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Joint Data QRDetection and Kalman Estimation for OFDM Timevarying Rayleigh Channel Complex Gains
"... called combtype pilot [9]. Assuming such a strategy, conventional methods consist generally of estimating the channel at pilot frequencies and next interpolating the channel frequency response [22]. For fast timevarying channels, many existing works resort to estimating the equivalent discretetim ..."
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called combtype pilot [9]. Assuming such a strategy, conventional methods consist generally of estimating the channel at pilot frequencies and next interpolating the channel frequency response [22]. For fast timevarying channels, many existing works resort to estimating the equivalent discretetime channel taps, which are modeled by the basis expansion model (BEM) [10] [11]. The BEM methods [10] are KarhunenLoeve BEM (KLBEM), prolate spheroidal BEM (PSBEM), complexexponential BEM (CEBEM) and polynomial BEM (PBEM). The KLBEM is optimal in terms of mean square error (MSE), but is not robust to statistical channel mismatches, whereas the PSBEM is a general approximation for all kinds of channel statistics, although its bandlimited orthogonal spheroidal functions have maximal time concentration within the
Approximative matrix inverse computation for verylarge MIMO and applications to linear precoding systems
 in Proc. IEEE Wireless Commun. Netw. Conf. (WCNC
, 2013
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PICBased Iterative SDR Detector for OFDM Systems in DoublySelective Fading Channels
"... Abstract—OFDM data detection in doublyselective fading channels requires high complexity due to intercarrier interferences (ICI). We present a lowcomplexity receiver consisting of a semidefinite relaxation (SDR) based detector and parallel interference cancellation (PIC). The entire band is divide ..."
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Abstract—OFDM data detection in doublyselective fading channels requires high complexity due to intercarrier interferences (ICI). We present a lowcomplexity receiver consisting of a semidefinite relaxation (SDR) based detector and parallel interference cancellation (PIC). The entire band is divided into clusters of adjacent subcarriers. SDR is applied on each cluster while PIC tackles ICI from other clusters. An upper bound of ICI power is derived and used to omit faraway clusters in performing PIC. Finally, an adaptive detector based on PIC, PICbased SDR and the snapshot SNR in channel is proposed to achieve a better tradeoff between complexity and performance. Index Terms—Maximum likelihood, parallel interference cancellation, semidefinite relaxation, intercarrier interference. I.
Open Access
"... Lowcomplexity iterative receiver design for mobile OFDM systems ..."
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“14ch072853369780123744838 ” — 2011/3/9 — 22:03 — page 285 — #1 CHAPTER
"... parallel data transmission in the frequency domain and mainly owes its success to the easy equalization for linear timeinvariant (LTI) frequencyselective channels. In OFDM systems, the data symbol stream is split into L parallel flows, which are transmitted on equispaced frequencies called subcar ..."
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parallel data transmission in the frequency domain and mainly owes its success to the easy equalization for linear timeinvariant (LTI) frequencyselective channels. In OFDM systems, the data symbol stream is split into L parallel flows, which are transmitted on equispaced frequencies called subcarriers, each one characterized by a transmission rate that is 1/L times lower than the original data rate. This is obtained by splitting the original data stream into multiple blocks, which are transmitted in consecutive time intervals, where each symbol of a block is associated to a specific subcarrier. This frequencydomain multiplexing can be efficiently performed by means of fast Fourier transform algorithms. Due to the use of orthogonal (equispaced) subcarriers, OFDM systems with LTI frequencyselective channels avoid the socalled intercarrier interference (ICI) among the data symbols of the same OFDM block. Differently from conventional frequencydivision multiplexing, a frequency overlapping among the spectra associated to different substreams is permitted, resulting in a significant reduction of the bandwidth requirements. Moreover, for LTI frequencyselective channels, the absence of ICI allows an easy channel equalization, which can be performed on a persubcarrier basis by means of scalar divisions. The intersymbol interference (ISI)1 among data symbols of different OFDM blocks, induced by multipath propagation, is avoided by a suitable cyclic extension of each OFDM block, usually
Enhanced Blind Maximum Ratio Combining in Broadcasting Systems
"... We propose an enhanced blind maximum ratio combiner (BMRC) allowing for a transmit signal independent diversity combining in multiantenna receivers. The underlying MultiChannel Frequency Least Mean Squares (MCFLMS) algorithm comes with reasonable computational complexity and estimates the channel ..."
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We propose an enhanced blind maximum ratio combiner (BMRC) allowing for a transmit signal independent diversity combining in multiantenna receivers. The underlying MultiChannel Frequency Least Mean Squares (MCFLMS) algorithm comes with reasonable computational complexity and estimates the channel impulse response for each receive antenna iteratively by means of second order statistics. In literature, the MCFLMS algorithm is mainly applied to audio signals. In this work, we describe several enhancements of this algorithm to ensure its proper convergence with oversampled communication signals which are distorted by frequencyselective fastfading channels. In addition, we provide BER simulation results for a 1x2 SIMO DVBT2 system and show that our blind MRC can even outperform conventional pilotbased MRC at the receiver side. 1.
ITERATIVE ICI CANCELLATION BASED ON FACTOR GRAPHS FOR LARGE FFT SIZES
"... This paper focuses on the challenging problem of signal reception for orthogonal frequency division (OFDM) systems in high mobility environments. A novel framework based on the wellknown belief propagation (BP) algorithm is proposed for joint intercarrier interference (ICI) cancellation, signal ..."
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This paper focuses on the challenging problem of signal reception for orthogonal frequency division (OFDM) systems in high mobility environments. A novel framework based on the wellknown belief propagation (BP) algorithm is proposed for joint intercarrier interference (ICI) cancellation, signal detection and channel decoding. The performance of the mentioned nearoptimal detection strategy is analyzed over a general bitinterleaved coded modulation (BICM) system applying lowdensity paritycheck (LDPC) codes. The inclusion of pilot symbols is also considered to analyze how they assist the detection process. A full parallel turbo receptor is derived which shows good performance when the ICI power is high due to high mobility or the use of large FFT sizes. 1.
unknown title
"... Abstract — In mobile environment, the performance of OFDM mobile receivers is degraded severely because of InterCarrierInterference (ICI) caused by Doppler Spread. So ICI canceller is an important task for designers of mobile OFDM receivers. [1] and [2] proposed an efficient method to reduce ICI. ..."
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Abstract — In mobile environment, the performance of OFDM mobile receivers is degraded severely because of InterCarrierInterference (ICI) caused by Doppler Spread. So ICI canceller is an important task for designers of mobile OFDM receivers. [1] and [2] proposed an efficient method to reduce ICI. The main idea of this method is to linearly approximate time varying channel within one OFDM symbol. Then a large ICI matrix equation is given. However, in [1] and [2], the estimated values of the channel transfer function—the diagonal of the ICI matrix is corrupted by ICI. Consequently, the equalized signal still is distorted. In this paper, we propose an iterative method to improve performance of the conventional method in [1] and [2]. We implement Jacobi iteration method to solve the big ICI matrix equation. Thereby, we are able to implement ICI canceller by a simple FIR filter rather than finding the inverse of ICI matrix. Next, at second iteration of Jacobi method, we improve the accuracy the diagonal by removing ICI from pilot symbols and reestimating the channel transfer function. Simulation results for ISDBT mode 3 demonstrated that our method could double performance of the conventional method under TU6 channel and Doppler Spread. The improvement is better for two paths and one path Doppler channel.
RESEARCH Open Access
"... FBMC receiver for multiuser asynchronous transmission on fragmented spectrum JeanBaptiste Doré*, Vincent Berg, Nicolas Cassiau and Dimitri Kténas Relaxed synchronization and access to fragmented spectrum are considered for future generations of wireless networks. Frequency division multiple access ..."
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FBMC receiver for multiuser asynchronous transmission on fragmented spectrum JeanBaptiste Doré*, Vincent Berg, Nicolas Cassiau and Dimitri Kténas Relaxed synchronization and access to fragmented spectrum are considered for future generations of wireless networks. Frequency division multiple access for filter bank multicarrier (FBMC) modulation provides promising performance without strict synchronization requirements contrary to conventional orthogonal frequency division multiplexing (OFDM). The architecture of a FBMC receiver suitable for this scenario is considered. Carrier frequency offset (CFO) compensation is combined with intercarrier interference (ICI) cancellation and performs well under very large frequency offsets. Channel estimation and interpolation had to be adapted and proved effective even for heavily fragmented spectrum usage. Channel equalization can sustain large delay spread. Because all the receiver baseband signal processing functionalities are proposed in the frequency domain, the overall architecture is suitable for multiuser asynchronous transmission on fragmented spectrum.
On the Banded Approximation of the Channel Matrix for Mobile OFDM Systems
"... Abstract—In the mobile orthogonal frequencydivision multiplexing (OFDM) systems, a frequencydomain channel matrix represents the samecarrier channel frequency response (CFR) in the diagonal and intercarrier interference (ICI) between the subcarriers in the offdiagonals, respectively. A variety ..."
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Abstract—In the mobile orthogonal frequencydivision multiplexing (OFDM) systems, a frequencydomain channel matrix represents the samecarrier channel frequency response (CFR) in the diagonal and intercarrier interference (ICI) between the subcarriers in the offdiagonals, respectively. A variety of the banded equalizers manipulated the banded approximation of the channel matrix to be exploited by the lowcomplexity equalizations. In this paper, we derive a simple and tight lower bound on the variance of the individual coefficients in the channel matrix for insights of the banded approximations. We obtain the errors introduced with the banded approximation and the ICImitigation gains of the banded equalizers in simple closed forms. The derivations of the banded approximation errors are beneficially applicable to the equalizers that perform the minimum mean square error (MMSE) estimation with the banded channel matrix. Simulations show that both the block MMSE banded equalizers and the block turbo MMSE banded equalizers significantly reduce the error floors by considering the banded approximation errors. Index Terms—Orthogonal frequencydivision multiplexing (OFDM), intercarrier interference (ICI), banded approximation. I.