• Title/Summary/Keyword: MIMO Antennas

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Beamformer-based Acquisition in CDMA-MIMO Communication Systems (CDMA-MIMO 통신 시스템에서 빔형성기 기반의 코드 동기 획득 기술)

  • Kim, Sang-Choon;Baek, Sun-Young;An, Jin-Young;Son, Kyoung-Soo
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.12 no.7
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    • pp.1271-1277
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    • 2008
  • This paper proposes the code acquisition scheme on a MIMO channel for preamble search in a CDMA-MIMO uplink system. The multiple transmit/receive antennas are used for beamforming. The performance of a ML code acquisition technique based on transmit and receive beamforming is analyzed by considering rho detection probability. The acquisition performance and MAT for a MIMO code acquisition system are numerically evaluated. It is shown that multiple transmit antennas can give the code acquisition system a transmit beamforming gain and result in much better performance than a SIMO case.

Signal Enhancement through Polarization Adaptivity on Transmit in a Near-Field MIMO Environment (근접장 MIMO 전송 환경에서의 편파 적응을 이용한 신호의 개선 방법)

  • Hwang, Seung-Hyeon;Koh, Jin-Hwan
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.37 no.8A
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    • pp.618-631
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    • 2012
  • In this paper polarization adaptivity on transmit has been used to enhance the received signals directed to a pre-selected receiver in a near-field multi-input multi-output (MIMO) environment. The objective here is to select a set of weights on the transmitting antennas adapted to individual receivers based on the principles of reciprocity. Using the polarization properties, when the number of receiving antennas is greater than the number of transmitting antennas, the transmitted signal may be directed more to a particular receiver location while simultaneously minimizing the reception signal strength at other receivers. Numerical simulations have been made to illustrate the novelty of the proposed approach.

Interference Cancellation Based on Adaptive Signal Processing for MIMO RF Repeaters (MIMO RF 중계기를 위한 적응 신호처리 기반의 간섭 제거)

  • Lee, Kyu-Bum;Choi, Ji-Hoon
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.35 no.9C
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    • pp.735-742
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    • 2010
  • In this paper, we propose adaptive algorithms for interference cancellation in RF repeaters with multiple transmit and receive antennas. When multiple antennas are used in a repeater, the imperfect isolation between transmit and receive antennas causes the feedback interference which is modeled as multi-input multi-output (MIMO) channel. To remove the feedback interference, we derive the least mean square (LMS) algorithm and the recursive least squares (RLS) algorithm for interference cancellation based on adaptive signal processing techniques. Through computer simulations for the proposed algorithms, we analyze the convergence characteristics and compare the steady-state performance for interference cancellation.

Performance Analysis for MIMO Multiuser Systems considering Selection of Transmit Antennas, Constellations and Powers in Low-to-medium Mobile Speed (중저속 이동체환경에서의 MIMO시스템 기반 안테나 선택과 전력할당 성능분석)

  • Yoo Hyun;Kim Jin-Su;Kim Jong-Ki;Seo Myoung-Seok;Kwak Kyung-Sup
    • Proceedings of the KSR Conference
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    • 2005.05a
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    • pp.776-781
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    • 2005
  • In this paper, using received channel information, we analyze performance in MIMO multiuser system in low-to-medium mobile speed by selecting each user's constellations, powers, and transmit antennas. Given a target of symbol error, we determine each user's constellations, powers, selected tranprobability smit antennas such that the required signal-to-noise(SNR) is minimized for MMSE, V-BLAST receiver according to each user's information and channel estimation information. When we do power control with antenna selection technique through uplink channels of MIMO system in low-to-medium mobile speed, we analyze system performance with wireless channel information from Base-Station(BS) to Users. By simulation, it has been shown that the proposed antenna selection scheme for transmitting data offer better performance improvement than all transmit antennas for transmitting data.

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Performance of MIMO-OFDM Systems using The Relay With Multi-Antennas for Cooperative Diversity (Put English Title Here) (다중 안테나의 relay를 가진 MIMO-OFDM시스템의 Cooperative diversity에 따른 성능)

  • Kim, Chan-Kyu;Kim, Young-Il
    • Journal of the Institute of Electronics Engineers of Korea TC
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    • v.45 no.6
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    • pp.13-19
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    • 2008
  • In this paper, the new cooperative communication techniques is proposed for multi-input multi-output(MIMO)-orthogonal frequency division multiplexing (OFDM) system using the relay with multiple antenna. As the MIMO channel is formed by space time coding at the MS(mobile station)-RS(relay station) and RS-BS(base station), we can get the cooperative diversity and MIMO diversity gain simultaneously. Therefore, the performance of MIMO-OFDM system using the relay with multiple-antennas is very improved. And the simple power allocation technique is Proposed for the transmitting power of the mobile station and the relay.

HARQ Switching Metric of MIMO-OFDM Systems using Joint Tx/Rx Antenna Scheduling (송.수신 안테나 스케줄링에 기반한 MIMO-OFDM 시스템의 HARQ 스위칭 기법)

  • Kim, Kyoo-Hyun;Knag, Seoung-Won;Chang, Kyung-Hi;Jeong, Byung-Jang;Chung, Hyun-Kyu
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.32 no.6A
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    • pp.519-536
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    • 2007
  • In this paper, we combine the Hybrid-Automatic Repeat reQuest (HARQ) algorithm with joint Tx and Rx antenna selection based on the reliability of the individual antennas links. The cyclic redundancy check (CRC) is applied on the data before being encoded using the Turbo encoder. In the receiver the CRC is used to detect errors of each antenna stream and to decide whether a retransmission is required or not. The receiver feeds back the transmitter with the Tx antennas ordering and the acknowledgement of each antenna (ACK or NACK). If the number of ACK antennas is higher than the NACK antennas, then the retransmission takes place from the ACK antennas using the Chase Combining (CC). If the number of the NACK antennas is higher than the ACK antennas then the ACK antennas are used to retransmit the data streams using the CC algorithm and additional NACK antennas are used to retransmit the remaining streams using Incremental Redundancy (IR, i.e. the encoder rate is reduced). Furthermore, the HARQ is used with the I-BLAST (Iterative-BLAST) which grantees a high transmission rate.

An Algorithm for Iterative Detection and Decoding MIMO-OFDM HARQ with Antenna Scheduling

  • Kim, Kyoo-Hyun;Kang, Seung-Won;Mohaisen, Manar;Chang, Kyung-Hi
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • v.2 no.4
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    • pp.194-208
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    • 2008
  • In this paper, a multiple-input-multiple-output (MIMO) hybrid-automatic repeat request (HARQ) algorithm with antenna scheduling is proposed. It retransmits the packet using scheduled transmit antennas according to the state of the communication link, instead of retransmitting the packet via the same antennas. As a result, a combination of conventional HARQ systems, viz. chase combining (CC) and incremental redundancy (IR) are used to achieve better performance and lower redundancy. The proposed MIMO-OFDM HARQ system with antenna scheduling is shown to be superior to conventional MIMO HARQ systems, due to its spatial diversity gain.

Efficient Channel Estimator based on Channel Correlation in a Mobile MIMO OFDM System (모바일 MIMO OFDM 시스템에서 채널의 상관성을 이용한 효율적인 채널 추정 기법)

  • 김지형;박병준;홍대식;강창언
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.29 no.4A
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    • pp.384-389
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    • 2004
  • In this paper, we investigate channel estimation techniques based on the comb-type pilot arrangement for a mobile MIMO OFDM system. Moreover, to enhance channel estimation, an efficient channel estimation technique is proposed. Simulation results show that the proposed channel estimator is accurate and effective for tracking variations of channels between multiple transmit antennas and receive antennas in time-varying radio channels.

Before/After Precoding Massive MIMO Systems for Cloud Radio Access Networks

  • Park, Sangkyu;Chae, Chan-Byoung;Bahk, Saewoong
    • Journal of Communications and Networks
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    • v.15 no.4
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    • pp.398-406
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    • 2013
  • In this paper, we investigate two types of in-phase and quadrature-phase (IQ) data transfer methods for cloud multiple-input multiple-output (MIMO) network operation. They are termed "after-precoding" and "before-precoding". We formulate a cloud massive MIMO operation problem that aims at selecting the best IQ data transfer method and transmission strategy (beamforming technique, the number of concurrently receiving users, the number of used antennas for transmission) to maximize the ergodic sum-rate under a limited capacity of the digital unit-radio unit link. Based on our proposed solution, the optimal numbers of users and antennas are simultaneously chosen. Numerical results confirm that the sum-rate gain is greater when adaptive "after/before-precoding" method is available than when only conventional "after-precoding" IQ-data transfer is available.

The performance of MIMO cooperative communication systems using the relay with multi-antennas and DSTC

  • Chan Kyu Kim
    • International Journal of Internet, Broadcasting and Communication
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    • v.15 no.3
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    • pp.14-23
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    • 2023
  • The cooperative communication systems using MIMO(multiple input multiple-output) relay are known as one of the most promising techniques to improve the performance and coverage of wireless communication systems. In this paper, we propose the cooperative communication systems using the relay with multi-antennas and DSTC(distributed space time coding) for decode-and-forward protocol. As using DSTC for DF(decode-and-forward), we can minimize the risk of error propagation at the wireless system using relay system. Also, the MIMO channel cab be formed by multi-antenna and DSTC at the MS(mobile station)-RS(relay station) and at the RS-BS(base station).Therefore, obtaining truly constructive the MIMO diversity and cooperative diversity gain from the proposed approach, the performance of system can be more improved than one of conventional system (relay with single antenna, no relay). The improvement in bit error rate is investigated through numerical analysis of the cooperative communication system with the proposed approach.