共查询到20条相似文献,搜索用时 78 毫秒
1.
MIMO-OFDM技术 总被引:5,自引:0,他引:5
多进多出(MIMO)系统在发射端和接收端分别设置多副发射天线和接收天线,采用MIMO技术可以提高信道容量和信道可靠性,降低误码率。正交频分复用(OFDM)是一种特殊的多载波传输方案,各子载波在整个符号周期上正交,各子载波信号频谱可以互相重叠,子载波正交复用技术大大减少了保护带宽,提高了频带利用率。MIMO-OFDM技术是OFDM与MIMO技术结合形成的一种新技术,该技术是在OFDM传输系统中采用阵列天线实现空间分集,提高了信号质量。MIMO-OFDM技术将成为下一代移动通信核心技术的解决方案。文中全面介绍了MIMO技术和OFDM技术及两者的结合,分析了实现MIMO-OFDM技术的关键,展望了发展前景。 相似文献
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David William Marques Guerra Rafael Masashi Fukuda Ricardo Tadashi Kobayashi Taufik Abrão 《ETRI Journal》2018,40(5):570-581
This work analyzes the performance of implementable detectors for the multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) technique under specific and realistic operation system conditions, including antenna correlation and array configuration. A time-domain channel model was used to evaluate the system performance under realistic communication channel and system scenarios, including different channel correlation, modulation order, and antenna array configurations. Several MIMO-OFDM detectors were analyzed for the purpose of achieving high performance combined with high capacity systems and manageable computational complexity. Numerical Monte Carlo simulations demonstrate the channel selectivity effect, while the impact of the number of antennas, adoption of linear against heuristic-based detection schemes, and the spatial correlation effect under linear and planar antenna arrays are analyzed in the MIMO-OFDM context. 相似文献
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Hongwei Yang 《Communications Magazine, IEEE》2005,43(1):53-60
Orthogonal frequency-division multiplexing is a popular method for high-data-rate wireless transmission. OFDM may be combined with multiple antennas at both the access point and mobile terminal to increase diversity gain and/or enhance system capacity on a time-varying multipath fading channel, resulting in a multiple-input multiple-output OFDM system. In this article we give a brief technical overview of MIMO-OFDM system design. We focus on various research topics for the MIMO-OFDM-based air interface, including spatial channel modeling, MIMO-OFDM transceiver design, MIMO-OFDM channel estimation, space-time techniques for MIMO-OFDM, and error correction code. The corresponding link-level simulation results are encouraging, and show that MIMO-OFDM is a promising road to future broadband wireless access. 相似文献
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Yanrong Zhao Wenjing Zhao Gongpu Wang Bo Ai Hervin Hidayat Putra Bagus Juliyanto 《中国通信》2020,(3):90-100
Channel estimation is a well-known challenge for wireless orthogonal frequency division multiplexing(OFDM)communication systems with massive antennas on high speed rails(HSRs).This paper investigates this problem and design two practicable uplink and downlink channel estimators for orthogonal frequency division multiplexing(OFDM)communication systems with massive antenna arrays at base station on HSRs.Specifically,we first use pilots to estimate the initial angle of arrival(AoA)and channel gain information of each uplink path through discrete Fourier transform(DFT),and then refine the estimates via the angle rotation technique and suggested pilot design.Based on the uplink angel estimation,we design a new downlink channel estimator for frequency division duplexing(FDD)systems.Additionally,we derive the Cramér-Rao lower bounds(CRLBs)of the AoA and channel gain estimates.Finally,numerical results are provided to corroborate our proposed studies. 相似文献
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《Vehicular Technology, IEEE Transactions on》2009,58(3):1281-1291
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The combination of Space–Time Coded Multiple Input Multiple Output systems (STC-MIMO) with Orthogonal Frequency Division Multiplexing
(OFDM) is recently being investigated as an effective means of providing high-speed data transmission over dispersive wireless
channels. The strengths of the two techniques coalesce and render MIMO-OFDM systems robust to ISI and IBI. However, the decoding
and demodulation of STC-OFDM needs reliable channel knowledge at the receiver, unless differential modulation techniques are
used. Semi-blind methods for channel estimation are seen to provide the best trade-off in terms of bandwidth overhead, computational
complexity and latency. The conventional Expectation-Maximization (EM) algorithm for semi-blind channel estimation improves
a pilot-based estimate with a two step process; however, it is computationally complex to implement. In this paper, we propose
a variant of the EM method, referred to as ML-EM, for semi-blind estimation of doubly dispersive channels in space–time coded
MIMO-OFDM systems. Here, the conventional EM algorithm is coupled with the ML decoder for space time block codes (STBCs).
The technique shows good performance, even in highly correlated antenna arrays, and is computationally simpler than conventional
EM. The method incurs a training overhead of less than 1%, and performs close to exact CSI through iterative processing at
the receiver. 相似文献
8.
In this paper we present a
multiple-input, multiple-output
(MIMO)-orthogonal frequency division multiplexing (OFDM) system that uses orthogonal Walsh sequences for block coding. Two
configurations, space-time block coding (STBC) and the Vertical Bell Laboratories Layered Space-Time (V-BLAST) architecture,
are considered for the proposed system. A least-squares channel estimation with the fast Fourier transform method is utilized
in the system to replicate real-life scenarios. The idea of employing block coding based on orthogonal Walsh sequences is
inspired by the IS-95 standard and is attempted for the first time in MIMO-OFDM systems. A simulation study is carried out
by considering different antenna configurations, code sizes, and channel delays. Computer simulations show that the proposed
system achieves a significant performance improvement compared to MIMO-OFDM systems that do not use the proposed block coding
scheme. It is also shown that the new system is superior to some previous systems in computational complexity. 相似文献
9.
介绍了MIMO技术,OFDM的基本原理,利用两者的优点将其结合起来运用到未来移动通信系统中,并将成为未来移动通信中的关键技术。空时编码技术在MIMO-OFDM系统中的应用,通过仿真表明OFDM技术通过FFT变换能将频率选择性的多径衰落信道分成多个平坦衰落信道,使空时编码技术的应用不再受到平坦信道条件的限制。 相似文献
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Reconfigurable antenna solution for MIMO-OFDM systems 总被引:2,自引:0,他引:2
A reconfigurable microstrip dipole antenna solution for multiple-input multiple-output (MIMO) communication systems making use of orthogonal frequency division multiplexing (OFDM) is presented. When applied to closely spaced antenna arrays, this method can increase link capacity. The benefits of this novel antenna solution are demonstrated by channel capacity measurements taken in an indoor environment with a 2/spl times/2 MIMO system. 相似文献
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Multiple receive antennas with optimal combining have been known to improve error performance over fading multipath channels by providing spatial diversity. This benefit is obtained at the cost of greatly increased system complexity due to the need for multiple RF chains and signal combiners. Best antenna selection is a technique that can provide multiple antenna gains with only a single RF chain and no combiners. Best antenna selection is complicated by frequency selectivity in orthogonal frequency division multiplexing (OFDM) as the signal at any one antenna may not be the best at all subcarriers. In this paper, we propose a novel technique for best antenna selection in coded OFDM. To simplify the receiver, we assume a block fading model for the underlying frequency selective channel. The best antenna will then determined based on coding theorems known for block fading channels. Our simulations show significant improvement in coded OFDM performance over existing techniques. 相似文献
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MIMO-OFDM系统中的关键技术研究 总被引:6,自引:6,他引:0
MIMO与OFDM技术的结合,有效对抗频率选择性衰落、提高数据传输速率、增大系统容量,是第四代移动通信系统研究的热点问题.本文介绍了4G移动通信中的MIMO-OFDM的基本原理及MIMO-OFDM系统的关键技术包括信道估计、同步、空时编码技术和分集技术. 相似文献
18.
Chang‐Jun Ahn 《Wireless Communications and Mobile Computing》2006,6(8):1037-1045
Recently, unitary matrix modulation (UMM) has been investigated in multiple antenna systems which is called unitary space‐time modulation (USTM). In an OFDM, different channel delay profiles and path strengths bring different frequency selective patterns. Therefore, OFDM system can potentially provide a diversity at the frequency selective fading due to the different channel delay profiles. When we consider only the diagonal components of UMM with splitting over the coherence bandwidth, the system can obtain a frequency diversity in a single antenna, since the channel response of the diagonal components of UMM that split over the coherence bandwidth shows to be totally different. In this paper, we propose the diagonal components of UMM/OFDM with splitting over the coherence bandwidth (UMM‐S/OFDM) in a single antenna. The proposed system can obtain the frequency diversity with splitting the diagonal components of UMM/OFDM over the coherence bandwidth. Therefore, the proposed system with a single antenna can obtain good BER performance like the USTM/OFDM with two antennas. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
19.
Dhanasekaran Selvaraj Ramalingam Shanmugam Thamaraimanalan Thangarajan 《International Journal of Communication Systems》2024,37(3):e5663
Several input high-data-rate transmissions over broadband wireless channels are possible using multiple input multiple output (MIMO) systems paired with orthogonal frequency division multiplexing (OFDM) technology. Channel estimation is an essential technique and a necessary component of MIMO-OFDM systems. However, the noise will be there in MIMO-OFDM due to the environment. As a result, the wireless system performs degrades in terms of bit error rate (BER). The suggested method offers a better pilot pattern strategy for MIMO-OFDM and an efficient power allocation to address this issue. The binomial distribution-based grey wolf optimization (BDGWO) algorithm is proposed to identify the optimal pilot patterns. The power is then adaptively distributed to each transmit antenna to increase the spectral efficiency and maximum channel capacity through an adaptive neuro-fuzzy inference system with a sigmoid membership function (SMFANFIS). The best pilot patterns in PDGSIP (pilot design with generalized shift invariant property) were determined using the BDGWO algorithm based on the binomial distribution. According to the simulation results, the proposed BDGWO established pilot design with generalized shift invariant property (BDGWO-DGSIP) achieves higher performance compared other existing approaches such as PDGSIP, TPDGSIP, and LS in terms of NMSE, BER, and SER. Compared to the PDGSIP technique, the proposed PDGSIP-BDGWO system minimizes NMSE at 10%, BER at about 12%, and SER at 15%. 相似文献
20.
Bashir Reza Karimi Mojtaba Beheshti Mohammad Javad Omidi 《Wireless Personal Communications》2014,79(3):1925-1940
Multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) technology is a promising solution for next generation wireless communications, due to high bandwidth efficiency, resistance to RF interference, and robustness to multipath fading. A major drawback of OFDM is its high peak-to-average power ratio (PAPR) which results in non-linearities in the output signal. In this paper, two methods based on spatial/temporal processing are proposed to reduce the PAPR of MIMO-OFDM systems. These methods divide the OFDM block at each transmit antenna into some subblocks. Then, spatial and temporal processing in the form of circular shifting or interleaving are applied to generate different candidate sequences. Finally, for each transmit antenna the candidate sequence with the lowest PAPR is chosen for transmission. Compared to the conventional PAPR reduction schemes such as ordinary partial transmit sequences (O-PTS), the proposed methods require lower computational complexity and have superior PAPR reduction performance. 相似文献