A Very Low Complexity Successive Symbol-by-Symbol Sequence Estimator for Faster-Than-Nyquist Signaling

In this paper, we investigate the sequence estimation problem of binary and quadrature phase shift keying faster-than-Nyquist (FTN) signaling and propose two novel low-complexity sequence estimation techniques based on concepts of successive interference cancellation. To the best of our knowledge, this is the first approach in the literature to detect FTN signaling on a symbol-by-symbol basis. In particular, based on the structure of the self-interference inherited in FTN signaling, we first find the operating region boundary---defined by the root-raised cosine (rRC) pulse shape, its roll-off factor, and the time acceleration parameter of the FTN signaling---where perfect estimation of the transmit data symbols on a symbol-by-symbol basis is guaranteed, assuming noise-free transmission. For noisy transmission, we then propose a novel low-complexity technique that works within the operating region and is capable of estimating the transmit data symbols on a symbol-by-symbol basis. To reduce the error propagation of the proposed successive symbol-by-symbol sequence estimator (SSSSE), we propose a successive symbol-by-symbol with go-back-$K$ sequence estimator (SSSgb$K$SE) that goes back to re-estimate up to $K$ symbols, and subsequently improves the estimation accuracy of the current data symbol. Simulation results show that the proposed sequence estimation techniques perform well for low intersymbol interference (ISI) scenarios and can significantly increase the data rate and spectral efficiency. Additionally, results reveal that choosing the value of $K$ as low as $2$ or $3$ data symbols is sufficient to significantly improve the bit-error-rate performance. Results also show that the performance of the proposed SSSgb$K$SE, with $K = 1$ or $2$, surpasses the performance of the lowest complexity equalizers reported in the literature, with reduced computational complexity.Comment: IEEE Access, accepte

Reduced complexity optimal detection of binary faster-than-Nyquist signaling

In this paper, we investigate the detection problem of binary faster-than-Nyquist (FTN) signaling and propose a novel sequence estimation technique that exploits its special structure. In particular, the proposed sequence estimation technique is based on sphere decoding (SD) and exploits the following two characteristics about the FTN detection problem: 1) the correlation between the noise samples after the receiver matched filter, and 2) the structure of the intersymbol interference (ISI) matrix. Simulation results show that the proposed SD-based sequence estimation (SDSE) achieves the optimal performance of the maximum likelihood sequence estimation (MLSE) at reduced computational complexity. This paper demonstrates that FTN signaling has the great potential of increasing the data rate and spectral efficiency substantially, when compared to Nyquist signaling, for the same bit-error-rate (BER) and signal-to-noise ratio (SNR)

Joint Coding for Proactive Caching with Changing File Popularities

Proactive caching is a promising technique used to minimize peak traffic rates by storing popular data, in advance, at different nodes in the network. We study a cellular network with one base station (BS) communicating with multiple mobile units (MUs). The BS has a number of cached files to be delivered to the MUs upon demand, and the popularities of these files are changing over time. We show that proactively and constantly updating the MU finite caches and jointly encoding the delivery of different demanded files to the MUs over different time slots minimize the delivery sum rate. We propose two different schemes for a two different scenarios, where the file popularities over time can be either arbitrary increasing or decreasing for the first scheme and decreases with demand for the second scheme. Numerical results show the benefits of the proposed schemes, over conventional caching schemes, in terms of reducing the delivery sum rate. 2017 IEEE.This work is supported by NSERC discovery grant. The research work of Tamer Khattab was made possible by grant number NPRP 7-923-2-344 from Qatar National Research Fund, QNRF (a member of the Qatar Foundation, QF). The statements made herein are the sole responsibilityScopu