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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Patent•
02 Nov 2017TL;DR: In this paper, the authors present a signal processing method and apparatus that performs M-way filtering on an input signal to obtain M filtered signals, performing extraction on the extracted signals separately to obtain m extracted signals, and finally determining output signals according to the M frequency-domain signals.
Abstract: Embodiments of the present invention provide a signal processing method and apparatus. The method includes: performing M-way filtering on an input signal to obtain M filtered signals, performing extraction on M filtered signals separately to obtain M extracted signals, performing fast Fourier transform (FFT) on the M extracted signals separately to obtain M frequency-domain signals, and finally determining output signals according to the M frequency-domain signals. According to the embodiments of the present invention, signal filtering and extraction are performed and then FFT is performed.
2Â citations
09 Feb 2012
TL;DR: Practical concepts for digital compensation of frequency selective I/Q-imbalance and modulator DC-offset are proposed for BS transmitters and both digital pre-equalization circuit and parameter estimation/tracking schemes are developed, which allow flexible and standard independent impairment compensation with comparatively low-complexity.
Abstract: This thesis addresses the challenges of rapidly increasing data rate requirements in future wireless communication systems, where the emphasis is on RF impairment compensation and system design. Two scenarios are considered: the mobile cellular scenario and the Wireless Local Access Network (WLAN) scenario. In the mobile cellular scenario, the concept of multi-band-/multi-standard Base Station (BS) is discussed, which allows to manage the coexistence of different technological standards (2G/3G/4G) with reasonable installation and operation costs. For the realization of such BSs, the issue of RF impairment compensation has to be addressed, especially at the transmitter with direct conversion architecture. In this thesis, practical concepts for digital compensation of frequency selective I/Q-imbalance and modulator DC-offset are proposed for such BS transmitters. Both digital pre-equalization circuit and parameter estimation/tracking schemes are developed, which allow flexible and standard independent impairment compensation with comparatively low-complexity. The effectiveness and advantages of these schemes are verified by both numerical simulations and laboratory experiments. In the WLAN scenario, the exploitation of the 60 GHz band is studied. A new design concept for 60 GHz WLAN systems is proposed to support both high data rate and high user density for potential applications e.g. the In-Flight Entertainment (IFE) systems. First, the general system design is described. For the parameterization in the downlink (DL), the optimization between the guardband size and time domain windowing of OFDM signals is studied. Afterwards, the focus is on the compensation of both Txand Rx RF impairments in the DL via Rx side digital signal processing. The considered RF impairments include Carrier Frequency Offset (CFO) and Tx-/Rx I/Q-imbalance. MIMO OFDM transmission is assumed. For impairment compensation, sophisticated preamble designs as well as efficient and effective parameter estimation schemes are developed, which require comparatively low computational complexity. Finally, the uplink is also studied, with the emphasis on efficient Multi-User Detection (MUD) using MIMO configuration. All results in both scenarios contribute to the data rate enhancement in future wireless communication systems.
2Â citations
Cites background from "Frequency domain equalization for s..."
...Moreover, SC signals have lower signal PAPR than OFDM signals and thus allow the application of low cost PA with high efficiency in the UTs [153]....
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25 Mar 2012
TL;DR: This paper seeks to quantify the amount of interferences resulting from wideband channels which assumed to follow the multi-scale/multi-lag (MSML) model, and measures for determining whether time-domain or frequency-domain should be undertaken are provided.
Abstract: OFDM suffers from inter-carrier interferences in the presence of the time variation. This paper seeks to quantify the amount of interferences resulting from wideband channels which assumed to follow the multi-scale/multi-lag (MSML) model. Due to the fact that the mobility in wideband channels induces scale effects, Doppler is revealed in a manner distinct from the frequency shifts experienced in narrowband systems. The MSML channel model results in full channel matrices both in the frequency and time domains. However, banded approximations are still possible, leading to significant reduction in the equalization complexity. Herein, measures for determining whether time-domain or frequency-domain should be undertaken are provided based on the amount of the resulting interference.
2Â citations
Cites background from "Frequency domain equalization for s..."
...In narrowband systems, it is well-known that we can equalize the time-varying channel either in the time domain (TD) or in the in the frequency domain [5]....
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...Although a similar conclusion has been made for narrowband systems [5], its extension to wideband systems is not straightforward as shown above....
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23 Jun 2009
TL;DR: The maximization of so-called signal-to-leakage-plus-noise ratio (SLNR) at each base station allows for closed form beamforming vector by using only locally available information.
Abstract: This paper considers a transmit beamforming and subcarrier power allocation method for orthogonal frequency division multiple access (OFDMA) systems. As the beamforming vector control criterion, we employ the maximization of so-called signal-to-leakage-plus-noise ratio (SLNR) at each base station, which enable us to obtain closed form beamforming vector by using only locally available information. We also discuss the local optimality of the SLNR based beamforming vector. As for the subcarrier power allocation, two different approaches are employed, namely, the equalization of signal-to-interference-plus-noise ratio (SINR) for subcarriers and the maximization of sum rate of subcarriers. Computer simulation results show the validity of the transmit beamforming and power allocation method with highlighting the difference between the two power allocation algorithms.
2Â citations
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.
16,062Â 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