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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Patent•
24 Feb 2006
TL;DR: In this paper, a corrected channel estimating apparatus is proposed, which is capable of removing side-lobe components mutually leaking into transmission paths from channel estimates to increase the accuracy of the estimation.
Abstract: A corrected channel estimating apparatus is disclosed, which is capable of removing side-lobe components mutually leaking into transmission paths from channel estimates to increase the accuracy. A channel estimation unit calculates channel estimates for a plurality of transmission paths due to a signal that arrives through multipath. A channel estimate correction unit removes side-lobe components mutually leaking into the transmission paths from the channel estimates calculated by the channel estimation unit to correct the channel estimates. In this way, the corrected channel estimating apparatus estimates transmission paths of a multipath.
2 citations
10 Sep 2015
TL;DR: This proposed scheme improves both the frequency reuse factor and the MTs' performance at cell edges, with further improved performance when low-density parity-check (LDPC) codes and turbo IB-DFE equalization schemes are considered.
Abstract: Base station (BS) cooperation architectures provide meaningful capacity gains, as they allow mobile terminals (MTs) in neighbor cells to share the same physical channel. Combining uplink signals received by the different BSs by employing iterative frequency-domain algorithms allows for the correct separation of the signals transmitted by each MT. To transmit those signals, MTs rely on single-carrier (SC) modulation with frequency-domain equalization (FDE). Those SC-FDE transmissions combined with iterative block decision feedback equalization (IB-DFE) techniques have been shown to be a effective mean to transmit cyclic-prefix (CP) assisted blocks within broadband wireless systems. In this paper, we aim to combine the aforementioned concepts of uplink transmission based on IB-DFE with BS cooperation in a clever manner. Our proposed scheme improves both the frequency reuse factor and the MTs' performance at cell edges, with further improved performance when low-density parity-check (LDPC) codes and turbo IB-DFE equalization schemes are considered.
2 citations
Cites background from "Frequency domain equalization for s..."
...Thus, BS cooperation schemes can (and should) be combined with block-based transmission techniques with FDE, acquiring the ability to transmit over severe time-dispersive channels [5]....
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15 May 2009
TL;DR: In this article, the authors employed non-coherent space-time modulation in single-carrier (SC) block systems over channel frequency-selectivity in high-speed wireless communications systems against channel fading.
Abstract: Space-time modulation exploiting diversity or/and coding gains has been a major focus in high-speed wireless communications systems against channel fading. To avoid channel estimation, we employ noncoherent space-time modulation in single-carrier (SC) block systems over channel frequency-selectivity in this Letter. Capitalizing on multi-channel input-output relation in time domain, we construct space-time codes of constant signaling amplitude by means of complex orthogonal sequences to achieve maximal diversity gain along with coding advantage. Numerical result suggests that SC block system can outperform its orthogonal frequency division multiplexing (OFDM) counterpart in terms of block error rate (BLER) under the same simulated scenario.
2 citations
Cites background from "Frequency domain equalization for s..."
...Other than OFDM transmission, single-carrier (SC) block systems employing frequency-domain equalization also have received considerable attention [10]....
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24 Oct 2008
TL;DR: A system combining FD turbo linear equalization with time-domain channel estimation is developed and evaluated for single-carrier modulation formats and the effect of estimated CSI on the equalizer form is shown.
Abstract: To date most frequency-domain (FD) turbo equalization schemes assume ideal channel state information (CSI) is available. In this paper, a system combining FD turbo linear equalization with time-domain channel estimation is developed and evaluated for single-carrier modulation formats. The effect of estimated CSI on the equalizer form is shown. Performance results employing convolutionally encoded QPSK and 16-QAM transmissions show the efficacy of the proposed system and its capability to operate in different wireless scenarios.
2 citations
Cites background from "Frequency domain equalization for s..."
...Single-carrier (SC) linear modulation techniques combined with frequency-domain (FD) equalization provide an alternative to multicarrier techniques for combating multipath fading in channels with large delay spread [1]....
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...They have comparable complexity to orthogonal frequency division multiplexing systems, and are more robust to synchronization errors [1]....
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01 Dec 2011
TL;DR: Computer simulation results show that CL type transmit diversity with precoding using intra-subframe FH is very effective in reducing the required average received signal-to-noise power ratio (SNR) when the fading maximum Doppler frequency, fD, is higher than approximately 50 Hz both for 2- and 4-antenna transmission in the uplink DFT-precoded OFDMA.
Abstract: This paper proposes applying intra-subframe frequency hopping (FH) to closed-loop (CL) type transmit diversity using codebook based precoding for a shared channel carrying user traffic data in the uplink discrete Fourier transform (DFT)-precoded Orthogonal Frequency Division Multiple Access (OFDMA). In the paper, we present two types of precoding schemes associated with intra-subframe FH: individual precoding vector selection between 2 slots where a 1-msec subframe comprises 2 slots among the reduced precoding codebooks, and common precoding vector selection between 2 slots. We investigate the effect of intra-subframe FH on the CL type transmit diversity with precoding in terms of the block error rate (BLER) performance while maintaining the same number of feedback bits required for notification of the selected precoding vector as that for CL type precoding based transmit diversity without FH. Computer simulation results show that CL type transmit diversity with precoding using intra-subframe FH is very effective in reducing the required average received signal-to-noise power ratio (SNR) when the fading maximum Doppler frequency, fD, is higher than approximately 50 Hz both for 2- and 4-antenna transmission in the uplink DFT-precoded OFDMA.
2 citations
Cites background or methods from "Frequency domain equalization for s..."
...8 LTE downlink and affinity to the frequency domain equalizer [4],[5]....
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...Using the channel estimate at each subcarrier after frequency and time domain averaging, the LMMSE weight at the u-th subcarrier at the h-th receiver branch, ( )( ) u W h b, , is computed as [5] ( )( ) ( ) ( ) ( ) ( ) ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ + ∑ = = σ 2 1 0 u H u H u W p h b h p h b p h b ' ' , * , , ....
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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 ]....
[...]
...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