• Title/Summary/Keyword: Frequency Diversity

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Adaptive Channel-Matched Extended Alamouti Space-Time Code Exploiting Partial Feedback

  • Badic, Biljana;Rupp, Markus;Weinrichter, Hans
    • ETRI Journal
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    • v.26 no.5
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    • pp.443-451
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    • 2004
  • Since the publication of Alamouti's famous space-time block code, various quasi-orthogonal space-time block codes (QSTBC) for multi-input multi-output (MIMO) fading channels for more than two transmit antennas have been proposed. It has been shown that these codes cannot achieve full diversity at full rate. In this paper, we present a simple feedback scheme for rich scattering (flat Rayleigh fading) MIMO channels that improves the coding gain and diversity of a QSTBC for 2$^n$ (n=3, 4, ${\cdots}$) transmit antennas. The relevant channel state information is sent back from the receiver to the transmitter quantized to one or two bits per code block. In this way, signal transmission with an improved coding gain and diversity near to the maximum diversity order is achieved. Such high diversity can be exploited with either a maximum-likelihood receiver or low-complexity zero-forcing receiver.

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A New Polarization Diversity Scheme for Orthogonal Polarization and Frequency Division Multiplexing System

  • Ido, Jun;Okada, Minoru;Komaki, Shozo
    • Proceedings of the IEEK Conference
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    • 2000.07b
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    • pp.973-976
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    • 2000
  • This paper proposes a new polarization diversity scheme for OPFDM (Orthogonal Polarization and Frequency Division Multiplexing). OPFDM is an extension of OFDM (Orthogonal Frequency Division Multiplexing) in conjunction with polarization multiplexing in order to ensure the orthogonality amongst subcarriers. Since OPFDM uses two orthogonally polarized channels, it can easily employ the polarization diversity. In order to get the diversity gain effectively in a frequency selective fading channel, the proposed scheme combines the signals in subcarrier-by-subcarrier basis. The computer simulation results confirm that the proposed scheme is superior to conventional one in the two orthogonally polarized two-ray Rayleigh fading channels with cross-talk between the two channels.

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Delay Determination of Cyclic Delay Diversity for Multi-user Scheduling in OFDMA Systems (OFDMA 시스템의 다중 사용자 스케줄링을 위한 순환지연 다이버시티의 지연값 결정)

  • Rim, Min-Joong;Hur, Seong-Ho;Song, Hyun-Joo;Lim, Dae-Woon;Jeong, Byung-Jang;Noh, Tae-Gyun
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.33 no.3A
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    • pp.248-255
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    • 2008
  • In an OFDMA system the performance of multi-user scheduling in the frequency domain is affected by the frequency selectivity of the channel. If the channel is too flat in the frequency domain, the multi-user scheduling gain might be degraded. On the contrary, if the frequency selectivity is too high and the magnitude of the frequency response severely fluctuates on the allocation bandwidth, it is also hard to get sufficient scheduling gain. For maximizing the multi-user scheduling gain, a cyclic delay diversity technique can be used to adjust the frequency selectivity of the channel. This paper proposes a method to determine the optimal delay value of cyclic delay diversity according to the allocation bandwidth and the channel characteristics.

Spatial and Frequency Diversity Combining Order in Uplink SC-FDMA with SIMO Systems (상향링크 SIMO 시스템에서 공간 및 주파수 다이버시티 컴바이닝 순서에 따른 SC-FDMA 성능 분석)

  • Lee, Jin-Hui;Choi, Kwonhue
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.40 no.3
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    • pp.432-440
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    • 2015
  • We investigate BER performance according to the order of spatial and frequency diversity combining in uplink SC-FDMA of SIMO systems. It is found that frequency diversity combining (FDC) after spatial diversity combining (SDC) is better than the reverse order combing in all SNR (Signal to Noise Ratio) range. Also, it is shown that FDC after SDC requires less computational complexity than the reverse order combining.

Performance of selective combining according to channel selection decision method of frequency diversity in underwater frequency selective channel (수중 주파수 선택적 채널에서 주파수 다이버시티의 채널 선택 판정법에 따른 선택 합성법의 성능)

  • Lee, Chaehui;Jeong, Hyunsoo;Park, Kyu-Chil;Park, Jihyun
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.26 no.3
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    • pp.436-442
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    • 2022
  • In this paper, the performance of the selective combining according to the channel selection decision method of frequency diversity is evaluated in the underwater frequency selective channel. The underwater acoustic channel in the shallow sea has a complex multipath characteristic by combining various environmental factors such as boundary surface reflection and sound wave refraction according to the water temperature layer. In particular, frequency selectivity due to multipath causes energy fluctuation in a communication channel, which reduces SNR (Signal to Noise Ratio) and deteriorates communication performance. In this paper, we applied the frequency diversity technique using multiple channels to secure the communication performance according to the frequency selectivity by multipath. For each channel, 4-FSK (Frequency Shift Keying) and selective combining were applied, the performance was evaluated by applying the maximum value, average value, and majority decision of the signal in order to decide the demodulation channel selection of the selective combining.

Frequency divided group beamforming with sparse space-frequency code for above 6 GHz URLLC systems

  • Chanho Yoon;Woncheol Cho;Kapseok Chang;Young-Jo Ko
    • ETRI Journal
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    • v.44 no.6
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    • pp.925-935
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    • 2022
  • In this study, we propose a limited feedback-based frequency divided group beamforming with sparse space-frequency transmit diversity coded orthogonal frequency division multiplexing (OFDM) system for ultrareliable low latency communication (URLLC) scenario. The proposed scheme has several advantages over the traditional hybrid beamforming approach, including not requiring downlink channel state information for baseband precoding, supporting distributed multipoint transmission structures for diversity, and reducing beam sweeping latency with little uplink overhead. These are all positive aspects of physical layer characteristics intended for URLLC. It is suggested in the system to manage the multipoint transmission structure realized by distributed panels using a power allocation method based on cooperative game theory. Link-level simulations demonstrate that the proposed scheme offers reliability by achieving both higher diversity order and array gain in a nonline-of-sight channel of selectivity and limited spatial scattering.

Performance Evaluation of Fill Rate Quasi-orthogonal STF-OFDM with DAC-ZF Decoder for Four Transmit Antennas MIMO System (4개의 송신 안테나 MIMO 시스템을 위한 DAC-ZF 수신 기법과 결합된 Full Rate 준직교 QOSTF-OFDM 관한 연구)

  • Jin, Ji-Yu;Ryu, Kwan-Woong;Park, Yong-Wan
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.31 no.11A
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    • pp.1092-1100
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    • 2006
  • In this paper, we propose a full rate quasi-orthogonal space-time-frequency block coded orthogonal frequency division multiplexing(QOSTF-OFDM) that can achieve full symbol rate with four transmit antennas. Sincr: the proposed QOSTF-OFDM can not achieve full diversity, we use diversity advantage collection with zero forcing (DAC-ZF) decoder to compensate the diversity loss at receive side. At the same frequency efficiency, compared with linear orthogonal space-time codes which can not achieve full rate with four transmit antennas over complex constellations, low level modulation can be employed by proposed scheme due to its full rate, i.e., modulation advantage can be achieved. Due to modulation advantage and collected diversify advantage, the proposed scheme exhibits better BER performance than other orthogonal schemes.

On Maximum Diversity Order over Doubly-Selective MIMO-OFDM Channes

  • Yang Qinghai;Kwak Kyung Sup
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.30 no.7A
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    • pp.628-638
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    • 2005
  • The analysis of maximum diversity order and coding gain for multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) systems over time-and frequency-selective (or doubly-selective) channels is addressed in this paper. A novel channel time-space correlation function is developed given the spatially correlated doubly-selective Rayleigh fading channel model. Based on this channel-model assumption, the upper-bound of pairwise error probability (PEP) for MIMO-OFDM systems is derived under the maximum likelihood (ML) detection. For a certain space-frequency code, we quantify the maximum diversity order and deduce the expression of coding gain. In this wort the impact of channel time selectivity is especially studied and a new definition of time diversity is illustrated correspondingly

Covariance Matrix Synthesis Using Maximum Ratio Combining in Coherent MIMO Radar with Frequency Diversity

  • Jeon, Hyeonmu;Chung, Yongseek;Chung, Wonzoo;Kim, Jongmann;Yang, Hoongee
    • Journal of Electrical Engineering and Technology
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    • v.13 no.1
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    • pp.445-450
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    • 2018
  • Reliable detection and parameter estimation of a radar cross section(RCS) fluctuating target have been known as a difficult task. To reduce the effect of RCS fluctuation, various diversity techniques have been considered. This paper presents a new method for synthesizing a covariance matrix applicable to a coherent multi-input multi-output(MIMO) radar with frequency diversity. It is achieved by efficiently combining covariance matrices corresponding to different carrier frequencies such that the signal-to-noise ratio(SNR) in the combined covariance matrix is maximized. The value of a synthesized covariance matrix is assessed by examining the phase curves of its entries and the improvement on direction of arrival(DOA) estimation.

STF-OFDM Transmission Scheme with Frequency Diversity (주파수 다이버시티를 갖는 STF-OFDM 전송 기법)

  • 박상순;황호선;백흥기
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.29 no.2C
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    • pp.206-212
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    • 2004
  • In this paper, we propose a STF(Space-Time-Frequency) coded OFDM(Orthogonal Frequency Division Multiplexing) transmission scheme as an attractive solution for high bit rate data transmission in a multipath fading environment. STBC(Space-Time Block Coding) has been proposed as a simple diversity scheme using two transmit antennas. Also ST-OFDM(Space-Time Block Coded OFDM) and SF-OFDM(Space-Frequency Block Coded OFDM) transmission scheme, that the STBC is applied to the OFDM, has been proposed. In this paper, we propose STF-OFDM transmission scheme that to coded in time, space and frequency domain. The STF-OFDM transmission scheme that we propose in this paper is the way to improve a performance of conventional ST-OFDM, by using frequency diversity.