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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TL;DR: It is shown through rigorous derivation that all three codes can completely eliminate MUI due to CFO, and despreading codes that were obtained by minimizing the interference power or their cross correlation with the spreading codes are shown to yield a performance close to a synchronous system.
Abstract: Using mutually shift-orthogonal spreading codes, block-spread code-division multiple access (BS-CDMA) systems have been shown to achieve multiuser interference (MUI)-free reception when synchronization between the base station and the subscriber stations is achieved. In practice, when carrier frequency offset (CFO) is present, orthogonality among users is destroyed, and MUI occurs. This paper presents three methods of designing the spreading and despreading codes for uplink BS-CDMA systems to reduce MUI due to CFO. We show through rigorous derivation that all three codes can completely eliminate MUI due to CFO. In particular, by fixing the spreading codes at the transmitter, despreading codes that were obtained by minimizing the interference power or their cross correlation with the spreading codes are shown to yield a performance close to a synchronous system. The advantages and disadvantages of the BS-CDMA systems using the three proposed codes are discussed.
5 citations
Cites background or methods or result from "Frequency domain equalization for s..."
...Similar to the case where the TDMA-type spreading and despreading codes are used, the circulant channel matrix facilitates the use of a low-complexity one-tap frequency-domain equalizer to detect the signal for each user [10], [13], [14]....
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...Another advantage of the TDMA-type codes is that they facilitate simple one-tap frequency-domain equalization for the signal detection of each user, which incurs a computational complexity of O(P log P ) [13]....
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...For fair comparison, a time-domain MMSE detector is employed for all systems to recover the signals for each user, although for the original BS-CDMA systems [1] that use DFT codes as both the spreading and despreading codes and systems that use the TDMA-type or CC-min codes, a simple one-tap frequency-domain equalizer may be employed without affecting the BER performance [10], [13], [14]....
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...The formation of a circulant channel matrix facilitates the use of a simple one-tap frequency-domain equalizer to recover the signal for the μth user [10], [13], [14]....
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Proceedings Article•
01 Sep 2005TL;DR: It is shown that the proposed multistage ALSFE significantly outperforms the previous RLS based single-stage adaptive FDE without channel estimation, at comparable complexity.
Abstract: We propose an adaptive layered space-frequency equalization (ALSFE) structure to deal with the multiple-input multiple-output (MIMO) time-varying frequency selective channels, where at each stage of detection, a group of selected data streams are detected and are then cancelled from the received signals. Two types of adaptive channel estimation approaches are employed for ALSFE, assuming respectively uncorrelated and correlated frequency bins. Noise power estimation is also exploited, which is based on the maximum likelihood (ML) criterion. It is shown that our proposed multistage ALSFE significantly outperforms the previous RLS based single-stage adaptive FDE without channel estimation, at comparable complexity. In particular, ALSFE based on the least-mean-square structured channel estimation (LMS-SCE) approaches the performance of LSFE with perfect channel state information (CSI) and has a fast convergence speed.
5 citations
Cites background from "Frequency domain equalization for s..."
...Frequency-domain equalization (FDE) [1-4] has been shown to be an effective solution for frequency selective channels in a single-carrier (SC) system....
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14 Mar 2010
TL;DR: This work proposes a new criterion for blind channel shortening based on high order statistical information derived from only second order output statistics of the unknown channel that is applicable to both single-input-single-output and single- input-multiple-output frequency selective channels.
Abstract: In this work, we propose a new criterion for blind channel shortening based on high order statistical information. This method overcomes the weakness of two existing channel shortening criteria derived from only second order output statistics of the unknown channel. It is applicable to both single-input-single-output and single-input-multiple-output frequency selective channels. The optimization criterion can be achieved through either a stochastic gradient descent algorithm or a batch algorithm. Simulation results demonstrate successful shortening of wireless channels that the existing criteria fail to shorten.
5 citations
01 Jan 2013
TL;DR: This chapter focuses on the problem of transmitting information sequences efficiently through a wireless channel and performing reception such that it can be implemented with state of the art signal processing tools.
Abstract: The data rates as well as quality of service (QoS) requirements for rich user experience in wireless communication services are continuously growing. While consuming a major portion of the energy needed by wireless devices, the wireless transceivers have a key role in guaranteeing the needed data rates with high bandwidth efficiency. The cost of wireless devices also heavily depends on the transmitter and receiver technologies. In this chapter, we concentrate on the problem of transmitting information sequences efficiently through a wireless channel and performing reception such that it can be implemented with state of the art signal processing tools. The operations of the wireless devices can be divided to RF and baseband (BB) processing. Our emphasis is to cover the BB part, including the coding, modulation, and waveform generation functions, which are mostly using the tools and techniques from digital signal processing. But we also look at the overall transceiver from the RF system point of view, covering issues like frequency translations and channelization filtering, as well as emerging techniques for mitigating the inevitable imperfections of the analog RF circuitry through advanced digital signal processing techniques.
5 citations
Cites background from "Frequency domain equalization for s..."
...From the SC-modulation point of view, the singletap subcarrier equalizers correspond to a frequency-domain implementation of a linear equalizer [145] [52]....
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TL;DR: The ongoing evolution of software-based receivers will provide the backbone for reliable reception indoors of arbitrarily formatted transmission that will not create new interference to other services.
Abstract: Commercially viable free DTTV will depend on adoption of new technologies, some already available, that will in turn generate new business models. These technologies will permit new real and virtual channels through more efficient spectrum usage and dynamic sharing of the maximum data rate among several applications. The ongoing evolution of software-based receivers will provide the backbone for reliable reception indoors of arbitrarily formatted transmission that will not create new interference to other services
5 citations
Cites methods from "Frequency domain equalization for s..."
...Replacing TDE with Frequency Domain Equalization (FDE) has been suggested as a possible solution to the implementation of on-channel, distributed repeaters, in single-carrier systems [17], [18]....
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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.
16,062 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