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RF Lens-Embedded Massive MIMO Systems: Fabrication Issues and Codebook Design
Kwon, Taehoon,Lim, Yeon-Geun,Min, Byung-Wook,Chae, Chan-Byoung IEEE 2016 IEEE transactions on microwave theory and techniqu Vol.64 No.7
<P>In this paper, we investigate a radio frequency (RF) lens-embedded massive multiple-input multiple-output (MIMO) system and evaluate the system performance of limited feedback by utilizing a technique for generating a suitable codebook for the system. We fabricate an RF lens that operates on a 77-GHz (millimeter-wave) band. Experimental results show a proper value of amplitude gain and an appropriate focusing property. In addition, using a simple numerical technique-beam propagation method-we estimate the power profile of the RF lens and verify its accordance with experimental results. We also design a codebook-multivariance codebook quantization-for limited feedback by considering the characteristics of the RF lens antenna for massive MIMO systems. Numerical results confirm that the proposed system shows significant performance enhancement over a conventional massive MIMO system without an RF lens.</P>
Optimal Duplex Selection for Decode and Forward Relay Systems with Power Allocation
( Taehoon Kwon ),( Sungmook Lim ) 한국인터넷정보학회 2016 KSII Transactions on Internet and Information Syst Vol.10 No.12
In decode and forward relay systems, choosing the duplex mode is an important factor to the performance. To satisfy the performance requirement, self-interference must be mitigated for the full-duplex relay (FDR), and the resource efficiency must be increased for the half-duplex ratio (HDR). Therefore, if a wise scheme to consider these two factors exists, decode and forward relay systems are used more effectively. This study proposes a new duplex selection scheme for decode and forward relay systems. The proposed duplex selection scheme chooses the better duplex mode according to the channel statistical conditions with optimal power allocation. The simulation results show that the proposed duplex scheme with optimal power allocation has lower outage probability than the FDR and the HDR.
Optimal Duplex Mode for DF Relay in Terms of the Outage Probability
Taehoon Kwon,Sungmook Lim,Sooyong Choi,Daesik Hong IEEE 2010 IEEE Transactions on Vehicular Technology VT Vol.59 No.7
<P>This paper deals with a full-duplex relay (FDR) system over Rayleigh fading channels. The exact outage probability of FDR is derived as a closed form to consider interferences from full duplex. Then, we obtain the conditions of the signal-to-noise ratio (SNR) and the signal to interface ratios (SIRs) for cases of FDR showing a lower outage probability than that of the half-duplex relay (HDR) system under the target outage probability. According to this condition, FDR is superior to HDR with lower SIRs in the low-SNR region rather than in the high-SNR region. In addition, the target outage probability is only satisfied when the SNR and SIRs are within the boundaries. These boundaries vary due to the target rate, the channel states of each link, and the target outage probability.</P>
Kwon, Taehoon,Cho, Hyeongrae,Lee, Jang-Woo,Henkensmeier, Dirk,Kang, Youngjong,Koo, Chong Min American Chemical Society 2017 ACS APPLIED MATERIALS & INTERFACES Vol.9 No.34
<P>Ionic polymer composite membranes based on sulfonated poly(arylene ether sulfone) (SPAES) and copper(II) phthalocyanine tetrasulfonic acid (CuPCSA) are assembled into bending ionic polymer actuators. CuPCSA is an organic filler with very high sulfonation degree (IEC = 4.5 mmol H+/g) that can be homogeneously dispersed on the molecular scale into the SPAES membrane, probably due to its good dispersibility in SPAES-containing solutions. SPAES/CuPCSA actuators exhibit larger ion conductivity (102 mS cm(-1)), tensile modulus (208 MPa), strength (101 MPa), and strain (1.21%), exceptionally faster response to electrical stimuli, and larger mechanical power density (3028 W m(-3)) than ever reported for ion-conducting polymer actuators. This outstanding actuation performance of SPAES/CuPCSA composite membrane actuators makes them attractive for next-generation transducers with high power density, which are currently developed, e.g., for underwater propulsion and endoscopic surgery.</P>
Taehoon Kwon,Sungmook Lim,Woohyun Seo,Daesik Hong IEEE 2010 IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS Vol.9 No.2
<P>Error propagation in the source-relay link limits the performance of demodulation-forward (MF) relay systems. In order to solve this problem and efficiently exploit the relay, we propose log likelihood ratio (LLR)-based symbol selective transmission with a near-optimum threshold to minimize the bit error probability (BEP). In the proposed scheme, the source information is forwarded by the relay only if it is likely to be detected correctly, as determined by a comparison of the LLR with the near-optimum threshold. To derive the near-optimum threshold, the BEP of the proposed scheme is analyzed in the case of binary phase shift keying (BPSK) signals. Simulation results confirm the accuracy of the analysis and prove that the proposed scheme efficiently mitigates error propagation.</P>
Optimal Duplex Selection for Decode and Forward Relay Systems with Power Allocation
Kwon, Taehoon,Lim, Sungmook Korean Society for Internet Information 2016 KSII Transactions on Internet and Information Syst Vol.10 No.12
In decode and forward relay systems, choosing the duplex mode is an important factor to the performance. To satisfy the performance requirement, self-interference must be mitigated for the full-duplex relay (FDR), and the resource efficiency must be increased for the half-duplex ratio (HDR). Therefore, if a wise scheme to consider these two factors exists, decode and forward relay systems are used more effectively. This study proposes a new duplex selection scheme for decode and forward relay systems. The proposed duplex selection scheme chooses the better duplex mode according to the channel statistical conditions with optimal power allocation. The simulation results show that the proposed duplex scheme with optimal power allocation has lower outage probability than the FDR and the HDR.
Bit Error Probability Performance Analysis of Full Duplex Relay System
Taehoon Kwon,Daesik Hong 대한전자공학회 2010 ICEIC:International Conference on Electronics, Inf Vol.1 No.1
This paper deals with a full duplex relay (FDR) system under Rayleigh fading channels. The bit error probability (BEP) performance of FDR is derived in order to consider interferences from full duplex. Then, we simplify BEP of FDR by approximation. Simulation results show that this approximation matches the exact BEP of FDR well.
Comparison of FDR and HDR Under Adaptive Modulation With Finite-Length Queues
Taehoon Kwon,Youngju Kim,Daesik Hong IEEE 2012 IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY Vol.61 No.2
<P>To identify the optimal duplex mode and maximize the offered gain in the relay system, we compare the performances of half-duplex relay (HDR) and full-duplex relay (FDR). Finite-state Markov chain (FSMC) models are presented, showing the joint effects of finite-length queues and adaptive modulation (AM) under uncorrelated Rayleigh fading channels. Transmission efficiency, packet loss rate, and delay are derived and compared based on these models. According to our results, FDR is superior to HDR in the low-signal-to-noise ratio (SNR) region but loses its advantage as the SNR increases. When the size of the queue is large enough, FDR can be superior to HDR, even in the high-SNR region.</P>
Three-Dimensional Reconstruction of a Cardiac Outline by Magnetocardiography
Ha, Taehoon,Kim, Kiwoong,Lim, Sanghyun,Yu, Kwon Kyu,Kwon, Hyukchan IEEE 2015 IEEE Transactions on Biomedical Engineering Vol.62 No.1
<P>A 3-D cardiac visualization is significantly helpful toward clinical applications of magnetocardiography (MCG), but the cardiac reconstruction requires a segmentation process using additional image modalities. This paper proposes a 3-D cardiac outline reconstruction method using only MCG measurement data without further imaging techniques. The cardiac outline was reconstructed by a combination of both spatial filtering and coherence mapping method. The strength of cardiac activities was first estimated by the array-gain constraint minimum-norm spatial filter with recursively updated gram matrix (AGMN-RUG). Then, waveforms were reconstructed at whole source grids, and the maximum source points of an atrium and ventricle were selected as a reference, respectively. Next, the coherence between each maximum source point and whole source points was compared by the coherence mapping method. A reconstructed cardiac outline was validated by comparing with an overlapped volume ratio when the reconstructed volume was identically matched with the original volume. The results obtained by the AGMN-RUG were compared to the results by other spatial filters. The accuracy of numerical simulation and phantom experiment by the AGMN-RUG was superior 10% and 8%, respectively, than the accuracy by the standardized low-resolution electromagnetic tomography. This accuracy demonstrated the efficacy of the proposed 3-D cardiac reconstruction method.</P>