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 Jan 2013
TL;DR: Improvements on OFDM, interference issues in uncoordinated networks are addressed in this dissertation considering different multicarrier schemes, and the efficacy of non-orthogonal schemes are shown along with POT to address the other-user interference, which relies on the fact that self-interference problem is easier than other- user interference problem in an un Coordinated network.
Abstract: In this dissertation, multicarrier schemes are reviewed within the framework of Gabor Systems. Their fundamental elements; what to transmit, i.e., symbols, how to transmit, i.e., filters or pulse shape, and where/when to transmit, i.e., lattices are investigated extensively. The relations between different types of multicarrier schemes are discussed. Within the framework of Gabor systems, a new windowing approach, edge windowing, is developed to address the out-of-band (OOB) radiation problem of orthogonal frequency division multiplexing (OFDM) based multicarrier schemes. To the best of our knowledge, for the first time, the diversity on the range of the users is exploited to suppress the sidelobes of OFDM. In addition to that, the concept of using different filters in OFDM structure is proposed. Besides the improvement on the OOB radiation performance of OFDM via edge windowing, conventional lattice structure of OFDM frame is enhanced considering the diversity in the network. The lattice structure of an OFDM frame is designed based on the statistical characteristics of the range of the users and the mobility. The concept of channel-aware frame structure is developed, which allows more efficient and reliable transmission. In addition to the aforementioned improvements on OFDM, interference issues in uncoordinated networks are addressed in this dissertation considering different multicarrier schemes. It is stressed that the interference from other links in the network sharing the same spectrum might degrade the link performance between the devices in an uncoordinated network, significantly. Considering the degradation due to other-user interference, the concept of partially overlapping tones (POT) is proposed. With the concept of partially overlapping tones, the interference energy observed at the victim receiver is mitigated via an intentional frequency offset between the links. The usefulness of intentional frequency offset to combat with the asynchronous nature of other-user interference without any timing constraint between interfering signals is emphasized. To the best of our knowledge, for the first time, the efficacy of non-orthogonal schemes are shown along with POT to address the other-user interference, which relies on the fact that self-interference problem is easier than other-user interference problem in an uncoordinated network. In the last part of this dissertation, required number of equalizer taps for multicarrier schemes is investigated to address the potential self-interference problems (e.g. due to the non-orthogonal multicarrier schemes with the concept of POT). Composite impact of transmit pulse shape, communication medium, and receive filter on the charac-
1 citations
16 Apr 2010
TL;DR: The optimized FBLMS algorithm is optimized by adding a PN moving correlation channel estimation algorithm and the simulation results show the optimized algorithm can shorten the time for convergence for more than half and improve the performance.
Abstract: This paper studies the frequency-domain block least-mean-square (FBLMS) algorithm for Single Carrier Frequency-Domain Equalization (SC-FDE) that used in ATSC Digital Television standard. It can resist the multi-path efficiently and have a low complicacy, but has a disadvantage that the start-up time is long. In order to improve the convergence speed of equalizer, this paper optimizes FBLMS algorithm by adding a PN moving correlation channel estimation algorithm. The simulation results show the optimized algorithm can shorten the time for convergence for more than half and improve the performance.
1 citations
Cites background from "Frequency domain equalization for s..."
...It has a good equalization performance, but the number of operations per signaling interval grows linearly with the ISI span, or, equivalently, with the data rates, thereby increasing the difficulty [1]....
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Patent•
29 Oct 2003
TL;DR: The technique of estimating the frequency response of the wireless channel in an OFDM system and the estimate of the impulse response based on the initial frequency response estimate are disclosed.
Abstract: The technique of estimating the frequency response of the wireless channel in an OFDM system are disclosed. In one method, an initial estimate of the frequency response of the wireless channel is obtained for a first group of subbands based on a pilot transmission received via the subbands in the first group. Then, the estimate of the impulse response of the wireless channel is then derived based on the initial frequency response estimate. Then, the enhanced estimate of the frequency response of the wireless channel based on the impulse response estimate is derived based on the subband of the second group. First and second groups may comprise only the usable subbands, or both subsets, respectively. Subband multiplexing may be used to transmit a co-pilot due to multiple terminals through the associated group of subbands. Frequency response, the impulse response, the sub-bands, the terminal
1 citations
15 Apr 2011
TL;DR: The simulation results show that the performance of TR pre-coder is close to that of optimized pre- coder and that of water filling in single-carrier IDMA systems based on iterative LMMSE-FDE algorithm when signal to noise ratio (SNR) is higher than 3.5dB.
Abstract: According to the high complexity of pre-coder in single-carrier interleave-division multiple access (IDMA) systems, in this paper, we propose a precoding technique based on time-reversal (TR) for single-carrier IDMA systems. The proposed scheme gets the channel impulse responses (CIR) through time-division duplexing (TDD) mode, and uses the time-reversed version of the CIR to pre-coder the transmitted signal at transmitter. The receiver adopts the iterative Linear Minimum Mean Square Error (LMMSE) frequency domain equalization (FDE) algorithm. Thus the pre-coder of transmitter is simple and easy to implement as compared with water filling pre-coder and optimal pre-coder, and the receiver can be simplified by canceling complex computation. The simulation results show that the performance of TR pre-coder is close to that of optimized pre-coder and that of water filling in single-carrier IDMA systems based on iterative LMMSE-FDE algorithm when signal to noise ratio (SNR) is higher than 3.5dB. The simulation results also demonstrate that TR pre-coder has potential advantages.
1 citations
Cites methods from "Frequency domain equalization for s..."
...There are two classical means to overcome the ISI, one is multi-carrier systems based on orthogonal frequency division multiplexing (OFDM) [1] [2], the other is single-carrier systems based on equalization techniques [3] [4]....
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DOI•
01 Jan 2014
TL;DR: This research attacked the mode confusion problem by developing a modeling framework to describe human interaction with gesture recognition systems and found it to be a simple and scalable process.
Abstract: SIGNAL PROCESSING IN WIRELESS COMMUNICATIONS: DEVICE FINGERPRINTING AND WIDE-BAND INTERFERENCE REJECTION
1 citations
Cites background from "Frequency domain equalization for s..."
...Block transmissions, for which groups of data symbols are processed as a unit, allow for the implementation of frequency domain channel equalization (FDE), which for broadband transmissions in rich multi-path environments can bring significant complexity relaxations when compared to time-domain equalization [98]....
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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