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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12 Nov 2015
TL;DR: This paper studies the coherent detection of MFSK signals based on MLD (Maximum Likelihood Detection) approach on MIMO frequency selective channels and reduces the complexity of MLD by using the SE (Schnorr Euchner) algorithm of Sphere Decoding to obtain ML (Maximum likelihood) solution.
Abstract: MFSK (M-ary Frequency Shift Keying) signal has a constant envelope and is suited to power efficient nonlinear amplification. However, the application of MFSK signals to spectrally efficient and reliable MIMO (Multiple Input Multiple Output) communication schemes has not been so popular up to now. Maybe this comes from the fact that the signal processing for spatially multiplexed MIMO signal is usually done using linear matrix algebra and the application of linear signal processing techniques to nonlinear FM signals such as MFSK is difficult. In this paper, we study the coherent detection of MFSK signals based on MLD (Maximum Likelihood Detection) approach on MIMO frequency selective channels. In the proposed receiver, the receive replica signal which is frequency and phase synchronized is generated and the signal distance between the receive signal and the receive replica signal is minimized. By extending the observation length of receive signal, we improved the BER characteristics. We also reduced the complexity of MLD by using the SE (Schnorr Euchner) algorithm of Sphere Decoding to obtain ML (Maximum Likelihood) solution.
2 citations
Cites methods from "Frequency domain equalization for s..."
...Following this idea, we had already shown that the FDE (Frequency Domain Equalization) scheme using CP (Cyclic Prefix) [2] is applicable to the equalization and signal separation of MIMO MFSK signals where the FDE is done before the demodulation process of MFSK signal [3],[4]....
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01 Jan 2015
TL;DR: Transmission rates for turbo coded transmission systems under the conditions of Nyquist signaling and FTN signaling are made equivalent and analysis of the simulation results show that the turbo code proficiency is improved by increasing the number of iterations.
Abstract: The future demand of increased transmission rate and bandwidth efficiency is of prime concern in the modern wireless communication systems. Faster than Nyquist signaling (FTN) is under the great interest of research to address this issue of high data rate, which is also a major requirement, for the fifth generation (5G) communication networks. The data bits are transmitted at a rate higher than the conventional methods which are bounded by the Nyquist condition and the outputs are compared so as to analyze the benefits. Receiver processing techniques are implemented to achieve the high data rate with improved error performance at the lower decoding complexity. Considering the bandwidth efficiency as a key factor, more data symbols are sent at the given time interval by reducing the time period for signal transmission. This ensures more data being transmitted. In the scenario of perfect Nyquist signaling, pulse designs were based on the principle of orthogonality. The signal pulse form h(t) is orthogonal with respect to shifts by nT , where T is the signaling interval. In the thesis, the time period is reduced to T < 1, which prompt more symbols to be transmitted. The pulses are no longer orthogonal. These non orthogonal FTN signals are accepted as a promising approach for the required solution of increased data rate. FTN comes as a tradeoff between the high data rate achievement and error probability. Reduction of the time factor affirms good data rate but at the same time, cost of high error rate has to be paid. Efficient receiver processing techniques are designed to compensate between these two factors. Main obstacle due to the reduction of time period in FTN signaling is to tackle the unavoidable inter symbol interferences (ISI). Going beyond the Nyquist bound, as a consequence, results high ISI. This necessitates an effective receiver processing to overcome the ISI. Minimum mean square error (MMSE) detection algorithm is employed to equalize the received signals and analyze the performance of the FTN system. Finally, the system portrayal is studied by processing the results under the implementation of turbo coding systems. The bit error rate (BER) characteristics are analyzed under these circumstances. Efficient encoding pattern and decoding algorithm helps in reducing the errors. Analysis of the simulation results show that the turbo code proficiency is improved by increasing the number of iterations. Performance indication is also related to the frame size or the interleaver size and the signal power. In other words, it comes as a trade-off between energy efficiency, bandwidth efficiency, complexity and error rates. Furthermore, for the fair comparison of the performance analysis, transmission rates for turbo coded transmission systems under the conditions of Nyquist signaling and FTN signaling are made equivalent.
2 citations
Cites background from "Frequency domain equalization for s..."
...As stated in [61], FDE provides lower complexity than its corresponding time domain equalization....
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01 Mar 2007
TL;DR: This paper proposes space-frequency coded BS-CDMA (SFC BS- CDMA) which performs space- frequencies coding instead of space-time encoding, which reduces the decoding delay significantly and transmission time of a single block, making it an attractive alternative in delay-critical communication systems.
Abstract: Space-time coded block spread CDMA (STC BS-CDMA) was previously proposed to enhance the advantages offered by CDMA system with block processing. However, STC BS-CDMA suffers from long decoding delay and large single block transmission time which makes it unsuitable for communication systems delivering delay-critical applications and poor performance in systems with high mobility conditions. This paper proposes space-frequency coded BS-CDMA (SFC BS-CDMA) which performs space-frequency coding instead of space-time encoding. This reduces the decoding delay significantly and transmission time of a single block, making it an attractive alternative in delay-critical communication systems. This paper also compares the two MIMO BS-CDMA systems and provides extensive simulation results.
2 citations
Cites background from "Frequency domain equalization for s..."
...SC-FDE has been proposed as a strong alternative to OFDM-based multicarrier (MC) systems [1] due to the following reasons....
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18 Jul 2004
TL;DR: A number of classical blind estimation techniques for FIR multichannels when applied to communication systems that are based on the introduction of a cyclic prefix are revisited, revealing immediately that temporal whiteness of the additive noise is unessential, only spatial whiteness matters.
Abstract: In this paper, we revisit a number of classical blind estimation techniques for FIR multichannels when applied to communication systems that are based on the introduction of a cyclic prefix. These techniques include techniques based on deterministic modeling of the unknown symbols such as (signal and noise) subspace fitting methods, subchannel response matching (SRM), deterministic maximum likelihood (DML), and techniques based on a Gaussian white noise model for the unknown symbols such as Gaussian ML (GML) methods and covariance matching. The presence of a cyclic prefix transforms spatiotemporal channels into a set of parallel spatial channels, coupled by the discrete Fourier transform (DFT) of the FIR channel impulse response. The associated blind channel estimation methods become computationally much more attractive and also become more straightforward to analyze and to compare in terms of performance. Working in the DFT domain reveals immediately that temporal whiteness of the additive noise is unessential, only spatial whiteness matters. Furthermore, the blind channel identifiability conditions become extremely weak when zero padded (ZP) systems are considered.
2 citations
Proceedings Article•
01 Apr 2007
TL;DR: This paper compares the suitability of two different air interfaces characterized by a low peak-to-average power ratio (PAPR) to support communications at 60 GHz and analyzes the degradation caused by the phase noise coming from the local oscillators and the nonlinearity in the PA.
Abstract: Short-range digital communications at 60 GHz have recently received a lot of interest because of the huge bandwidth available at those frequencies. The capacity offered to the users could finally reach 2 Gbps, enabling the deployment of new multimedia applications. However, the design of analog components is critical, leading to a possible high nonideality of the front end (FE). The goal of this paper is to compare the suitability of two different air interfaces characterized by a low peak-to-average power ratio (PAPR) to support communications at 60 GHz. On one hand, we study the offset-QPSK (OQPSK) modulation combined with a channel frequency-domain equalization (FDE). On the other hand, we study the class of continuous phase modulations (CPM) combined with a channel time-domain equalizer (TDE). We evaluate their performance in terms of bit error rate (BER) considering a typical indoor propagation environment at 60 GHz. For both air interfaces, we analyze the degradation caused by the phase noise (PN) coming from the local oscillators; and by the clipping and quantization errors caused by the analog-to-digital converter (ADC); and finally by the nonlinearity in the PA.
2 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