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
Journal Article•
TL;DR: In this paper, the channel response of SC-FDMA is modeled and LMS and VSS-LMS channel estimation techniques are applied to the model in order to estimate channel response.
Abstract: In 3GPP LTE, OFDMA is used as a multiple access technique in downlink while SC-FDMA is used in uplink since it has low PAPR compared with ODFMA and that will lead to saving power of transmitter (MS). In this paper SC-FDMA is modeled and LMS and VSS-LMS channel estimation techniques is applied to the model in order to estimate the channel response. The performance is analyzed under different channel environments by calculating BER and MSE for both algorithms. The results show that the performance of both algorithms degrades under high Doppler shifts however VSS-LMS has better performance compared with LMS.
2 citations
01 Oct 2012
TL;DR: Computer simulation results show that for the star 16QAM scheme, the average block error rate (BLER) using the iterative DDCE is very close to that with ideal channel estimation for a low channel coding rate such as an R = 1/3 turbo code.
Abstract: This paper presents the average block error rate (BLER) performance of the star 16QAM scheme using iterative decision-directed channel estimation (DDCE) for discrete Fourier transform (DFT)-precoded orthogonal frequency division multiple access (OFDMA). The star 16QAM scheme achieves more efficient modulation compared to square 16QAM in that it decreases the actual required average received signal-to-noise power ratio (SNR) satisfying the target average BLER considering the peak-to-average power ratio (PAPR) of the transmitted signal for a low channel coding rate. Hence, the feature of the paper is that we apply iterative DDCE using soft-decision symbol estimation based on the log-likelihood ratio (LLR) of an extrinsic probability at the Max-Log-MAP (maximum a posteriori probability) decoder output to achieve an efficient modulation scheme with a low required average received SNR. Computer simulation results show that for the star 16QAM scheme, the average BLER using the iterative DDCE is very close to that with ideal channel estimation for a low channel coding rate such as an R = 1/3 turbo code. We also show that when iterative DDCE is employed, the (8, 8) star 16QAM scheme decreases the required average received SNR considering the cubic metric at the average BLER of 10-2 by approximately 0.7 dB compared to the square 16QAM scheme.
2 citations
Cites background from "Frequency domain equalization for s..."
...…transform (DFT)-precoded orthogonal frequency division multiple access (OFDMA) (also called DFT-spread OFDMA) is adopted for SC-FDMA signal generation in the frequency domain [2],[3], to achieve high commonality with OFDMA in the downlink and affinity to frequency domain equalizers (FDEs) [4],[5]....
[...]
04 Jul 2018
TL;DR: A new unique word (UW) OFDM waveform based on zero-tail discrete Sine transform spread OFDM (ZT UW DST-S OFDM) is proposed that has better BER and channel tracking (Doppler) performance than the conventional OFDM and ZT DFT-S OfDM systems.
Abstract: In this paper, it is proposed a new unique word (UW) OFDM waveform based on zero-tail discrete Sine transform spread OFDM (ZT UW DST-S OFDM). The proposed waveform improves the ZT DST-S-OFDM and UW OFDM methods by removing the influence of the data symbols on the tail of the transmitted signal. In this study, the effects of different UW sequences such as Zadoff-Chu, CAZAC, 15 bit PN, 8 bit complementary code keying (CCK), 0-word, 1-word and −1-word on the bit error rate (BER) and channel tracking (Doppler) performance of the proposed ZT UW DST-S OFDM systems are investigated. In order to test the performance of the proposed method, computer simulation studies are performed on time invariant and time variant frequency selective Rayleigh fading channels. The obtained results confirm that the proposed waveform has better BER and channel tracking (Doppler) performance than the conventional OFDM and ZT DFT-S OFDM systems. In particular, it is observed that the ZT UW DST-S OFDM using Zadoff-Chu sequence has the best BER and channel tracking performance.
2 citations
Cites methods from "Frequency domain equalization for s..."
...The other methods proposed in [2-7] follow a different logic for ISI reduction and produce a constant array, a unique word (UW), at the end of each symbol (or tail)....
[...]
TL;DR: Issues and prevailing solutions to performance enhancements and QoS provisioning for IP services over mobile wireless networks from a layered view are reviewed.
Abstract: SUMMARY With the convergence of wireless communication and IP-based networking technologies, future IP-based wireless networks are expected to support real-time multimedia. IP services over wireless networks (e.g. wireless access to Internet) enhance the mobility and flexibility of traditional IP network users. Wireless networks extend the current IP service infrastructure to a mix of transmission media, bandwidth, costs, coverage, and service agreements, requiring enhancements to the IP protocol layers in wireless networks. Furthermore, QoS provisioning is required at various layers of the IP protocol stack to guarantee different types of service requests, giving rise to issues related to cross-layer design methodology. This paper reviews issues and prevailing solutions to performance enhancements and QoS provisioning for IP services over mobile wireless networks from a layered view. Copyright # 2006 John Wiley & Sons, Ltd.
2 citations
Cites background from "Frequency domain equalization for s..."
...Typical schemes for providing uncorrelated antenna signals include space diversity (use multiple physically separated antennas), polarization diversity (use a dual antenna system with orthogonal polarizations), angle diversity (use multiple directional antennas receiving signals with different angle of arrivals), frequency diversity (transmit and receive signals at different carrier frequencies), and time diversity (transmit and receive data on multiple different time slots whose time separation are large enough) (please see [35, 36] for detailed description of each scheme)....
[...]
...Figure 3 [36] shows a comparison of computation complexity between SC-TDE and SC-FDE....
[...]
...• Adaptive equalization [35, 36]: This is a traditional way of using an adaptive filter to compensate for intersymbol interference (ISI) by gathering the dispersed symbol energy back together into its original time interval....
[...]
Proceedings Article•
31 Dec 2012TL;DR: Numerical analysis reveals that the proposed scheme can achieve satisfactory average channel capacity due to a good balance between frequency diversity effect by the dynamic spectrum selection and enhanced reliability by the selection of a certain amount of spectrum uniformly from the entire system band.
Abstract: This paper proposes a channel prediction scheme suitable for selfish dynamic spectrum control (Selfish DSC) in which each link dynamically chooses a necessary amount of spectrum having the highest signal to noise plus interference power ratio (SINR) from the entire shared band For channel prediction in such a Selfish DSC, although it is mandatory to predict channel frequency response for the entire system band to choose the best spectrum for the next transmission, it is quite difficult because each link can measure only a part of the band In other words, each user has to solve an ill-conditioned least square (LS) problem Thus, the proposed scheme chooses a certain amount (which is smaller than the total amount) of spectrum with the highest SINR, followed by the selection of the rest of spectrum uniformly from the other part to mitigate the impact of ill-conditioned LS problem Then data and reference signals are transmitted via the selected spectrum Numerical analysis reveals that the proposed scheme can achieve satisfactory average channel capacity due to a good balance between frequency diversity effect by the dynamic spectrum selection and enhanced reliability by the selection of a certain amount of spectrum uniformly from the entire system band
2 citations
Cites background or methods from "Frequency domain equalization for s..."
...If a single carrier (SC) transmission [7] is employed, discrete Fourier transform (DFT) is applied to xi to form data spectrum xi....
[...]
...Evolution in the last decade in physical layer techniques, especially in signal detection [5]–[7], enables us to allow mutual interference to achieve higher spectrum efficiencies....
[...]
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