Daesik Hong

Yonsei University, Sŏul, Seoul, South Korea

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Publications (308)288.93 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Cognitive radio networks using relays have been introduced to enhance secondary network performance by having secondary users (SUs) transmit in two hops. This paper develops a framework for a random cognitive relay network (RCRN) where the primary, secondary, and relay nodes are randomly distributed according to Poisson point processes (PPPs) to investigate the effect of the random nature of the relays on secondary outage performance. We first derive the optimal relay location in terms of the outage probability of the secondary network. In addition, we provide the outage probability of the RCRN based on the optimal relay selection strategy that compares the instantaneous channel state information (CSI) of all relays. We then propose an efficient relay selection strategy that reduces the selection complexity and the feedback burden by limiting candidate relays to those located close to the optimal relay location. This paper sheds new light on the design of an efficient RCRN with respect to elements such as the effects of network parameters and the candidate relay set size on the RCRN outage probability.
    IEEE Transactions on Wireless Communications 03/2015; 14(3):1555-1566. DOI:10.1109/TWC.2014.2370036 · 2.76 Impact Factor
  • Dongkyu Kim, Haesoon Lee, Daesik Hong
    IEEE Communications Surveys &amp Tutorials 01/2015; DOI:10.1109/COMST.2015.2403614 · 6.49 Impact Factor
  • Hyungjong Kim, Hanho Wang, Daesik Hong
    10/2014; 3(5):285-297. DOI:10.5573/IEIESPC.2014.3.5.285
  • Youngju Kim, Hano Wang, Daesik Hong
    10/2014; 3(5):275-284. DOI:10.5573/IEIESPC.2014.3.5.275
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    ABSTRACT: This paper investigates the network capacity of bidirectional communication systems based on full-duplex transmission in ad hoc networks while satisfying both the delay and target outage constraints. Bidirectional full-duplex transmission (BFD) has been proposed as a way to increase the system performance of two-way communications with multiple antennas. This type of system enables simultaneous exchange of data between two nodes via the bidirectional use of spatial resources. As the node density is increased to improve network capacity, however, the network performance decreases because of the simultaneous transmissions of adjacent pairwise interferers. To overcome this capacity degradation, we apply an automatic repeat request (ARQ) protocol to two-way communications. We then extend the analysis of the transmission capacity (TC) to account for packet retransmissions within the maximum allowed delay while satisfying the target outage constraint for two extreme cases (high mobility and static). After determining the optimized maximum number of packet retransmissions, the network capacity of the BFD system is then investigated as a function of the effective node density, node mobility, and required delay and target outage constraints. We can conclude that the benefits for TC obtained through full-duplex transmission and packet retransmission by an ARQ protocol outweigh the increase in interference caused by the bidirectional use of spatial resources and packet retransmissions.
    IEEE Transactions on Vehicular Technology 09/2014; 63(7):3167-3183. DOI:10.1109/TVT.2014.2302013 · 2.64 Impact Factor
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    ABSTRACT: A filter-bank multicarrier - quadrature amplitude modulation (FBMC-QAM) system with two prototype filters for transmitting QAM signal is proposed. The proposed transmitter performs separate filtering for the even-numbered sub-carrier symbols and the odd-numbered sub-carrier symbols. We derive the orthogonality conditions for a FBMC-QAM system without the intrinsic interference. In order to satisfy the suggested orthogonality conditions, we perform a kind of block interleaving for the odd-numbered sub-carrier filtering. The receiver structure is the counterpart to the transmitter. Numerical results showed that the proposed FBMC-QAM system has almost the same bit error rate (BER) performance compared to the FBMC-OQAM and the orthogonal frequency division multiplexing (OFDM) system. with the proposed FBMC-QAM, multiple-input multiple-output transmission schemes and channel estimation schemes can be utilized similarly as in OFDM.
    ICC 2014 - 2014 IEEE International Conference on Communications; 06/2014
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    ABSTRACT: In this paper, we consider a full-duplex amplify-and-forward (AF) relaying with guaranteeing quality of service (QoS). In order to evaluate the QoS guaranteeing ability of FDR, we derive the effective capacity with considering residual self-interference. Based on the analysis and numerical results, it is verified that the stringent QoS constraint degrades effective capacity performance of full-duplex relay (FDR) more severely than that of half-duplex relay. The simulation results also show that the better link quality at S-R link is required in order to guarantee QoS constraint at FDR.
    2014 International Symposium on Consumer Electronics (ICSE); 06/2014
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    ABSTRACT: We consider an energy-harvesting cognitive radio system where the secondary transmitter harvests energy. This system operates under an energy causality constraint mandating that the average energy consumption must not exceed the average harvested energy, and a collision constraint mandating the protection of the primary system. The purpose of this paper is to identify the optimal pairing of the sensing duration and the energy detector's sensing threshold in order to maximize the average throughput of the secondary network. Since the sensing duration and sensing threshold are intertwined with the energy causality constraint, they need to be redesigned with the purpose of conserving energy in mind. Hence, the sensing duration must be shorter while still satisfying the collision constraint. The numerical results show that the optimal sensing duration is determined based on which constraint, collision or energy causality, needs to have priority. In addition, the simulation results show a pairing of the optimal sensing duration and sensing threshold provided by the coordination between the two constraints, which gives insight into how to design them.
    IEEE Transactions on Wireless Communications 05/2014; 13(5):2601-2613. DOI:10.1109/TWC.2014.032514.130637 · 2.76 Impact Factor
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    ABSTRACT: In cognitive radio, spectrum sensing is used to find the white spectrum or protect the primary user from interference caused by the secondary user (SU). There are two conventional spectrum sensing approaches: quiet and active. However, these conventional approaches have several problems. In quiet sensing, the quiet period degrades the SU capacity. With active sensing, the SU capacity is also degraded by the need for additional resource consumption and the mismatch in feedback information. In order to mitigate these problems, the structure of simultaneous PU sensing and data transmission is introduced. This structure is equipped with antenna isolation and self-interference cancellation in which the communication and the sensing radios are already assumed to be significantly isolated. This approach is designed so that the SU transmitter can sense PU signals and transmit data signals at the same time by dividing its spatial resources. Expanding on this work, we propose a concept of "TranSensing" which adaptively uses spatial resource according to the surrounding environments. To effectively use TranSensing, we propose a two-stage algorithm (TSA). Finally, the impact of residual interference on TranSensing is investigated. Simulation results show that TranSensing with TSA enhances the SU capacity over the conventional quiet or active sensing.
    IEEE Transactions on Wireless Communications 04/2014; 13(4):1948-1959. DOI:10.1109/TWC.2014.030614.130532 · 2.76 Impact Factor
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    ABSTRACT: In this paper, we propose a load balancing and a dynamic overlay clustering procedures including the fusion procedure. The proposed load balancing gets some loss for the throughput of the overall system but it improves the throughput of the cell-edge users. Through the simulations, we verify that the load and the number of users of the proposed system are changed uniformly. In addition, we demonstrate that the proposed system can improve the quality of service for cell-edge users while guaranteeing user fairness.
    2014 International Conference on Information Networking (ICOIN); 02/2014
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    ABSTRACT: This paper investigates the effect of the transmit power fluctuation of the primary user on the ergodic capacity of the secondary user in a spectrum sharing environment. Considering an average received-power constraint at the primary user receiver, we derive the closed-form expression for the ergodic capacity of the secondary user and the average received-power assuming Rayleigh fading channels. Numerical results show that the transmit power fluctuation can enhance the ergodic capacity of the secondary user if the secondary user properly control its transmit power so as to fully exploit the transmit power fluctuation.
    2014 International Conference on Computing, Networking and Communications (ICNC); 02/2014
  • Sungsoo Park, Daesik Hong
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    ABSTRACT: We consider energy harvesting cognitive radio networks to improve both energy efficiency and spectral efficiency. The goal of this paper is to analyze the theoretically achievable throughput of the secondary transmitter, which harvests energy from ambient sources or wireless power transfer systems while opportunistically accessing the spectrum licensed to the primary network. By modeling the temporal correlation of the primary traffic according to a time-homogeneous discrete Markov process, we derive the upper bound on the achievable throughput as a function of the energy arrival rate, the temporal correlation of the primary traffic, and the detection threshold for a spectrum sensor. The optimal detection threshold is then derived to maximize the upper bound on the achievable throughput under an energy causality constraint and a collision constraint. The energy causality constraint mandates that the total consumed energy should not exceed the total harvested energy, while the collision constraint is required to protect the primary network from secondary transmission. Analytical results show the temporal correlation of the primary traffic to enable efficient usage of the harvested energy by preventing the secondary transmitter from accessing the spectrum that may be occupied by the primary network.
    IEEE Transactions on Wireless Communications 02/2014; 13(2):1010-1022. DOI:10.1109/TWC.2013.121713.130820 · 2.76 Impact Factor
  • Sungsoo Park, Daesik Hong
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    ABSTRACT: We consider energy harvesting cognitive radio networks in which a secondary transmitter harvests energy from ambient sources or wireless power transfer systems while opportunistically accessing the spectrum licensed to the primary network. The primary traffic is modeled as a time-homogeneous discrete Markov process, and the secondary transmitter may not be able to operate continuously due to sporadic and unstable energy sources. At the beginning of each time slot, the secondary transmitter thus needs to determine whether to remain idle so as to conserve energy, or to execute spectrum sensing to acquire knowledge of the current spectrum occupancy state. It also needs to configure the spectrum sensor detection threshold to achieve an effective tradeoff between false alarms and misdetections. This sequential decision-making, done to maximize the expected total throughput, requires the joint design of a spectrum sensing policy and a detection threshold under the energy causality and collision constraints. We formulate this stochastic optimization problem as a constrained partially observable Markov decision process (POMDP), and then convert it to a computationally tractable unconstrained POMDP. Numerical results show that the proposed approach enables efficient usage of the harvested energy by exploiting the temporal correlation of the primary traffic.
    IEEE Transactions on Wireless Communications 12/2013; 12(12):6166-6179. DOI:10.1109/TWC.2013.103113.130018 · 2.76 Impact Factor
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    ABSTRACT: This paper investigates an attempt to improve reliability in two-way communication through the bi-directional use of spatial resources when time selectivity exists and instantaneous channel information is not available at the transmitter. The system, which uses spatial resources bi-directionally and employs beamforming, is called a 'bi-directional beamforming (BBF)' system. The use of full bandwidth and the reciprocity between time and frequency allow the BBF system to reduce the symbol duration. Focusing on this reduction in symbol duration, we propose a transmit antenna-switched receive diversity for BBF (TAS-BBF) scheme designed to improve reliability in time selective environments. The resulting TAS-BBF scheme with N antennas can achieve diversity order of 2(N-1) in fast fading environments without channel state information at the transmitter, whereas conventional schemes are only able to achieve a diversity order of N in this environment.
    2013 Asilomar Conference on Signals, Systems and Computers; 11/2013
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    ABSTRACT: Bidirectional communication systems based on full-duplex transmission have been proposed as a way to increase the ergodic capacity of multiantenna two-way networks. This type of system enables simultaneous exchange of data between two nodes via bidirectional use of spatial resources. However, when channel estimation error is present, each node experiences both desired-channel interference (DI) and echo-channel interference (EI). This paper investigates the effect of channel estimation errors on the ergodic capacities for bidirectional full-duplex transmission (BFD) using one of two combining schemes: maximal-ratio combining (MRC) or optimum combining (OC). We derive the ergodic capacities as closed-form expressions and quantify the effect of channel estimation errors on ergodic capacities for BFD with MRC (BFD-MRC) or OC (BFD-OC). Numerical results demonstrate that full-duplex transmission in two-way networks is an attractive option when channel estimation error is present.
    IEEE Transactions on Vehicular Technology 11/2013; 62(9):4666-4672. DOI:10.1109/TVT.2013.2265407 · 2.64 Impact Factor
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    ABSTRACT: In this paper, we propose a non-orthogonal multiple access-based multiuser beamforming (NOMA-BF) system designed to enhance the sum capacity. In the proposed NOMA-BF system, a single BF vector is shared by two users, so that the number of supportable users can be increased. However, sharing a BF vector leads to interference from other beams as well as from the other user sharing the BF vector. Therefore, to reduce interference and improve the sum capacity, we additionally propose a clustering and power allocation algorithm. This clustering algorithm, which selects two users with high correlation and a large gain-difference between their channels, can reduce the interference from other beams and from the other user as well. Furthermore, power allocation ensures that each user's transmit power is allocated so as to maximize the sum capacity. Numerical results verify that the proposed NOMA-BF system improves the sum capacity, compared to the conventional multiuser BF system.
    MILCOM 2013 - 2013 IEEE Military Communications Conference; 11/2013
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    ABSTRACT: In this paper, we propose an optimal tone space selection scheme for orthogonal frequency division multiple access with variable tone spaces (OFDMA-VTS) in carrier aggregation based on user-specific channels. We begin by analyzing inter-symbol interference (ISI) and inter-carrier interference (ICI) in non-contiguous carrier aggregation, which differ according to the delay and Doppler spreads associated with each user, as well as the tone space that each user utilizes. Based on that, we propose an optimal tone space selection scheme as a way to minimize both ISI and ICI. We also derive an upper bound on OFDMA-VTS capacity when it is applied to the proposed scheme. Furthermore, we investigate the effect of inter-user interference (IUI) in contiguous carrier aggregation and show that the proposed scheme can be applied to OFDMA-VTS in contiguous carrier aggregation as a suboptimal solution. Numerical results demonstrate that the proposed scheme maximizes OFDMA-VTS capacity by minimizing the total ISI and ICI interference, thereby enhancing the system capacity over what is possible with conventional OFDMA.
    IEEE Transactions on Wireless Communications 11/2013; 12(11):5679-5691. DOI:10.1109/TWC.2013.092513.121999 · 2.76 Impact Factor
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    ABSTRACT: This paper investigates a dynamic spectrum access (DSA) scheme for low power wireless sensor networks (WSN) in an open spectrum where multiple systems coexist and interfere with each other. Low transmission power and a simple communication protocol are significant obstacles to the operation of low power WSN in the open spectrum. As a result, available spectrum is more scarce for a low power WSN than for the other coexisting systems. To address this, we are proposing a new DSA scheme with an energy efficient channel switching criterion that can improve the expected throughput by chasing the low interference channel. OPNET-based system level simulation results, designed under the framework of ZigBee and IEEE 802.15.4, demonstrates that the proposed DSA scheme shows improved energy efficiency and throughput compared to conventional ZigBee systems.
    Proceedings of the 8th International Conference on Body Area Networks; 09/2013
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    ABSTRACT: There are two important factors for the nodes of Wireless Body Area Network (WBAN): the lasting lifetime and the low loss of significant biometric data. Therefore, the stabilities of both the data queue and the energy queue are an important point on the WBAN nodes. In this paper, Minimum Distance Adaptive Allocation (MDAA) is proposed which is an adaptive queue management scheme to maintain the stabilities of both the data queue and the energy queue. MDAA adjusts the time ratio between energy harvesting and data transmission to minimize the Euclidean distance between the next state and the ideal state. The performance of the proposed scheme is evaluated and takes positive assessments rather than that of the control group.
    Proceedings of the 8th International Conference on Body Area Networks; 09/2013
  • Gosan Noh, Sungmook Lim, Daesik Hong
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    ABSTRACT: This letter presents an exact closed-form expression for the ergodic capacity of the secondary user in a spectrum sharing environment under an average received-power constraint, considering the effect of the interference from the primary user. Using capacity maximizing water-filling power allocation, we provide the closed-form expressions for the ergodic capacity and the average received-power assuming Rayleigh fading channels. Numerical results show that the primary user interference significantly affects the ergodic capacity of the secondary user. The obtained formulas can be used when predicting whether spectrum sharing is beneficial in a practical channel environment.
    IEEE Communications Letters 05/2013; 17(5):884-887. DOI:10.1109/LCOMM.2013.040913.122827 · 1.46 Impact Factor

Publication Stats

3k Citations
288.93 Total Impact Points

Institutions

  • 1995–2014
    • Yonsei University
      • Department of Electrical and Electronic Engineering
      Sŏul, Seoul, South Korea
  • 2011
    • University of Texas at Austin
      • Department of Electrical & Computer Engineering
      Austin, Texas, United States
    • Princeton University
      • Department of Electrical Engineering
      Princeton, New Jersey, United States
  • 2007
    • Myongji University
      • Department of Information and Communication Engineering
      Sŏul, Seoul, South Korea
  • 2004
    • Samsung Advanced Institute of Technology
      Usan-ri, Gyeonggi Province, South Korea
  • 2002
    • Oklahoma State University - Stillwater
      Stillwater, Oklahoma, United States
    • Tsinghua University
      Peping, Beijing, China
    • Huazhong University of Science and Technology
      Wu-han-shih, Hubei, China
  • 2000–2001
    • The Seoul Institute
      Sŏul, Seoul, South Korea
  • 1998
    • Dongguk University
      • Division of Electronics and Electrical Engineering
      Seoul, Seoul, South Korea