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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20 May 2012
TL;DR: A new technique which can blindly perform the fine synchronization for single-carrier block-transmission (SCBT) systems without using unique words (UW) is presented, which has much better estimation accuracy than the well-known linear least-square (LLS) method for SC systems.
Abstract: This work presents a new technique which can blindly perform the fine synchronization for single-carrier block-transmission (SCBT) systems without using unique words (UW). The proposed technique, called simplified weighted LS method for single-carrier systems (SWLS-SC), combines the concept of the decision feedback structure and SWLS estimator for OFDM systems. Together with specifically derived weighting factors, the proposed scheme has much better estimation accuracy than the well-known linear least-square (LLS) method for SC systems, while its BER performance can approach that of the ideal synchronization condition. With the proposed estimator, the system throughput can be further increased, because there is no need to insert UW for fine synchronization. The theoretical estimation bounds are also derived to prove the effectiveness of the proposed scheme.
1 citations
01 Dec 2012
TL;DR: Simulation results show that the proposed SC-FDE designs outperform orthogonal frequency-division multiplexing based MIMO relay systems in terms of both uncoded and coded bit error rate.
Abstract: In this paper, we propose a joint transceiver design for multiple-input multiple-output (MIMO) relay systems employing single-carrier frequency-domain equalization (SC-FDE). We first derive the optimal minimum mean-squared error (MMSE) frequency-domain linear equalization filter at the destination and the associated stream-wise MSEs at the output of the equalizer. Subsequently, we optimize the source and relay precoding matrices for various optimality criteria by minimizing a general function of the MSEs subject to separate source and relay power constraints. The structures of the optimal source and relay precoding matrices are obtained in closed form and the remaining power allocation problems are solved using an alternating optimization algorithm. Simulation results show that the proposed SC-FDE designs outperform orthogonal frequency-division multiplexing based MIMO relay systems in terms of both uncoded and coded bit error rate.
1 citations
Cites methods from "Frequency domain equalization for s..."
...In this case, block based single-carrier transmission with frequency-domain equalization (SC-FDE) is a promising alternative to OFDM due to its similar implementation complexity and lower PAPR [9]....
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...However, OFDM-based transmission may result in large peakto-average power ratios (PAPRs) at the transmitter, which is not a desirable feature for application in the uplink....
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21 Feb 2006
TL;DR: In this paper, a hybrid decision feedback equaliser (DFE) with a feedback filter whose length can be dynamically adjusted is presented and investigated; the equaliser is an adaptive DFE with a feedforward filter (FFF) implemented in the frequency domain with its length fixed by the FFT/IFFT size.
Abstract: In the paper, a hybrid decision feedback equaliser (DFE) with a feedback filter (FBF) whose length can be dynamically adjusted is presented and investigated. The equaliser is an adaptive DFE with a feedforward filter (FFF) implemented in the frequency domain with its length fixed by the FFT/IFFT size and a feedback filter (FBF) in the time domain. The FBF length is adjusted according to the achieved mean squared error (MSE). In addition, the impact of small FBF coefficients on system BER performance is taken into account so that a shorter filter length can be considered. Computer simulations show that the proposed approach is capable of adjusting the feedback filter length to a satisfactory level in terms of MSE and system BER performance and is able to track channel changes successfully.
1 citations
26 Oct 2018
TL;DR: The proposed method of equalization can simply counteract inter-symbol interference without inserting training sequences and be used for multi-channel and single-carrier frequency domain minimum mean squared error equalization.
Abstract: This paper proposes a new equalization of indoor visible light communication based on mobile localization. Compared with zero-forcing equalization which has a large noise gain occurring at the deep fading points. Minimum mean square error equalization is more suitable for multi-channel and it performs well in equalization. By combining the mobile positioning technology and the single-carrier frequency domain minimum mean squared error equalization, the proposed method of equalization can simply counteract inter-symbol interference without inserting training sequences.
1 citations
Cites methods from "Frequency domain equalization for s..."
...The equalized signal is then subjected to a decision feedback circuit to determine and feedback the signal to eliminate severe frequency selective fading signals [10]....
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TL;DR: By repeating each consecutive modulation symbol prior to the spreading, the DFT of the spreading sequence becomes a window function, which compared to the existing method of repeating the whole block of modulation symbols, offers a signal with both lower cubic metric and block error rate (BLER).
Abstract: Enhanced time-domain spreading is proposed for block-interleaved frequency division multiple access (B-IFDMA) with discrete Fourier transform spread orthogonal frequency division multiplexing (DFT-s-OFDM). By repeating each consecutive modulation symbol prior to the spreading, we show that the DFT of the spreading sequence becomes a window function, which compared to the existing method of repeating the whole block of modulation symbols, offers a signal with both lower cubic metric (CM) and block error rate (BLER). Modulation symbol-specific spreading sequences are further shown to improve the BLER. The new transmission scheme is supported by both time- and frequency domain despreaders, as well as by two channel estimation methods for B-IFDMA.
1 citations
Cites methods from "Frequency domain equalization for s..."
...The receiver performs a T -point DFT, applies FD equalization (FDE) [11], [12], demaps the subcarriers, performs an L-point IDFT and then despreads the symbols in the TD....
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...A receiver could therefore perform the despreading on the received FD elements Y (a)kn+xM on receive antenna a together with FDE, e.g., MMSE, followed by summation over the NRX receive antennas according to X (i) kn = NRX−1∑ a=0 NSF−1∑ x=0 Ĥ ∗(a) kn+x·MW ∗(i) kn+x·M |Ĥ(a)kn+x·M |2 + 1/SNR Y (a) kn+x·M ....
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...Since the FDE is imperfect, the block (3) of L TD samples will effectively be cyclically convoluted with a residual CIR LEFT: SNR AT 1% BLER WITH NSF = 4 FOR DIFFERENT NUMBER OF INTERFERING USERS, U , WITH SYMBOL REPETITION (3), USING DFT SPREADING SEQUENCE WITHOUT SEQUENCE CYCLING AND ZC SPREADING SEQUENCES WITH SEQUENCE CYCLING....
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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