• Title/Summary/Keyword: MIMO-OFDM systems

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Efficient pipelined FFT processor for the MIMO-OFDM systems (MIMO-OFDM 시스템을 위한 효율적인 파이프라인 FFT 프로세서의 설계)

  • Lee, Sang-Min;Jung, Yun-Ho;Kim, Jae-Seok
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.32 no.10C
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    • pp.1025-1031
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    • 2007
  • This paper proposes an area-efficient pipeline FFT processor for MIMO-OFDM systems with four transmitting and four receiving antennas. Since the MIMO-OFDM system transmits multiple data streams, the complexity for the MIMO-OFDM system with a single-channel FFT processor increases linearly with the increase of the number of transmit channels. The proposed FFT processor is based on multi-channel structure, and therefore it can efficiently support multiple data streams. With the mixed radix algorithm, the number of non-trivial multiplications of the proposed FFT processor is decreased. The proposed FFT processor is synthesized with CMOS $0.18{\mu}m$ process and reduces the logic gates by 25% over a 4-channel Radix-4 multi-path delay commutator (R4MDC) FFT processor. Since the MIMO-OFDM FFT processor is one of the largest modules in the systems, the proposed FFT processor will be a vast contribution improvement to the low complexity design of MIMO-OFDM systems.

Hybrid Symbol Offset Estimation Algorithm for MIMO OFDM Systems (MIMO OFDM 시스템을 위한 하이브리드 심볼 옵셋 추정 알고리즘)

  • Jung, Hyeok-Koo
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.19 no.4
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    • pp.461-469
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    • 2008
  • This paper proposes a hybrid symbol offset estimation algorithm for MIMO(Multiple Input Multiple Output) OFDM system. As MIMO OFDM systems are multiple transmitter and receiver antenna systems, apart from SISO(Single Input Single Output) system, it is possible to use several combining techniques which are used in multiple receive antenna system. In this paper, we propose hybrid symbol offset estimation algorithms using combining techniques in multiple receive antenna systems, simulate and show the performances in MIMO system environments. The proposed equal gain combining correlation algorithm has better performance 1.8 times in searching the ideal symbol offset rather than the conventional early symbol offset algorithm in severe ISI channel.

An Analysis of Multiuser Diversity Technology in the MIMO-OFDM System (MIMO-OFDM 시스템에서 다중사용자 다이버시티 기술의 성능분석)

  • Zhang, Ke;Suh, Hee-Jong
    • The Journal of the Korea institute of electronic communication sciences
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    • v.14 no.6
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    • pp.1121-1128
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    • 2019
  • In this paper, we introduce the combination of OFDM(Orthogonal Frequency Division Multiplexing) and MIMO(Multiple-Input Multiple-Output) technology, and explain that this combination seems to be very preferable when designing very high-rate wireless mobile systems. The application of OFDM, with the block diagrams of an OFDM modulator and demodulator and a MIMO-OFDM system, are described. The several diversities are studied at the receiver, analyzed the performances of diversity in OFDM-MIMO system and simulated results.

Performance of MIMO-OFDM systems with multi-beamforming based on MMSE (MMSE 기반의 다중 빔형성기법을 가진 MIMO-OFDM 시스템의 성능)

  • Kim, Chan-Kyu
    • Journal of the Institute of Electronics Engineers of Korea TC
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    • v.48 no.6
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    • pp.6-13
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    • 2011
  • Multiple-input multiple-output (MIMO)-orthogonal frequency division multiplexing (OFDM) with space-time coding (STC) is a promising technology for future wireless communication systems. However, MIMO-OFDM systems are greatly impaired by large cochannel interference (CCI) from the multiple transmitters. In this paper, we propose pre-fast Fourier transform (FFT) multibeamforming based on MMSE(minimizing the mean squared error) for a MIMO-OFDM system to preserves the STC diversity and to remove the CCI. The improvement in bit error rate is investigated through computer simulation of a MIMO-OFDM system in a multipath channel with CCI.

A Channel Estimation Method by Orthogonalizing of the time domain training signals in MIMO-OFDM systems (MIMO-OFDM 시스템에서 시간영역 훈련신호들의 직교화를 통한채널추정 방법)

  • Jeon, Hyoung-Goo
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.17 no.12
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    • pp.2818-2825
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    • 2013
  • In this paper, a channel estimation method by orthogonalizing of the time domain training signal in MIMO-OFDM systems is proposed. It has shown that Jeon's method[8] cannot be directly used in 4 Tx antenna MIMO-OFDM systems since the delayed Rx signals interfere the orthogonal property of the time domain training signals. As a possible solution to the problem, in this paper, a guard interval is inserted into the center of the training signals so that the orthogonal property between the Rx training signals can be maintained. It is shown by using computer simulations that the proposed method can estimate the channel response in time domain in 4 Tx antenna MIMO-OFDM systems.

A New Techniques for Estimation of Carrier Frequency Offset in MIMO OFDM Systems (다중 입출력 직교 주파수 분할 다중화 시스템에서의 반송파 주파수 오프셋 추정을 위한 새로운 기법)

  • Altaha, Mustafa;Hwang, Humor
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.66 no.6
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    • pp.949-954
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    • 2017
  • Multiple input, multiple output orthogonal frequency division multiplexing (MIMO OFDM) systems are the candidate for the future wireless communications. However, the main drawback of MIMO OFDM systems is their sensitivity to carrier frequency offset (CFO) similar to the single input, single output OFDM (SISO OFDM) systems. The demodulation of a signal with CFO causes large bit error rate and degrade the performance of a symbol synchronizer. It is important to estimate the frequency offset and minimize or eliminate its impact. In this paper, we propose a technique based on observation training symbols for estimating CFO by employing block-by-block estimation for SISO OFDM systems. The technique of SISO OFDM is extended to the MIMO OFDM systems. Simulation results show that the proposed techniques have a superior performance and better accuracy compared to the conventional techniques in the sense of mean square error.

Channel Estimation Scheme Using Modified ICA in MIMO-OFDM Systems (MIMO-OFDM 시스템에서 Modified ICA를 이용한 채널 추정 기법)

  • Kim Jong-Deuk;Byun Youn-Shik
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.31 no.5A
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    • pp.475-483
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    • 2006
  • If channel coefficients errors exist in MIMO-OFDM systems, the performance degradation of systems will occurs. In order to improve the performance of MIMO-OFDM systems, the technique of obtaining accurate channel estimation in multipath fading channel is necessary. In this paper, we introduce and propose new channel estimation-modified ICA algorithm. Simulation results shows from BER and SER curves which compare the proposed algorithm under time-varying Rayleigh fading with perfect known channel. The result of channel estimation by the proposed algorithm in this simulation, it shows that PDF(amplitude of channel) are close to the case with perfect known channel at the receiver with respect to uncoded QPSK/16-QAM/64-QAM modulation. Also, we can see that BER and SER curves are very close to the case with perfect known channel. Therefore, we see that the proposed algorithm have a good performance in MIMO-OFDM systems.

Performance Analysis of Adaptive Bitloading Algorithm in MIMO-OFDM Systems (MIMO-OFDM 시스템에서 적응비트로딩 알고리즘의 성능평가)

  • Lee Min-Hyouck;Byon Kuk-Sik
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.10 no.4
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    • pp.752-757
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    • 2006
  • In the case of the requirement of high speed transmission, OFDM is a powerful technique employed in communications systems suffering from frequency selective fading. In this paper, we apply an optimal adaptive bitloading algorithm technique. The BER performance of the fixed-rate SISO and adaptive SISO is simulated. Specially, we can decompose the MIMO channel into the SISO channel by making use of the singular value decomposition(SVD) assuming channel knowledge in a multipath environment. As a results of simulation, we confirmed that the BER enhancement of MIMO-OFDM system with the bitloadins algorithm was superior to the SISO-OFDM system.

Performance Analysis for SVR-MMSE Detection of Constant Modulus Signals in MIMO-OFDM Systems (MIMO-OFDM 시스템에서 Constant Modulus 신호의 SVR-MMSE 검출 성능 분석)

  • Shin, Chul-Min;Seo, Myoung-Seok;Yang, Qing-Hai;Kwak, Kyung-Sup
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.31 no.12A
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    • pp.1198-1204
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    • 2006
  • In this paper, we extend SVR-MMSE detection scheme which is proposed in MIMO system to MIMO-OFDM system, and evaluate performance of the system in frequency selective fading channel. First of all, we explain about typical MIMO-OFDM system and detection scheme of constant modulus signals in this system. And compare proposed SVR-MMSE with Zero Forcing, Minimum Mean Square Error which is conventional detection scheme. we identify that the performance of the proposed system is shown different by varying doppler frequency in frequency selective fading channel using jakes channel model. The result of detection performance by the proposed SVR-MMSE in this simulation, it shows that proposed algorithm have a good performance in MIMO-OFDM systems.

Performance Evaluation of High-performance MIMO-OFDM System using Carrier Interferometry Codes in Frequency Selective Fading Channels (주파수 선택적 페이딩 채널에서 반송파 간섭 부호를 이용한 고성능 MIMO-OFDM 시스템의 성능분석)

  • Seo Wan-woo;Chung Yeon-ho
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.9 no.8
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    • pp.1643-1648
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    • 2005
  • MIMO system takes advantage of the spatial diversity obtained by spatially separated antennas for high- performance and high-capacity broadband wireless access. In this paper, we propose Carrier Interferometry coded MIMO-OFDM system (MIMO-CI/OFDM) which provides frequency and spatial diversity. One combined diversity gains featly improve the performance of OFDM systems. To perform a performance analysis, we have used SPW platform that provides an easy tool to analyze the performance. The results show that the performance of MIMO-CI/OFDM shows an approximately 4dB gain over the MIMO-OFDM even in highly frequency selective fading channels.