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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01 Oct 2003
TL;DR: In this article, the authors propose a channel estimation method for single-carrier MIMO systems with frequency-domain equalization/detection, which is extremely bandwidth efficient in that the total training overhead required to obtain full CSI is just one block period.
Abstract: This paper proposes a novel method for channel estimation in a single-carrier MIMO system with frequency-domain equalization/detection. To this end, we construct novel short MIMO training sequences that have a constant envelope in the time domain to preclude the peak-to-mean power problem encountered in many systems that utilize the frequency domain for data recovery. Simultaneously, the spectrum in the frequency domain is flat except for a grid of nulls for predefined frequency tones. Such construction allows us to interpolate over nulled tones to recover the full set of MIMO channel state information (CSI). The interpolation is performed by a specially crafted algorithm which iteratively reconstructs the full CSI by a series of FFT and IFFT operations. This algorithm is extremely bandwidth efficient in that the total training overhead required to obtain full CSI is just one block period.
22 citations
Cites background from "Frequency domain equalization for s..."
...Lately, however, much attention has been focused on another broadband technique, namely single-carrier (SC) transmission with frequencydomain equalization (FDE) [1], [2], [3]....
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26 Sep 2004
TL;DR: In this paper, the effect of the resolution bits of the digital to analog converter (DAC) at the transmitter and the analog to digital converter (ADC) at receiver on multi-carrier code division multiple access (MC-CDMA) with cyclically prefixed direct sequence CDMA in an uplink channel was investigated.
Abstract: This paper compares multi-carrier code division multiple access (MC-CDMA) with cyclically prefixed direct sequence CP-DS-CDMA in an uplink channel. For the CP-DS-CDMA scheme, we propose an MMSE-based multi-user detection (MUD) technique, which recovers code orthogonality among users destroyed by frequency-selective fading in the frequency domain. On the other hand, it is well known that the peak to power average ratio (PAPR) of a single carrier transmission scheme is lower than that of a multi-carrier transmission scheme. Thus, from the viewpoint of the PAPR issue, this paper studies the effect of resolution bits of the digital to analog converter (DAC) at the transmitter and the analog to digital converter (ADC) at the receiver on both schemes. Then, this paper evaluates the performance of the two schemes by computer simulations.
22 citations
Cites background from "Frequency domain equalization for s..."
...Recently, a single carrier transmission system with cyclic prefix (SC-CP) has been also drawing much attention as a candidate for next generation mobile communications systems [3]....
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TL;DR: A new frequency-domain channel equalization and symbol detection scheme is proposed for multiple-input-multiple-output (MIMO) single-carrier broadband wireless systems in the presence of severely frequency-selective channel fading and multiple unknown carrier-frequency offsets (CFOs).
Abstract: A new frequency-domain channel equalization and symbol detection scheme is proposed for multiple-input-multiple-output (MIMO) single-carrier broadband wireless systems in the presence of severely frequency-selective channel fading and multiple unknown carrier-frequency offsets (CFOs). Multiple CFOs cause severe phase distortion in the equalized data for large block lengths and/or constellation sizes, thus yielding poor detection performance. Instead of explicitly estimating the CFOs and then compensating them, the proposed scheme estimates the rotated phases (not frequencies) caused by multiple unknown CFOs and then removes the phase rotations from the equalized data before symbol detection. The estimation accuracy of the phase rotation is improved by utilizing a groupwise method rather than symbol-by-symbol methods. This paper differs from other related work in orthogonal frequency division multiplexing (OFDM) studies in that it can combat multiple CFOs that are time varying within each block. Numerical examples for 4 × 2 and 8 × 4 single-carrier systems with quaternary phase-shift keying (QPSK) and eight-phase-shift keying (8PSK) modulation illustrate the effectiveness of the proposed scheme in terms of scatter plots of constellation, mean square error (MSE), and bit error rate (BER).
22 citations
Cites methods from "Frequency domain equalization for s..."
...Compared with the widely adopted orthogonal frequency-division multiplexing (OFDM), SC-FDE exhibits similar or better performance at comparable complexity while avoiding some problems inherent in OFDM, such as sensitivity to carrier frequency offsets (CFOs) and peak-to-average power ratio [2]....
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01 Jun 2019
TL;DR: Li-Fi needs an open architecture, consensus building towards standards, a roadmap to support future IoT and technology demonstrations in real environments, such as indoors, manufacturing, logistics, conference rooms and outdoors for fixed-wireless access.
Abstract: Today's Internet of Things (IoT), covering any communication between devices, is narrowband and not always provides reliability and low latency at the same time. A wide range of future IoT applications, i.e. flexible manufacturing, augmented reality and autonomous cars, will use artificial intelligence in the cloud to process sensor data jointly in real time. This future IoT will need mobile communication providing high bandwidth, reliable connectivity and low latency at the same time. While radio spectrum is densely populated, light communication (LC) can use unlicensed optical spectrum and enable high data rates over short distances for future IoT. By networking multiple LC-enabled access points, also known as Li-Fi, one can build a new mobile communication system integrated with lighting infrastructure that enables the future IoT. The main challenge to approach future IoT is to develop Li-Fi further into the mass-market serving a greater variety of use cases than today. Therefore, Li-Fi needs an open architecture, consensus building towards standards, a roadmap to support future IoT and technology demonstrations in real environments, such as indoors, manufacturing, logistics, conference rooms and outdoors for fixed-wireless access.
22 citations
Cites methods from "Frequency domain equalization for s..."
...6 in [13])....
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...The essential functions of a new MIMO MAC protocol are outlined in [13, 14]....
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TL;DR: The proposed subspace GMD scheme requires only two layers of detection/decoding, regardless of the total number of subchannels, thus alleviating the latency issue associated with conventional GMD, and makes the optimization of ML beamforming and ML detection itself feasible for any K timesK MIMO system.
Abstract: A subspace beamforming method is presented that decomposes a multiple-input multiple-output (MIMO) channel into multiple pairs of subchannels. The pairing is done based on singular values such that similar channel capacity is obtained between different subchannel pairs. This new capacity balancing concept is key to achieving high performance with low complexity. We apply the subspace idea to geometric mean decomposition (GMD) and maximum-likelihood (ML) detection. The proposed subspace GMD scheme requires only two layers of detection/decoding, regardless of the total number of subchannels, thus alleviating the latency issue associated with conventional GMD. We also show how the subspace concept makes the optimization of ML beamforming and ML detection itself feasible for any K timesK MIMO system. Simulation results show that subspace beamforming performs nearly as well as optimum GMD performance, and to within only a few decibels of the Shannon bound.
22 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