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Distributed Block Diagonalization with Selective Zero Forcing for Multicell MU-MIMO Systems
Yo-Seb Jeon,Young-Jin Kim,Moonsik Min,Gi-Hong Im IEEE 2014 IEEE signal processing letters Vol.21 No.5
<P>This letter proposes a distributed beamforming scheme based on block diagonalization (BD) for multicell multiuser multiple-input multiple-output (MU-MIMO) downlink systems. Although conventional BD can be directly extended to these systems in a distributed manner, it suffers from sum-rate degradation due to strict zero-forcing (ZF) constraints. To overcome this problem, we introduce a sum-rate maximization problem for BD, to find the optimal selection of ZF constraints. Then we propose a search algorithm to solve the problem in a distributed and heuristic manner. Simulation results show that the proposed scheme effectively finds a near-optimal solution and significantly improves simple extended BD such that it can provide higher sum rate than the conventional schemes.</P>
Time-Domain Differential Feedback for Massive MISO-OFDM Systems in Correlated Channels
Yo-Seb Jeon,Hyun-Myung Kim,Yong-Sang Cho,Gi-Hong Im IEEE 2016 IEEE TRANSACTIONS ON COMMUNICATIONS Vol.64 No.2
<P>Massive multiple-input multiple-output (MIMO) orthogonal frequency-division multiplexing (OFDM) is a promising technology for next-generation wireless communications. However, when channel state information (CSI) at the transmitter is obtained using channel feedback, the benefits of this system are severely limited by the tradeoff between downlink capacity and feedback overhead. To solve this problem, we propose a time-domain differential feedback scheme for massive multiple-input single-output (MISO) OFDM systems. The proposed scheme exploits channel correlations in time, frequency, and space domains simultaneously by considering differential channel impulse response (CIR). To simplify the codebook design, and to reduce codeword-search complexity, we partition and then quantize the differential CIR using a number of subcodebooks. Because the total feedback bits are shared by the subcodebooks, we further optimize the bit allocation for them to minimize the total quantization error. For this, we analyze the quantization error of the proposed scheme and then use the analysis results for the bit-allocation optimization. In simulations, the proposed scheme efficiently exploits all correlations and achieves significant spectral-efficiency gain compared to conventional feedback schemes.</P>
Yo Seb Han,Byung Ho Kim,Tae Hyung Kim,Seok Ho Dong,Hyo Jong Kim,Young Woon Chang,Joung Il Lee,Rin Chang,Youn Wha Kim,Joo Chul Park 대한내과학회 2000 The Korean Journal of Internal Medicine Vol.15 No.2
Myasthenia gravis is an autoimmune disease that results from an antibody- mediated reaction and occurs with thymoma in 15% of patients. It is very rarely associated with autoimmune hepatitis. Four cases of myasthenia gravis with autoimmune hepatitis have b
Large System Analysis of Two-Stage Beamforming With Limited Feedback in FDD Massive MIMO Systems
Jeon, Yo-Seb,Min, Moonsik IEEE 2018 IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY Vol.67 No.6
<P>Two-stage beamforming is a transmit strategy that uses two types of beamformers to reduce the feedback overhead of frequency-division-duplexing massive multiple-input multiple-output systems that are spatially correlated. In this paper, we present large system analysis of two-stage beamforming when a transmitter has limited channel information from feedback and when regularized-zero-forcing (RZF) is used as a second-stage beamformer. We consider two random-vector-quantization-based feedback schemes that can be respectively applied when users have perfect channel information or perfect effective channel information. For each feedback method, we analyze both expected signal-to-interference-plus-noise ratio (SINR) and expected rate loss and then characterize their bounds as a function of the number of feedback bits. From the characterization, we reveal that the sum rate of two-stage beamforming is very sensitive to the regularization parameter of RZF, especially when the number of feedback bits is limited. Motivated by this, we derive the optimal regularization parameter that maximizes the SINR of two-stage beamforming with limited feedback. Using simulations, we verify the tightness of the characterized bounds and quantify how the use of the optimal regularization parameter improves the sum rate of two-stage beamforming.</P>
Enoxaparin as an Anticoagulant in a Multipara with a Mechanical Mitral Valve: A Case Report
Lee Yo Seb,Kim Jun Seok 대한심장혈관흉부외과학회 2023 Journal of Chest Surgery (J Chest Surg) Vol.56 No.6
Patients who have undergone mechanical valve replacement require anticoagulation therapy with warfarin to prevent thromboembolism. However, administering warfarin to pregnant patients increases their risk of warfarin embryopathy or central nervous system disorders. Consequently, safer alternatives, such as heparin or low-molecular-weight heparin injection, are substituted for warfarin. However, limited research has been conducted on this subject, with no large-scale studies and particularly few investigations involving multiparous patients. A patient who had previously undergone mechanical mitral valve replacement for atrial septal defect and mitral stenosis received anticoagulant therapy with enoxaparin during 2 pregnancies. Upon confirmation of pregnancy, warfarin was replaced with subcutaneously injected enoxaparin with a dosage of 1 mg/kg at 12-hour intervals. The enoxaparin dosage was controlled using an anti-factor Xa assay, with a target range of 0.3–0.7 IU/mL. Intravenous heparin injections were administered starting 3 days prior to the expected delivery date and were continued until delivery, after which warfarin was resumed. No complications were observed during the deliveries.