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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22 Apr 2007
TL;DR: Computer simulation results show that the proposed time domain channel estimation scheme can achieve almost the same channel estimation accuracy in multi-cell scenario as that in single-cell environment with small number of iterations.
Abstract: This paper investigates downlink channel estimation schemes for multi-cell block transmission systems with cyclic prefix and proposes a time domain channel estimation scheme using iterative least square interference cancellation. The proposed scheme takes advantage of the fact that each received pilot signal exists in up to the length of the cyclic prefix pulse one dimensional subspace in the fast Fourier transform (FFT) size dimensional received signal vector space. Computer simulation results show that the proposed scheme can achieve almost the same channel estimation accuracy in multi-cell scenario as that in single-cell environment with small number of iterations.
6Â citations
05 Apr 2009
TL;DR: A theoretical analysis of joint THP/pre-FDE is presented and the conditional bit error rate (BER) for the given channel realization is derived by taking into account the modulo operation error in a receiver and the achievable BER performance is numerically evaluated.
Abstract: Frequency-domain pre-equalization (pre-FDE) can improve the single-carrier (SC) signal transmission performance in a severe frequency-selective channel. However, the performance improvement is limited by the residual inter-symbol interference (ISI). The residual ISI can be eliminated by the joint use of Tomlinson-Harashima precoding and frequency-domain pre-equalization (called joint THP/pre-FDE) and its performance improvement was confirmed by computer simulation in [8]. In this paper, we present a theoretical analysis of joint THP/pre-FDE. The conditional bit error rate (BER) for the given channel realization is derived by taking into account the modulo operation error in a receiver and the achievable BER performance is numerically evaluated.
6Â citations
TL;DR: An analytical expression for the TF of the FS MMSE equalizer is derived, which includes the effects of the continuous-time to discrete-time (C/D) converter used at the receiver front end, and the sources of instability of theFS least-mean-square (LMS) algorithm are explained.
Abstract: In the communication systems that use a linear modulation scheme for transmission, the fractionally-spaced (FS) samples of the received signal constitute a wide-sense cyclostationary time series. Hence, the standard Fourier transform techniques cannot be used to study the spectral characteristics of the received FS samples or to derive the transfer function (TF) of the corresponding digital minimum mean-square error (MMSE) receiver. In this paper, an analytical expression for the TF of the FS MMSE equalizer is derived, which includes the effects of the continuous-time to discrete-time (C/D) converter used at the receiver front end. Using this TF, the sources of instability of the FS least-mean-square (LMS) algorithm and the effects of the equalizer length and sampling phase on convergence of the LMS algorithm are explained. For stabilization of the FS LMS algorithm, conditions on the front-end C/D converter are provided, such that, when satisfied the LMS algorithm becomes more stable and the learning characteristics of the modified receiver are better than the leaky-FS LMS algorithm. Theoretical results are corroborated by simulations.
6Â citations
Cites background from "Frequency domain equalization for s..."
...Single carrier frequency-domain equalization (SC-FDE) [13], [27], [28] is...
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24 Sep 2007
TL;DR: This paper proposes a technique that allows an efficient packet separation in the presence of successive collisions, considering an SC (Single-Carrier) modulation with FDE (Frequency-Domain Equalization) and a frequency-domain multi-packet detection scheme.
Abstract: Usually, packets involved in a collision are lost, requiring the retransmission of all packets. However, if we do not discard collided packets and we use proper retransmissions we can efficiently resolve collisions. In this paper we propose a technique that allows an efficient packet separation in the presence of successive collisions. We consider an SC (Single-Carrier) modulation with FDE (Frequency-Domain Equalization) and we propose a frequency-domain multi-packet detection scheme. Since our technique requires uncorrelated channels for different retransmissions, we also propose a PS technique (Packet-Shift) for retransmissions using the same channel. Our technique allows high throughputs, since the total number of transmissions is equal to the number of packets involved in the collision. Moreover, the complexity is concentrated in the receiver, making this technique particularly appealing to the uplink of broadband wireless systems. By employing the PS scheme we can use the same channel for the retransmissions, with only a small performance degradation.
6Â citations
Cites background from "Frequency domain equalization for s..."
...In fact, if we do not discard collided packets and we use proper retransmissions we can efficiently resolve collisions [1]....
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TL;DR: 2-step maximum likelihood block signal detection can significantly reduce the computational complexity while achieving almost the same BER performance as the conventional QRM-MLBD.
Abstract: Maximum likelihood block signal detection employing QR decomposition and M-algorithm (QRM-MLBD) can significantly improve the bit error rate (BER) performance of single-carrier (SC) transmission while significantly reducing the computational complexity compared to maximum likelihood detection (MLD). However, its computational complexity is still high. In this paper, we propose the computationally efficient 2-step QRM-MLBD. Compared to conventional QRM-MLBD, the number of symbol candidates can be reduced by using preliminary decision made by minimum mean square error based frequency-domain equalization (MMSE-FDE). The BER performance achievable by 2-step QRM-MLBD is evaluated by computer simulation. It is shown that it can significantly reduce the computational complexity while achieving almost the same BER performance as the conventional QRM-MLBD.
6Â citations
Cites background from "Frequency domain equalization for s..."
...…likelihood block signal detection employing QR decomposition and M-algorithm (QRM-MLBD) can significantly improve the bit error rate (BER) performance of single-carrier (SC) transmission while significantly reducing the computational complexity compared to maximum likelihood detection (MLD)....
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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