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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TL;DR: A channel capacity expression for MC-CDMA assuming perfect ICI cancellation taking into account both frequency diversity gain and space diversity gain is derived and compared to that of OFDM.
Abstract: Orthogonal frequency division multiplexing (OFDM), which uses a number of narrowband orthogonal sub-carriers, is a promising transmission technique. Also multi-carrier code division multi-access (MC-CDMA), which combines OFDM and frequency-domain spreading, has been attracting much attention as a future broadband wireless access. It was shown that MC-CDMA has lower channel capacity than OFDM, due to inter-code interference (ICI) resulting from orthogonality distortion caused by frequency-selective fading. Recently, many ICI cancellers have been proposed to mitigate the effect of ICI. In this paper, we derive a channel capacity expression for MC-CDMA assuming perfect ICI cancellation taking into account both frequency diversity gain and space diversity gain and compare it to that of OFDM. Furthermore, we derive a channel capacity expression for the case of imperfect ICI cancellation to discuss the impact of the residual ICI.
2 citations
Cites background from "Frequency domain equalization for s..."
...Furthermore, we derive a channel capacity expression for the case of imperfect ICI cancellation to discuss the impact of the residual ICI. key words: MC-CDMA, channel capacity, ICI cancellation, theoretical study...
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01 Dec 2007
TL;DR: In this paper, the authors considered using only a block of pilots as the preamble and used a frequency-domain equalizer to reduce the complexity of channel estimation and data detection.
Abstract: Various forms of cyclic-prefixed block transmission have been considered for signal transmission over multipath fading channels Among them the most well-known is orthogonal frequency-division multiplexing, or OFDM Whatever the form, such systems usually transmit many known pilots to assist channel estimation and data detection We consider receiver techniques that can help improve the bandwidth efficiency by reducing the needed amount of pilots In particular, we consider using only a block of pilots as the preamble Then the receiver tracks the channel variation via jointly iterative channel estimation and data detection It uses a frequency-domain equalizer to reduce the complexity Simulations show that the tracking ability of the proposed method is good
2 citations
Cites background from "Frequency domain equalization for s..."
...Among them are the orthogonal frequency-division multiplexity (OFDM), the multi-carrier code-division multiple access (MC-CDMA), and the single carrier with frequency-domain equalization (SC-FDE) [1], to name a few....
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24 Nov 2020
TL;DR: In this article, a multiple-input-multiple-output (MIMO) visible light communications utilizing single-carrier modulation combined with frequency domain equalization is investigated, and it is shown that MIMO with RC offers improved performance compared with single input-single output (SISO) system.
Abstract: In this paper, a multiple input – multiple output (MIMO) visible light communications utilizing single-carrier modulation combined with frequency domain equalization is investigated. We study the repetition coding (RC) and spatial multiplexing (SMP) schemes and show that MIMO with RC offers improved performance compared with single input – single output system, however MIMO with SMP increases the spectral efficiency at the cost of bit error rate degradation.
2 citations
Posted Content•
TL;DR: This paper analyzes the most important marked prototype filters reported in literature, and their corresponding waveforms proposed as prominent candidates for wireless air interface and shows that the filter properties impact the waveform performances and that a close filter-waveform interrelationship is there.
Abstract: The perspective for the next generation of wireless communications prognosticates that the communication should take place with high heterogeneity in terms of services and specifications. The emergence of new communication networks, especially between devices like internet of things (IoT) networks, machine type communications (MTC) and unmanned aerial vehicles (UAV), makes the redesign of the radio air-interfaces even higher significant. High data rate, efficient use of the spectrum, low latency, flexibility, scalable ability, energy efficiency and reduced complexity are in the vanguard of the challenging needs. This highlights the necessity to overrides classical waveforms and propose new air interface that best fits these requirements. Several attempts were conducted to propose the most suitable prototype filters and their associated waveforms that support the future applications with these crucial prerequisites. In the present paper, we analyze the most important marked prototype filters reported in literature, and their corresponding waveforms proposed as prominent candidates for wireless air interface. We will show that the filter properties impact the waveform performances and that a close filter-waveform interrelationship is there. The principal contribution is to give a deep insight on the structure of these filters and waveforms and to come up with a fair comparison regarding different criteria and distinct figures of merit.
2 citations
Additional excerpts
...Equalization [83], [84] [99], [100] [108] [109], [85] [110], [111] [114], [84] [114], [120] [85], [86] [101] [83], [115]...
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Posted Content•
TL;DR: This study shows that even if a memoryless nonlinearity is utilized, received signal is impaired by nonlinear inter-symbol interference (ISI) and proposes a class of post-distortion techniques, which use neighbouring received symbols to supress the nonlinear interference.
Abstract: In this paper, we propose a novel receiver structure for single carrier transmission with frequency domain equalization (FDE) that is exposed to power amplifier (PA) nonlinearities. A two stage approach is adopted, in which linear communication channel is equalized at first stage and it is followed by a post-distortion unit where nonlinear distortion is reduced. In literature, there are some techniques that are proposed for the memoryless compensation of nonlinear distortion together with FDE. However, in this study, we show that even if a memoryless nonlinearity is utilized, received signal is impaired by nonlinear inter-symbol interference (ISI). Therefore, we propose a class of post-distortion techniques, which use neighbouring received symbols to supress the nonlinear interference. Two different, post-distortion techniques, namely Gaussian process regression (GPR) and neural network (NN) based post-distorters, are considered. In addition, a receiver structure, combining outputs of fractional delayed bank of FDE's, is proposed to overcome performance degradation problem of FDE for highly frequency selective channels under nonlinear distortion. Performance of the proposed techniques are compared with that of the state-of-the-art techniques in terms of bit error rate (BER) and achievable information rate (AIR) metrics via simulations. Simulation results demonstrate that GPR and NN based post-distortion methods outperform state-of-the-art techniques. Lastly, it is observed that proposed receiver architecture performs very close to linear system with the help of proposed fractionally delayed FDE bank.
2 citations
Cites background from "Frequency domain equalization for s..."
...It is known that performance of SC-FDE degrades significantly due to noise enhancement especially for the frequency-selective channels having deep fades in the spectrum [7]....
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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