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: This paper considers the single-carrier block transmission with cyclic prefix, in which a recently proposed diagonal-precoding assisted blind channel estimation scheme via covariance matching is adopted to acquire the channel information.
Abstract: Transmit precoding is a key technique for facilitating blind channel estimation at the receiver but the impact due to precoding on the channel capacity is scarcely addressed in the literature. In this paper we consider the single-carrier block transmission with cyclic prefix, in which a recently proposed diagonal-precoding assisted blind channel estimation scheme via covariance matching is adopted to acquire the channel information. It is shown that, when perfect channel knowledge is available at the receiver, the optimal noise resistant precoder proposed in the literature incurs the worst-case capacity penalty. When the coherent interval is finite, channel mismatch occurs due to finite-sample covariance matrix estimation. Thus, we aim to determine how much of the coherent interval should be dedicated to precoding in order to trade channel estimation accuracy for the maximal capacity. Toward this end, we leverage the matrix perturbation theory to derive a closed-form capacity measure which explicitly takes account of the channel uncertainty in the considered blind estimation setup. Such a capacity metric is seen to be a complicated function of the precoding interval. To facilitate analysis, an approximate formula for the derived capacity measure is further given. This allows us to find a closed-form estimate of the capacity-maximizing precoding time fraction, and can also provide insights into the optimal tradeoff between channel estimation accuracy and achievable capacity. Numerical simulations are used for evidencing the proposed analytic study.
1 citations
Additional excerpts
...I. INTRODUCTION...
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01 May 2011
TL;DR: In this paper, an efficient repeated clipping and filtering (RCF) algorithm is applied to a single carrier frequency division multiple access (SC-FDMA) system, which results in a significant peak-to-average power ratio (PAPR) reduction.
Abstract: A single carrier frequency division multiple access (SC-FDMA), is a technique that has a similar performance and essentially the same overall complexity as those of orthogonal frequency division multiple access (OFDMA). The main advantage of SC-FDMA over OFDMA is its lower peak-to-average power ratio (PAPR). In this paper, an enhancement of aSC-FDMA by decreasing the PAPR is addressed. An efficient repeated clipping and filtering (RCF) algorithm is applied to a SC-FDMA system, which results in a significant PAPR reduction. System performance remains the same after applying the RCF algorithm. Simulations show the proposed scheme provides a bit error as that of the conventional system. That is, due to the selection of the optimum clipping ratio (CR). For more accurate validation, simulations of the conventional system and the proposed system have been performed using different types of channels. The proposed scheme provides a PAPR reduction by a gain of approximately 4 dB with a slight increase of complexity.
1 citations
Cites background from "Frequency domain equalization for s..."
...Despite the benefits of OFDM and OFDMA, they suffer a number of drawbacks such as the high PAPR [2]....
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09 May 2019
TL;DR: Through the simulation results, it is shown that CDM-based pilot signal multiplexing with different cyclic shifts and the frequency domain averaging of the estimated channel response are effective in achieving accurate channel estimation with a short delay and a low pilot-overhead loss for single-carrier LOS- MIMO.
Abstract: This paper presents the bit error rate (BER) performance of frequency domain equalization (FDE) using cyclic-shifted code division multiplexing (CDM) pilot signals for single-carrier line-of- sight (LOS) - multiple-input multiple-output (MIMO) multiplexing. We use different cyclic-shift resources of the same Zadoff-Chu sequence for transmission-stream-specific pilot signals that are essential for estimating the channel response for FDE and phase noise in LOS-MIMO. Computer simulation results show that the required received signal-to-noise power ratio satisfying the BER of 10^(-4) by averaging approximately 4 channel responses after despreading the pilot signal in the frequency domain is decreased by approximately 2.0 dB compared to that without averaging of the channel response for 256QAM, 1024QAM, and 4096QAM in 2x2 and 4x4 LOS-MIMO. Through the simulation results, we show that CDM-based pilot signal multiplexing with different cyclic shifts and the frequency domain averaging of the estimated channel response are effective in achieving accurate channel estimation with a short delay and a low pilot-overhead loss for single-carrier LOS- MIMO.
1 citations
Additional excerpts
...So far, the received signal-to-noise power ratio (SNR) performance has been investigated using time domain equalization (TDE) with the minimum mean square error (MMSE) algorithm for LOS-MIMO in a frequency-selective fading channel [7]....
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...TDE has been used in commercial LOS-MIMO systems....
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...Recently, frequency domain equalization (FDE) was proposed because it provides lower computational complexity compared to TDE [8]....
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01 Dec 2010
TL;DR: A PAPR reduction technique is proposed where the precoding is done in the first step and at the second step, clipping is performed using SC-FDMA environment, which shows that the P APR is reduced at the increase in number of clips.
Abstract: 3rd Generation Partnership Project Long Term Evolution (3GPP LTE) has adopted orthogonal frequency division multiple access (OFDMA) as downlink and single carrier frequency division multiple access (SC-FDMA) as uplink for multiple access scheme. SC-FDMA is adopted in uplink due to its low peak to average power ratio (PAPR). To reduce PAPR in OFDMA, several techniques are used in literature. SC-FDMA is adopted in 3GPP as it shows better PAPR characteristics than OFDMA. Many researches are still going on to find the impact of different parameters on PAPR in SC-FDMA. In this paper, a PAPR reduction technique is proposed where the precoding is done in the first step and at the second step, clipping is performed using SC-FDMA environment. Result shows that the PAPR is reduced at the increase in number of clips.
1 citations
Cites methods from "Frequency domain equalization for s..."
...Most of the well- known time domain equalization techniques, such as minimum mean square error (MMSE) equalization, decision feedback equalization (DFE), and turbo equalization, can be applied to the frequency domain equalization [7]....
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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