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  • Title/Summary/Keyword: Transmission matrix

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Performance Analysis of STBC Concatenated Convolutional Code for Improvement of Transmission Reliability (STBC의 전송 신뢰성 향상을 위한 컨볼루션 코드 연계 시스템)

  • Shin, Hyun-jun;Oh, Chang-Heon
    • Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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    • 2013.05a
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    • pp.586-589
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    • 2013
  • In this paper, the proposed scheme is STBC system combined with convolutional code to ensure the reliability of data transmission for a high rate wireless communication. In addition, this scheme uses a modified viterbi algorithm in order to get a high system gain when data is transmitted. Because we combine STBC and comvolutional code, the proposed scheme can get a diversity gain of STBC and coding gain of convolutional code at the same time. Unlike existing viterbi docoding algorithm using Hamming distance in order to calculate branch matrix, the modified viterbi algorithm uses Euclidean distance value between received symbol and reference symbol. To analyze the system proposed, it was simulated by changing the constraint length of the convolutional code and the number of transmit and receive antennas of STBC.

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Microstructure and Mechanical Properties of ODS Ferrite Produced by Reactive Milling for the MSR Suppression (MSR (Mechanically induced Self-sustaining Reaction)이 억제된 반응성 밀링에 의해 제조된 분산강화 페라이트의 미세조직과 기계적 특성)

  • Hwang, Seung J.
    • Journal of the Korean Society for Heat Treatment
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    • v.26 no.6
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    • pp.279-287
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    • 2013
  • Oxide Dispersion Strengthened (ODS) Fe with Al2O3 dispersoid was successfully produced by reactive milling with a mixture of Fe, Fe3O4 (Magnetite), Fe2O3 (Hematite) and Al reactants at cryogenic temperature. The milled powders were consolidated by Vacuum Hot Press (HP) at 1323 K, and the consolidated materials were characterized by Transmission Electron Microscopy (TEM), Scanning Transmission Electron Microscopy (STEM), and Energy Dispersive Spectroscopy (EDS); the yield strength and the hardness of the consolidated materials were determined by compressive test and Vickers hardness test at room temperature. The grain size of the materials was estimated by X-ray Diffraction technique using the scherrer's formula. The TEM observations showed that the microstructure was comprised with a mixture of nanocrystalline Fe matrix and Al2O3 nano-dispersoids with a bimodal size distribution; the 0.2% off-set yield strength of the materials was as high as 758±29 MPa and the Vickers hardness was 358±2. The effect of the cryogenic milling and addition of extra Fe powder was discussed on the suppression of MSR (Mechanically induced Self-sustaining Reaction) for the desired microstructural evolution of ODS alloys.

A Comparative Analysis of Orthogonal SIBC Algorithms in Spatially Correlated Rayleigh Fading Environments (공간 코릴레이션이 존재하는 레일리이 페이딩 환경에서 직교 STBC 알고리즘의 성능 비교 분석)

  • Jang, Eun-Kyoung;Park, Hyung-Rae;Kim, Chang-Ju
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.33 no.10C
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    • pp.836-843
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    • 2008
  • In this paper we derive the theoretical performance of orthogonal STBC algorithms in spatially correlated Rayleigh fading environments and compare their performances for various correlation conditions. We first derive the theoretical BER of the orthogonal STBC algorithms for both M-ary PSK and M-ary QAM modulation schemes by using the eigenvalues of the channel correlation matrix and then investigate the effect of the spatial correlation on the performance for various transmission rates of 14bps/Hz. Performance analysis illustrates that the Alamouti scheme provides the better performance than the Tarokh scheme for all the transmission rates in highly correlated fading environments with a correlation being larger than 0.9.

Optimal Design of Electric Field Driven Liquid Crystal Fresnel Lens Using Taguchi's Method (다구찌 실험계획법을 이용한 액정 전계 프레넬 렌즈의 최적 설계)

  • Kim, Bong-Sik;Kim, Jong-Woon;Park, Woo-Sang
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.25 no.3
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    • pp.218-223
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    • 2012
  • A rigorous electro-optical simulation and ray tracing for an electric field driven liquid crystal Fresnel lens was proposed to obtain design parameters of the electrode pattern of the Fresnel lens. The optimal design was carried out using Taguchi's experimental method for 17.1"(368×229.5 mm) wide LCD panels with 9 views. For the calculation of the distribution of liquid crystal molecules and the optical transmission of the panel, finite difference method and extended Jones matrix method were used to deal effectively with highly nonlinear and complicated motional equations of the liquid crystal molecules and to obtain the oblique transmission characteristics of the LCD panel. As simulation results, the optimal lengths of the 3 electrodes of the Fresnel lens are 4.0 μm, 30 μm and 83 μm, respectively, and the locations of the second and third electrodes are 32.9-33.0 μm and 45.9-46.0 μm, respectively. The optimal applied voltage of the 3 electrodes are found to be 5.75 V, 7.80 V and 11.9 V, respectively.

VLSI Implementation of Forward Error Control Technique for ATM Networks

  • Padmavathi, G.;Amutha, R.;Srivatsa, S.K.
    • ETRI Journal
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    • v.27 no.6
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    • pp.691-696
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    • 2005
  • In asynchronous transfer mode (ATM) networks, fixed length cells of 53 bytes are transmitted. A cell may be discarded during transmission due to buffer overflow or a detection of errors. Cell discarding seriously degrades transmission quality. The quality degradation can be reduced by employing efficient forward error control (FEC) to recover discarded cells. In this paper, we present the design and implementation of decoding equipment for FEC in ATM networks based on a single parity check (SPC) product code using very-large-scale integration (VLSI) technology. FEC allows the destination to reconstruct missing data cells by using redundant parity cells that the source adds to each block of data cells. The functionality of the design has been tested using the Model Sim 5.7cXE Simulation Package. The design has been implemented for a 5×5 matrix of data cells in a Virtex-E XCV 3200E FG1156 device. The simulation and synthesis results show that the decoding function can be completed in 81 clock cycles with an optimum clock of 56.8 MHz. A test bench was written to study the performance of the decoder, and the results are presented.

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Optimal Amplify-and-Forward Scheme for Parallel Relay Networks with Correlated Relay Noise

  • Liu, Binyue;Yang, Ye
    • ETRI Journal
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    • v.36 no.4
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    • pp.599-608
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    • 2014
  • This paper studies a parallel relay network where the relays employ an amplify-and-forward (AF) relaying scheme and are subjected to individual power constraints. We consider correlated effective relay noise arising from practical scenarios when the relays are exposed to common interferers. Assuming that the noise covariance and the full channel state information are available, we investigate the problem of finding the optimal AF scheme in terms of maximum end-to-end transmission rate. It is shown that the maximization problem can be equivalently transformed to a convex semi-definite program, which can be efficiently solved. Then an upper bound on the maximum achievable AF rate of this network is provided to further evaluate the performance of the optimal AF scheme. It is proved that the upper bound can be asymptotically achieved in two special regimes when the transmit power of the source node or the relays is sufficiently large. Finally, both theoretical and numerical results are given to show that, on average, noise correlation is beneficial to the transmission rate - whether the relays know the noise covariance matrix or not.

Minimization of Crosstalk by Optimum Synthesis of Profiles of Multiple Coupled Data Transmission Lines on Microstrip (다중결합된 마이크로스트립 데이터 전송로 자태의 최적합성을 통한 누화 최소화)

  • 박의준
    • Journal of the Korean Institute of Telematics and Electronics D
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    • v.35D no.12
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    • pp.1-11
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    • 1998
  • A line profile synthesis method is presented that minimizes the nearest-neighbor crosstalk peak level for high-speed pulse transmission in multi-coupled microstrip signal buses. We adopted the optimization technique for the reflected wave control on bus lines resulting in increasing the average spacing between strip conductors, since in a parallel-conductor bus the crosstalk energy is concentrated at the nearest neighbors of the driven line. The generalized S-matrix technique is applied for the input and output waveform prediction, and crosstalk characteristics of various nonuniform lines synthesized for increasing the average spacing are analyzed by comparing each other. Simulation results demonstrate that the Chebyshev taper with dips is adequate to significantly minimize the crosstalk peak level under the satisfactory waveform integrity since the profile is oriented to evenly reflect significant pulse spectra within the frequency range of pulse.

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Microstructural characterization of accident tolerant fuel cladding with Cr-Al alloy coating layer after oxidation at 1200 ℃ in a steam environment

  • Park, Dong Jun;Jung, Yang Il;Park, Jung Hwan;Lee, Young Ho;Choi, Byoung Kwon;Kim, Hyun Gil
    • Nuclear Engineering and Technology
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    • v.52 no.10
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    • pp.2299-2305
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    • 2020
  • Zr alloy specimens were coated with Cr-Al alloy to enhance their resistance to oxidation. The coated samples were oxidized at 1200 ℃ in a steam environment for 300 s and showed extremely low oxidation when compared to uncoated Zr alloy specimens. The microstructure and elemental distribution of the oxides formed on the surface of Cr-Al alloys have been investigated by transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). A very thin protective layer of Cr2O3 formed on the outer surface of the Cr-Al alloy, and a thin Al2O3 layer was also observed in the Cr-Al alloy matrix, near the surface. Our results suggest that these two oxide layers near the surface confers excellent oxidation resistance to the Cr-Al alloy. Even after exposure to a high temperature of 1200 ℃, inter-diffusion between the Cr-Al alloy and the Zr alloy occurred in very few regions near the interface. Analysis of the inter-diffusion layer by high-resolution transmission electron microscopy (HRTEM) and energy dispersive X-ray spectroscopy (EDS) measurement confirmed its identity as Cr2Zr.

Preparation of melamine-grafted graphene oxide and evaluation of its efficacy as a flame retardant additive for polypropylene

  • Monji, Parisa;Jahanmardi, Reza;Mehranpour, Milad
    • Carbon letters
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    • v.27
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    • pp.81-89
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    • 2018
  • The present study aimed to prepare a novel efficient flame retardant additive for polypropylene. The new flame retardant was prepared by chemical grafting of melamine to graphene oxide with the aid of thionyl chloride. Fourier-transform infrared spectroscopy and thermogravimetric analysis proved that melamine had been successfully grafted to the graphene oxide. The modified graphene oxide was incorporated into polypropylene via solution mixing followed by anti-solvent precipitatio. Homogeneous distribution as well as exfoliation of the nanoplatelets in the polymer matrix was observed using transmission electron microscopy. Thermogravimetric analysis showed a significant improvement in the thermo-oxidative stability of the polymer after incorporating 2 wt% of the modified graphene oxide. The modified graphene oxide also enhanced the limiting oxygen index of the polymer. However, the amount of improvement was not enough for the polymer to be ranked as a self-extinguishing material. Cone calorimetry showed that incorporating 2 wt% of the modified graphene oxide lowered total heat release and the average production rate of carbon monoxide during burning of the polymer by as much as 40 and 35%, respectively. Hence, it was concluded that the new flame retardant can retard burning of the polymer efficiently and profoundly reduce suffocation risk of exposure to burning polymer byproducts.

The Observation of Intermetallic Compound Microstructure Under Sn Whisker in Lead-free Finish

  • Yu, Chong-Hee
    • Journal of the Microelectronics and Packaging Society
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    • v.16 no.2
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    • pp.27-31
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    • 2009
  • Sn whiskers can grow from the pure Sn and high Sn-based finish and cause the electrical shorts and failures. Even with the wealth of information on whiskers, we have neither the clear understanding of whisker growth nor methods for its prevention. In this study, the whisker grain roots which connected with intermetallic layer were analyzed by high-resolution transmission electron microscopy (HR-TEM). In the Sn-Cu plated leadframe (LF) that was stored at ambient condition for 540 days, filament-shaped whiskers were grown on the Sn-plated surface and ηCu6Sn5 precipitates were widely distributed along the grain boundaries at the Sn matrix. The measured of the lattice fringes at the ηCu6Sn5 was 4.71\AA at the coarse grain and 2.91\AA at the fine grain. The Cu3Sn which generates the tensile stresses was not observed. The formation of Cu6Sn5 precipitates and intermetallic layer were strongly related to whisker growth, but, the whisker growth tendency does not closely relate with the geometric morphology of irregularly grown intermetallic compound (lMC).

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