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: An iterative detection method for an uncoded pretransformed (PT) orthogonal frequency division multiplexing (OFDM) system where the channel is not known at the transmitter is proposed and achieves a diversity advantage of i+1 in the ith iteration, thus providing an explanation of its superior performance.
Abstract: In this paper, an iterative detection method for an uncoded pretransformed (PT) orthogonal frequency division multiplexing (OFDM) system where the channel is not known at the transmitter is proposed. The iterative detection starts with linear detection. The noiseless received signal at the weakest subcarrier (corresponding to the smallest channel amplitude) is estimated based on all the detected data symbols using a hard or soft decision. Then, the actual received signal at the weakest subcarrier is replaced by the estimated one. This process is referred to as reconstruction here. After reconstruction, linear detection is carried out again to generate the next set of symbol estimates. The whole process proceeds iteratively to reconstruct the received signal at the next-weakest subcarrier. The transform coefficients and the iterative process are designed to maximize the minimum signal-to-noise power ratio. Under the assumption that the previous detection is error free, it is shown analytically that the iterative method achieves a diversity advantage of i+1 in the ith iteration, thus providing an explanation of its superior performance. Due to the flexibility of the transform design, the analysis conducted is applicable for other common systems as well. Simulations in realistic channels are carried out, and the bit-error rate performance of the iterative detection is superior as compared to that of the conventional detectors for the PT-OFDM or OFDM system.
18 citations
17 Nov 2008
TL;DR: By combining the advantages of SC-FDE schemes with soft combining ARQ, the proposed technique is particularly interesting for the uplink of wireless systems.
Abstract: This paper considers the use of SC-FDE techniques (single-carrier with frequency-domain equalization) with low-complexity soft combining ARQ schemes (automatic repeat request). With our technique, packets associated to different transmission attempts are combined in a soft way, allowing improved performances. Moreover, the transmitter and receiver complexities are low and we can have excellent performances, especially when we have deep fading effects in slow-varying channels. By combining the advantages of SC-FDE schemes with soft combining ARQ, the proposed technique is particularly interesting for the uplink of wireless systems.
18 citations
Cites background from "Frequency domain equalization for s..."
...Moreover, we are not bounded by the performance of the basic code, since it is not a conventional punctured code....
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09 Jul 2006
TL;DR: This paper shows that in the case of multiple subchannels, the diversity of infinite length filters can also be attained by FIR equalizers of sufficient length, and shows that increasing the filter lengths improves the coding gain.
Abstract: Since the introduction of the diversity-rate tradeoff by Zheng and Tse for ML reception in frequency-flat MIMO channels, some results have been obtained also for the diversity behavior of suboptimal receivers such as linear and decision-feedback equalizers for frequency-selective SIMO channels. However, these results are limited to infinite length equalizers. Furthermore, so far attention has focused mostly on just diversity order aspects of diversity. In this paper we analyze the diversity of more practical FIR equalizers. We show in particular that in the case of multiple subchannels, the diversity of infinite length filters can also be attained by FIR equalizers of sufficient length. Increasing the filter lengths improves the coding gain though. Whereas the diversity order determines the slope of the asymptote at high SNR, the coding gain determines its position.
18 citations
Cites background from "Frequency domain equalization for s..."
...The problem of infinite length non-causal feedforward filters (FFFs) in the DFE can be overcome by introducing a CP and performing the FFF’ing in the frequency domain (SC-CP) and the feedback filtering in the time domain, see [12],[13] (where oversampling leads to increased DFT size which is not necessary)....
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...The use of the DFE appears in [11] (FIR) and [12],[13] (SC-CP) where in the last two references diversity behavior is investigated through simulations....
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TL;DR: The results show that the use of chaotic interleaving with CPM-OFDM andCPM-SC-FDE systems provides a good trade-off between system performance and bandwidth efficiency.
Abstract: In this paper, we present a chaotic interleaving scheme for both the Continuous Phase Modulation (CPM) based Orthogonal Frequency Division Multiplexing (CPM-OFDM) and CPM-based Single-Carrier Frequency-Domain Equalization (CPM-SC-FDE) systems. Chaotic interleaving is used to generate permuted versions from the sample sequences to be transmitted with low correlation among their samples, and hence a better Bit Error Rate (BER) performance can be achieved. The proposed CPM-OFDM and CPM-SC-FDE systems with chaotic interleaving combine the advantages of the frequency diversity and the high power efficiency of the CPM-based systems and the performance improvements due to chaotic interleaving. The BER performance of the both systems with and without chaotic interleaving is evaluated by computer simulations. Also, a comparison between chaotic interleaving and block interleaving is performed. Simulation results show that, the proposed chaotic interleaving scheme can greatly improve the performance of the CPM-OFDM system and the CPM-SC-FDE system. Furthermore, the results show that the chaotic interleaving scheme outperforms the traditional block interleaving scheme in both systems. The results also show that the use of chaotic interleaving with CPM-OFDM and CPM-SC-FDE systems provides a good trade-off between system performance and bandwidth efficiency.
18 citations
04 Dec 2007
TL;DR: This paper compares the relative performance of coded single carrier frequency domain equalisation (SC-FDE) and orthogonal frequency-division multiplexing (OFDM) on frequency-selective fading channels, focusing on the extent to which the two schemes can exploit the frequency diversity inherent in such channels.
Abstract: This paper compares the relative performance of coded single carrier frequency domain equalisation (SC-FDE) and orthogonal frequency-division multiplexing (OFDM) on frequency-selective fading channels We focus on the extent to which the two schemes can exploit the frequency diversity inherent in such channels Channels with different impulse response lengths, and therefore available diversity order are considered, with convolutional codes of different rates and constraint lengths, and also turbo-codes We show that on all channels SC-FDE has better performance with codes having smaller minimum distance However with more powerful codes, which enable it to exploit the full frequency diversity available in the channel, OFDM has better performance, particularly on channels with greater diversity
18 citations
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