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In this paper, we propose an efficient carrier frequency offset (CFO) estimation technique based on the space alternating generalized expectation-maximization (SAGE) for uplink orthogonal frequency division multiple access (OFDMA) systems. In general, the SAGE method transforms a multidimensional search problem into a sequence of one-dimensional searches, which greatly simplifies the estimation procedure...
In this paper, a piece-wise approximation for doubly selective channel is presented for improving the structure of the frequency-domain channel gain matrix of OFDM. The proposed model is exploited to simplify the zero-forcing (ZF) equalizer, of which the linearized case is studied and applied to the DVB-H receiver design. The simulation indicates that the developed equalizer enforces considerably...
In this study, the problem of blind channel estimation for single-input single-output (SISO) orthogonal frequency-division multiplexing (OFDM) systems, is considered. Based on auto-correlation matrix, we develop a precoding-assisted blind channel estimation algorithm which is suitable for practical SISO-OFDM applications. Compared to the popular subspace-based blind channel estimation methods, the...
The Fourth generation (4G) wireless networks are expected to afford high data rate transmission of multimedia services such as wireless video, wireless Internet access and mobile computing. Orthogonal frequency division multiplexing (OFDM) is an effective technique for the future 4G communications because of its great immunity to impulse noise and intersymbol interference. Ultra wide band (UWB) wireless...
Turbo equalization schemes based on minimum mean square error (MMSE) criteria available in the literature are computationally involved as they require some form of matrix inversion. In this paper, we propose a low complexity turbo-equalization scheme with successive interference cancellation (TE-SIC) for the equalization of doubly dispersive channels for orthogonal frequency division multiplexing...
The impulse response of a typical wireless multipath channel can be modeled as a tapped delay line filter whose non-zero components are sparse relative to the channel delay spread. In this paper, a novel method of estimating such sparse multipath fading channels for OFDM systems is explored. In particular, Sparse Bayesian Learning (SBL) techniques are applied to jointly estimate the sparse channel...
For pilot-aided channel estimation in orthogonal frequency-division multiplexing (OFDM) systems, adaptive algorithms enable tracking of a time-varying channel. Using several subcarriers for the update step in the adaptive algorithm, i.e., performing block processing, improves the robustness and convergence speed of the adaptation. To decrease the complexity of these algorithms, simplified versions...
In cooperative relay systems, relayed signals propagate through different channels and are received at the destination node with distinct timing and carrier frequency offsets (CFOs). This feature makes synchronization a rather challenging task as compared with centralized multiple-input multiple-output systems. Unlike conventional preamble designs with good correlation properties only in time domain...
Fast and accurate Carrier Frequency Offset (CFO) estimation is a problem of significance in many multi-carrier modulation based systems, especially in uplink Orthogonal Frequency Division Multiple Access (OFDMA) where the presence of multiple users exacerbates the inter-carrier interference (ICI) and results in multi-user interference (MUI). In this paper, a new technique called partial FFT demodulation...
Abstract-In this paper, we suggest novel criteria for pilot designs which minimize outliers for consistent carrier frequency offset (CFO) estimation in the orthogonal frequency division multiplexing (OFDM) systems. In order to derive the criteria, we first analyze the average pairwise error probability (PEP) of integer CFO (iCFO) estimation with consistent pilots in the OFDM systems where fadings...
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)...
This paper proposes a superimposed training strategy to estimate the individual frequency and channel parameters in an amplify-and-forward (AF) two-way relay network (TWRN). Two efficient suboptimal estimation algorithms and an iterative process to further improve the performance are proposed. The estimation Cramér-Rao Bound (CRB) on the proposed estimation strategy is also derived. The simulations...
This paper addresses the issue of blind estimation of common phase error (CPE) in OFDM systems affected by phase noise (PHN). Common approaches to blind CPE detection detect the symbols, and estimate the phase noise in an iterative manner. An important assumption that these decision-directed algorithms make is that a majority of the symbols detected in the first iteration, while ignoring the presence...
TCH (Tomlinson, Cercas and Hughes) sequences have been studied for code-spreading and channel coding, but their true purpose is for synchronization and channel estimation. This is due to their property of being (virtually) orthogonal to all of their sequences obtained via circular shifts, and the use of the FFT (Fast Fourier Transform) for decoding. This property is extremely useful for time-offset...
In this paper, a new fast algorithm is proposed to suppress inter-carrier interference (ICI) in SISO-OFDM systems. Previous algorithms, due to high computation time, are impractical for OFDM systems especially with large number of subcarriers. To overcome this problem, our proposed algorithm computes rather than K2 elements of carrier frequency offset (CFO) matrix used by previous algorithms, only...
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...
Asymptotic analysis of the dual-diagonal (DD) linear-minimum-mean-square-error (LMMSE) channel estimation for orthogonal frequency-division multiplexing (OFDM) systems is presented. We prove that the DD-LMMSE estimator is asymptotically optimal among all DD estimators as the number of subcarriers tends to infinity. Based on the asymptotic analysis, we propose an evolution tool to predict the performance...
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...
This paper presents a low-complexity architecture compensating for carrier frequency offset (CFO) and IQ imbalance circuits in MIMO-OFDM receiver systems. A coordinate rotation digital computer based sinusoid iteration generator is also developed for CFO estimation and correction in wireless communication receivers. Besides the main effect from the multi-path, some non-ideal effects from imperfect...
In this paper, a software defined radio (SDR) structure based carrier frequency offset (CFO) estimation and compensation circuit is designed for an orthogonal frequency division multiplexing (OFDM) system using the reconfigurable coordinate rotation digital computer (CORDIC) field programmable gate array (FPGA) rotation and vectoring circuit modules. The SDR architecture of the CFO estimation and...
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