Symbol‐based multi‐layer iterative successive interference cancellation for faster‐than‐Nyquist signalling

Abstract

A symbol-based multi-layer iterative successive interference cancellation (MLISIC) algorithm is proposed to eliminate the inter-symbol interference (ISI) for faster-than-Nyquist (FTN) signaling. The computational complexity of the proposed MLISIC algorithm is much lower than most existing block-based estimation algorithms. By comparison with existing symbol-based algorithms, the proposed MLISIC algorithm has higher estimation accuracy. Furthermore, by means of utilizing more accurate symbols and elaborate length of successive interference cancellation, an improved MLISIC (IMLISIC) algorithm is presented to further promote the estimation accuracy. Simulation results show in mild ISI cases, the proposed MLISIC and IMLISIC algorithms can approximate the theoretical performance even using 256amplitude phase shift keying (APSK) which is adopted in digital video broadcasting-satellite-second generation extension (DVB-S2X), i.e., bit error rate (BER) performance degradation is about 0.03 dB when the signal-to-noise ratio is high. In other words, using the proposed MLISIC and IMLISIC algorithms in mild ISI cases, the spectrum efficiency can be improved with negligible BER performance degradation. In moderate ISI cases, BER performance degradation of our proposed IMLISIC algorithm is no more than 0.13 dB when adopting 64/128/256-APSK, which is still satisfying. Besides, compared with existing symbol-based algorithms, the greater BER performance improvement can be achieved under severer ISI circumstances.Index Terms-Successive interference cancellation, intersymbol interference (ISI), faster-than-Nyquist (FTN) signaling, amplitude phase shift keying (APSK), digital video broadcastingsatellite-second generation extension (DVB-S2X).

Pre-Equalized Interference Cancellation for Faster-Than-Nyquist Signaling

“…The SSSgbK SE and MLISIC algorithms are not taken into account in this part because the IMLISIC algorithm has higher estimation accuracy than the former ones [25]. Some universal parameters adopted in the simulations are shown in Table 2, where and represent the length of block and cyclic prefix respectively.…”

“…As shown in [25], the performance of the IMLISIC algorithm in moderate ISI cases is unsatisfactory although its performance degradation in mild cases can be neglected. We observed that its performance is quite bad after the first iteration, which means that desired performance cannot be achieved even with more iterations.…”

“…Assuming that the iteration times is K E and the singleside symbol length used for ISI elimination in the K -th (1 ≤ K ≤ K E ) iteration is L K − 1. Onceâ 0,k−ψ is obtained with APE, it can be used to perform the first iteration as [25] where deci (x) rounds x to the nearest symbol in the constellation.â i,k , i ≥ 1 indicates the symbol after the i-th iteration of IMLISIC. In addition, it should be noted that symbols after APE and the first iteration are used as transmitted symbols to perform the first iteration.…”

“…However, extending such an algorithm to FTN systems with higher-order modulations still results in extremely high computational complexity. Low-complexity symbolbased multi-layer iterative successive interference cancellation (MLISIC) algorithm and its improved algorithm, i.e., the IMLISIC algorithm are used to eliminate ISI for FTN signaling in [25]. In mild cases (for example, the time acceleration parameter and rolling factor equal to 0.8 and 0.5 respectively), the IMLISIC algorithm can approximate the BER performance of the ISI-free Nyquist signaling even using 256-amplitude phase shift keying (APSK), which is adopted in digital video broadcasting-satellite-second generation extension (DVB-S2X) [26].…”

Efficient frequency‐domain linear distortion equaliser in faster‐than‐Nyquist systems

“…In contrast, low complexity ISI algorithms based on successive interference cancellation can be found in [8–10], but these algorithms are applicable only in mild ISI cases. Besides, cyclic prefix (CP)‐based frequency‐domain equalisers for FTN signalling were evaluated over additive white Gaussian noise (AWGN) and frequency‐selective fading channels [11, 12].…”