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
More filters
14 Mar 2007
TL;DR: Simulation results show that the proposed iterative FDE with explicit FDCE for non-cyclic-prefixed SC systems offers lower mean-square-error (MSE) in channel prediction, lower bit error rate (BER) after decoding, and robustness to relatively fast fading channels.
Abstract: Compared to the conventional time-domain methods, frequency-domain equalization (FDE) and frequency-domain channel estimation (FDCE) present computationally-efficient methods for the reception of single carrier (SC) transmissions. In this paper, we consider iterative FDE (IFDE) with explicit FDCE for non-cyclic-prefixed SC systems. First, an improved IFDE algorithm is presented based on soft iterative interference cancellation. Second, a new adaptive FDCE (AFDCE) algorithm based on per-tone Kalman filtering is proposed to track and predict the frequency-domain channel coefficients. The AFDCE algorithm employs across-tone noise reduction, exploits time-correlation between successive blocks, and adaptively updates the auto-regressive (AR) model coefficients, bypassing the need for priori knowledge of channel statistics. Finally, a block overlapping idea is proposed which facilitates the joint operation of IFDE and AFDCE. Simulation results show that, compared to other existing IFDE and adaptive channel estimation schemes, the proposed scheme offers lower mean-square-error (MSE) in channel prediction, lower bit error rate (BER) after decoding, and robustness to relatively fast fading channels.
11 citations
Cites background from "Frequency domain equalization for s..."
...While orthogonal frequency division multiplexing (OFDM) is a popular means of combating these multipath effects, its drawbacks include high peak-to-average power ratio (PAPR) and high sensitivity to carrier-frequency offset (CFO)....
[...]
TL;DR: In this paper, maximal-ratio combining (MRC) and selection combining (SC) are proposed in spectrum sharing single-carrier networks with multiple primary user receivers (PU-Rxs) and it is shown that the asymptotic diversity gain depends only on the number of receive antennas and theNumber of multipath channels.
Abstract: In this paper, maximal-ratio combining (MRC) and selection combining (SC) are proposed in spectrum sharing single-carrier networks with multiple primary user receivers (PU-Rxs). Taking into account the peak interference power at the PU-Rx's and the maximum transmit power at the secondary user (SU), the impact of multiple PU-Rx's on the secondary network is characterized when the secondary user receiver (SU-Rx) is equipped with multiple antennas. In doing so, exact and asymptotic expressions are derived for the cumulative distribution function, taking into account two realistic scenarios: non-identical frequency selective fading between the secondary user transmitter (SU-Tx) and the PUs, and frequency selective fading between the SU-Tx and the SU-Rx. Based on these, exact and asymptotic expressions for the outage probability and average bit error rate are derived. Furthermore, an exact closed-form expression for the ergodic capacity is derived. It is shown that the asymptotic diversity gain depends only on the number of receive antennas and the number of multipath channels. It is further shown that the number of PU-Rx's and fading severities between the SU-Tx and the PU-Rx's have no impact on the asymptotic diversity gain.
11 citations
Cites background from "Frequency domain equalization for s..."
...Frequency domain equalization (FDE) has been widely adopted due to its low computational requirements [20], [21]....
[...]
04 Oct 2010
TL;DR: This paper considers the design of linear frequency-domain receivers with oversampling for OQPSK signals and proposes a receiver structure able to eliminate the residual interference between in-phase (I) and quadrature (Q) components at the sampling instants.
Abstract: This paper considers the design of linear frequency-domain receivers with oversampling for OQPSK (Offset Quaternary Phase Shift Keying) signals. Based on a receiver structure able to eliminate the residual interference between in-phase (I) and quadrature (Q) components at the sampling instants, a method that minimizes the overall residual ISI (Inter-Symbol Interference) plus IQI (I-Q interference) is proposed. Therefore, this receiver significantly outperforms previous frequency-domain OQPSK receivers.
11 citations
Cites background or methods from "Frequency domain equalization for s..."
...In this case, conventional FDE designs, which are developed for non-offset modulations such as QPSK [1], [5], [6], are unsuitable for OQPSK....
[...]
...where r(t) is the adopted pulse shape and NCP is the length of the cyclic prefix required for an efficient FDE implementation [5] (assuming that the block {an;n = 0, 1, ....
[...]
01 Jan 2011
TL;DR: In this article, a power and bit-error rate (BER) constraint was proposed to optimize the number of equalizer taps and the distribution of signal processing between analog and digital domains.
Abstract: There is a growing interest in the use of the 7 GHz of unlicensed bandwidth around 60 GHz for high-speed wireless data transfers Complementary metal-oxide-semiconductor (CMOS) radio frequency (RF) circuits have been demonstrated to effectively operate in this band, but the challenge remains to design a complete high data-rate, energy-efficient system With data rates of several Gb/s and short wavelengths, the baseband signal processing that compensates for the distortion of the wireless channel presents a significant challenge This work demonstrates the design of a power-efficient baseband at different levels of abstraction from the algorithm level down to the transistor level
A method for optimizing the equalizer architecture under power and bit-error rate (BER) constraints has been developed This method has been used to optimize the number of equalizer taps and the distribution of signal processing between analog and digital domains Two chips were built to demonstrate the methodology based on the IEEE wireless personal area network (WPAN) standard
The first, fully-digital chip implements a single-carrier demodulator that minimizes the power consumption using a parallelized distributed arithmetic architecture A 2mm x 2mm test chip in a 65 nm CMOS process implements a 6-tap feedforward and 32-tap feedback equalizer for binary phase-shift keying (BPSK) that can be configured to cancel the response of up to 72 symbols while consuming 56mW at 2 Gb/s throughput
The second 186mm x 186mm chip implements a reconfigurable 4-bit ADC and 6-tap analog equalizer in addition to the digital equalizer for quadrature phase-shift keying (QPSK) demodulation The analog preprocessor is measured to consume 13mW for the driver and 300 μW/tap for the analog equalization The ADC power consumption varies from 12mW to 38mW depending on the resolution at 176 Gs/s It is shown that, given a BER requirement, the mixed-signal reconfigurable receiver architecture can reduce the total link power consumption compared to a full-digital fixed transceiver depending on the propagation condition
11 citations
07 Sep 2009
TL;DR: A CP free OFDM transmission system is used that allows shortening the OFDM symbol length to reduce the maximum PAPR without transmission overhead trade-off, based on overlapping MMSE frequency domain equalization to remove interference between OFDM symbols.
Abstract: Orthogonal Frequency Division Multiplexing (OFDM) enables high data rate transmissions over frequency selective fading channels. Its beneficial qualities are a low implementation complexity and the possible application of power loading schemes to increase data throughput. Drawbacks of OFDM are the requirement for a cyclic prefix (CP) to avoid interference between OFDM symbols and the high peak to average power ratio (PAPR). The CP causes transmission overhead and hence reduces throughput, while a high PAPR requires the use of less efficient linear amplifiers. The CP overhead can be reduced by increasing the OFDM symbol length, which will, however, increase processing delay and PAPR. In conventional OFDM the symbol length directly determines PAPR and transmission overhead. In this paper we use a CP free OFDM transmission system that allows shortening the OFDM symbol length to reduce the maximum PAPR without transmission overhead trade-off. The proposed system, called Ov-OFDM, is based on overlapping MMSE frequency domain equalization to remove interference between OFDM symbols.
11 citations
Cites methods from "Frequency domain equalization for s..."
...Prior to data detection the received frame is equalized by a frequency domain equalizer (FDE) [6] to remove interference between the OFDM symbols....
[...]
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]....
[...]
...Overlap-save or overlap-add signal processing techniques could also be used to avoid the extra overhead of the cyclic prefix [Fer85], [Hay96]....
[...]
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 ]....
[...]
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