• Title/Summary/Keyword: Space-Time

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Improved Differential Detection Scheme of Space-Time Trellis Coded MDPSK For MIMO (MIMO에서 시공간 부호화된 MDPSK의 성능을 향상시키기 위한 차동 검파 시스템)

  • Kim, Chong-Il;Lee, Ho-Jin;Yoo, Hang-Youal;Kim, Jin-Yong;Kim, Seung-Youal
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.10 no.10
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    • pp.1869-1876
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    • 2006
  • Recently, STC techniques have been considered to be candidate to support multimedia services in the next generation mobile radio communications and have been developed the many communications systems in order to achieve the high data rates. In this paper, we Nose the Trellis-Coded Differential Space Time Modulation system with multiple symbol detection. The Trellis-code performs the set partition with unitary group codes. The Viterbi decoder containing new branch metrics is introduced in order to improve the bit error rate (BER) in the differential detection of the unitary differential space time modulation. Also, we describe the Viterbi algorithm in order to use this branch metrics. Our study shows that such a Viterbi decoder improves BER performance without sacrificing bandwidth and power efficiency.

English Performance of MIMO-OFDM Combing Bemaformer with Space-time Decoder in Multiuser Environments (다중 사용자 환경에서 빔 형성기와 결합된 Space-Time decoder을 가진 MIMO-OFDM 시스템의 성능)

  • Kim Chan-Kyu
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.31 no.8A
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    • pp.775-783
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    • 2006
  • In this paper, the new technique combining beamforming with space-time coding is proposed for an orthogonal frequency division multiplexing(OFDM) system with multi-input multi-output(MIMO). When MIMO-OFDM system is employing Nt(the number of transmitterantenna) beamfomers and one S-T decoder at Nr receiver antennas, Nt signals removed CCI are outputted at the beamformer and then diversity gain can be got through space-time decoding. As the proposed technique can reduce cochannel interference and get diversity gain in the multi-user environment, the performance of MIMO-OFDM system is very improved. BER performance improvement and convergence behavior of the proposed approach are investigated through computer simulation by applying it to MIMO-OFDM system in the multi-user environment.

High Data Rate Ultra Wideband Space Time Coded OFDM (고속 전송률 UWB 시공간 부호화 OFDM)

  • Lee Kwang-Jae;Chen Hsiao-Hwa;Lee Moon-Ho
    • Journal of the Institute of Electronics Engineers of Korea TC
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    • v.43 no.7 s.349
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    • pp.132-142
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    • 2006
  • In this paper, we present a candidate high data rate space time coded OFDM system for short range personal networking. The system transmits the complex space time coded signals with a hybrid orthogonal frequency division multiplexing (OFDM) based on ultra wideband (UWB) pulses. The transmitted signals are sparse pulse trains modulated by a frequency selected from a properly designed set of frequencies. Additionally, a widely linear (WL) receive filter and a space time frequency transmission are designed by using two simple parallel linear detectors. To overcome the deeply fade in the propagation system, a beamforming combined with space time block codes also 따 e briefly discussed.

Multiple Symbol Detection of Trellis coded Differential space-time modulation for OFDM (OFDM에서 트렐리스 부호화된 차동 시공간 변조의 다중 심벌 검파)

  • 유항열;한상필;김진용;김성열;김종일
    • Journal of the Institute of Convergence Signal Processing
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    • v.5 no.3
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    • pp.223-229
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    • 2004
  • Recently, OFDM and STC techniques have been considered to be candidate to support multimedia services in the next generation mobile radio communications and have been developed the many communications systems in order to achieve the high data rates. In this paper, we propose the Trellis-Coded Differential Space Time Modulation-OFDM system with multiple symbol detection. The Trellis-code performs the set partition with unitary group codes. The Viterbi decoder containing new branch metrics is introduced in order to improve the bit error rate (BER) in the differential detection of the unitary differential space time modulation. Also, we describe the Viterbi algorithm in order to use this branch metrics. Our study shows that such a Viterbl decoder improves BER performance without sacrificing bandwidth and power efficiency.

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A study on the Temporality through Haptic Space - Focused on Joh Sung-yong's Seonyudo Park and Kkummaru - (촉지적 공간을 통한 시간성에 관한 연구 - 건축가 조성룡의 선유도 공원과 꿈마루를 중심으로 -)

  • Park, Miyoung
    • Korean Institute of Interior Design Journal
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    • v.22 no.6
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    • pp.68-78
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    • 2013
  • The purpose of this study is to investigate Seonyudo Park and Kkummaru in terms of haptic space. This is an attempt to escape from the limits of optical space that identifies the space with abstract concepts. Haptic perception of the space refers to feeling the space with all the senses through non-hierarchical interactions. Time of the haptic space is revealed by Deleuze's crystalline description and Bergson's pure recollection that is not useful to identify objects. According to two concepts, the running present forks into the past and the future, and the nature of time appears at the point of indiscernibility in which the past, present, and future coexist. Thought on time about the architecture provides a valid point of view to understand the relationship of visitor's sensory experience of space, recollection, and emotion. In this respect, it can be said that Joh sung-yong's two works explored for new areas of architectural experience by building up the potential image of the subject which is placed in the human memory. And then this study shows that two works recover the relationship between the past and the present so that they give an opportunity to consider the meaning of time in the architecture.

An Empirical Study on the Economic Benefit of Space Chartering (정기선 선복 확보를 위한 Space Chartering의 경제성에 관한 연구)

  • Park Doo-Jin;Kim Hyun;Na Chel-Su;Nam Ki-Chan
    • Proceedings of the Korean Institute of Navigation and Port Research Conference
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    • 2005.10a
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    • pp.335-340
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    • 2005
  • This thesis tries to evaluate the economic benefit of space chartering in comparison with time chartering with respect to mega container ships. For this it reviews the method of obtaining ship's carrying capacity such as time chartering and space chartering. Based on this, it tries to make comparison between the time chartering and space chartering on economic base. Finally, it suggest the economic benefit of space chartering with direction for further study.

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The TIME AS SPACE Metaphor in English and in French: A Cognitive Analysis

  • Hamdi, Sondes
    • Cross-Cultural Studies
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    • v.28
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    • pp.67-86
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    • 2012
  • Metaphors were conceived of as a figure of speech whose role consisted in merely ornamenting the language. However, with their seminal book Metaphors we live by (1980), Lakoff and Johnson have revolutionized the conception of metaphors by placing them as central to human language, thought and action. Cognitive linguists argue that humans tend to conceptualize abstract concepts, such as time, through more experiential and tangible concepts. For instance, it has been observed that the abstract concept of time is conceptualized as space in several unrelated languages. According to the Conceptual Metaphor Theory (CMT), TIME AS SPACE metaphor covers two more specific metaphors: (1) The MOVING TIME metaphor wherein the observer is conceived as a stationary entity, as in The end of the academic year is getting closer; and (2) The TIME AS A LOCATION metaphor wherein times are conceived as stationary points and the observer is conceived as moving relative to these locations, as in We are first approaching the end of the year. This paper aims at probing the validity of the CMT representations of time on the basis of an analysis of time metaphors in two languages: English and French. This analysis is conducted within the framework of CMT. The results corroborate the CMT representations of time, suggesting that in both languages the abstract concept of time is expressed in spatial terms. In English, as in French, time is conceptualized as a moving entity and as having extension in space. In both languages, time can be seen as bounded; therefore, one can perform actions within defined limits of time.

Development of a Data Reduction Algorithm for Optical Wide Field Patrol (OWL) II: Improving Measurement of Lengths of Detected Streaks

  • Park, Sun-Youp;Choi, Jin;Roh, Dong-Goo;Park, Maru;Jo, Jung Hyun;Yim, Hong-Suh;Park, Young-Sik;Bae, Young-Ho;Park, Jang-Hyun;Moon, Hong-Kyu;Choi, Young-Jun;Cho, Sungki;Choi, Eun-Jung
    • Journal of Astronomy and Space Sciences
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    • v.33 no.3
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    • pp.221-227
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    • 2016
  • As described in the previous paper (Park et al. 2013), the detector subsystem of optical wide-field patrol (OWL) provides many observational data points of a single artificial satellite or space debris in the form of small streaks, using a chopper system and a time tagger. The position and the corresponding time data are matched assuming that the length of a streak on the CCD frame is proportional to the time duration of the exposure during which the chopper blades do not obscure the CCD window. In the previous study, however, the length was measured using the diagonal of the rectangle of the image area containing the streak; the results were quite ambiguous and inaccurate, allowing possible matching error of positions and time data. Furthermore, because only one (position, time) data point is created from one streak, the efficiency of the observation decreases. To define the length of a streak correctly, it is important to locate the endpoints of a streak. In this paper, a method using a differential convolution mask pattern is tested. This method can be used to obtain the positions where the pixel values are changed sharply. These endpoints can be regarded as directly detected positional data, and the number of data points is doubled by this result.

Space-Time Carrier Interferometry Techniques with Low-density Parity Check Code for High-speed Multimedia Communications

  • Chung Yeon-Ho
    • Journal of Korea Multimedia Society
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    • v.9 no.6
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    • pp.728-734
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    • 2006
  • Carrier interferometry code is considered as a promising scheme that provides significant performance improvement via frequency diversity effect. Space-time coding is commonly employed to achieve a performance gain through space diversity. The combination of these techniques and forward error correction coding will lead to enhanced system capacity and performance. This paper presents a low-density parity check (LDPC) coded space-time orthogonal frequency division multiplexing (OFDM) transmission scheme with carrier interferometry code for high-capacity and high-performance mobile multimedia communications. Computer simulations demonstrate that the proposed mobile multimedia transmission system offers a considerable performance improvement of approximately 9dB in terms of Eb/No in the Rayleigh fading channel with relatively low delay spread, in comparison with space-time OFDM. Performance gains are further increased, comparing with traditional OFDM systems.

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STUDY OF P-CURVATURE TENSOR IN THE SPACE-TIME OF GENERAL RELATIVITY

  • Ganesh Prasad Pokhariyal;Sudhakar Kumar Chaubey
    • Honam Mathematical Journal
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    • v.45 no.2
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    • pp.316-324
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    • 2023
  • The P-curvature tensor has been studied in the space-time of general relativity and it is found that the contracted part of this tensor vanishes in the Einstein space. It is shown that Rainich conditions for the existence of non-null electro variance can be obtained by P𝛼𝛽. It is established that the divergence of tensor G𝛼𝛽 defined with the help of P𝛼𝛽 and scalar P is zero, so that it can be used to represent Einstein field equations. It is shown that for V4 satisfying Einstein like field equations, the tensor P𝛼𝛽 is conserved, if the energy momentum tensor is Codazzi type. The space-time satisfying Einstein's field equations with vanishing of P-curvature tensor have been considered and existence of Killing, conformal Killing vector fields and perfect fluid space-time has been established.