Hyuncheol Park

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

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Publications (101)52.67 Total impact

  • 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.
    IEEE Transactions on Vehicular Technology 03/2015; 64(3):1235-1243. DOI:10.1109/TVT.2014.2329477 · 2.64 Impact Factor
  • Hyuncheol Park, Dae-Soon Cho, Yeonggyu Shim
    IET Communications 09/2014; 8(14):2469-2475. DOI:10.1049/iet-com.2014.0253 · 0.72 Impact Factor
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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.
    IEEE Transactions on Wireless Communications 05/2014; 13(5):2741-2755. DOI:10.1109/TWC.2013.033114.131350 · 2.76 Impact Factor
  • 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.
    IEEE Communications Letters 05/2014; 18(5):721-724. DOI:10.1109/LCOMM.2014.022514.132755 · 1.46 Impact Factor
  • 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.
    IEEE Photonics Technology Letters 03/2014; 26(5):465-468. DOI:10.1109/LPT.2013.2296934 · 2.18 Impact Factor
  • 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.
    2014 IEEE International Wireless Symposium (IWS); 03/2014
  • IEEE Transactions on Vehicular Technology 01/2014; DOI:10.1109/TVT.2014.2338075 · 2.64 Impact Factor
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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.
    MILCOM 2013 - 2013 IEEE Military Communications Conference; 11/2013
  • 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.
    IEEE Transactions on Wireless Communications 11/2013; 12(11):5780-5787. DOI:10.1109/TWC.2013.093013.130107 · 2.76 Impact Factor
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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.
    2013 Asilomar Conference on Signals, Systems and Computers; 11/2013
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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.
    MILCOM 2013 - 2013 IEEE Military Communications Conference; 11/2013
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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.
    2013 Asilomar Conference on Signals, Systems and Computers; 11/2013
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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.
    2013 Asilomar Conference on Signals, Systems and Computers; 11/2013
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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.
    2013 51st Annual Allerton Conference on Communication, Control, and Computing (Allerton); 10/2013
  • Kwanghoon Kim, Hyuncheol Park, H.M. Kwon
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    ABSTRACT: Inter-carrier interference (ICI) and multiuser interference (MUI) occur in an uplink orthogonal frequency division multiple access system if a channel between a mobile user and a base station is rapidly time-varying. To reduce the ICI and MUI, this letter proposes a subcarrier allocation method. The key idea is to allocate a high-speed user's subcarrier near a low-speed user's one. Then, a wide Doppler spread of a high-speed user can be spilled over a low-speed user's subcarrier band with insignificant influence, and the signal-to-interference-plus-noise ratio (SINR) at each high-speed user's subcarrier can be maximized. This can provide a significant performance improvement of multiuser detection in an uplink-OFDMA.
    IEEE Transactions on Communications 01/2013; 61(1):7-12. DOI:10.1109/TCOMM.2012.100512.110011 · 1.98 Impact Factor
  • 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.
    ICT Convergence (ICTC), 2013 International Conference on; 01/2013
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    ABSTRACT: This paper proposes amplify-and-forward (AF) relay matrices for a one-source-one-destination pair and cooperative distributed N relay nodes under three adverse wireless relay communication environments: (1) broadband noise jamming (BNJ), (2) node geometry (NG), and (3) channel uncertainty (CU). The main objective of this paper is to analytically derive the minimum mean square error (MMSE)-based optimal relay amplifying matrix. Another objective of this paper is to analyze the MMSE cost function, relay power usage, and signal component power of the received signal at the destination using the derived optimal relay amplifying matrix. Finally, the impacts on these three wireless communication environments for the wireless relay networks will be observed by presenting bit error rate (BER) performance.
    Vehicular Technology Conference (VTC Spring), 2013 IEEE 77th; 01/2013
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    ABSTRACT: This paper presents both cooperative and noncooperative amplify-and-forward (AF) relay networks consisting of a one-source-one-destination pair and N-relays under receiver power constraint (RPC) at the destination. The optimal AF relay amplifying matrices for the relays by minimizing the mean square error are analytically derived. This paper also shows that the performance of the optimum cooperative relay network is identical to that of the optimum noncooperative network, as long as the same receiver power constraint is applied. The purpose of the RPC is to reduce the interference level for users located in neighboring cells. Finally, using the derived optimal relay amplifying matrices, the achievable rate, the pairwise error probability, and the outage probability are investigated.
    Vehicular Technology Conference (VTC Spring), 2013 IEEE 77th; 01/2013
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    ABSTRACT: An amplify-and-forward (AF) relay network has been studied extensively, but a closed form of an optimal AF relaying matrix is not available yet for the distributed AF relay network with the destination power constraint (DPC) and the following adverse environments: (a) partial-band noise jamming (PBNJ), (b) node geometry (NG), and (c) channel uncertainty (CU). Hence, this paper presents a closed form of an optimum AF relaying matrix consisting of a one-source-one-destination pair and N relay nodes under such adverse PBNJ, NG, CU, and DPC environments, based on the minimum mean square error (MMSE). By adopting the optimal relay amplifying matrix, the MMSE cost function behaviors are analytically and numerically studied.
    Vehicular Technology Conference (VTC Fall), 2013 IEEE 78th; 01/2013
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    ABSTRACT: This paper proposes a cooperative wireless relay network consisting of a one-source-one-destination node pair and N relay nodes in three wireless communication environments, i.e., jamming, node geometry, and channel uncertainty. The main objective of this paper is to analytically derive the optimal cooperative amplify-and-forward (AF) wireless relay matrix under three conditions with the relay power constraint based on the minimum mean square error (MMSE) criterion. Using the derived amplifying relay matrix, the MMSE cost function and achievable rate will be investigated numerically and analytically.
    Communications (ICC), 2013 IEEE International Conference on; 01/2013

Publication Stats

335 Citations
52.67 Total Impact Points

Institutions

  • 2009–2014
    • 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
  • 2004–2009
    • Daejeon University
      Daiden, Daejeon, South Korea