Jinyoung Jang

Smart Small Cell with Hybrid Beamforming for 5G: Theoretical Feasibility and Prototype Results

In this article, we present a real-time 3D hybrid beamforming approach for 5G wireless networks. One of the key concepts in 5G cellular systems is the small cell network, which settles the high mobile traffic demand and provides uniform user-experienced data rates. The overall capacity of the small cell network can be enhanced with the enabling technology of 3D hybrid beamforming. This study validates the feasibility of 3D hybrid beamforming, mostly for link-level performance, through the implementation of a real-time testbed using a SDR platform and fabricated antenna array. Based on the measured data, we also investigate system-level performance to verify the gain of the proposed smart small cell system over LTE systems by performing system-level simulations based on a 3D ray-tracing tool.

Endoscopic versus open release in patients with de Quervain's tenosynovitis: a randomised trial.

The purpose of this study was to compare the outcome and complications of endoscopic versus open release for the treatment of de Quervains tenosynovitis. Patients with this condition were randomised to undergo either endoscopic (n = 27) or open release (n = 25). Visual Analogue Scale (VAS) pain and Disabilities of Arm, Shoulder, and Hand (DASH) scores were measured at 12 and 24 weeks after surgery. Scar satisfaction was measured using a VAS scale. The mean pain and DASH scores improved significantly at 12 weeks and 24 weeks (p < 0.001) in both groups. The scores were marginally lower in the endoscopic group compared to the open group at 12 weeks (p = 0.012 and p = 0.002, respectively); however, only the DASH score showed a clinically important difference. There were no differences between the groups at 24 weeks. The mean VAS scar satisfaction score was higher in the endoscopic group at 24 weeks (p < 0.001). Transient superficial radial nerve injury occurred in three patients in the endoscopic group compared with nine in the open release group (p = 0.033). We conclude that endoscopic release for de Quervains tenosynovitis seems to provide earlier improvement after surgery, with fewer superficial radial nerve complications and greater scar satisfaction, when compared with open release.

Reassessment of alkaline phosphatase as serum tumor marker with high specificity in osteosarcoma

The goal of this study was to reassess serum alkaline phosphatase (ALP) as tumor marker in osteosarcoma. We retrospectively examined serum ALP levels at diagnosis, every therapeutic step (neoadjuvant chemotherapy, surgery, and adjuvant chemotherapy), metastasis, and follow‐up and analyzed the role of ALP as tumor marker in 210 osteosarcomas. The diagnostic performances of ALP were validated with pathology‐proven 899 other primary bone lesions. Elevated ALP at diagnosis was associated with inferior overall survival (OS) (Log Rank P < 0.001) and disease‐free survival (Log Rank P = 0.005) and independently significant for OS in multivariate analysis (hazard ratio [HR]=2.12, P = 0.032). During therapy, the ALP level significantly changed according to therapeutic steps (P < 0.001 for patients ≥15 years old, P < 0.001 for patients <15 years old) and survival (P = 0.015 for ≥15 years, P = 0.002 for <15 years), and the response of ALP to therapy and survival were associated (P = 0.042 for ≥15 years, P = 0.036 for <15 years). Initial ALP level was linearly correlated with tumor burden (total tumor volume; P = 0.016 for ≥15 years, bone tumor volume; P = 0.012 for ≥15 years). The sensitivity and specificity of ALP on diagnosis were 53.2% (95% Confidence Interval [CI]: 0.475–0.586) and 90.1% (95% CI: 0.888–0.913). The sensitivity of ALP on metastasis was 53.2% (95% CI: 0.431–0.624), and the specificity was 78.2% (95% CI: 0.720–0.839) at15 months postoperative and 90.0% (95% CI: 0.824–0.952) at 3 years postoperative. Serum ALP was found to be a valuable tumor marker with high specificity in osteosarcoma.

Generalized Inverse Aided PAPR-Aware Linear Precoder Design for MIMO-OFDM System

We propose a linear precoding scheme for a single user multiple-input-multiple-output orthogonal frequency division multiplexing (OFDM) system to minimize peak to average power ratio (PAPR) by using redundant spatial resources at the transmitter through a singular-value-decomposition-based generalized inverse. The proposed precoder based on the generalized inverse is composed of two parts. One is for minimizing PAPR, and the other is for obtaining the multiplexing gain. Moreover, the proposed precoder contains a scalar parameter α that quantifies the received signal-to-noise power ratio (SNR) loss at the cost of PAPR reduction. Even in cases of small SNR loss, the proposed scheme dramatically reduces PAPR. Furthermore, simulation results show that we can obtain a PAPR close to 1 by using dozens of transmission antennas with small SNR loss.

Low Complexity Zeroforcing Precoder Design Under Per-Antenna Power Constraints

The K-user multiple-input single-output broadcast channel is considered under per-antenna power constraints, i.e., each transmit antenna must satisfy its own power constraint. A low complexity zeroforcing (ZF) precoder is proposed when the number of transmit antennas M is greater than K. The proposed precoder design significantly reduces computational complexity for the precoder construction while attaining the sum spectral efficiency close to that achievable by the optimal ZF precoder.

A closed-form upper bound of the sum rate of blind interference alignment and its application to control of the number of active users

Blind interference alignment (B-IA) achieves the optimal degrees of freedom (DoF) in multiple-input single-output (MISO) broadcast channels (BC) when the number of users goes infinity. However, supporting infinite number of users requires to infinite length of symbol extension that is infeasible in practical systems, and maximizing DoF does not guarantee sum rate maximization especially at the low and medium SNR regime. In this paper, we derive the sum rate upper bound of B-IA schemes of [1] and [2] as a closed-form expression. Using the closed-form upper bound, we determine the sub-optimal number of active users for a given SNR and the total number of users in the system. Numerical results show that the upper bound captures the optimal number of active users well, and that controlling number of active users enhances the sum rate performance of the B-IA schemes.

In-band full duplex cellular operation with reconfigurable uplink antennas at base station

In this paper, we propose an in-band full duplex (IBFD) cellular operation with reconfigurable uplink (UL) antennas at base station (BS). For handling mobile station (MS)-to-MS interference in an IBFD cellular system, a repetition coding of UL MSs is considered. While the repetition coding of UL MSs is applied, downlink (DL) MSs can cancel MS-to-MS interference by using one silent symbol to measure MS-to-MS interference. To avoid UL system throughput loss due to the repetition coding of UL MSs, we propose using reconfigurable antennas to enable to serve more UL users simultaneously than the number of UL antennas. The proposed scheme does not require any MS-to-MS channel estimation or channel information feedback, as well as any interference cancellation receiver at the DL MSs. We analyze the degrees of freedom (DoF) gain of the proposed scheme. It is shown that the proposed scheme achieves the double DoF gain compared with half duplex scheme when the number of UL MSs and the preset modes of reconfigurable antennas go infinity. Numerical results show that the proposed scheme has a significant sum rate performance gain even though the number of UL MSs and the number of preset modes of reconfigurable antennas do not go infinity.

Uncontrolled diabetes as a potential risk factor in tibiotalocalcaneal fusion using a retrograde intramedullary nail

BACKGROUND Tibiotalocalcaneal (TTC) fusion using a retrograde intramedullary (IM) nail is an effective salvage option for terminal-stage hindfoot problems. However, as many patients who receive TTC fusion bear unfavorable medical comorbidities, the risk of nonunion, infection and other complications increases. This study was performed to identify the factors influencing outcomes after TTC fusion using a retrograde IM nail. METHODS Between September 2008 and February 2012, 34 consecutive patients received TTC fusion using a retrograde IM nail for limb salvage. All patients had a minimum follow-up of two years. Throughout follow-up, standard ankle radiography was performed along with clinical outcome assessment using a visual analog scale (VAS) for pain, the American Orthopaedic Foot and Ankle Society Ankle-Hind Foot Scale (AOFAS A/H scale) and the Foot and Ankle Outcome Score (FAOS). For the retrospective analysis, demographic factors, preoperative medical status, laboratory markers, and etiology were comprehensively reviewed using medical records. The success of the index operation was determined using clinical and radiological outcomes. Finally, the effect of each factor on failure after the operation was analyzed using univariate logistic regression. RESULTS In a mean of seven months, 82% (28/34) achieved union, as evaluated by standard radiography. All clinical outcome parameters improved significantly after the operation, including VAS, AOFAS A/H scale, and FAOS (P<0.001). At the last follow-up, five cases of nonunion with less than AOFAS A/H scale of 80 and two cases of below knee amputation due to uncontrolled infection were determined to be failures. None of the factors (etiology, demographics, laboratory markers and medical status) significantly influenced failures. However, uncontrolled DM significantly increased the failure rate with an odds ratio of 10 (P=0.029). CONCLUSIONS TTC fusion with a retrograde intramedullary nail is a successful treatment for complicated hindfoot problems such as traumatic osteoarthritis, Charcot arthropathy and failed TAA. However, it should be used judiciously in patients with uncontrolled DM, as the risk of failure increases. DESIGN Retrospective cohort study.

An efficient feedback architecture design for three-user MIMO interference channels

In this paper, an efficient feedback structure is proposed to reduce the feedback overhead of three-user multiple input multiple output interference channels (MIMO-IFC). We present a sequential and iterative feedback structure based on interference cancellation condition. Compared to the previous feedback structure for interference alignment (IA) in K-user MIMO-IFC [1], the proposed method does not need a cooperation between receivers. Even though the proposed scheme inherently requires the infinite number of iterations to remove the residual interference clearly, almost all of the residual interference is eliminated by the low number of iterations enough that its total feedback overhead is dramatically reduced compared to the conventional approach [2]. Furthermore, in order to improve throughput performance, we propose a concatenated receive filter for maximizing the effective SINR.