The Experts below are selected from a list of 9267 Experts worldwide ranked by ideXlab platform
Jianguo Zhang - One of the best experts on this subject based on the ideXlab platform.
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Recursive semi-blind decoding of a space-time block code over Frequency-Selective Channel
2005 IEEE International Symposium on Circuits and Systems, 2005Co-Authors: Yiwen Zhang, Jianguo ZhangAbstract:In this paper, a recursive semi-blind decoding method for Alamouti space-time block code over Frequency-Selective Channel is proposed. The method combines subspace-based blind equalization with the structure of Alamouti space-time block code, and recursively recovers the information symbols from a temporally oversampled received signal on multiple receive antennas without Channel state information. With the aid of a few training symbols, the proposed recursive algorithm has two fortes: First, because different transmit antennas employ distinct training sequences, it can resolve the ambiguity inherent in Alamouti code when employing blind equalization method; Second, on each recursion, by using the previously detected symbols, the number of unknown symbols in the processing window can be reduced, consequently, the computation complexity is decreased.
Jan C. Olivier - One of the best experts on this subject based on the ideXlab platform.
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Time-Varying and Frequency-Selective Channel Estimation with Unequally Spaced Pilot Symbols
International Journal of Wireless Information Networks, 2004Co-Authors: Jingxian Wu, Chengshan Xiao, Jan C. OlivierAbstract:In this paper, an accurate and computationally efficient algorithm is proposed for estimating time-varying and Frequency-Selective fading Channel with unequally spaced pilot symbols. By employing the time-varying coefficient polynomial interpolation method, it is proved that the time-varying Channel impulse response can be estimated by the product of a constant matrix and the fading information at pilot symbol positions. Furthermore, a least square off-line training algorithm is presented to optimally calculate the constant matrix, taking into consideration of the statistics of Channel fading and noise. The new algorithm can also be applied for estimating flat fading Channel with equally spaced pilot symbols as a special case. Simulation results indicate that our new Channel estimation algorithm leads to small mean square error for fading estimation and provides bit error rate performance close to that of the perfect Channel estimation.
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Time-varying and Frequency-Selective Channel estimation with unequally spaced pilot symbols
2003 IEEE International Conference on Acoustics Speech and Signal Processing 2003. Proceedings. (ICASSP '03)., 2003Co-Authors: Jingxian Wu, Chengshan Xiao, Jan C. OlivierAbstract:In this paper, an accurate and computationally efficient algorithm is proposed for estimating a time-varying and Frequency-Selective fading Channel with unequally spaced pilot symbols. By employing the time-varying coefficient polynomial interpolation method, it is proved that the time-varying Channel impulse response can be estimated by the product of a constant interpolation matrix and the fading information at pilot symbol positions. Furthermore, a least square off-line training algorithm is presented to optimally calculate the constant matrix, taking into consideration the statistics of Channel fading and noise. Simulation results indicate that the bit error rate performance of our new estimation algorithm is close to that of the perfect Channel estimation.
Ridha Bouallegue - One of the best experts on this subject based on the ideXlab platform.
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Closed BER of STBC-MIMO-OFDM systems over nonlinear frequency selective Channel and cancellation technique for HPA distortion
2014 International Conference on Multimedia Computing and Systems (ICMCS), 2014Co-Authors: Oussama B. Belkacem, Mohamed Lassaad Ammari, Rafik Zayani, Ridha BouallegueAbstract:Multiple-input multiple-output (MIMO) technology and orthogonal frequency-division multiplexing (OFDM) can be combined to design a robust communications scheme with increased spectral efficiency and system capacity. To reach high power efficiency, MIMO-OFDM systems are equipped with high-power amplifiers (HPA). When it operates near its saturation region, the HPA causes nonlinear distortions. Unfortunately, the nonlinearity of HPA has a crucial impact on the global system performance. In this paper, we focus on the effect of the HPA nonlinearity on the space-time block coded (STBC) MIMO-OFDM systems. Analytic expression of the average Bit error rate (BER) is delivered running under frequency selective Channel. We also note an excellent agreement between analytic expressions and Monte Carlo simulation curves. In addition, this work introduces a new iterative cancelation technique for the nonlinearly detected by the receiver. The new proposed approach is based on the Bussgang theorem and consists in iterative estimation and annulation of the nonlinear distortion caused by the high power amplifier of the transmitter.
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The capacity performance of ASTC-MIMO-OFDM system in a correlated rayleigh Frequency-Selective Channel
Wireless Personal Communications, 2013Co-Authors: Ahmed Bannour, Yichuang Sun, Mohamed Lassaad Ammari, Ridha BouallegueAbstract:Algebraic Space-Time Codes (ASTC) for MIMO systems are based on quaternion algebras. Thanks to their algebraic construction, the ASTC codes are full-rank, full-rate and have the non-vanishing determinant property. These codes have been proposed for MIMO flat fading Channels in order to increase the spectral efficiency and to maximize the coding gain. The purpose of this work is to analyze the performance of the ASTC in a frequency selective Rayleigh Channel. To deal with the frequency selectivity, we use the OFDM modulation. Methods for Channel estimation using pilot symbol have been proposed. BER performances of ASTC-MIMO-OFDM system, under several propagation conditions, have been evaluated.
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Neural network equalization for frequency selective nonlinear MIMO Channels
2012Co-Authors: Oussema Belkacem O. B., Mohamed Lasaad Ammari M. L., Ridha Bouallegue, Rafik Zayani, Daniel RovirasAbstract:In order to provide high data rate over wireless Channels and improve the system capacity, Multiple-Input Multiple-Output (MIMO) wireless communication systems exploit spatial diversity by using multiple transmit and receive antennas. Moreover, to achieve high date rate and fulfill the power, MIMO systems are equipped with High Power Amplifiers (HPAs). However, HPAs cause nonlinear distortions and affect the receiver's performance. In this paper, we investigate the joint effects of HPA nonlinearity and frequency selective Channel on the performance of MIMO receiver. Then, we propose two equalization schemes to compensate simultaneously nonlinear distortions and frequency selective Channel effects. The first one is based on a feedforward Neural Network (NN) named (NN-MIMO-Receiver) and the second uses NN technique and LMS equalizer (LMS-NN-MIMO). The Levenberg-Marquardt algorithm (LM) is used for neural network training, which has proven [1] to exhibit a very good performance with lower computation complexity and faster convergence than other algorithms used in literature. These proposed methods are compared in term of Symbol Error Rate (SER) running under nonlinear frequency selective Channel.
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On the Capacity of ASTC-MIMO-OFDM System in a Correlated Rayleigh Frequency-Selective Channel
2011 IEEE 73rd Vehicular Technology Conference (VTC Spring), 2011Co-Authors: Bannour Ahmed, Mohamed Lassaad Ammari, Ridha BouallegueAbstract:Algebraic Space-Time Codes (ASTC) for MIMO systems are based on quaternion algebras. Thanks to their algebraic construction, the ASTC codes are full-rank, full-rate and have the non-vanishing determinant property. These codes have been proposed for MIMO flat fading Channels in order to increase the spectral efficiency and to maximize the coding gain. The purpose of this work is to analyze the performance of the ASTC in a frequency selective Rayleigh Channel. To deal with the frequency selectivity, we use the OFDM modulation. The capacity performances of an ASTC-MIMO-OFDM system, under correlated Rayleigh Frequency-Selective Channel, have been evaluated.
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Algebraic Carrier Frequency Offset estimator for ASTC-MIMO-OFDM systems over correlated frequency selective Channel
2011 11th Mediterranean Microwave Symposium (MMS), 2011Co-Authors: Ahmed Bannour, Mohamed Lassaad Ammari, Ridha BouallegueAbstract:This work presents a new Algebraic Carrier Frequency Offset (CFO) estimation technique for multi-input multi-output (MIMO) orthogonal frequency division multiplexing (OFDM) systems employing Algebraic Space Time Coding (ASTC), in Channels time-varying correlated Rayleigh Frequency-Selective fading. The technique uses a preamble and is thus especially suitable for burst mode communication. The preamble consists of orthogonal training sequences simultaneously transmitted from the various transmit antennas. The proposed system exploits all subcarriers in frequency domain, which provides a remarkable performance improvement, and reach the Cramer-Rao Lower Bound (CRLB). A new algebraic estimation method is proposed, in order to exploit the powerful algebraic ASTC technique in wide-band systems, when the CFOs occur with small variation and to overcome the sensitivity of the ASTC codes in frequency synchronization problemof OFDM system.
T. Kirubarajan - One of the best experts on this subject based on the ideXlab platform.
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Blind particle filtering for detection in a time-varying frequency selective Channel with non-Gaussian noise
IEEE 6th Workshop on Signal Processing Advances in Wireless Communications 2005., 2005Co-Authors: J.p. Reilly, T. KirubarajanAbstract:In this paper, we present efficient particle filtering and smoothing algorithms to solve the problem of blind detection in a time-varying frequency selective Channel with additive non-Gaussian noise. The proposed algorithms are efficiently implemented via a combination of the optimal importance distribution and the principle of Rao-Blackwellization. The proposed particle smoothing algorithms which results in significantly improved performance, employ the method of delayed sampling, delayed weights, or a combination of the former. Simulation results are provided to illustrate the effectiveness of the proposed algorithms.
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Channel equalization and phase noise suppression for OFDM systems in a time-varying frequency selective Channel using particle filtering
Proceedings. (ICASSP '05). IEEE International Conference on Acoustics Speech and Signal Processing 2005., 2005Co-Authors: J.r. Reilly, T. KirubarajanAbstract:In this paper we address the problem of Channel equalization and phase noise suppression in orthogonal frequency division multiplexing (OFDM) systems. For OFDM systems, random phase noise introduced by the local oscillator causes two effects: the common phase error (CPE), and the intercarrier interference (ICI). The performance of coherent OFDM systems greatly depends on the ability to accurately estimate the effective dynamic Channel, i.e. the combined effect of the CPE and the time-varying frequency selective Channel. The proposed approach uses a pilot tone aided particle filter to track/estimate the effective dynamic Channel in the time domain and equalizes in the frequency domain. The particle filter is efficiently implemented by combining sequential importance sampling, principles of Rao-Blackwellization, and strategies stemming from the auxiliary particle filter. Simulation results are provided to illustrate the effectiveness of the proposed algorithm.
Z. Ding - One of the best experts on this subject based on the ideXlab platform.
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Frequency selective Channel estimation in time-reversed space-time coding
2004 IEEE Wireless Communications and Networking Conference (IEEE Cat. No.04TH8733), 2004Co-Authors: N. Ammar, Z. DingAbstract:Time reversed space-time block code (TR-STBC) was originally proposed to handle frequency selective fading Channels. Its detection requires accurate Channel knowledge at the receiver side. In this work, we present a Channel estimation approach that does not require training data under TR-STBC encoding. We provide identification conditions that are based on the known code parameters as well as Channel matrix rank. We present a simple subspace algorithm for Channel estimation. Additionally, simulations results are presented to highlight the performance of the estimation scheme.
