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 Jan 2005
TL;DR: It is proven that when minimum mean-squared-error (MMSE) equalization is adopted, ZP transmission outperforms CP transmission and uncoded orthogonal frequency-division multiplexing (OFDM) on the average over random channels.
Abstract: We study uncoded bit-error rate (BER) performance of single-carrier block transmissions, zero-padded (ZP) transmission and cyclic-prefixed (CP) transmission, when minimum mean-squared error (MMSE) equalizers are applied We show analytically that the BER of ZP transmission with MMSE equalization degrades as the bandwidth efficiency increases, ie there is a trade-off between BER and bandwidth efficiency in ZP transmission It is also proven that ZP transmission outperforms CP transmission and uncoded orthogonal frequency-division multiplexing (OFDM) on the average Numerical examples are provided to validate our theoretical findings and to compare the block transmission systems
40Â citations
Cites background from "Frequency domain equalization for s..."
...Although there is no IFFT operation at the transmitter, efficient frequency-domain equalization is available at the receiver [4], [5]....
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Patent•
29 Mar 2010
TL;DR: In this article, a Fourier transform is used to distribute elements of the data vector over an available frequency space, thus providing robustness to channel anomalies such as fading and/or interference.
Abstract: Numerous embodiments are provided that may be used to provide enhanced capacity and/or Quality-of-Service for OFDM-based systems such as LTE and/or WiMAX. Various service/device modes and/or applications are also provided. According to embodiments of the invention, a transformation may be performed on a data vector by a transmitter, prior to the transmitter transmitting the data vector, to distribute elements of the data vector over an available frequency space, thus providing robustness to channel anomalies such as fading and/or interference. The transformation may be based upon a Fourier transform or a truncated Butler matrix. At a receiver, an inverse of the transformation may be applied to recover data. The receiver and/or transmitter may be configured with an antenna array that may comprise a two-dimensional lattice of antenna elements, and may further be configured to estimate a number of resolvable signal paths and to form a spatial filter/rake that is matched to the number of resolvable signal paths. Embodiments relating to architectures, systems, methods, devices, software, firmware and/or computer program products are provided.
40Â citations
TL;DR: PAM-SCFDE requires lower per bit signal-to-noise ratio to achieve a BER of 10-4 or smaller for modulation sizes common in practice, both with and without considering the effects of light-emitting diode transmitters, such as nonlinearity, forward current restriction, and bandwidth limitation.
Abstract: Multipath dispersion is a serious challenge in visible light communication (VLC) systems as these systems are used for indoor applications where there can be many reflections of the transmitted signal from the ceiling, walls, equipment, etc. These reflected signals cause intersymbol interference in the receiver and can degrade the performance of the system considerably. Orthogonal frequency-division multiplexing (OFDM) for optical wireless communications was introduced to mitigate multipath dispersion and has been well investigated in the literature. Recently, single-carrier systems with frequency-domain equalization (SCFDE) have been proposed as alternatives to OFDM. In this paper, we present pulse amplitude modulated SCFDE (PAM-SCFDE) to mitigate multipath dispersion in VLC systems. We also compare the proposed PAM-SCFDE with existing OFDM and SCFDE techniques for optical wireless communications in terms of analytical and simulated bit-error-rate (BER) performance, power-spectral efficiency, peak-to-average power ratio (PAPR), and overall system complexity. The proposed PAM-SCFDE requires lower per bit signal-to-noise ratio to achieve a BER of $10^{-4}$ or smaller for modulation sizes common in practice, both with and without considering the effects of light-emitting diode transmitters, such as nonlinearity, forward current restriction, and bandwidth limitation. Furthermore, it exhibits better power efficiency for data rates less than $3$ bit/s/Hz, lower PAPR and system complexity compared to other systems.
39Â citations
16 May 2010
TL;DR: Two improved recursive maximum expansion scheduling algorithms for SC-FDMA are proposed, one of which can exhibit the gain about 15% in terms of spectral efficiency with a linear increase of computational complexity, and the performance can be further improved to 18% with proposed ITRME scheme if further higher complexity is permitted.
Abstract: Single-carrier frequency division multiple access (SC-FDMA) has been selected as the uplink access scheme in the UTRA Long Term Evolution (LTE) due to its low peak-to-average power ratio properties. Nevertheless, in order to achieve such a benefit, it requires a localized allocation of the resource blocks (RBs), which naturally imposes a severe constraint on the scheduler design. In this paper, two improved recursive maximum expansion scheduling algorithms for SC-FDMA are proposed. Compared with conventional recursive maximum expansion (RME) scheme in which UE can only expand the resource allocation on neighboring RBs with the highest metrics, in proposed improved recursive maximum expansion (IRME) scheme, higher degree of freedom in RB expansion is achieved by allowing RB expansion within certain ranking threshold. Moreover, to further increase the flexibility in resource allocation, multiple surviving paths are introduced in proposed improved tree-based recursive maximum expansion (ITRME) scheme. The simulation results show that, compared with conventional RME scheme, the proposed IRME scheme can exhibit the gain about 15% in terms of spectral efficiency with a linear increase of computational complexity, and the performance can be further improved to 18% with proposed ITRME scheme if further higher complexity is permitted.
39Â citations
Cites methods from "Frequency domain equalization for s..."
...Contiguous allocation of the RBs for each user has been assumed as a constraint in order to preserve the low PAPR properties of the SC-FDMA signal....
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...In SC-FDMA, the contiguous resource blocks (RBs) allocation is required for each user in order to benefit in terms of PAPR....
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...Keywords-SC-FDMA,propotional fairness, uplink scheduling I. INTRODUCTION Single Carrier Frequency Division Multiple Access (SC- FDMA) has been chosen as the uplink access scheme of UTRA long term evolution (LTE) standardized by the 3rd Generation Partnership Project (3GPP) because of low peak-to-average power ratio (PAPR) [1-5]....
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...Single Carrier Frequency Division Multiple Access (SCFDMA) has been chosen as the uplink access scheme of UTRA long term evolution (LTE) standardized by the 3rd Generation Partnership Project (3GPP) because of low peak-to-average power ratio (PAPR) [1-5]....
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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