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

摘要

In this paper, we investigate the sequence estimation problem of binary andquadrature phase shift keying faster-than-Nyquist (FTN) signaling and proposetwo novel low-complexity sequence estimation techniques based on concepts ofsuccessive interference cancellation. To the best of our knowledge, this is thefirst approach in the literature to detect FTN signaling on a symbol-by-symbolbasis. In particular, based on the structure of the self-interference inheritedin FTN signaling, we first find the operating region boundary---defined by theroot-raised cosine (rRC) pulse shape, its roll-off factor, and the timeacceleration parameter of the FTN signaling---where perfect estimation of thetransmit data symbols on a symbol-by-symbol basis is guaranteed, assumingnoise-free transmission. For noisy transmission, we then propose a novellow-complexity technique that works within the operating region and is capableof estimating the transmit data symbols on a symbol-by-symbol basis. To reducethe error propagation of the proposed successive symbol-by-symbol sequenceestimator (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 datasymbol. Simulation results show that the proposed sequence estimationtechniques perform well for low intersymbol interference (ISI) scenarios andcan significantly increase the data rate and spectral efficiency. Additionally,results reveal that choosing the value of $K$ as low as $2$ or $3$ data symbolsis sufficient to significantly improve the bit-error-rate performance. Resultsalso 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 theliterature, with reduced computational complexity.