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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08 Dec 2008
TL;DR: An algorithm is proposed for the recognition of CP-tSCLD against SCLD and orthogonal frequency division multiplexing (OFDM) signals that obviates the need for signal pre-processing tasks, such as symbol timing, carrier and waveform recovery and estimation of signal and noise powers.
Abstract: The second-order cyclostationarity of cyclically prefixed single carrier linear digital (CP-tSCLD) modulated signals is investigated with emphasis on its applicability to signal recognition. Analytical closed-form expressions for the second-order (one-conjugate) cyclic cumulants (CCs) and the set of cycle frequencies (CFs) for CP-SCLD modulated signals are derived. Based on these results, an algorithm is proposed for the recognition of CP-tSCLD against SCLD and orthogonal frequency division multiplexing (OFDM) signals. This algorithm obviates the need for signal pre-processing tasks, such as symbol timing, carrier and waveform recovery and estimation of signal and noise powers.
20 citations
Cites background or methods from "Frequency domain equalization for s..."
...Cyclically prefixed single carrier modulation [3], another efficient approach for dealing with frequency selective fading, has the advantage of low complexity equalization while avoiding the peak-to-average power problem of OFDM [4]....
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...Block transmission is employed in CP-SCLD schemes, in which a CP of L symbols is added at the beginning of each block of N information data symbols [3]-[4], [8]....
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TL;DR: The proposed IB-DFE schemes allow an efficient user separation, with a performance close to the one given by the matched filter bound for severely time-dispersive channels, with only a few iterations.
Abstract: The aim of this paper is to propose and evaluate multi-user iterative block decision feedback equalization (IB-DFE) schemes for the uplink of single-carrier frequency-division multiple access (SC-FDMA)-based systems. It is assumed that a set of single antenna users share the same physical channel to transmit its own information to the base station, which is equipped with an antenna array. Two space-frequency multi-user IB-DFE-based processing are considered: iterative successive interference cancellation and parallel interference cancellation. In the first approach, the equalizer vectors are computed by minimizing the mean square error (MSE) of each individual user, at each subcarrier. In the second one, the equalizer matrices are obtained by minimizing the overall MSE of all users at each subcarrier. For both cases, we propose a simple yet accurate analytical approach for obtaining the performance of the discussed receivers. The proposed schemes allow an efficient user separation, with a performance close to the one given by the matched filter bound for severely time-dispersive channels, with only a few iterations.
20 citations
Cites background from "Frequency domain equalization for s..."
...Single-carrier frequency domain equalization (SC-FDE) is widely recognized as an excellent alternative to OFDM, especially for the uplink of broadband wireless systems [4,5]....
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TL;DR: The improvement in the BER performance in a frequency-selective Rayleigh fading channel is evaluated by computer simulation and the single-user and multi-user cases are considered and the BERN performances achievable with MMSE, MRC and ZF equalizations are compared.
Abstract: SUMMARY Joint frequency-domain equalization (FDE) and antenna diversity combining is applied to the reception of multi-rate DS-CDMA signals to achieve the frequency diversity effect while suppressing interpath interference (IPI) resulting from the asynchronism of different propagation paths. At a receiver, fast Fourier transform (FFT) is applied for FDE and then inverse FFT (IFFT) is used to obtain a frequency-domain equalized DS-CDMA chip sequence for the succeeding despreading operation. An arbitrary spreading factor SF can be used for the given value of FFT window size; an extreme case is the nonspread SC system with SF=1. This property allows a flexible design of multi-rate DS-CDMA systems. Three types of FDE are considered; minimum mean square error (MMSE) equalization, maximal-ratio combining (MRC) equalization and zero-forcing (ZF) equalization. Matched filter bound analysis for achievable BER performance is presented. The improvement in the BER performance in a frequency-selective Rayleigh fading channel is evaluated by computer simulation. First, we consider the single-user case and compare the BER performances achievable with MMSE, MRC and ZF equalizations. How the fading rate and the spreading factor affect the BER performance is also evaluated. Furthermore, the BER performance comparison between FDE and rake combining is presented for various values of SF and also performance comparison between DS-CDMA and SC signal transmissions, both using FDE, is presented. Finally, we extend our evaluation to the multi-user case. Both downlink and uplink are considered and how the BER performances of downlink and uplink differ is discussed.
20 citations
06 Jun 2007
TL;DR: A joint synchronization and equalization method is proposed which is based on maximum a priori estimation of the phase error caused by frequency offset and phase noise, generated using the log likelihood ratios of the bits provided by the decoder during iterations.
Abstract: In this paper we investigate the effect of frequency offset and phase noise on a turbo frequency domain equalization system. We propose a joint synchronization and equalization method which is based on maximum a priori estimation of the phase error caused by frequency offset and phase noise. This estimation is generated using the log likelihood ratios of the bits provided by the decoder during iterations. This estimator has the form of a decision directed phase lock loop which can compensate for the effect of the phase error after a few iterations.
20 citations
Cites methods from "Frequency domain equalization for s..."
...To use FDE, the transmission should be block-wise [ 8 ]....
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...Turbo equalization is a turbo processing based method which improves the performance of the system by transferring the soft information between the equalizer and the decoder iteratively [6, 7]. In this paper we consider an interference cancellation turbo equalizer in which the equalizer coefficients are determined based on the MMSE criterion in the frequency domain due to the simplicity of the equalization process [ 8 ]....
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TL;DR: An analytical model is proposed to compute the BER and PER of DC, MPD and hybrid techniques, considering a Single-Carrier with Frequency-Domain Equalization (SC-FDE) scenario and two frequency-domain detection methods: a simple linear receiver and a powerful iterative receiver.
Abstract: Diversity Combining (DC) and Multipacket Detection (MPD) are efficient techniques that cope with packet errors due to severe propagation conditions and/or collisions. To evaluate their network performance on a network simulator, an accurate characterization of the Bit Error Rate (BER) and Packet Error Rate (PER) can successfully replace the behavior of the PHY layer. This choice is better in terms of computational time than implementing a full PHY layer to be jointly simulated with the upper layers. In this paper, an analytical model is proposed to compute the BER and PER of DC, MPD and hybrid techniques, considering a Single-Carrier with Frequency-Domain Equalization (SC-FDE) scenario. The paper also considers two frequency-domain detection methods: a simple linear receiver and a powerful iterative receiver. The proposed model is simple and versatile, since it can support nonhomogeneous transmitting powers, and different channel conditions concerning retransmissions and channel randomization techniques. Several simulations show that the proposed model provides accurate BER and PER results for a wide range of scenarios.
20 citations
Cites background or methods from "Frequency domain equalization for s..."
...For L > P , L = 6 and P = [1, 2, 3, 4]; for L = P , P = [1, 2, 3, 4]....
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...16-QAM BER performance for the MPD technique, for P = 3 and L = [3, 4, 5, 6] for a linear receiver structure regarding the SP transmission technique....
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...Multipacket Detection for P = 2 MTs, L = [2, 4] and up to 4 iterations regarding an iterative receiver structure....
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...L = [3, 4, 5, 6], for a 16-QAM constellation and the SP technique....
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...Diversity Combining technique up to 4 iterations and L = [1, 2, 4]....
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References
More filters
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