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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01 Nov 2013
TL;DR: This paper considers SC-FDE schemes (Single-Carrier with Frequency-Domain Equalization) combined with multilevel constellations that can be decomposed as the sum of BPSK (Binary Shift Keying) signals, which allows the definition of new efficient IB-DFE (Iterative Block Decision Feedback Feedback Equalization), with low impact on system complexity.
Abstract: Multilevel modulations have good spectral efficiency, although at the expense of power efficiency. In mobile wireless systems, where there are strict power and bandwidth constrains, we must maximize the power efficiency. This means the use of high-efficiency amplification schemes at the transmitter side and compact constellations combined with powerful equalizers at the receiver side. In this paper we consider SC-FDE schemes (Single-Carrier with Frequency-Domain Equalization) combined with multilevel constellations that can be decomposed as the sum of BPSK (Binary Shift Keying) signals. These components can be separately amplified and besides this decomposition allows the definition of new efficient IB-DFE (Iterative Block Decision Feedback Equalization) implementations suitable for multilevel constellations, with low impact on system complexity.
6Â citations
Cites background from "Frequency domain equalization for s..."
...SC-FDE schemes (Single-Carrier with Frequency-Domain Equalization) [7] are known to be excellent candidates for future broadband wireless systems since they can have good performance in severely time-dispersive channels without requiring complex receiver implementation [8], [9]....
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Journal Article•
TL;DR: Simulation results show that the new scheme employing the energy of a few paths to obtain better performance than the traditional maximum ratio combining (MRC) Rake receiver.
Abstract: In this paper, a robust adaptive MMSE Rake-equalizer receiver scheme is presented with channel estimation that has been transmitted in Direct Sequence-Ultra Wideband (DS-UWB) system. The DS-UWB has a fine path resolution by transmitting information with ultra short pulses. The Rake receiver is known as a technique that can effectively combine paths with different delays and obtain the path diversity gain. Due to sub-nano seconds narrow pulse and the large transmission bandwidth in the systems, we therefore use equalizer to overcome the resulting ISI and a long delay spread in the characterization of the UWB channel. The proposed receiver structure reduces intense multi-path destruction and severe inter-symbol interference (ISI) by using a combined adaptive Rake and equalizer structure referred to as the MMSE (minimum mean square error) algorithm. Channel information is obtained through the use of a least mean square (LMS) adaptive algorithm on the training sequence of a preamble. The indoor environment is represented by dense multipath channel models proposed by IEEE 802.15.3a. Simulation results show that the new scheme employing the energy of a few paths to obtain better performance than the traditional maximum ratio combining (MRC) Rake receiver.
6Â citations
Cites background from "Frequency domain equalization for s..."
...Meanwhile, due to sub-nano seconds narrow pulse and the large transmission bandwidth in the UWB system, the equalizer has also recently attracted much attention [9] as a means to overcome the resulting inter-symbol interference (ISI) and a long delay spread in the characterization of the UWB channel....
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01 May 2019
TL;DR: A thorough performance evaluation of the pulsed modulation PHY is presented and it is demonstrated that, by using an advanced synchronization scheme and FDE, packets can reliably be transmitted at clock rates up to 200 MHz over line-of-sight (LOS) and strong multi-path OWC channels considered typical for industrial wireless scenarios.
Abstract: Most literature on the physical layer (PHY) for optical wireless communication (OWC) considers the down-link from lighting infrastructure to mobile devices, and focuses on achieving high data rates by combining large bandwidth and high spectral efficiency. However, some applications, such as the corresponding up-link, device-to-device (D2D) communication, and Internet of Things (IoT), rely on energy-efficient transmission due to limited battery power. According to Shannon's theorem, this can be achieved through using a large bandwidth with power-efficient modulation. The IEEE P802.15.13 task group recently defined the pulsed modulation (PM) PHY with these objectives in mind. The key is to enable robust synchronization and header detection by means of binary modulation. Block-based transmission with a cyclic prefix (CP) and frequency domain equalization (FDE) are used to enable a large bandwidth. In this paper, we present a thorough performance evaluation of the PM PHY. It is demonstrated that, by using an advanced synchronization scheme and FDE, packets can reliably be transmitted at clock rates up to 200 MHz over line-of-sight (LOS) and strong multi-path OWC channels considered typical for industrial wireless scenarios.
6Â citations
Cites background from "Frequency domain equalization for s..."
...For long channel impulse responses (CIRs), computational complexity can even be significantly lower [19]....
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TL;DR: The results show that the proposed ranging method can achieve unbiased estimate and its root mean square errors will reach the order of centimeter at medium-to-high signal- to-noise ratio region in flat-fading channels, whereas the observed performance degradation in frequency selective channel can be mitigated by using equalized oversampled signals.
Abstract: Ground-based positioning systems are necessary as the conventional satellite-based systems suffer from weak received signals. In this paper, we proposed a precise ranging method in single-carrier frequency domain equalization (SC-FDE) system using the amplitude nonlinearity of oversampled signals. A new pattern of the preamble and the unique word was designed for SC-FDE system, where the preamble can be exploited in correlation-based timing algorithm to obtain impulse-like timing metric. Combining with the coarse timing procedure, we proposed a fine ranging method relying on the oversampled signals in SC-FDE receiver employing Qth-power nonlinearity, and then analyzed its estimation mean and variance. The extensive simulations were conducted to validate the proposed method with distinct modulation schemes, rolling-off factors, block lengths, and nonlinearity factors. The results show that the proposed ranging method can achieve unbiased estimate and its root mean square errors will reach the order of centimeter at medium-to-high signal-to-noise ratio region in flat-fading channels, whereas the observed performance degradation in frequency selective channel can be mitigated by using equalized oversampled signals.
6Â citations
Cites background from "Frequency domain equalization for s..."
...SC-FDE SIGNAL MODEL The time-domain adaptive equalizer are mainly one or more transversal filters for which the number of adaptive tap coefficients is on the order of the number of data symbols spanned by the multipath, with at least several hundred multiplication operations per data symbol [29]....
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TL;DR: A new 2-step maximum likelihood channel estimation (MLCE) for DS-CDMA with FDE in a very slow frequency-selective fading environment is proposed and the BER performance improvement achieved by 2- step MLCE over pilot assisted MMSE-CE is confirmed by computer simulation.
Abstract: Frequency-domain equalization (FDE) based on the minimum mean square error (MMSE) criterion can provide better downlink bit error rate (BER) performance of direct sequence code division multiple access (DS-CDMA) than the conventional rake combining in a frequency-selective fading channel. FDE requires accurate channel estimation. In this paper, we propose a new 2-step maximum likelihood channel estimation (MLCE) for DS-CDMA with FDE in a very slow frequency-selective fading environment. The 1st step uses the conventional pilot-assisted MMSE-CE and the 2nd step carries out the MLCE using decision feedback from the 1st step. The BER performance improvement achieved by 2-step MLCE over pilot assisted MMSE-CE is confirmed by computer simulation.
6Â citations
Cites methods from "Frequency domain equalization for s..."
...Frequency-domain pilot assisted CE was proposed in [4], [5]....
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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.
16,062Â 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