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Modified RLS Algorithm and Its Application to Channel Estimation for CDMA Systems
CHOI, Jihoon,JUNG, Young-Ho The Institute of Electronics, Information and Comm 2010 IEICE TRANSACTIONS ON COMMUNICATIONS - Vol.93 No.5
<P>A new adaptive algorithm is proposed by introducing some modifications to the recursive least squares (RLS) algorithm. Except for the noise variance, the proposed algorithm does not require any statistics or knowledge of the desired signal, thus, it is suitable for adaptive filtering for channel estimation in code division multiple access (CDMA) systems in cases where the standard RLS approach cannot be used. A theoretical analysis demonstrates the convergence of the proposed algorithm, and simulation results for CDMA channel estimation show that the proposed algorithm outperforms existing channel estimation schemes.</P>
Wireless Powered Information Transfer Based on Zero-Forcing for Multiuser MIMO Systems
Choi, Jihoon,Song, Choonggeun,Joung, Jingon IEEE 2018 IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY Vol.67 No.9
<P>A zero-forcing (ZF)-based transmission method is proposed for a wireless powered communication network (WPCN) with multiuser multi-input multi-output (MU-MIMO) channels. We formulate the max–min user rate optimization problem based on ZF-based uplink transmission, under the transmit power constraints determined by the downlink power transfer, and derive a Newton-like iterative algorithm to find the optimal solution of the proposed problem. Using the proposed ZF-based method, we design a downlink energy beamformer, and optimize the uplink power allocation vector, precoder, and combiner in terms of the max–min user rate for a MU-MIMO WPCN system. Numerical simulations show that the proposed method provides at least 3 dB signal-to-noise ratio gain compared to the conventional transmission schemes for WPCN. Moreover, through complexity analysis and simulations, it is shown that the proposed method can reduce at least 92% of the computation load in terms of runtime with moderate achievable rate loss, compared to the optimal method obtained by the interior-point method.</P>
Thickness and Refractive Index Measurements by Full-Field Optical Coherence Microscopy
Jihoon Na,Choi, W.J.,Hae Young Choi,Seon Young Ryu,Eun Seo Choi,Byeong Ha Lee IEEE 2009 IEEE SENSORS JOURNAL Vol.9 No.12
<P>We present the noble sensing method that can simultaneously measure the physical thickness and the refractive index of a transparent specimen based on full-field optical coherence microscopy. As a sample, a small drop of epoxy was placed on a flat glass plate and high-resolution depth resolved en-face images were taken. With adopting the reference plane from a cross-sectional image, the physical thickness, and the refractive index distribution could be obtained.</P>
FTTP: A Fast Tree Traversal Protocol for Efficient Tag Identification in RFID Networks
Jihoon Choi,Inkyu Lee,Ding-Zhu Du,Wonjun Lee IEEE 2010 IEEE communications letters Vol.14 No.8
<P>This letter presents an efficient tag collision arbitration protocol, viz., the Fast Tree Traversal Protocol (FTTP). It estimates the number of tags using maximum likelihood estimation and adjusts the splitting factor to reduce the identification delay. We show that our protocol effectively reduces the identification delay via the performance analysis and simulation results.</P>
Choi, Jihoon,Lee, Bobin,Yu, Chan-Mo Royal Society of Chemistry 2011 Chemical communications Vol.47 No.13
<P>An enantioselective synthesis of the homoallenyl alcohols was achieved from the reaction of chiral 2-borylbutadiene with aldehydes through an allylic transfer reaction in good yields and enantioselectivities.</P> <P>Graphic Abstract</P><P>An enantioselective synthesis of the homoallenyl alcohols was achieved from the reaction of chiral 2-borylbutadiene with aldehydes through an allylic transfer reaction in good yields and enantioselectivities. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c0cc05751g'> </P>
Low-Complexity Multiuser MIMO Precoder Design Under Per-Antenna Power Constraints
Choi, Jihoon,Han, Suyong,Joung, Jingon IEEE 2018 IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY Vol.67 No.9
<P>A new precoder design method is proposed for multi-input multioutput (MIMO) systems with per-antenna power constraints (PAPCs). In the proposed scheme, the optimal zero-forcing (ZF) based precoder maximizing the sum rate is evaluated for MIMO systems under the conventional sum power constraint (SPC), after which a new ZF-based precoder conforming to the PAPCs is designed by finding the linear precoder closest to the optimal ZF-based SPC precoder. Using the proposed design procedure, we derive an iterative algorithm based on the modified Newton's method to construct a PAPC precoder for a multiuser MIMO system. The complexity order of the proposed method is compared with those of the existing precoding schemes, and it is shown through numerical simulations that the proposed PAPC precoder achieves near-optimal performance while reducing the power consumption at macrocell base stations.</P>
THE m-STEP COMPETITION GRAPHS OF d-PARTIAL ORDERS
Jihoon Choi 충청수학회 2020 충청수학회지 Vol.33 No.1
The notion of m-step competition graph was introduced by Cho et al. in 2000 as an interesting variation of competition graph. In this paper, we study the m-step competition graphs of d-partial orders, which generalizes the results obtained by Park et al. in 2011 and Choi et al. in 2018.
Jihoon Kim,Joo Myung Lee,Seung-Hyuk Choi,Ki Hong Choi,Taek Kyu Park,Sung-Ji Park,Jeong Hoon Yang,Young Bin Song,Joo-Yong Hahn,Mi Ja Jang,Bon-Kwon Koo,Hyeon-Cheol Gwon 대한심장학회 2020 Korean Circulation Journal Vol.50 No.5
Background and Objectives: Although percutaneous coronary intervention (PCI) is recommended to improve symptoms in patients with stable ischemic heart disease (SIHD), improvement of exercise performance is controversial. This study aimed to investigate changes in exercise duration after PCI according to functional completeness of revascularization by comparing pre- and post-PCI exercise stress test (EST). Methods: Patients with SIHD were enrolled from a prospective PCI registry, and divided into 2 groups: 1) functional complete revascularization (CR) group had a positive EST before PCI and negative EST after PCI, 2) functional incomplete revascularization (IR) group had positive EST before and after PCI. Primary outcome was change in exercise duration after PCI and secondary outcome was major adverse cardiac events (MACE, a composite of any death, any myocardial infarction, and any ischemia-driven revascularization) at 3 years after PCI. Results: A total of 256 patients (149 for CR group, and 107 for IR group) were eligible for analysis. Before PCI, exercise duration was not significantly different between the functional CR and IR groups (median 540 [interquartile range; IQR, 414, 602] vs. 480 [402, 589] seconds, p=0.091). After PCI, however, the CR group had a significantly higher increment of exercise duration than the IR group (median 62.0 [IQR, 12.0, 141.0] vs. 30.0 [−11.0, 103.5] seconds, p=0.011). The functional CR group also had a significantly lower risk of 3-year MACE (6.2% vs. 26.1%; adjusted hazard ratio, 0.19; 95% confidence interval, 0.09–0.41; p<0.001). Conclusions: Functional CR showed a higher increment of exercise duration than functional IR.
On the Calculation of the Maximal MOT Throughput in T-DMB
Jihoon Choi,Donghwan Lee,Jieun Yu,Kyunghwi Kim,Wonjun Lee IEEE 2007 IEEE transactions on consumer electronics Vol.53 No.3
<P>Digital multimedia broadcasting (DMB) is one of burgeoning communication technologies, which can provide audio, video, and data services to mobile terminals using broadcasting infrastructures. Data services in terrestrial- digital multimedia broadcasting (T-DMB) inherently have the disadvantage of retransmitting a lot of data unnecessarily for reliability. This paper proposes a novel optimized transmission policy using segment size and repetition number variability, which maximizes the object- level throughput as well as improves reliability. The theoretical modeling and simulation results demonstrate that our policy provides a throughput gain over the conventional protocol.</P>