• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.5
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• pp.520-530
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• 2016

Since FDD massive MIMO (multiple-input multiple-output) system deploys hundreds of transmit antennas at base station (BS) compared to conventional MIMO system, the overhead of transmitting channel state information reference signal (CSI-RS) increases proportionally to the number of transmit-antennas. To overcome these disadvantages, we proposed beamforming based CSI-RS transmission technique for FDD massive MIMO system which transmit CSI-RS by limited amount of downlink resources.

• Journal of Positioning, Navigation, and Timing
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• v.9 no.3
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• pp.169-173
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• 2020

Location-based services are used as core services in various fields. In particular, in the field of public services such as emergency rescue, accurate location estimation technology is very important. Recently, the technology of tracking the location of self-isolation subjects for COVID-19 has become a major issue. Therefore, location estimation technology using personal smart devices is being studied in various ways, and the most widely used method is to use GPS. Other representative methods are using Wi-Fi, Pedestrian Dead Reckoning (PDR), Bluetooth Low Energy (BLE) beacons, and LTE signals. In this paper, we introduced a positioning technology using deep learning based on LTE Channel State Information-Reference Signal (CSI-RS) data, and confirmed the possibility through an outdoor location estimation experiment using a commercial LTE signal.

• Clinics in Shoulder and Elbow
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• v.26 no.1
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• pp.64-70
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• 2023

Background: This study aimed to analyze the efficacy of single-dose corticosteroid injection (CSI) administered at 6 weeks postoperative to treat stiffness following arthroscopic rotator cuff repair (ARCR). Methods: In this prospective, multicentric, case-control study, post-ARCR stiffness at 6 weeks was treated with either a single dose of intra-articular CSI (CSI group) or physical therapy with oral analgesics (non-CSI group). Pain intensity according to visual analog scale (VAS), functional outcome using the Constant Murley Shoulder Score, time to return to activities of daily living (ADLs), and retear rate were recorded at 6 weeks, 9 weeks, 12 weeks, 6 months, 12 months, and 18 months postoperatively in both groups. Results: A total of 149 patients (54.5%) in the CSI group and 124 patients (45.5%) in the non-CSI group were included in this study. Pain and function were significantly better in the CSI group at 9-week, 12-week, and 6-month (P<0.001) follow-up, whereas they were not significantly different when the groups were compared at 12- and 18-month follow-up. The mean duration to return to ADLs was significantly shorter (P<0.001) in the CSI group. The incidence of retears was not significantly different (P=0.36) between groups at the end of 18 months of follow-up. Conclusions: Single-dose intra-articular CSI administered at 6 weeks postoperative to treat post-ARCR stiffness significantly improved pain, function, and duration of return to ADLs without increasing the risk of retears compared to patients who did not receive intra-articular CSI. Level of evidence: III.

• Clinics in Shoulder and Elbow
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• v.26 no.1
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• pp.49-54
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• 2023

Background: Lateral epicondylitis is an increasingly debilitating condition in working population. Evidence for conservative treatment modalities has been inconclusive. Percutaneous pie crusting of the common extensor origin at the lateral epicondyle at the time of local corticosteroid injection (CSI) has been proposed sparsely. The objective of this study was to analyze if concomitant CSI and pie-crusting of the common extensor origin provides better outcome than CSI alone in lateral epicondylitis. Methods: This case-control study on 236 patients was conducted at a single center between January 1, 2020, and May 31, 2022. Patients were divided into two groups (n=118 each) based on their preference. Group A underwent CSI alone and group B underwent pie crusting along with CSI. The clinical and functional outcomes of all patients were evaluated at 2, 4, 6, and 12-week post-procedure using the visual analog scale (VAS) and Nirschl score. The mean time for return to daily activities was also compared. Results: Both groups showed significant improvement in post-procedure outcome at successive follow-ups on intragroup longitudinal analysis (VAS: F=558.384 vs. F=1,529.618, Nirschl: F=791.468 vs. F=1,284.951). On intergroup analysis, VAS of group B was superior to that of group A; however, it was statistically significant (P<0.05) only from the 6-week follow-up onwards. Nirschl score of group B was significantly better throughout the period of follow-up (P<0.05). Group B returned to daily activities faster than Group A (6.2±0.44 weeks vs. 7.18±0.76 weeks). Conclusions: Concomitant pie crusting with CSI is recommended for lateral epicondylitis as it provides significantly better results than CSI alone.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.7
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• pp.723-731
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• 2016

A core technological base to provide enhanced data rates required by 5G mobile wireless communications is the improved bandwidth efficiency using massive multiple-input multiple-output (MIMO) transmission. MIMO transmission requires the channel estimation using the channel state information reference signaling (CSI-RS) and appropriate beamforming, thus the design of the codebook defining proper beamforming vectors is an important issue. In this paper, we propose a multi-rank codebook based on the discrete Fourier transform (DFT) matrix, by utilizing statistical properties of the channel generated by the spatial channel model (SCM). The proposed method includes a structural change of the precoding matrix indicator (PMI) by considering the phase difference distributions between adjacent antenna elements, as well as the selected codevector characteristics of each transmission layer. Performance gain of the proposed method is evaluated and verified by making the performance comparison to the 3GPP standard codebooks adopted by Long-Term Evolution (LTE) systems.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.42 no.7 s.337
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• pp.27-34
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• 2005

Iterative detection (ID) has proven to be a near-optimal solution for concatenated Finite State Machines (FSMs) with interleavers over an additive white Gaussian noise (AWGN) channel. When perfect channel state information (CSI) is not available at the receiver, an adaptive ID (AID) scheme is required to deal with the unknown, and possibly time-varying parameters. The basic building block for ID or AID is the soft-input soft-output (SISO) or adaptive SISO (A-SISO) module. In this paper, Reduced State SISO (RS-SISO) algorithms have been applied for complexity reduction of the A-SISO module. We show that serially concatenated CPM (SCCPM) with AID has turbo-like performance over fading ISI channels and also RS-A-SISO systems have large iteration gains. Various design options for RS-A-SISO algorithms are evaluated. Recently developed density evolution technique is used to analyze RS-A-SISO algorithms. We show that density evolution technique that is usually used for AWGN systems is also a good analysis tool for RS-A-SISO systems over frequency-selective fading channels.