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: It is shown that a multirate equalizer (MRE) is substantially less complex compared to the conventional channel equalizers, which makes single-carrier transmission feasible in channels having much longer delay-spreads or wider bandwidths than it was possible earlier.
Abstract: Multirate signal processing techniques for the equalization of frequency selective communications channels are proposed. It is shown that a multirate equalizer (MRE) is substantially less complex compared to the conventional channel equalizers. This feature makes single-carrier transmission feasible in channels having much longer delay-spreads or wider bandwidths than it was possible earlier. The proposed algorithms do not require transmission of a cyclic prefix. They have both linear and nonlinear versions, wherein the latter employs successive interference cancellation similar to the decision-feedback equalizer (DFE). It is possible to perform decoding prior to interference cancellation. Thus, successive interference canceling (SIC) MRE does not suffer from error propagation if operating on an achievable rate. The SIC-MRE can provably achieve the independent identically distributed information rate of the channel if a Gaussian input alphabet is used. For finite input alphabets, numerical results demonstrate that the single-carrier transmission with the SIC-MRE outperforms multicarrier transmission in terms of throughput. This result holds not only for low-order modulations and relatively narrow bandwidths but also for high-order modulations and wide bandwidths.
3Â citations
Cites background from "Frequency domain equalization for s..."
...Therefore, the SC-FDE has been adopted as the airinterface solution for the uplink of Long Term Evolution (LTE) or the Fourth Generation (4G) cellular standard [15]....
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...The MRE framework might also bring the equalizer design complexity to the SC-FDE and OFDM levels....
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...The SC-FDE supports also higher order modulations, because it does not suffer from the error-floors....
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...The CP based transmission techniques such as SC-FDE and OFDM dominating the current 4G and 5G system design are clearly advantageous against the conventional time-domain MMSE and decision-feedback equalizers....
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...SC-FDE does not suffer from finite length effects either, but it looses spectral efficiency due to the transmission of the CP....
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16 May 2010
TL;DR: A method to mitigate the interferences for single carrier frequency domain equalizer (SC-FDE) without cyclic prefix (CP) outperforms that of conventional CP reconstruction method, and it is verified by computer simulations.
Abstract: In this paper, we propose a method to mitigate the interferences for single carrier frequency domain equalizer (SC-FDE) without cyclic prefix (CP). SC-FDE systems suffer from the interferences when CP is appended insufficiently. Inter block interference (IBI) is introduced by the previous block, and inter symbols interference (ISI) is also generated by imperfection of the circulant channel matrix. The proposed method can effectively restore the channel matrix to be circulant, but the interference is also increased. Thus, some method, to make a compromise between compensating ISI and increasing the interference, is needed and is that the criterion is adopted to maximize the signal to interference plus noise ratio in this paper. However, the improvement of the performance is limited since the interferences are not removed. To overcome it, the interferences are cancelled using iterative MMSE receiver structures. The performance of the system outperforms that of conventional CP reconstruction method, and it is verified by computer simulations.
3Â citations
Cites background from "Frequency domain equalization for s..."
...SC-FDE equalizes the channel as if OFDM does so [5], but its performance is similar to that of OFDM or better in some scenarios [1][4]....
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TL;DR: Two receiver structures for spatially multiplexed transmission on MIMO frequency selective fading channels are investigated and the bit error rates of two time domain receivers are examined through computer simulations and their BER characteristics are compared.
Abstract: In this paper, we investigate two receiver structures for spatially multiplexed transmission on MIMO frequency selective fading channels. Those receivers compensate the IAI (Inter-Antenna Interference) and ISI (Inter-Symbol Interference) in the time domain. We first propose the MIMO sequential equalizer in which the block of several receives symbols is processed symbol by symbol by MLD (Maximum Likelihood Detection). Next we investigate the MIMO MLSE (Maximum Likelihood Sequence Estimation) receiver in which the terminated block trellis is decoded by the Viterbi algorithm. The bit error rates of two time domain receivers are examined through computer simulations and we also compare their BER characteristics to those of the conventional MIMO SC-FDE.
3Â citations
05 Jun 2011
TL;DR: The blind and semiblind channel estimation and equalization are investigated for zero-padding single-carrier block transmission (ZP-SCBT) systems using second-order statistics to demonstrate that the performance of the proposed approach is superior to the subspace-based blind methods.
Abstract: In this paper, the blind and semiblind channel estimation and equalization are investigated for zero-padding single-carrier block transmission (ZP-SCBT) systems using second-order statistics. Unlike the conventional channel estimation techniques, the proposed approach focuses on identifying the inverse of the channel impulse response rather than the channel response itself by skillfully exploiting the redundancy of the zero-padding. One interesting advantage of the proposed blind and semiblind approach is that the number of received blocks needed for blind identification is significantly reduced compared to the subspace method. Moreover, the computational complexity of the proposed approaches is much lower than the existing subspace methods. Simulation results are provided to demonstrate that the performance of the proposed approach is superior to the subspace-based blind methods.
3Â citations
Cites background from "Frequency domain equalization for s..."
...The peak-to-average power ratio (PAPR) of SCBT systems is much smaller than OFDM, and more power efficient transmitters can be used [1], [2]....
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...Single-carrier block transmission (SCBT) with frequencydomain equalization (FDE) constitutes a promising technology for high speed transmission in frequency selective fading environment [1]....
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01 Nov 2012
TL;DR: This paper considers a single carrier system in which for achieving higher spectral efficiency the cyclic prefix is not transmitted at the beginning of blocks, and suggests using an iterative structure, known as iterative block frequency domain equalizer (IBDFE), to reduce the residual interference.
Abstract: Single carrier systems with frequency domain equalization (FDE) have attracted much attention for their efficient implementation of equalization and superiority over multi-carrier schemes from the practical point of view. In this paper, we consider a single carrier system in which for achieving higher spectral efficiency the cyclic prefix is not transmitted at the beginning of blocks. This poses a major inter block interference at the receiver which we suppress by a method known as overlap FDE. However, even by using this method we still deal with a significant amount of residual interference from the previous block. In this paper, we suggest using an iterative structure, known as iterative block frequency domain equalizer (IBDFE), to reduce the residual interference. We also utilize a Gaussian approximation approach to model the residual interference and modify the filter design in IBDFE accordingly. We show that with this modification we are able to reduce the residual interference very efficiently such that for a major part of the block the overall interference is comparable with that of a CP-assisted single carrier system.
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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.
16,062Â 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