faster-than-Nyquist Signaling Research Articles

전송효율 향상을 위한 위성 및 수중 통신의 효율적인 융합 모델 연구

In this paper, we analyzed efficient decoding scheme with FTN(Faster than Nyquist) method that is transmission method faster than Nyquist theory and increase the throughput. Applying the FTN method to satellite and underwater communication, we proposed an efficient transceiver model. To minimize ISI(Inter-Symbol Interference) induced by FTN signal, turbo equalization algorithms that iteratively exchange probabilistic information between Viterbi equalizer based on BCJR algorithm and LDPC decoder are used in satellite communication. In others, for underwater communication, DFE equalizer and LDPC decoder are concatenated to improve performance.

Method of timing estimation for FTN signalling with high‐order modulation

In the digital communications, due to the timing-offset existing between the transmitter and receiver, timing synchronisation is a critical problem which may have dramatic effect on the transmission performance in the faster-than-Nyquist (FTN) signalling system. For solving this problem, considering the intentionally intersymbol interference introduced by FTN, a new non-data aided timing-delay estimation scheme is proposed. Moreover, the proposed method can be also applied into the M-ary quadrature amplitude modulation. In the end, the performance of the proposed scheme for FTN system is tested and verified.

Blind recognition of BCH codes in faster‐than‐Nyquist signalling system

Proposed is a blind recognition method for Bose–Chaudhuri–Hocquenghem (BCH) codes in the faster-than-Nyquist (FTN) signalling system which is based on the Galois field Fourier transform of the code polynomial. Considering the signal-to-noise ratio estimation in coloured noise, the proposed method can maximise the correct recognition probability of the roots of the generator polynomial by an appropriate decision criterion. Moreover, an optimal threshold of the decision criterion is deduced. Simulation results demonstrate that the proposed method can recognise the BCH codes efficiently in the FTN signalling system.

Faster-Than-Nyquist Broadcasting in Gaussian Channels: Achievable Rate Regions and Coding

We consider the concept of faster-than-Nyquist rate (FTN) broadcasting, which nonorthogonally multiplexes more than one user message in the continuous-time domain for transmission over broadcast channels. Two FTN broadcasting approaches, namely, sub-FTN and full-FTN, are considered for broadcasting of $K$ independent messages over $K$ -user continuous time Gaussian broadcast channel. The derived achievable rate regions of the two approaches are shown to be, in general, greater than the capacity region of the optimally coded Nyquist-rate broadcasting using a same modulating pulse. The full-FTN broadcasting provides larger degrees of freedom (capacity pre-log factor) to each user of the broadcast channel while the sub-FTN improves signal-to-interference-plus-noise-ratios of the individual link. The amount of capacity gains in high SNR regime is linearly proportional to excess bandwidth in the modulating pulse used and dependent on FTN signaling rates, channel SNRs, and number of users in the broadcast channel. The simulated sub-FTN and full-FTN broadcast transceivers outperform coded Nyquist-rate systems both in BER performances and in capacity.

An effective carrier phase estimation scheme in faster than Nyquist WDM transmission system

We propose a carrier phase estimation method using unequaled digital pilot tone in a faster than Nyquist WDM transmission system, in which the digital pilot tone is employed to estimate laser phase noise induced by the lasers located at the transmitter and the receiver ends. The method can effectively overcome the scale of the inter-symbol interference introduced by FTN signaling, with the good features of high phase noise tolerance and simple hardware complexity.

超奈奎斯特速率(FTN)传输进展

在数字通信系统中，奈奎斯特准则指出，为了实现无码间干扰的传输，符号速率必须满足奈奎斯特准则。然而1975年Mazo发现在带限加性高斯白噪声信道中，当码元速率超过奈奎斯特速率在25%以内时，信号的归一化最小欧式距离并不会减小，并称为Faster-Than-Nyquist signaling (超奈奎斯特，FTN)。本文首先介绍FTN传输的发展历史，分析FTN系统的Mazo限，并对FTN传输以及奈奎斯特速率下的限制信道容量进行比较。从仿真结果可以看出，当脉冲存在过剩带宽时，FTN传输可以得到比奈奎斯特速率下更高的信道容量。 In digital communication system, the Nyquist criterion states that the symbol rate must satisfy the Nyquist criterion in order to achieve transmission without intersymbol interference. However, in 1975, Mazo found that in band-limited Additive White Gaussian Noise channel, the normalized minimum Euclidean distance does not decrease when the symbol rate exceeds within 25% of the Nyquist rate and name it as Faster-Than-Nyquist signaling (FTN). In this paper, we first introduce the history of FTN transmission, analyze the Mazo limit of FTN system, and finally compare the capacity of FTN and Nyquist rate transmission. Simulation result shows that when the transmitted pulse has excessive bandwidth, FTN transmission can achieve higher capacity than transmission under Nyquist rate.

Frequency-Domain-Equalization-Aided Iterative Detection of Faster-than-Nyquist Signaling

A reduced-complexity three-stage-concatenated faster-than-Nyquist signaling (FTNS)-based transceiver architecture is proposed, which operates with the aid of soft decision (SoD) frequency-domain equalization (FDE) at the receiver. More specifically, the decoding algorithm conceived allows us to attain near-capacity performance as an explicit benefit of iterative detection, which is capable of eliminating the intersymbol interference imposed by FTNS. The proposed SoD FDE-aided FTNS detector has low decoding complexity that linearly increases upon increasing the FTNS block length and, hence, is particularly beneficial for practical long-dispersion scenarios. Furthermore, extrinsic information transfer charts are utilized for designing a near-capacity three-stage-concatenated turbo FTNS system, which exhibits an explicit turbo cliff in the low-signal-to-noise-ratio region, hence outperforming its conventional two-stage-concatenated FTNS counterpart.

FTN 채널에서의 효율적인 비터비 등화기 연구

본 논문은 인접 심볼 간의 간섭이 발생하지 않는 최대 데이터 전송률인 Nyquist rate 보다 빠르게 데이터를 전송하여 전송량을 증가시키는 FTN(Faster than Nyquist) 기법을 이용하여 효율적인 복호 방식을 분석한다. FTN 신호 전송시 발생하는 ISI(Inter-Symbol Interference) 를 최소화하기 위해 간섭량을 비터비 등화기의 가지 정보로 활용하여 비터비 등화기 모델을 제안한다. 본 논문에서는 FTN 신호를 복호하기 위해 BCJR 기법을 이용한 비터비 등화기와 LDPC 복호기간의 반복으로 이루어진 터보 등화 기법을 이용하여 복호한다. BCJR 복호시 트렐리스 구조를 본 논문에서는 유클리디언 거리를 최대로 함으로써 기존의 방식보다 성능이 향상됨을 알 수 있으며, 이에 따른 FTN 신호의 전송량 증가별 성능을 비교한다. In this paper, we analyzed efficient decoding scheme with FTN (Faster than Nyquist) method that is transmission method faster than Nyquist theory and increase the throughput. we proposed viterbi equalizer model to minimize ISI (Inter-Symbol Interference) when FTN signal is transmitted. the proposed model utilized interference as branch information. In this paper, to decode FTN singal, we used turbo equalization algorithms that iteratively exchange probabilistic information between soft Viterbi equalizer (BCJR method) and LDPC decoder. By changing the trellis diagram in order to maximize Euclidean distance, we confirmed that performance was improved compared to conventional methods as increasing throughput of FTN signal.

Frequency-Domain Equalization of Faster-than-Nyquist Signaling

In this letter, motivated by the recent rediscovery of faster-than-Nyquist (FTN) signaling transmissions, we conceive a frequency-domain equalization (FDE)-assisted FTN receiver architecture, which is capable of attaining a low demodulating complexity. The proposed scheme is especially beneficial for a long channel tap FTN scenario. More specifically, in our scheme the resultant inter-symbol interference imposed by FTN signaling is approximated by a finite-tap circulant matrix structure, which allows us to employ an efficient fast Fourier transform operation and a low-complexity channel-inverse-based minimum mean-square error detection algorithm. Our simulation results demonstrate that the proposed scheme is capable of attaining a near-optimal error-rate performance without imposing any substantial demodulating complexity as well as power penalty.

Faster-Than-Nyquist Signaling

In this paper, we survey faster-than-Nyquist (FTN) signaling, an extension of ordinary linear modulation in which the usual data bearing pulses are simply sent faster, and consequently are no longer orthogonal. Far from a disadvantage, this innovation can transmit up to twice the bits as ordinary modulation at the same bit energy, spectrum, and error rate. The method is directly applicable to orthogonal frequency division multiplex (OFDM) and quadrature amplitude modulation (QAM) signaling. Performance results for a number of practical systems are presented. FTN signaling raises a number of basic issues in communication theory and practice. The Shannon capacity of the signals is considerably higher.

Reduced-Complexity Receivers for Strongly Narrowband Intersymbol Interference Introduced by Faster-than-Nyquist Signaling

We propose new M-algorithm BCJR (M-BCJR) algorithms for low-complexity turbo equalization and apply them to severe intersymbol interference (ISI) introduced by faster than Nyquist signaling. These reduced-search detectors are evaluated in simple detection over the ISI channel and in iterative decoding of coded FTN transmissions. In the second case, accurate log likelihood ratios are essential and we introduce a 3-recursion M-BCJR that provides this. Focusing signal energy by a minimum phase conversion before the M-BCJR is also essential; we propose an improvement to this older idea. The new M-BCJRs are compared to reduced-trellis VA and BCJR benchmarks. The FTN signals carry 4-8 bits/Hz-s in a fixed spectrum, with severe ISI models as long as 32 taps. The combination of coded FTN and the reduced-complexity BCJR is an attractive narrowband coding method.

Multicarrier Faster-Than-Nyquist Transceivers: Hardware Architecture and Performance Analysis

This paper evaluates the hardware aspects of multicarrier faster-than-Nyquist (FTN) signaling transceivers. The choice of time-frequency spacing of the symbols in an FTN system for improved bandwidth efficiency is targeted towards efficient hardware implementation. This work proposes a hardware architecture for the realization of iterative decoding of FTN multicarrier modulated signals. Compatibility with existing systems has been considered for smooth switching between the faster-than-Nyquist and orthogonal signaling schemes. One such being the use of fast Fourier transforms (FFTs) for multicarrier modulation. The performance of the fixed point model is very close to that of the floating point representation. The impact of system parameters such as number of projection points, time-frequency spacing, finite wordlengths and their design tradeoffs for reduced complexity iterative decoders in FTN systems have been investigated. The FTN decoder has been designed and synthesized in both 65 nm CMOS and FPGA. From the hardware resource usage numbers it can be concluded that FTN signaling can be used to achieve higher bandwidth efficiency with acceptable complexity overhead.

{ Asymptotic Optimality of Binary Faster-than-Nyquist Signaling}

In this letter, the asymptotic information rate of faster-than-Nyquist (FTN) signaling is examined when the data sequence consists of independent and identically distributed (i.i.d.) binary symbols. It is shown that, as the FTN rate tends to infinity, the information rate converges to that of the FTN signaling with i.i.d. Gaussian symbols. This leads to the optimality of the i.i.d. binary FTN signaling in the sense that the channel capacity can be asymptotically achieved by employing a transmit pulse that results in the same power spectral density as the water-filling solution.

Multistream Faster than Nyquist Signaling

We extend Mazo's concept of faster-than-Nyquist (FTN) signaling to pulse trains that modulate a bank of subcarriers, a method called two dimensional FTN signaling. The signal processing is similar to orthogonal frequency division multiplex(OFDM) transmission but the subchannels are not orthogonal. Despite nonorthogonal pulses and subcarriers, the method achieves the isolated-pulse error performance; it does so in as little as half the bandwidth of ordinary OFDM. Euclidean distance properties are investigated for schemes based on several basic pulses. The best have Gaussian shape. An efficient distance calculation is given. Concatenations of ordinary codes and FTN are introduced. The combination achieves the outer code gain in as little as half the bandwidth. Receivers must work in two dimensions, and several iterative designs are proposed for FTN with outer convolutional coding.

Constrained Capacities for Faster-Than-Nyquist Signaling

This paper deals with capacity computations of faster-than-Nyquist (FTN) signaling. It shows that the capacity of FTN is higher than the orthogonal pulse linear modulation capacity for all pulse shapes except the sinc. FTN signals can in fact achieve the ultimate capacity for the signal power spectral density (PSD). The paper lower- and upper-bounds the FTN capacity under the constraint of finite input alphabet. It is often higher than the capacity for comparable orthogonal pulse systems; sometimes it is superior to all forms of orthogonal signaling with the same PSD.