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The MIMO system convincingly promises a better bit rate in comparison with a SISO system. The system gets even efficient when OFDM is implemented with MIMO to obtain better data rates even in hostile channel environment. Research establishes OFDM as a potential candidate for use in MIMO systems for the reasons like inherent FFT, waveform adaptation, advanced antenna techniques, multiple access, interoperability,...
The MIMO system convincingly promises a better bit rate in comparison with a SISO system. The system gets even efficient when OFDM is amalgamated with MIMO to obtain better data rates even in hostile channel environment. Research establishes OFDM as a potential candidate for use in MIMO systems for the reasons like inherent FFT, waveform adaptation, advanced antenna techniques, multiple access, interoperability,...
In the MIMO-OFDM system channel estimation based on the superimposed pilot is one of most potential and powerful techniques for broad-band wireless communications. In most traditional algorithms, the channel parameters are estimated by calculating the first-order statistical properties of receiving information. However, there are some limitations in such methods. These methods require the first-order...
In this paper, a Forward Error Coded (FEC) Decision-Directed (FEC-DD) channel estimation scheme is proposed for Multiple-Input Multiple-Output (MIMO) Orthogonal Frequency Division Multiplexing/Space Division Multiple Access (OFDM/SDMA) systems which is based on the Expectation-Conditional Maximization Either (ECME) algorithm. The proposed DD technique is combined with the Optimised Hierarchy Reduced...
This paper addresses the problem of frequency synchronization in multiuser multiple-input multiple-output orthogonal frequency-division multiplexing (MIMO-OFDM) systems. Different from existing work, a Bayesian approach is used in the parameter estimation problem. In this paper, the Bayes estimator for carrier frequency offset (CFO) estimation is proposed and the Bayesian Cram'er-Rao bound (BCRB)...
In this contribution, a multi-user receiver for M-QAM MIMO-OFDM operating in time-varying and frequency-selective channels is derived. The proposed architecture jointly performs semi-blind estimation of the channel weights and noise inverse variance, serial interference cancellation and decoding in an iterative manner. The scheme relies on a variational message-passing approach, which enables a joint...
This paper presents baseband receiver design for the third Generation Partnership Project (3GPP) Long Term Evolution (LTE) downlink systems under fast-fading channels. We aim to support 2×2 open-loop spatial multiplexing at high mobility up to 240 Km/hr with well-synchronized capability. The proposed receiver contains the functional blocks of mode detection, synchronization, channel tracking, inter-carrier...
Direct-conversion radio architecture is a low-cost, small-size design for the analog front-end subsystem in a wireless communication transceiver. This architecture, however, induces radio impairments such as I-Q imbalance and dc offset that, along with frequency offset, incur severe degradation in communication performance. This paper aims to improve the performance of estimation and compensation...
In this paper, we consider design optimization of low-density parity-check (LDPC) coded multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) systems for high data rate wireless transmission. First, starting from the maximum-likelihood (ML) principle, we devise a novel expectation-maximization (EM)-based scheme for joint estimation of carrier frequency-offset (CFO)...
It is well known that precoding techniques in multiuser multiple-input multiple-output (MU-MIMO) communication systems improve the whole data throughput since they allow for spatial multiplexing of different users. However, these techniques require a precise knowledge of the channel information at the transmitter. In most of the current systems, transmitter can not estimate the channel so feedback...
A channel estimation scheme for a multi-input multi-output orthogonal frequency division multiplexing (MIMO-OFDM) system was presented. The scheme makes use of the pilots to estimate the channel impulse response based on least square criteria. To improve the estimation performance, a neural network approach was applied to track the varying of the channel, which using a variable step-size RLS. The...
MIMO OFDM is a promising technique for the future wireless communications. However, the performance of MIMO OFDM systems is very sensitive to carrier frequency offset (CFO) which introduces inter-carrier-interference (ICI). Therefore, frequency synchronization is a critical problem in MIMO OFDM systems. In this paper, we study the problem of frequency synchronization in MIMO OFDM systems and propose...
This paper deals with the problem of channel estimation for multiple-input multiple-output/orthogonal frequency-division multiplexing (MIMO/OFDM) systems based on superimposed training (ST). Channel coefficients are firstly estimated by judicious designing superimposed pilot sequences across different users. Then, we analyze the channel estimation performance and derive a closed-form expression for...
Since the received MIMO-OFDM signal is usually corrupted in the time-domain due to some adverse factors such as frequency offset and large peak-to-average power ratio (PAPR) etc., a high-quality signal may only be obtained in the frequency domain. However, the second-order statistics of the time-domain signal are very often used in a blind or semi-blind channel estimation, which means that an IFFT...
MIMO-OFDM is the promising technique in the future of wireless communications as it combines the properties of Multiple Input Multiple Output (MIMO) systems with the properties of Orthogonal Frequency Division Multiplexing (OFDM). However, its sensitivity to frequency offsets, usually resulting in inter-carrier interference (ICI), makes frequency synchronization necessary for data recovery in the...
In this paper, A novel method for OFDM-MIMO channel estimation using QR-RLS(Square Root-Recursive Least Square) estimator is presented. Preamble aided channel estimation is performed in time-domain, estimated channel is then used for data detection during data transmission within that frame. The performance results are compared with wiener RLS channel estimator in terms of channel estimator MSE performance...
This paper considers a semi-blind channel estimation method based on receiver diversity for Multiple Input Multiple Output (MIMO) systems using Orthogonal Frequency Division Multiplexing (OFDM) modulation. Unlike conventional channel estimation methods, where channel parameters are directly estimated from the pilot data, the proposed semi-blind estimator based on Cholesky decomposition, incorporated...
MIMO OFDM is a very promising technique for high-speed wireless transmission. By applying the Direct Conversion Architecture (DCA), low-cost, low-power and fully integrated implementation of such systems is enabled. However, the performance of DCA may be seriously limited by I/Q-imbalance, which shows frequency selectivity in broadband systems. In this paper, we consider an indoor scenario and present...
We propose a compressive estimator of doubly selective channels within pulse-shaping multicarrier MIMO systems (including MIMO-OFDM as a special case). The use of multichannel compressed sensing exploits the joint sparsity of the MIMO channel for improved performance. We also propose a multichannel basis optimization for enhancing joint sparsity. Simulation results demonstrate significant advantages...
This paper introduces a novel semi-blind channel estimation algorithm based on Orthogonal Procrustes (OP) approach for Multiple Input Multiple Output (MIMO) systems using Orthogonal Frequency Division Multiplexing (OFDM) modulation. The presented joint estimator is based on decomposition of channel matrix H as a whitening matrix R and a unitary rotation matrix Q. The whitening matrix R can be estimated...
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