computational complexity, and its theoretical performance analysis is mostly finished in a spatially uncorrelated environment. In this paper, we investigate the effect of spatial correlation on the sum rate of a two-cell multiuser downlink channel. We analyze the scaling laws of the sum rate with a large number of users. To improve the performance, different roles are assigned to the two cells: One is a master cell, and the other is a slave cell. The base station (BS) of the master cell requests the interference cancelation to the slave cell, and the BS of the slave cell performs precoding to cancel the interference influencing over the master cell, although the achievable rate of the slave cell is decreased. The decision of the master and slave cells can be affected by the number of users and the degree of spatial correlations. From computer-based simulations, we show that our proposed algorithm can achieve a higher sum rate than other previous approaches with lower overhead.
    No preview · Article · Mar 2015 · IEEE Transactions on Vehicular Technology
  • Cheolkyu Shin · Hyuncheol Park · H.M. Kwon
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    ABSTRACT: An aggregate medium access control (MAC) service data unit (A-MSDU) contains multiple subframes with a single sequence number. Hence, it has a major drawback in environments with high error rates because if any subframes are corrupted, then the entire A-MSDU will be lost. In addition, performance of the A-MSDU depends strongly on the choice of parameters, such as frame size, modulation level, coding rate, and spatial mode. In this paper, a novel link-adaptation mechanism, dubbed physical (PHY)-supported frame aggregation (PSFA), is proposed over IEEE 802.11 networks, and its performance is analyzed. The proposed PSFA technique is based on a cross-layer interaction that enables joint optimization of various parameters between the PHY and MAC layers. This paper derives a new packet error rate (PER) expression for convolutionally coded multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) systems as an example. Then, this PER expression is used to efficiently estimate the link quality, given the channel conditions and system parameters, and most importantly, it is able to facilitate a parametric study of the cross-layer interaction. In the proposed PSFA algorithm, we present a rule for selecting the parameters so that MAC throughput is maximized. It is shown analytically and verified using Monte Carlo simulations that this choice of parameters can improve throughput performance significantly and also ensure quality of service (QoS) requirements compared to existing conventional algorithms.
    No preview · Article · Oct 2014 · IEEE Transactions on Mobile Computing
  • Hyuncheol Park · Dae-Soon Cho · Yeonggyu Shim
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    ABSTRACT: This study proposes an optimal time allocation scheme for two-way relay channel (TWRC) using the physical-layer network coding (PNC). In other words, this study analytically determines the optimal transmit time durations for the first and the second time slot, which maximise the achievable sum rate under a sum time constraint for a given squared magnitude of the channel coefficients and transmit power values. Numerical results show that the achievable sum rate for the proposed optimal time allocation is greater than or equal to that for equal time allocation.
    No preview · Article · Sep 2014 · IET Communications
  • Girim Kwon · Yeonggyu Shim · Hyuncheol Park · Hyuck M. Kwon
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    ABSTRACT: Millimeter wave (mmWave) signals experience a significant path-loss in free space. To overcome this weakness, a large number of antennas are needed to obtain a high beamforming gain. Although a large number of antennas can be implemented in small area due to the short wavelength, the digital beamforming techniques cannot be implemented easily due to the high complexity of hardwares. To solve this problem, the hybrid beamforming systems which have smaller number of radio frequency (RF) chains are proposed in the literature. Although the hybrid beamforming systems may achieve the spectral efficiencies of the digital beamforming systems closely, the spectral efficiency cannot be monotonically increase along with the number of data streams due to the limited scattering in mmWave channel. In this paper, we provide a guide for the design of mmWave hybrid beamforming systems. We find the optimal number of streams, and present the spectral efficiency achievable region in which the system guarantees the reliable communications with the lowest cost.
    No preview · Conference Paper · Sep 2014
  • Yeonggyu Shim · Hyuncheol Park
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    ABSTRACT: In this paper, we propose the optimal time allocation for two-way relay using decode-and-forward (DF) multiple access broadcast (MABC) protocol. We analytically determine the optimal transmit time durations for the first and the second time slots, which maximize the achievable sum rate under a sum time constraint for a given squared magnitude of the channel coefficients and transmit power values. Numerical results show that the achievable sum rate of the optimal time allocation is greater than or equal to that of the equal time allocation.
    No preview · Article · May 2014 · IEEE Communications Letters
  • Kanghee Lee · Jie Yang · Hyuck M. Kwon · Hyuncheol Park · Yong H. Lee
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    ABSTRACT: This paper presents a closed form of an optimal cooperative amplify-and-forward (AF) relay amplifying matrix for a distributed relay network of M-source-M-destination pairs and N relays, called a cooperative distributed AF relay network. The objective of this paper is to derive closed forms of minimum mean square error (MMSE)-based and zero-forcing (ZF)-based optimal AF relay amplifying matrices for the cooperative distributed AF relay network under the transmitter power constraint (TPC) at the relays, the receiver power constraint (RPC) at the destinations, and the no-power constraint (NPC) condition. Additionally, by substituting the derived optimum AF relay amplifying matrices into the original cost functions (CFs), the behavior of the optimum CFs and the total optimum signal component power (SCP) at the destinations are compared to each other for different cases. Finally, using the MMSE criterion, a novel relay selection scheme is proposed for the cooperative distributed AF relay network.
    No preview · Article · May 2014 · IEEE Transactions on Wireless Communications
  • Gibum Kim · Jinwoo Kim · Hyungsik Han · Hyuncheol Park
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    ABSTRACT: In this paper, we describe a low complexity greedy user selection scheme for multiuser MIMO systems. We propose a new metric which has significantly reduced computational complexity and improved performance compared to Frobenius norm. The approximation of projection matrix is applied to reduce the number of singular value decomposition (SVD) operations. We analyze the computational complexity of metrics, and verify the reduced complexity by numerical evaluation. Our simulation result shows that the proposed metric can achieve the improved sum rate as the number of user antenna increases.
    No preview · Conference Paper · Mar 2014
  • Jinwoo Kim · Hyuncheol Park
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    ABSTRACT: For visible light communications (VLCs), dimming support is desirable to provide variable levels of lighting brightness. When error correction coding schemes are used for VLC systems, different code rates should be employed according to target dimming levels. In this letter, we propose a coding scheme, which can provide a wide range of brightness and a simple encoding/decoding structure for all different rates by using a rate-compatible punctured code. Puncturing patterns having the minimum bit error rate are provided by computer search. The results show that the VLC system with the proposed coding scheme can achieve optimum performances as well as a precise dimming support.
    No preview · Article · Mar 2014 · IEEE Photonics Technology Letters
  • Kanghee Lee · Jie Yang · Hyuck M. Kwon · Hyuncheol Park · Yong H. Lee
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    ABSTRACT: This paper considers a two-way amplify-and-forward (AF) multiple-input multiple-output (MIMO) relay network consisting of two sources (each with multiple antennas) and multiple physically dispersed single-antenna relays. A central station finds the optimum relay amplifying matrices and transmit/receive beamforming vectors explicitly and iteratively under the transmit power constraints at the sources and the relays. The minimum-mean-square-error criterion is used. Numerical results show that the proposed scheme outperforms the existing two-way AF MIMO network schemes proposed by Arti et al. and Wang et al.
    No preview · Article · Jan 2014 · IEEE Transactions on Vehicular Technology
  • Bongseop Song · Hyuncheol Park
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    ABSTRACT: In this paper, we introduce a bit-interleaved binary space-time code (B-STC) for a coded multiple-input multiple-output (MIMO) system to obtain an additional diversity gain over the full-rate spatial multiplexing (SM) transmission. By applying the B-STC scheme, codeword bits from each stream are transmitted effectively through N_t or (N_t - 1) layers in N_r x N_t MIMO systems. At the receiver, the iterative decoding is performed. The extrinsic information provided by the soft-in/soft-out (SISO) decoder is applied as an improved priori information after the B-STC decoding at the next iteration. Since a priori information can be extracted from multiple layers independently by the B-STC scheme, codeword bits have an improved diversity gain of (N_t - 1). In order to verify the proposed scheme, we derive the asymptotic bit error probability, which can be achieved after convergence of the iterative decoder. Because the proposed B-STC scheme is a binary code for coded MIMO systems, different types of channel codes and various space-time codes can be also concatenated.
    No preview · Article · Nov 2013 · IEEE Transactions on Wireless Communications
  • Kanghee Lee · Hyuck M. Kwon · Edwin M. Sawan · Hyuncheol Park
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    ABSTRACT: This paper investigates minimum mean square error (MMSE)-based amplify-and-forward (AF) relay amplifying matrices and source/destination beamforming vectors under perfectly known channel state information by imposing constraints on the transmit power of source and relays, separately and individually. The main contribution of this paper is the derivation of a set of relay amplifying matrices and source/destination beam-forming vectors under transmit power constraints on the source and relay. Additionally, the SNR and the MMSE cost function behaviors will be investigated numerically and analytically.
    No preview · Conference Paper · Nov 2013
  • Kanghee Lee · Hyuck M. Kwon · Jie Yang · Edwin M. Sawan · Hyuncheol Park
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    ABSTRACT: This paper proposes a two-way amplify-and-forward (AF) multiple-input multiple-output (MIMO) beamforming relay network for the benefit of determining a set of relay amplifying matrices and transmit/receive beamforming vectors by imposing constraints on the transmit power of the sources and relay based on the minimum mean square error (MMSE) criterion. It is proven that minimizing the mean square error (MSE) in the two-way AF MIMO beamforming relay system is equivalent to maximizing the signal-to-noise ratio (SNR). Additionally, various analysis, such as SNR and MMSE cost function, will be investigated. Finally, the iterative algorithm is proposed to solve the desired optimization problem.
    No preview · Conference Paper · Nov 2013
  • Kanghee Lee · Hyuck M. Kwon · Edwin M. Sawan · Hyuncheol Park
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    ABSTRACT: This paper proposes a two-way amplify-and-forward (AF) wireless relay network consisting of two sources with a single antenna and one relay with multiple antennas. The relay amplifying matrix under a power constraint at the relay is presented. The minimum mean square error (MMSE) criterion with self-interference cancelation is employed using vectorization and singular value decomposition (SVD) methods, while the MMSE and matched-filter (MF) criteria without self-interference cancelation are implemented. Using the derived optimal relay amplifying matrix, the average bit error rate (BER) and average mean square error (MSE) behaviors are evaluated.
    No preview · Conference Paper · Nov 2013
  • Kanghee Lee · Hyuck M. Kwon · Edwin M. Sawan · Hyuncheol Park
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    ABSTRACT: This paper presents an optimal relay amplifying matrix based on various schemes, such as zero-forcing (ZF) and minimum mean square error (MMSE), for a cooperative amplify-and-forward (AF) wireless relay network consisting of a one-source-one-destination pair with a single antenna and one relay with N antennas. The total relay transmission power constraint is employed. Even though different schemes and methods are applied to determine the optimal relay amplifying matrix, the identical one is derived. By adopting the derived optimal relay amplifying matrix, various analytical and numerical discussions, such as achievable rate (AR), are presented.
    No preview · Conference Paper · Nov 2013
  • Sangku Lee · Hyuck M. Kwon · Kanghee Lee · Hyuncheol Park
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    ABSTRACT: This paper studies amplify-and-forward (AF) multiple-input multiple-output (MIMO) beamforming relay networks based on the minimum mean square error (MMSE) criterion under various transmit power constraints. The primary contribution of this paper is the derivation of a set of optimal relay amplifying matrices and source-destination beamforming vectors under diverse conditions of transmit power constraints on the source and the relay for the AF MIMO wireless relay network. By comparing the bit error rate (BER) performance of each case, an efficient design of a half-duplex AF relay system is presented.
    No preview · Conference Paper · Nov 2013
  • Dae-Soon Cho · Il-Kyu Kim · Hyuncheol Park
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    ABSTRACT: Currently, the high speed data rate services for mobile group vehicles moving at high speed are acutely required. In ETRI (Electronics and Telecommunications Research Institute), we have been developing the Mobile Hotspot Network (MHN) system that can support over 1.2Gbps data rate services for mobile group vehicles moving at high speed over 400km/h, e.g., KTX, TGV, etc. In this paper, new frame structures and pilot patterns for FDD (Frequency Division Duplex) and TDD (Time Division Duplex) of MHN system are proposed. Furthermore, the physical downlink control channels are defined, and we show the structure of designed downlink control channels. We verified the performance of the downlink control channels by computer simulation. Currently, we are developing the test-bed of MHN system and having a target to demonstrate the real time performance of the MHN system on the outdoor environment in 2014. In this paper, we are focusing at the performance of MHN DL control channels. We also show the performance of these channels meet the required SNR.
    No preview · Conference Paper · Oct 2013
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    ABSTRACT: This paper studies relay amplifying matrices and transmitter/receiver beamforming vectors of the amplify-and-forward (AF) multiple-input multiple-output (MIMO) half-duplex (HD)/full-duplex (FD) wireless distributed relay systems. The main objective of this paper is to determine a set of relay amplifying matrices and transmitter/receiver beamforming vectors under transmit power constraints at the source and the relays, individually and independently, based on the minimum mean square error (MMSE) criterion. Additionally, the achievable rate and the MMSE cost function (CF) behaviors will be investigated numerically and analytically for both FD and HD distributed relaying systems. Finally, an iterative algorithm is proposed to solve the desired optimization problem.
    No preview · Conference Paper · Oct 2013
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    ABSTRACT: This paper addresses a more practical relay network consisting of a mobile source, multiple distributed mobile amplify-and-forward (AF) relays, and a mobile destination node. It considers an appropriate channel model between nodes, which is a cascaded Rayleigh fading channel. The objective of this paper is to determine an optimum AF relay vector (or matrix) using the minimum mean square error (MMSE) criteria for these distributed AF relay networks. The effects of jamming and imperfect channel state information (ICSI) on network performance are included in the analysis. Additionally, by substituting the derived amplifying relay vectors into the MMSE cost functions, it can be predicted which case will yield a better BER performance.
    No preview · Conference Paper · Sep 2013
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    ABSTRACT: This paper studies both cooperative and noncooperative amplify-and-forward (AF) wireless relay strategies with power constraints at the source and at the relays. The main objective is to design jointly and iteratively the closed form of a source scaling factor and a relay amplifying matrix, based on the minimum mean square error (MMSE) criterion under the conditions of both no- channel and channel phase misalignments. With the derived optimal source scaling factors and relay amplifying matrices, impacts on the system performance of both no-channel and channel phase misalignment are investigated by presenting the bit error rate and cost function behavior. Finally, this paper presents the iterative algorithm to solve the constrained Lagrangian optimization problem with a low computational complexity.
    No preview · Conference Paper · Sep 2013

Publication Stats

450 Citations
50.12 Total Impact Points

Institutions

  • 2009-2015
    • Korea Advanced Institute of Science and Technology
      • • Department of Electrical Engineering
      • • Department of Information and Communication Engineering
      Sŏul, Seoul, South Korea
  • 2005-2009
    • Information and Communications University
      Daiden, Daejeon, South Korea
  • 2004-2008
    • Daejeon University
      Daiden, Daejeon, South Korea