• Title, Summary, Keyword: LTE

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Efficient Low-Complexity Soft MIMO Symbol Detector for MIMO Systems (다중안테나 통신시스템을 위한 저복잡도 연판정 MIMO 심볼검출기법 연구)

  • Jang, Soo-Hyun;Shin, Dae-Kyo;Yoon, Sang-Hun;Jung, Han-Gyun;Jin, Seong-Keun;Lim, Ki-Taeg
    • The Journal of The Korea Institute of Intelligent Transport Systems
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    • v.16 no.2
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    • pp.153-160
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    • 2017
  • Recently, the demand has continued to increase for higher data rates and improved multimedia services through wireless internet access. In order to increase the data rate and link reliability, 3GPP LTE/A and IEEE 802.16e/m WiMAX systems incorporate MIMO transmission schemes. Since the hardware complexity increases with the number of transmit data streams and mobile devices have limited physical dimensions, an multiple input multiple output (MIMO) ystem with two antennas at both the transmitter and the receiver ($2{\times}2$) is considered to be a possible solution for mobile devices. In this paper, a low-complexity soft output MIMO symbol detector based on Modified-SQRD is proposed for mobile devices with two transmit and two receive antennas.

Enhanced Random Resource Selection Scheme for V2X (V2X를 위한 향상된 랜덤 자원 선택 기술)

  • Yoon, Sung-jun;Choi, Sang Won;Kwon, Ki-bum;Park, Dong-hyun;Li, Jianjun
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.42 no.5
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    • pp.1058-1068
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    • 2017
  • In V2X communication, a random based resource selection scheme is needed with considerations of cases that support devices without sidelink reception capabilities and require reduction of UE's power consumption. In this paper, as improvement of D2D's resource section scheme that one TRP is repeated to data subframe pool within a PSCCH period, it is proposed that different TRPs is applied for enhanced random resource selection based on pseudo-random sequence having UE-specific seed value. By results of proposed scheme's performance by numerical analysis, it is confirmed that collision probability among resources allocated to each UE for data TB is reduced, and a number of UEs which can avoid resource collision as much as possible and have simultaneous resource allocation is increased.

Performance Evaluation of V2X Communication System Under a High-Speed Driving (고속 주행 환경에서의 V2X 통신 성능 측정 시스템)

  • Kang, Bo-young;Bae, Jeongkyu;Seo, Woo-Chang;Park, Jong Woo;Yang, EunJu;Seo, Dae-Wha
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.42 no.5
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    • pp.1069-1076
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    • 2017
  • C-ITS(Cooperative-Intelligent Transportation System) provides services that require strict real-time such as forward collision warning, road safety service and emergency stop. WAVE(Wireless Access in Vehicular Environments), a core technology of C-ITS, is a technology designed for high-speed driving. However, in order to provide stable communication service by applying to real road environment, various performance tests of real vehicular environment are required. In the real road environment, WAVE communication performance is influenced by the surrounding environment such as moving vehicle, road shape and topography. Especially, when the vehicle is moving at high speed, the traveling position according to the speed of the vehicle, The surrounding environment changes rapidly. Such changes are factors affecting the communication performance, therefore a system and methods for analyzing them are needed. In this paper, we propose the configuration and test method of an effective performance evaluation system under high-speed driving and describe the results of analyzing the communication performance based on the data measured through the actual vehicle test.

8 Antenna Interleaved Quasi Orthogonal Space Time Block Code TBH with PIC Group Decoding (8 안테나 인터리브 시스템을 위한 준직교 시공간 블록 부호 TBH의 부분 간섭 제거 그룹 복호 알고리즘)

  • Lee, Moon-Ho;Lee, Mi-Sung;Hanif, Mohammad Abu;Park, Ju-Yong
    • Journal of the Institute of Electronics Engineers of Korea TC
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    • v.48 no.8
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    • pp.7-14
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    • 2011
  • In this paper we studied a conventional system and propose a new decoding scheme for Space-time Frequency Code with Interleaved System. We also addressed the quasi orthogonal function with Jacket matrices in modern 3GPP LTE uplinked advance system. We also introduce the Partial Interference Cancellation (PIC) group decoding which provides a framework to adjust the complexity-performance tradeoff by choosing the sizes of the information symbols groups.

Measurement of EUV Emission and its Plasma Parameters Generated from the Coaxial Plasma Focus of Mather and Hypocycloidal Pinched Electrodes

  • Lee, Sung-Hee;Lee, Kyung-Ae;Hong, Young-June;Uhm, Han-Sup;Choi, Eun-Ha
    • Proceedings of the Korean Vacuum Society Conference
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    • pp.332-332
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    • 2011
  • The extreme ultraviolet (EUV) radiation, whose wavelength is from 120 nm down to 10 nm, and the energy from 10 eV up to 124 eV, is widely utilized such as in photoelectron spectroscopy, solar imaging, especially in lithography and soft x-ray microscopy. In this study, we have investigated the plasma diagnostics as well as the debris characteristics between the two types of dense plasma focusing devices with coaxial electrodes of Mather and hypocycloidal pinch (HCP), respectively. The EUV emission intensity, electron temperature and plasma density have been investigated in these cylindrical focused plasma along with the debris characteristics. An input voltage of 5 kV has been applied to the capacitor bank of 1.53 uF and the diode chamber has been filled with Ar gas at pressure ranged from 1 mTorr and 180 mTorr. The inner surface of the cathode was covered by polyacetal insulator. The central anode electrode has been made of tin. The wavelength of the EUV emission has been measured to be in the range of 6~16 nm by a photo-detector (AXUV-100 Zr/C, IRD). The visible emission has also been measured by the spectrometer with the wavelength range of 200~1,100 nm. The electron temperature and plasma density have been measured by the Boltzmann plot and Stark broadening methods, respectively, under the assumption of local thermodynamic equilibrium (LTE).

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Feasibility of Ultrasonic Log Sorting in Manufacturing Structural Lamination from Japanese Cedar Logs

  • Oh, Jung-Kwon;Yeo, Hwan-Myeong;Choi, In-Gyu;Lee, Jun-Jae
    • Journal of the Korean Wood Science and Technology
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    • v.39 no.2
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    • pp.163-171
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    • 2011
  • Because Japanese cedar shows lower mechanical performance, glued-laminated timber (glulam) can be a better way to utilize Japanese cedar for structural purpose. However, low yield of higher grade lamination from log makes it difficult to design structural glulam. This study was aimed to increase the yield of higher grade lamination and provide higher efficiency of manufacturing structural lamination by ultrasonic log sorting technology. Logs were sorted by an existing log grading rule regulated by Korea Forest Research Institute (KFRI). It was found that the KFRI log grading rule contributed to finding better logs in viewpoint of the volumetric yield and it can reduce the number of rejected lumber by visual grading. However, it could not identify better logs to produce higher-grade products. To find an appropriate log-sorting-method for structural products, log diameter and ultrasonic time of flight (TOF) for the log were considered as factors to affect mechanical performance of resulting products. However, it was found that influence of log diameter on mechanical performance of resulting products was very small. The TOF showed a possibility to sort logs by mechanical performance of resulting products even though a coefficient of correlation was not strong (R = 0.6). In a case study, the log selection based on the ultrasonic TOF of the log increased the yield of the outermost tension lamination (E8 or better grade, KS F 3021) from 2.6% to 12.5% and reduced LTE5 (lower than E5 grade) lamination from 43.6% to 10.3%, compared with the existing KFRI log grading rule.

Multicast Coverage Prediction in OFDM-Based SFN (OFDM 기반의 SFN 환경에서의 멀티캐스트 커버리지 예측)

  • Jung, Kyung-Goo;Park, Seung-Young
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.36 no.3A
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    • pp.205-214
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    • 2011
  • In 3rd generation project partnership long term evolution, wireless multicast techniques which send the same data to multiple users under single frequency networks have attracted much attention. In the multicast system, the transmission mode needs to be selected for efficient data transfer while satisfying the multicast coverage requirement. To achieve this, users' channel state information (CSI) should be available at the transmitter. However, it requires too much uplink feedback resource if all the users are allowed to transmit their CSI at all the time. To solve this problem, in this paper, the multicast coverage prediction is suggested. In the proposed algorithm, each user measures its transition probabilities between the success and the fail state of the decoding. Then, it periodically transmits its CSI to the basestation. Using these feedbacks, the basestation can predict the multicast coverage. From the simulation results, we demonstrate that the proposed scheme can predict the multicast system coverage.

Near-Infrared Spectroscopy and Modeling of Luminous Blue Variables

  • Kim, Hyun-Jeong;Koo, Bon-Chul;Park, Yong-Sun
    • The Bulletin of The Korean Astronomical Society
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    • v.36 no.2
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    • pp.152.1-152.1
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    • 2011
  • We report preliminary results of long-slit near-infrared (NIR) spectroscopy of Luminous Blue Variables (LBVs) with moderate resolution of R ~ 2400. We obtained Jshort (1.04-1.26 micron) and Ks (2.02-2.31 micron) band spectra of 4 LBVs and 3 LBV candidates in Southern hemisphere using IRIS2, infrared imager and spectrograph, mounted on the 4-m Anglo-Australian Telescope. All targets are fairly bright in NIR so that we can obtain high signal-to-noise ratio for clear line detection and modeling. They are also widely distributed in the HR diagram so that we can compare the spectral properties of LBVs in different temperature and luminosity ranges. Among them, we present the results of two well-known LBVs AG Car and HR Car. Their spectra show similar properties with hydrogen, He I, and metallic lines such as Fe II and Mg II, most of them in emission. We discuss, in particular, the He I 1.083 micron lines formed in stellar wind because these two LBVs show large variation in their He I line intensities, compared to previous studies. Since the He I 1.083 line is known to be anticorrelated with the photometric variation of LBVs, strong line intensities with P-Cygni profiles in both stars indicate that they are now near the visual minimum phase. We model the obtained spectra using non-LTE atmosphere code CMFGEN of Hillier (1998) to derive stellar parameters such as wind velocity and mass loss rate, and discuss the long-term variability of stellar parameters of these LBVs. deduced from our otometric solution.

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An Improved LLR Generation Technique for SC-FDMA Systems Using Frequency Domain MMSE Equalization (주파수 영역 MMSE 등화방식 기반의 SC-FDMA 시스템을 위한 개선된 LLR 생성 기법)

  • Kim, Jin-Min;Im, Tae-Ho;Kim, Jae-Kwon;Yi, Joo-Hyun;Cho, Yong-Soo
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.34 no.12C
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    • pp.1197-1207
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    • 2009
  • Orthogonal Frequency Division Multiple Access (OFDMA) is widely used as a multiple access technique for next generation mobile communication systems, however, its main drawback is the high peak-to-average ratio (PAPR). Thus for the uplink case where the transmit power is strictly limited due to the battery life of mobile units, single carrier frequency division multiple access (SC-FDMA) with low PAPR is preferred to OFDMA method. In this paper, we propose a method to improve the performance of SC-FDMA using frequency domain MMSE equalization. The proposed improved log-likelihood ratio (LLR) generation method exploits both the diversity characteristic of channels and the reciprocity that is obtained from the received signals. The complexity of the proposed method is analyzed and its performance gain is demonstrated via a set of computer simulations.

Handover Latency Improvement & Performance Analysis over Inter-LMA (Inter-LMA 이동시 Handover Latency 개선 방안 및 성능 분석)

  • Chang, Jae-Cheol;Park, Byung-Joo;Kim, Dae-Young
    • Journal of the Institute of Electronics Engineers of Korea TC
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    • v.46 no.8
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    • pp.34-42
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    • 2009
  • Mobile communication traffic is changing from voice to data/internet, e.g. wireless internet access, SMS/MMS. more and more. Therefore many data services are coming out over 3G, Mobile WiMAX(WIBRO), LTE etc. Wireless internet market is growing and MIPv6 is more important and many protocols being studied and developed from MIPv6 to Fast MIPv6, Hierachical MIPv6, Proxy MIPv6, etc. The significant factor over MIPv6 is Hand-over latency and Packet-loss PMIPv6 is efficient for reducing mobility related messages and hand-over latency, but it considers single LMA domain. If mobile node is moving inter-LMAs, hand-over delay time affects the real-time communications. To overcome this hand-over delay, we propose present and new enhanced schemes and analize the performance and show the results.