Frequency domain equalization for single-carrier broadband wireless systems
TL;DR: This article surveys frequency domain equalization (FDE) applied to single-carrier (SC) modulation solutions and discusses similarities and differences of SC and OFDM systems and coexistence possibilities, and presents examples of SC-FDE performance capabilities.
Abstract: Broadband wireless access systems deployed in residential and business environments are likely to face hostile radio propagation environments, with multipath delay spread extending over tens or hundreds of bit intervals. Orthogonal frequency-division multiplex (OFDM) is a recognized multicarrier solution to combat the effects of such multipath conditions. This article surveys frequency domain equalization (FDE) applied to single-carrier (SC) modulation solutions. SC radio modems with frequency domain equalization have similar performance, efficiency, and low signal processing complexity advantages as OFDM, and in addition are less sensitive than OFDM to RF impairments such as power amplifier nonlinearities. We discuss similarities and differences of SC and OFDM systems and coexistence possibilities, and present examples of SC-FDE performance capabilities.
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TL;DR: A distributed space–time transmission scheme for a general asynchronous cooperative relay network that provides asymptotic full cooperative diversity, even when the signals arrive at the receiver asynchronously, which can be achieved by a low-complexity minimum-mean-square-error (MMSE) decision feedback equalizer (DFE) instead of the maximum-likelihood (ML) detector.
Abstract: Due to the distributed nature of cooperative communications systems, the cooperative signals arriving at the destination may not be perfectly aligned, i.e., the system is inherently asynchronous, and signal coordination among multiple relay nodes is imperative. In this paper, we propose a distributed space–time transmission scheme for a general asynchronous cooperative relay network. The scheme provides asymptotic full cooperative diversity, even when the signals arrive at the receiver asynchronously, which can be achieved by a low-complexity minimum-mean-square-error (MMSE) decision feedback equalizer (DFE) instead of the maximum-likelihood (ML) detector. Furthermore, signal coordination is no longer required, which avoids extra coordinating overhead. The proposed scheme applies for both general amplify-and-forward (AF) and decode-and-forward (DF) cooperative communications networks, such as coordinated multipoint/networked multiple-input–multiple-output (MIMO) systems, distributed antenna systems, and relay architecture for cellular systems. Simulation results confirm our analytical results.
27 citations
Cites background or methods from "Frequency domain equalization for s..."
...1) Due to the special structure of the signal model (7), FD equalization (FDE) will be much more computationally convenient since the fast Fourier transform algorithm can be exploited [43], [44]....
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...In practice, we insert these beginningL symbols perfectly known by the receiver, as in [43] and [44]....
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TL;DR: The performance of the proposed OSDM system is evaluated through both numerical simulations and a field experiment, and its reliability over underwater acoustic channels is confirmed.
Abstract: Orthogonal signal-division multiplexing (OSDM) is a promising modulation scheme that provides a generalized framework to unify orthogonal frequency-division multiplexing (OFDM) and single-carrier frequency-domain equalization. By partitioning each data block into vectors, it allows for a flexible configuration to trade off resource management flexibility with peak-to-average power ratio. In this paper, an OSDM system is proposed for underwater acoustic communications. The channel Doppler effect after front-end resampling is modeled as a common time-varying phase on all propagation paths. It leads to a special signal distortion structure in the OSDM system, namely, intervector interference, which is analogous to the intercarrier interference in the conventional OFDM system. To counteract the related performance degradation, the OSDM receiver performs iterative detection, integrating joint channel impulse response and phase estimation, equalization, and decoding in a loop. Meanwhile, to avoid inversion of large matrices in channel equalization, frequency-domain per-vector equalization is designed, which can significantly reduce the computational complexity. Furthermore, the performance of the proposed OSDM system is evaluated through both numerical simulations and a field experiment, and its reliability over underwater acoustic channels is confirmed.
27 citations
TL;DR: This paper presents a meta-modelling system that automates the very labor-intensive and therefore time-heavy and therefore expensive and expensive process of computer programming called “hacking”.
Abstract: 1Department of Communications Engineering, Tampere University of Technology, P.O. Box 553, 33101 Tampere, Finland 2Orange Labs, France Telecom, 4 Rue du Clos Courtel, B.P. 91226, 35512 Cesson Sevigne Cedex, France 3Department of Electrical and Computer Engineering, University of Utah, Salt Lake City, UT 84112-9206, USA 4Centre Tecnologic de Telecommunication de Catalunya (CTTC), Parc Mediterrani de la Tecnologia, Avinguda del Canal Olimpic, Casstelldefels, 08860 Barcelona, Spain
27 citations
TL;DR: In this article, the authors demonstrate the transmission of 1.0 Tb/s unique-word DFTS-OFDM superchannel signal over 8000 km standard single-mode fiber with 80 km span engineering and erbium-doped fiber amplification (EDFA) using quadrature phase shift keying (QPSK) modulation.
Abstract: Conventional coherent optical orthogonal frequency-division multiplexed (CO-OFDM) system has inferior nonlinear tolerance due to high peak-to-average power ratio (PAPR). Discrete Fourier transform spread OFDM (DFTS-OFDM) has recently been proposed as a promising candidate that possesses similar spectral characteristics as conventional CO-OFDM, but has much better nonlinear tolerance. We demonstrate experimentally the transmission of 1.0 Tb/s unique-word DFTS-OFDM superchannel signal over 8000 km standard single-mode fiber with 80 km span engineering and erbium-doped fiber amplification (EDFA) using quadrature phase shift keying (QPSK) modulation, representing a record spectral efficiency and reach product in transmission systems compatible with most of the deployed links.
27 citations
Cites background or methods from "Frequency domain equalization for s..."
...In this paper, we implement a novel variant of DFTS-OFDM with unique words (UW) [16]–[19] embedded at both ends of OFDM symbols to facilitate the estimation and compensation of linear and nonlinear phase noise, which we called UW-assisted DFTS-OFDM (UW-DFTS-OFDM)....
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...UW was first proposed for SC frequency-domain equalization (SC-FDE) systems and has been extensively studied in wireless communications [16]–[19]....
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TL;DR: Simulation results show that the proposed system gives better BER performance than the FDSPT and approaches the lower bound of SC-FDE.
Abstract: In this letter, we propose a simple pilot position selection/detection technique for channel estimation of single- carrier frequency domain equalization (SC-FDE). Unlike the conventional channel estimation techniques such as frequency domain superimposed pilot technique (FDSPT), the proposed scheme selects the pilot positions to minimize the distortion of original signals caused by the loss of useful data tones in frequency domain. The corresponding receiver structure is also presented, where the pilot positions are blindly detected and the distorted data symbols are iteratively reconstructed. Simulation results show that the proposed system gives better BER performance than the FDSPT and approaches the lower bound of SC-FDE.
27 citations
Cites background from "Frequency domain equalization for s..."
...Both OFDM and SC-FDE require precise channel state information (CSI) for the equalization....
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...Using the concept of iterative amplitude reconstruction (IAR) for OFDM systems in [8], we iteratively reconstruct the signals as follows S̃ (i) k = { Ŝ (i−1) k , k (mod M) = d̂o S̃ (0) k , otherwise (16) where {Ŝ(i−1)k }N−1k=0 are DFT of {ŝ(i−1)n }N−1n=0 ....
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...To estimate the CSI, frequency domain multiplexed (FDM) pilots have been typically used for OFDM systems, while the pilots of SC-FDE are time domain multiplexed (TDM) on dedicated blocks....
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...INTRODUCTION S INGLE-CARRIER with frequency domain equalization (SC-FDE) has similar performance and essentially the same overall complexity as orthogonal frequency division multiplexing (OFDM) [1]-[3]....
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...Recently the SC-FDE has drawn a great attention as an alternative to the OFDM, especially in the uplink communications, because it alleviates carrier synchronization problem and the peak-to-average power ratio (PAPR) of transmitted sequences is much lower than that of OFDM....
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References
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Book•
01 Jan 1986
TL;DR: In this paper, the authors propose a recursive least square adaptive filter (RLF) based on the Kalman filter, which is used as the unifying base for RLS Filters.
Abstract: Background and Overview. 1. Stochastic Processes and Models. 2. Wiener Filters. 3. Linear Prediction. 4. Method of Steepest Descent. 5. Least-Mean-Square Adaptive Filters. 6. Normalized Least-Mean-Square Adaptive Filters. 7. Transform-Domain and Sub-Band Adaptive Filters. 8. Method of Least Squares. 9. Recursive Least-Square Adaptive Filters. 10. Kalman Filters as the Unifying Bases for RLS Filters. 11. Square-Root Adaptive Filters. 12. Order-Recursive Adaptive Filters. 13. Finite-Precision Effects. 14. Tracking of Time-Varying Systems. 15. Adaptive Filters Using Infinite-Duration Impulse Response Structures. 16. Blind Deconvolution. 17. Back-Propagation Learning. Epilogue. Appendix A. Complex Variables. Appendix B. Differentiation with Respect to a Vector. Appendix C. Method of Lagrange Multipliers. Appendix D. Estimation Theory. Appendix E. Eigenanalysis. Appendix F. Rotations and Reflections. Appendix G. Complex Wishart Distribution. Glossary. Abbreviations. Principal Symbols. Bibliography. Index.
16,062 citations
"Frequency domain equalization for s..." refers methods in this paper
...Adaptation can be done with LMS (least mean square), RLS, or least squares minimization (LS) techniques, analogous to adaptation of time domain equalizers [Hay96], [Cla98]....
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...Overlap-save or overlap-add signal processing techniques could also be used to avoid the extra overhead of the cyclic prefix [Fer85], [Hay96]....
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TL;DR: The analysis and simulation of a technique for combating the effects of multipath propagation and cochannel interference on a narrow-band digital mobile channel using the discrete Fourier transform to orthogonally frequency multiplex many narrow subchannels, each signaling at a very low rate, into one high-rate channel is discussed.
Abstract: This paper discusses the analysis and simulation of a technique for combating the effects of multipath propagation and cochannel interference on a narrow-band digital mobile channel. This system uses the discrete Fourier transform to orthogonally frequency multiplex many narrow subchannels, each signaling at a very low rate, into one high-rate channel. When this technique is used with pilot-based correction, the effects of flat Rayleigh fading can be reduced significantly. An improvement in signal-to-interference ratio of 6 dB can be obtained over the bursty Rayleigh channel. In addition, with each subchannel signaling at a low rate, this technique can provide added protection against delay spread. To enhance the behavior of the technique in a heavily frequency-selective environment, interpolated pilots are used. A frequency offset reference scheme is employed for the pilots to improve protection against cochannel interference.
2,627 citations
"Frequency domain equalization for s..." refers background in this paper
...OFDM transmits multiple modulated subcarriers in parallel [ 1 ]....
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...Several variations of orthogonal frequency-division multiplexing (OFDM) have been proposed as effective anti-multipath techniques, primarily because of the favorable trade-off they offer between performance in severe multipath and signal processing complexity [ 1 ]....
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TL;DR: In this contribution the transmission of M-PSK and M-QAM modulated orthogonal frequency division multiplexed (OFDM) signals over an additive white Gaussian noise (AWGN) channel is considered and the degradation of the bit error rate is evaluated.
Abstract: In this contribution the transmission of M-PSK and M-QAM modulated orthogonal frequency division multiplexed (OFDM) signals over an additive white Gaussian noise (AWGN) channel is considered. The degradation of the bit error rate (BER), caused by the presence of carrier frequency offset and carrier phase noise is analytically evaluated. It is shown that for a given BER degradation, the values of the frequency offset and the linewidth of the carrier generator that are allowed for OFDM are orders of magnitude smaller than for single carrier systems carrying the same bit rate. >
1,816 citations
TL;DR: This correspondence describes the construction of complex codes of the form exp i \alpha_k whose discrete circular autocorrelations are zero for all nonzero lags.
Abstract: This correspondence describes the construction of complex codes of the form exp i \alpha_k whose discrete circular autocorrelations are zero for all nonzero lags. There is no restriction on code lengths.
1,624 citations