共查询到20条相似文献,搜索用时 15 毫秒
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在下一代的无线通信正交频分复用(OFDM)系统中,提出一种基于交织迭代软解调接收机。发射机和接收机结合了交织分多址(IDMA),所提出的信号估计器(ESE)利用交织码消除邻小区干扰(ICI),结合软解调技术,通过迭代获得低误码率的高阶调制邻小区干扰抑制性能。蒙特卡洛仿真结果显示,所提出的接收机模型在16QAM的OFDM系统中,高斯以及瑞利信道条件下,均能获得较好的误码率性能。 相似文献
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相位噪声也能引起信道间干扰( ICI) ,本文系统的分析了采用ICI自消除方案前后相位噪声对OFDM系统的影响,得出了载波干扰比和信噪比的近似计算公式,在AWGN信道上仿真了系统的误码性能。从仿真结果看,ICI自消除的方案能够显著提高系统的载波干扰比和误码率 相似文献
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An efficient packet detection scheme based on Wi-Fi interface was proposed.It was implemented by employing a novel normalized factor as a denominator in OFDM symbol synchronization-timing metric.Compared to the old-tradition schemes,the proposed scheme can not only obtain great detection probability,but also achieve the threshold setting without pre-estimation of frequency offset.Both theoretical analysis and conducted simulation results show that the new scheme facilitates threshold selection for a wide range of signal-to-noise ratio (SNR) in additive white Gaussian noise (AWGN) channel.Besides,the threshold setting in multi-path Rayleigh fading channels can be determined according to the AWGN case straight forwardly. 相似文献
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《Vehicular Technology, IEEE Transactions on》2009,58(2):636-643
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《Digital Communications & Networks》2018,4(4):258-263
Orthogonal Frequency Division Multiplexing (OFDM) is the most preferred and widely used multiplexing technique in current wireless environment for sidelining the spectrum scarcity problem by splitting a signal into N signals and subsequently modulating them through several orthogonal subcarriers (which bears high frequency). With several great features, OFDM is severely affected by undesirable effects of frequency offset errors and Local Oscillator (LO) frequency synchronization errors. This paper proposes an approach that devises a new hybrid technique, which is a combination of Maximum Likelihood Estimation (MLE) and Self Cancellation (SC) techniques through wavelet implication, to enhance BER performance of the OFDM system. A comparative analysis of SC, MLE, and wavelet-based hybrid InterCarrier Interference (ICI) cancellation techniques was conducted using 64-QAM and differential offset (0.02 and 0.01) for differential data bits (4 Mb and 16 Mb) to justify the outstanding results. The simulation results showed a significant byte-error-rate improvement over different legacy techniques based on fast Fourier transform. 相似文献
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Volkan Kumbasar Ouz Kucur A. Arif Ergin Ertan
ztürk 《Wireless Communications and Mobile Computing》2009,9(9):1243-1250
Using genetic algorithm (GA), optimal wavelets are obtained to reduce ISI and ICI powers of a wavelet‐based orthogonal frequency division multiplexing (OFDM) system over a practical two path low‐voltage powerline channel or two path fading channel by relaxing the perfect quadrate mirror filter (QMF) orthogonality. Optimum wavelet‐based OFDM system experiences less interference compared to conventional and Daubechies (Db) wavelet‐based OFDM systems. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
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《Broadcasting, IEEE Transactions on》2009,55(1):84-94
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Zahraa Abdel Hamid Moataz Samir Saied M. Abd El-atty Adel E. El-Hennawy Hamed El Shenawy Saleh A. Alshebeili Fathi E. Abd El-Samie 《Wireless Personal Communications》2014,78(2):1495-1510
The efficiency of data transmission over fading channels in orthogonal frequency division multiplexing (OFDM) systems depends on the employed interleaving method. In this study, we propose an improved chaotic interleaving scheme which aims to improve the performance of OFDM system under fading channel. In the proposed scheme, the binary data is interleaved with chaotic Baker map prior to the modulation process. In the sequel, significant degree of encryption is being added during data transmission. The performance of the proposed approach is tested on the conventional fast Fourier transform OFDM, discrete wavelet transform OFDM, and discrete cosine transform OFDM with and without chaotic interleaving. Furthermore, an expectation–maximization (EM) algorithm is proposed for improving channel impulse response (CIR) estimation based on a maximum likelihood principle. The proposed scheme makes use of EM algorithm to update the channel estimates until convergence is reached. The simulation results show the efficiency of the proposed algorithms under Rayleigh fading environments where the symbol error rate essentially coincides with that of the perfect channel case after the fifth EM iteration. 相似文献
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In this paper, we provide an exact analysis of phase-noise effects on orthogonal frequency division multiplexing (OFDM) performance.
We focus on the phase-noise inter-carrier interference (ICI) and derive a closed-form expression for the signal-to-interference-noise
ratio (SINR), which helps in understanding how system behavior changes with a certain parameter. An ICI reduction (ICIR) scheme
was proposed in [14] and the algorithm performance over AWGN channel was thoroughly studied. In this paper, we further extend
this work to Rayleigh fading channel and investigate the effects of multipath fading on the phase-noise mitigation. It is
shown by the study that the ICIR algorithm reduces the phase-noise ICI a great deal before channel estimation and improves
greatly system performance. Finally, numerical results show the effectiveness of the proposed approaches.
Guanghui Liu was born in Sichuan, China, in 1976. He received the B.S. degree from Sichuan Teachers College, Nanchong, Sichuan, China
in 1999, received the M.Sc. and Ph.D. degrees in electronic engineering from University of Electronic Science and Technology
of China (UESTC), Chengdu, Sichuan, China, in 2002 and 2005 respectively. Dr. Liu serves as a reviewer for the IEEE Transactions
on Communications, the IEEE Transactions on Broadcasting and the IEEE Transactions on Wireless Communications. As a research
engineer, he is now with Samsung Electronics, Suwon, Republic of Korea. His research interests include synchronization, channel
estimation and equalization, phase-noise suppression in OFDM communication systems.
Weile zhu was born in Sichuan, China, in 1940. Since 1988 he has been a professor of signal processing with University of Electronic
Science and Technology of China, Chengdu, China. He was a visiting scholar researching image processing in University of Illinois
from 1980 to 1981, researching pattern recognition in Purdue University from 1982 to 1983, and researching intelligent robot
in Stanford University from 1990 to 1991. His research interests include digital video codec and transmission, multicarrier
modulation, and HDTV etc. 相似文献
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OFDM是一项能有效对抗高速无线通信中多径衰落的关键技术,为了进一步提高OFDM系统的误码性能,许多信道编码技术已被应用于OFDM系统中,二元域LDPC码以其近香农限的误码性能和较低的译码复杂度成为研究的热点。在AWGN信道下,多元域LDPC码比等效码长的二元域LDPC码有更好的纠错性能。本文提出了一种将多元域LDPC码经过MPSK调制后用于OFDM系统的新方法。仿真结果表明,在多径衰落信道下,通过合理选择多元LDPC码域的阶数和调制的方法,多元域LDPC编码的高阶调制OFDM系统比等效码长的二元域LDPC编码OFDM系统具有更好的性能,并且由于采用了多元域LDPC的快速BP译码,译码复杂度只是稍有增加。 相似文献
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Bounding performance and suppressing intercarrier interference in wireless mobile OFDM 总被引:2,自引:0,他引:2
While rapid variations of the fading channel cause intercarrier interference (ICI) in orthogonal frequency-division multiplexing (OFDM), thereby degrading its performance considerably, they also introduce temporal diversity, which can be exploited to improve performance. We first derive a matched-filter bound (MFB) for OFDM transmissions over doubly selective Rayleigh fading channels, which benchmarks the best possible performance if ICI is completely canceled without noise enhancement. We then derive universal performance bounds which show that the time-varying channel causes most of the symbol energy to be distributed over a few subcarriers, and that the ICI power on a subcarrier mainly comes from several neighboring subcarriers. Based on this fact, we develop low-complexity minimum mean-square error (MMSE) and decision-feedback equalizer (DFE) receivers for ICI suppression. Simulations show that the DFE receiver can collect significant gains of ICI-impaired OFDM with affordable complexity. In the relatively low Doppler frequency region, the bit-error rate of the DFE receiver is close to the MFB. 相似文献
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Mojtaba Beheshti Mohammad Javad Omidi Ali Mohammad Doost-Hoseini 《Wireless Personal Communications》2013,71(2):1193-1215
Shallow underwater acoustic (UWA) channel exhibits rapid temporal variations, extensive multipath spreads, and severe frequency-dependent attenuations. So, high data rate communication with high spectral efficiency in this challenging medium requires efficient system design. Multiple-input multiple-output orthogonal frequency-division multiplexing (MIMO–OFDM) is a promising solution for reliable transmission over highly dispersive channels. In this paper, we study the equalization of shallow UWA channels when a MIMO–OFDM transmission scheme is used. We address simultaneously the long multipath spread and rapid temporal variations of the channel. These features lead to interblock interference (IBI) along with intercarrier interference (ICI), thereby degrading the system performance. We describe the underwater channel using a general basis expansion model (BEM), and propose time-domain block equalization techniques to jointly eliminate the IBI and ICI. The block equalizers are derived based on minimum mean-square error and zero-forcing criteria. We also develop a novel approach to design two time-domain per-tone equalizers, which minimize bit error rate or mean-square error in each subcarrier. We simulate a typical shallow UWA channel to demonstrate the desirable performance of the proposed equalization techniques in Rayleigh and Rician fading channels. 相似文献
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Performance of a system design for digital video broadcasting is examined with emphasis on mobile reception. Orthogonal frequency division multiplexing (OFDM) is used to achieve good bandwidth efficiency and to mitigate the intersymbol interference resulting from the channel delay spread. The resulting equivalent channel including OFDM can be modeled as a flat Rayleigh fading channel plus an interchannel interference (ICI) term due to the channel Doppler spread. This ICI term is analyzed and shown to result in an error floor. Performance improvements due to antenna diversity and trellis-coded modulation (TCM) are given. Finally, multiresolution modulation is discussed as a means of achieving graceful degradation and giving degrees of freedom for further performance improvement.This research was supported by the Multimedia Systems R & D Laboratory, Hitachi, Ltd. 相似文献
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Cebrail Çiflikli A. Tuncay Özşahin A. Çağrı Yapici 《Wireless Personal Communications》2009,51(2):221-229
The many advantages responsible for the widespread application of orthogonal frequency division multiplexing (OFDM) systems
are limited by the multipath fading. In OFDM systems, channel estimation is carried out by transmitting pilot symbols generally.
In this paper, we propose an artificial neural network (ANN) channel estimation technique based on levenberg-marquardt training
algorithm as an alternative to pilot based channel estimation technique for OFDM systems over Rayleigh fading channels. In
proposed technique, there are no pilot symbols which added to OFDM. Therefore, this technique is more bandwidth efficient
compared to pilot-based channel estimation techniques. Also, this technique is making full use of the learning property of
neural network. By using this feature, there is no need of any matrix computation and the proposed technique is less complex
than the pilot based techniques. Simulation results show that ANN based channel estimator gives better results compared to
the pilot based channel estimator for OFDM systems over Rayleigh fading channel. 相似文献
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Yantao Qiao Songyu Yu Pengcheng Su Lijun Zhang 《Broadcasting, IEEE Transactions on》2005,51(1):149-153
An iterative Least Square (LS) channel estimation algorithm for MIMO OFDM systems was proposed in this paper. Compared to common LS channel estimation, this algorithm can greatly improve estimation accuracy, and the low-pass filtering in time domain reduces AWGN and ICI significantly. MIMO OFDM system with this algorithm also works well in mobile situations. Simulation results have shown good MSE performance for this algorithm. 相似文献