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.
Citations
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TL;DR: This paper presents a new class of block turbo-equalizers for single-carrier transmission over multiple-input multiple-output (MIMO) broadband wireless channels, and selected algorithms in the proposed class are compared in terms of performance under various transmission scenarios.
Abstract: This paper presents a new class of block turbo-equalizers for single-carrier transmission over multiple-input multiple-output (MIMO) broadband wireless channels. The key underlying idea consists in equalizing (nonoverlapping) groups of symbols and detecting their individual space-time components in a disjoint and iterative fashion. This functional split naturally induces new design options that have been accurately listed and described, i.e., choice of distinct criteria for intergroup interference (IGI) equalization and intragroup components detection, yielding hybrid structures, multiple iterative loops, and related scheduling variants. Selected algorithms in the proposed class are compared in terms of performance under various transmission scenarios. For all of them, minimum mean square error IGI equalization certainly occupies a central role (at least for the first iteration) and may be identified as the computational bottleneck. Fortunately, block spread transmission together with cyclic prefix operations make the channel matrix block circulant, thus allowing low-complexity inversion in the Fourier domain
47Â citations
Cites background from "Frequency domain equalization for s..."
...Not only do we content with generalizing [4] to the MIMO case, but we focus our derivations on a recently introduced concept implemented in the time domain with a sliding window approach [8] that is nonexistent in [5] and [6]....
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TL;DR: A minimum mean-squared error-based scheme is derived to mitigate the effect of both phase noise and time-selective fading in MIMO-OFDM systems over doubly selective Rayleigh fading channels.
Abstract: In this paper, we analyze the effects of phase noise to multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) systems over doubly selective Rayleigh fading channels. Similar to single-antenna OFDM, MIMO-OFDM suffers from significant performance degradation due to phase noise and time-selective fading, which causes inter- carrier interference (ICI). We derive the expressions of carrier- to-interference and signal-to-interference-plus-noise ratios. After characterizing the common phase error (CPE) caused by phase noise and ICI caused by phase noise, as well as time-selective fading, we then derive a minimum mean-squared error-based scheme to mitigate the effect of both phase noise and time-selective fading. We also evaluate and compare the performances of various detection schemes combined with the proposed CPE mitigation scheme. Through numerical results, we examine the relative performances and the potential error floors of these detection schemes.
47Â citations
TL;DR: Three different ways of using SCFDE with DOW communications are proposed and it is shown that they exhibit lower PAPR and provide better bit-error rate (BER) performance in the presence of the LED nonlinearity.
Abstract: We investigate the use of single carrier frequency domain equalization (SCFDE) over a diffuse optical wireless (DOW) communications. Recently orthogonal frequency division multiplexing (OFDM) has been applied to DOW communications. However, due to high peak-to-average power ratio (PAPR), the performance of OFDM can severely be affected by the nonlinear characteristics of light emitting diodes (LED). To avoid a PAPR problem, we present in this paper a modified form of SCFDE for DOW communications. We propose three different ways of using SCFDE with DOW communications and show that they exhibit lower PAPR and provide better bit-error rate (BER) performance in the presence of the LED nonlinearity.
46Â citations
TL;DR: Two kinds of robust formulations are proposed to jointly combat the MAI, ISI and phase uncertainties and can attain 80% or more by extensive simulations in an indoor two-user 60 GHz environment if RF beam patterns of the users do not highly overlap in space.
Abstract: A hybrid architecture is presented for downlink beamforming (BF) with phased antenna arrays (PAA) in indoor 60 GHz spatial division multiple access (SDMA) channels. To manage the multiple access and inter-symbol interferences (MAI/ISI) encountered in SDMA with limited feedbacks, a cost-effective time-domain hybrid BF (HBF) method is presented to exploit the directivity provided by PAA in radio frequency (RF) beam patterns and the spatial diversity offered by multiple baseband processing modules. To maintain signal qualities under unpredictable MAI/ISI in wireless multimedia streaming to which indoor 60 GHz radio mainly applies, robust beamformers are designed to maintain the signal to interference-plus-noise ratio (SINR) for each user with minimum total transmit power. The percentages in which the target SINRs can be satisfied with the proposed HBF schemes are found sensitive to uncertainties in the phase shifters of PAA. Two kinds of robust formulations are thus proposed to jointly combat the MAI, ISI and phase uncertainties. Robust beamformers with semi closed-form expressions can be obtained with a nonlinear kind of them, whose SINR satisfaction ratio can attain 80% or more by extensive simulations in an indoor two-user 60 GHz environment if RF beam patterns of the users do not highly overlap in space.
46Â citations
Additional excerpts
...The proposed HBF architecture can thus be applied to systems that employ single-carrier frequency domain equalization (SCFDE) [25], [26] or orthogonal frequency-domain multiplexing (OFDM)....
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27 Dec 2004
TL;DR: It is found that joint use of STTD, receive antenna diversity and frequency-domain MMSE equalisation can significantly improve the BER performance in a severe frequency-selective fading channel.
Abstract: In a frequency-selective fading channel, the performance of non-spread-spectrum single- carrier (SC) transmission degrades significantly due to severe intersymbol interference (ISI). The joint use of space-time transmit diversity (STTD), receive antenna diversity and frequency-domain minimum mean square error (MMSE) equalisation in non-spread SC transmission is studied. Space-time encoding and decoding for frequency-domain MMSE equalisation and receive antenna diversity is presented. The achievable bit error rate (BER) performance of non-spread SC transmission is evaluated by computer simulation. It is found that joint use of STTD, receive antenna diversity and frequency-domain MMSE equalisation can significantly improve the BER performance in a severe frequency-selective fading channel.
46Â citations
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.
16,062Â 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.
2,627Â 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. >
1,816Â 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.
1,624Â citations