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 the OFDM/TDM using MMSE-FDE achieves a lower BER and a better tracking ability against fast fading in comparison with conventional OFDM.
Abstract: MMSE-FDE can improve the transmission performance of OFDM combined with time division multiplexing (OFDM/TDM), but knowledge of the channel state information and the noise variance is required to compute the MMSE weight. In this paper, a performance evaluation of OFDM/TDM using MMSE-FDE with pilot-assisted channel estimation over a fast fading channel is presented. To improve the tracking ability against fast fading a robust pilot-assisted channel estimation is presented that uses time-domain filtering on a slot-by-slot basis and frequency-domain interpolation. We derive the mean square error (MSE) of the channel estimator and then discuss a tradeoff between improving the tracking ability against fading and the noise reduction. The achievable bit error rate (BER) performance is evaluated by computer simulation and compared with conventional OFDM. It is shown that the OFDM/TDM using MMSE-FDE achieves a lower BER and a better tracking ability against fast fading in comparison with conventional OFDM.
5 citations
Cites background or methods from "Frequency domain equalization for s..."
...Various channel estimation techniques for conventional OFDM and SC-FDE have been presented in [4–11]....
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...Similar frame structure was presented for SC transmission in [8]....
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...We adopt a pilot-structure for SC transmission [8] and apply recursive least-square (RLS) algorithm [12] in time domain (in this paper called time-domain first-order filtering (TDFF)) on a slot-by-slot basis within the OFDM/TDM frame to improve the tracking ability against fast fading....
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...One-tap MMSE-FDE similar to SC-FDE [8] is applied over the entire frame with K concatenated OFDM signals as [3] R̂g(n) = Rg(n)Wg(n) = Sg(n)Ĥg(n) + Îg(n) + N̂g(n) (4) with Ĥg(n) = Hg(n)Wg(n) and Îg(n) = Ig(n)Wg(n), where Wg(n) denotes the MMSE equalization weight given by Wg(n) = H∗g (n)∣∣∣Hg(n)∣∣∣2 + 2σ2g , (5) where σ2g and (·)∗ denote the noise variance and the complex conjugate operation, respectively....
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...One-tap MMSE-FDE similar to SC-FDE [8] is applied over the entire frame with K concatenated OFDM signals as [3] R̂g(n) = Rg(n)Wg(n) = Sg(n)Ĥg(n) + Îg(n) + N̂g(n) (4)...
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18 May 2015
TL;DR: This paper presents a widely linear equalizer in single carrier systems with frequency-domain equalization (SC-FDE) for underwater acoustic communications that allows the distance between transmitter and receiver for a given transmitted power to be increased while maintaining the same bit error performance in a variety of scenarios.
Abstract: This paper presents a widely linear equalizer in single carrier systems with frequency-domain equalization (SC-FDE) for underwater acoustic communications. The usage of this equalizer instead of its common strictly linear counterpart allows the distance between transmitter and receiver for a given transmitted power to be increased while maintaining the same bit error performance in a variety of scenarios.
5 citations
Cites background from "Frequency domain equalization for s..."
...Single carrier systems with frequency domain equalization (SC-FDE) maintain the convenient low complexity equalization in the frequency domain of multicarrier systems while avoiding their characteristic high PAPR [6], [7]....
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23 May 2010
TL;DR: The goal of the present paper is to demonstrate how the SC-FDE system can further support polarization division multiplexing (PDM) to double the communication capacity.
Abstract: High order linear modulations, combined with coherent detection and signal processing at the receiver, are nowadays considered to reach the new capacity targets for the communications over the optical fibers. In order to reduce the computational complexity of the algorithms at the receiver, it has recently been proposed to compensate for the chromatic dispersion (CD) and polarization mode dispersion (PMD) in the frequency domain. Orthogonal frequency-division multiplexing (OFDM) and single- carrier with frequency domain equalization (SC-FDE) are two alternative coding strategies to support frequency domain signal processing. Compared to OFDM, SC-FDE is particularly interesting because it potentially facilitates the implementation of the transmitter and it generates a lower peak-to-average power ratio (PAPR) waveform. The goal of the present paper is to demonstrate how the SC-FDE system can further support polarization division multiplexing (PDM) to double the communication capacity. The SC-FDE PDM system is derived analytically and its performance is assessed by numerical simulations. It is shown that a 72 Gbps bit rate can be obtained in a 10 GHz bandwidth.
5 citations
Cites background from "Frequency domain equalization for s..."
...• While OFDM is known to suffer from a high peak-to-average power ratio (PAPR), the PAPR of SC-FDE is much lower [10]....
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04 Jun 2012
TL;DR: The CAZAC (constant amplitude zero autocorrelation) property of Zadoff-Chu sounding reference sequence is exploited to accomplish multiuser (MU) channel estimation in this paper.
Abstract: For the 4G Single-Carrier Frequency-Division-Multiple-Access (SC-FDMA) uplink system, the CAZAC (constant amplitude zero autocorrelation) property of Zadoff-Chu sounding reference sequence (SRS) is exploited to accomplish multiuser (MU) channel estimation in this paper. First, letting each user use an appropriate circular shift of the base SRS, the MU-SC-FDMA signal model is given. Then we derive an efficient MU channel estimation (MUCE) algorithm, which needs only a pair of FFT/IFFT operation to obtain all the users' channel impulse responses. Moreover, the computer simulation results show that only a small degradation in bit error performance is incurred by MUCE. Finally, we set up a Instruments-in-MATLAB Software-Defined Radio (IM-SDR) platform to verify the feasibility of the MUCE algorithm. Real-world measurement results of a two-user experiment show that the MUCE can simultaneously and accurately estimate the two-user channel responses specified by the RF channel emulator.
5 citations
TL;DR: A broadband wireless transceiver which can be reconfigured to any type of cyclic-prefix (CP) -based communication systems, including orthogonal frequency-division multiplexing (OFDM), single-carriercyclic- prefix (SCCP) system, multicarrier (MC) code-divisionmultiple access (MC-CDMA), MC direct-sequence CDMA, CP-based CDMA (CP- CDMA), and CP- based direct- sequence CDMA
Abstract: This paper proposes a broadband wireless transceiver which can be reconfigured to any type of cyclic-prefix (CP) -based communication systems, including orthogonal frequency-division multiplexing (OFDM), single-carrier cyclic-prefix (SCCP) system, multicarrier (MC) code-division multiple access (MC-CDMA), MC direct-sequence CDMA (MC-DS-CDMA), CP-based CDMA (CP-CDMA), and CP-based direct-sequence CDMA (CP-DS-CDMA). A hardware platform is proposed and the reusable common blocks in such a transceiver are identified. The emphasis is on the equalizer design for mobile receivers. It is found that after block despreading operation, MC-DS-CDMA and CP-DS-CDMA have the same equalization blocks as OFDM and SCCP systems, respectively, therefore hardware and software sharing is possible for these systems. An attempt has also been made to map the functional reconfigurable transceiver onto the proposed hardware platform. The different functional entities which will be required to perform the reconfiguration and realize the transceiver are explained.
5 citations
Cites methods from "Frequency domain equalization for s..."
...For SCCP systems, the input-output relation at the nth block after FFT can be expressed as [20]...
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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.
16,062 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