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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27 Jan 2014
TL;DR: The frequency-domain based precoder design is presented and a tradeoff between PAPR and bit-error rate (BER) is discussed in this paper.
Abstract: There are two types of signal waveform: single-carrier (SC) and multi-carrier (MC). A representative of MC signal is orthogonal frequency division multiplexing (OFDM). SC signal can be considered as a linear precoded OFDM signal and has lower peak-to-average power ratio (PAPR) than OFDM signal. There exist many variants between SC and MC signals depending on the linear precoder. The linear precoder can be designed to generate a SC signal having very-low-PAPRbased on the minimum variance of instantaneous transmit power (VIP) criterion, or can be extended to generate SC spread spectrum (SS) signal. The frequency-domain based precoder design is presented and a tradeoff between PAPR and bit-error rate (BER) is discussed in this paper.
3 citations
Cites background from "Frequency domain equalization for s..."
...The use of frequency-domain equalization (FDE) can take advantage of the channel frequency selectivity to improve the bit-error rate (BER) performance of SC transmission [4]....
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Posted Content•
TL;DR: It is proved that the SC-DFE capacity is always superior to that of an OFDM scheme for 4- and 16-QAM for any given channel.
Abstract: This letter provides a capacity analysis between OFDM and the ideal SC-DFE when no channel knowledge is available at the transmitter. Through some algebraic manipulation of the OFDM and SC-DFE capacities and using the concavity property of the manipulated capacity function and Jensen's inequality, we are able to prove that the SC-DFE capacity is always superior to that of an OFDM scheme for 4- and 16-QAM for any given channel. For higher-order modulations, however, the results indicate that OFDM may only surpass the ideal SC-DFE capacity by a small amount in some specific scenarios.
3 citations
TL;DR: The proposed scheme provides a low complexity implementation of any dispersion in space and frequency over SCFDE systems, which alternatively would require the use of FFT/IFFT also at the transmitter side.
Abstract: This letter addresses the application of Linear Dispersion Codes (LDC) in space and frequency domains in Single Carrier-Frequency Domain Equalization (SCFDE) systems. Space-frequency (SF)-LDCs are more suitable than space-time (ST) LDC in high mobility environments. However, the application of LDCs in space and frequency domains in SCFDE systems is not straightforward as in orthogonal frequency division multiplexing (OFDM) systems because in this case there is no direct access to subcarriers at the transmitter. This letter shows that it is possible to induce a target SF symbol dispersion in SCFDE by using a simple linear pre-coder and a conventional LDC that spreads the symbols in time and space domains according to specific ST dispersion matrices. The letter shows how to derive the ST dispersion matrices to be used at the transmitter as a function of the dispersion matrices describing the target SF dispersion. The presented procedure can be applied to both pure transmit diversity and pure multiplexing schemes, which are special cases of LDCs. Therefore, the proposed scheme provides a low complexity implementation of any dispersion in space and frequency over SCFDE systems, which alternatively would require the use of FFT/IFFT also at the transmitter side. The letter also shows a performance comparison of SF-LDCs and ST-LDCs in a typical propagation environment for future radio systems. The comparison confirms the suitability of using the dispersion in frequency rather than time for a wide range of coherence bandwidths.
3 citations
Cites methods from "Frequency domain equalization for s..."
...The transmitter also includes a Cyclic Prefix (CP) insertion block for each antenna to cope with the inter-block interference, as in conventional SC systems with FDE [9]....
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24 Jun 2007
TL;DR: This paper considers a reduced-PMEPR, clipped-OFDM transmission, where an advanced receiver performs the iterative cancellation of the deliberate nonlinear distortion effects, and shows a very significant overall advantage for the SC side.
Abstract: A CP-assisted (cyclic prefix) block transmission is widely accepted as a good choice for future mobile systems, taking advantage of low-cost, flexible, FFT-based (fast Fourier transform) signal processing technology with both OFDM (orthogonal frequency division multiplexing) and SC (single carrier) alternatives. The OFDM alternative provides a simple receiver implementation which allows good performances, by exploiting the channel coding effort, but is known to suffer from a high PMEPR (peak-to-mean envelope power ratio), leading to power amplification difficulties. The SC/FDE (frequency-domain equalization) alternative is easily compatible with low PMEPR values, but the FDE (MMSE) receiver performance is known to be far from the optimum. In this paper, we consider a reduced-PMEPR, clipped-OFDM transmission , where an advanced receiver performs the iterative cancellation of the deliberate nonlinear distortion effects. In parallel, we consider an advanced turbo FDE receiver, as well as simplified iterative FDE receiver implementations, within the SC alternative. The "SC vs OFDM" comparisons of this paper, under the use of iterative receiver techniques in both cases, show a very significant overall advantage for the SC side.
3 citations
Cites background from "Frequency domain equalization for s..."
...Mixed CPassisted solutions have already been proposed, with OFDM for the downlink and SC for the uplink [2], [3], [4]....
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...The ”SC vs OFDM” comparisons, involving a rate-1/2 convolutional code in both cases, show a very clear overall advantage for the SC side, much more significant than the advantage, already reported in the literature, concerning conventional (noniterative) receiver implementations [2], [3], [4]....
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01 Mar 2007
TL;DR: This paper presents a novel concept of virtual receive antennas (VRA) for spatial multiplexing system in flat fading channels with low complexity frequency domain equalizer (FDE) and presents the noise decorrelating filter design.
Abstract: Vertical Bell laboratory layered space-time (V-BLAST) is one of the promising multiple input multiple output (MIMO) architectures. Layered space time processing in V-BLAST requires the number of receive antennas to be equal to or larger than the number of transmit antennas. However, it is impractical for small-sized mobile units to accommodate all the required antennas. Focusing on this problem, we have presented a novel concept of virtual receive antennas (VRA) for spatial multiplexing system in flat fading channels. In that work, time domain equalization is utilized to eliminate inter-symbol interference, which is generated in the VRA. However, the employed time domain equalizer has a high computational complexity. In this paper, the VRA system with low complexity frequency domain equalizer (FDE) is investigated. Moreover, as the noise in the VRA system is correlated due to oversampling, we also present the noise decorrelating filter design. Through complexity and performance evaluation, FDE is demonstrated to be more suitable for the VRA system.
3 citations
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