• Journal of Microbiology and Biotechnology
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• v.28 no.5
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• pp.816-820
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• 2018

The stringent response (SR), which is activated by accumulation of (p)ppGpp under conditions of growth-inhibiting stresses, plays an important role on growth and virulence in Vibrio cholerae. Herein, we carried out a genome-wide screen using transposon random mutagenesis to identify genes controlled by SR in a (p)ppGpp-overproducing mutant strain. One of the identified SR target genes was flaC encoding flagellin. Genetic studies using flaC and SR mutants demonstrated that FlaC was involved in bacterial growth, toxin production, and normal flagellum function under conditions of high (p)ppGpp levels, suggesting FlaC plays an important role in SR-induced pathogenicity in V. cholerae.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.11
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• pp.6838-6844
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• 2014

3GPP LTE-Advanced systems adopt multiple antennas for high speed data transmission. In general, the receiver complexity of a spatially mutiplexed (SM) multiple-input multiple-output (MIMO) system grows in proportion to the number of candidate vectors. A large number of candidate vectors increases the reliability of the soft output values. The maximum likelihood (ML) signal detection with a large number of candidate vectors achieves high performance. On the other hand, low complexity receiver techniques with a small number of candidate vectors provide soft output values, such as low reliability. This paper addresses the improving reliability of the soft output obtained from a small number of candidate vectors. The improved performance of the proposed technique with the aid of computer simulations is reported.

• Computers and Concrete
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• v.20 no.3
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• pp.283-290
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• 2017

The aim of this study is to investigate the effect of the bond strength of self-compacting mortars (SCMS) produced from ground pumice powder (GPP) as a mineral additive. In this scope, six series of mortars including control mix were prepared that consist of 7%, 12%, 17%, 22% and 27% of ground pumice powder by weight of cement. A total of 54 specimens of $40{\times}40{\times}160mm$ were produced and cured at the age of 3, 28 and 90-day for compressive and tensile strength tests and 18 specimens of $150{\times}150{\times}150mm$ mortar were prepared and cured at 28 days for bond strength tests. Flexural tensile strength and compressive strength of $40{\times}40{\times}160mm$ specimens were measured at the curing age of 7, 28 and 90-day. Mini V-funnel flow time and mini slump flow diameter tests were also conducted to obtain rheological properties. As a result of the study, it was observed that the SCMs containing 12% of GPP has the highest bond strength as compared to control and GPP mortars. Compressive strength slightly increased up to 12% of GPP.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39A no.9
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• pp.497-507
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• 2014

This paper investigates the standard features of Carrier aggregation (CA), the related UE RF requirements in 3GPP release 12 and estimated CA evolution in future. The main CA feature of 3GPP release 12 in WG4 perspectives includes 2Uplink(UL) CA, 3Downlink(DL) CA and TDD-FDD CA. To support these features in UE, UE-to-UE coexistence problem and RF requirements generated by unwanted emissions such as inter-modulation and harmonics are analyzed. Also, future CA technology such as LTE in unlicensed bands is described.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.7A
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• pp.654-659
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• 2010

In this paper, we propose a new frequency allocation method for improvement of edge and low 5% user throughputs. Although many kinds of inter cell interference mitigation methods have been proposed, those have still high complexity of implementation. The proposed algorithm has lower complexity and higher edge user throughput than conventional algorithms since the same frequency allocation method is applied in all cell. Finally, we analyze and compare the edge and low 5% user throughputs using a system level simulation (SLS).

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2008.02a
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• pp.99-102
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• 2008

차세대 이동 통신 서비스 4G는 이동 중 100Mbps, 정지 중 1Gbps급 전송 속도를 제공하는 미래 무선 통신 기술이다. 이것은 현재 상용서비스가 이뤄지고 있는 3G HSDPA(High Speed Packet Access)의 전송속도 14Mbps에 비해 10~100배까지 빠른 속도로 무선 인터넷이 가능함으로 유선으로 인터넷을 사용할 필요가 없어진다. 현재 4G 기술로 진화하기 위한 중간 단계로써 ITU-R, 3GPP, 3GPP2, IEEE 등 세계 각국의 표준 및 기술 단체에서 새로운 무선 이동 통신 기술을 제안하고 있다. 이 중에서 2G의 GSM과 3G의 비동기식 기술 WCDMA의 진화 기술인 3GPP LTE(Long Term Evolution) 및 SAE(System Architecture Evolution)가 유력한 4G 이동 통신 기술 후보로 평가 받고 있다. 본 논문에서는 4G 기술로 주목 받고 있는 3GPP LTE 및 SAE 네트워크에서 3G 시스템 보다 진화된 서비스를 제공하기 위한 목적으로 논의되고 있는 일반적인 요구사항과 이를 만족시키기 위한 기술에 대하여 알아본다. 또한 LTE 표준화와 병행하여 네트워크의 구조를 결정하는 SAE의 구성요소와 프로토콜 구조를 소개하고 LTE 및 SAE 네트워크의 보안위협과 안전한 통신을 위한 키 관리 방법에 대하여 논의한다.

• Proceedings of the IEEK Conference
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• 2003.07a
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• pp.65-68
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• 2003

3GPP's RLC protocol specification adopted an error control scheme based on selective repeat ARQ. In 3GPP ARQ, distinctive windows are provide at transmitting and receiving stations so that those stations are prohibited to send or receive data PDU's out of window. An increase in window size enhances delay performance. Such an increase, however, raises the occupancy at reordering buffer, which results in a long reordering time. Aiming at suppressing the occupancy at reordering buffer, we propose a occupancy control scheme in this paper. In this scheme, a threshold is created in the receiving station's window and a data PDU out of the threshold (but within the window) is treated according to go back N ARQ. By the employment of the occupancy control scheme, the occupancy at the reordering buffer is apparently reduced, while the delay performance may be degraded due to the properties of go back N ARQ. We, thus, investigate the peak occupancy and mean delay performance by a simulation method. From numerical examples, we observe a trade-off in both performance measures and conclude that the peak occupancy is effectively reduced by setting a proper threshold under a constraint on mean delay performance.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.6A
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• pp.607-613
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• 2008

In this paper, we investigate the performance of SMP-assisted 3GPP GERAN evolution system employing high order modulation and turbo coding. When applying the SMP which maps systematic bits into highly reliable bit positions, it is confirmed that there is the performance gain for the modulation and coding schemes of 16QAM(DAS-8) as well as 32QAM(DAS-11) by link level simulation.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.45 no.5
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• pp.111-117
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• 2008

In this paper, we propose an approach to improve the performance of voiced/unvoiced (V/UV) decision under background noise environments for the selectable mode vocoder (SMV) of 3GPP2. We first present an effective analysis of the features and the classification method adopted in the SMV. And then feature vectors which are applied to the GMM are selected from relevant parameters of the SMV for the efficient voiced/unvoiced classification. For the purpose of evaluating the performance of the proposed algorithm, different experiments were carried out under various noise environments and yields better results compared with the conventional scheme of the SMV.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2015.10a
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• pp.827-829
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• 2015

This paper presents process of the UE obtains the cell system information in order to achieve communication with the LTE network on the LTE. This paper deals with the process of extracting MIB(Master Information Block) cell system information in LTE. To study the 3GPP LTE standard spec series 36.200 and 36.300, the simulation is implemented to extract the MIB in MATLAB program. The simulation process is divided into three parts. It consisted of a part that extracts the PSS, SSS and MIB. Called a cell search process for detecting the PSS and SSS, the process is to be done in order to extract only the cell system information. The simulation program is verified based on the signal captured from the real Air.