Faster-than-Nyquist transmission for wireless and optical fibre communication

Faster-than-Nyquist transmission (FTN) is a well-known paradigm for digital communication which has received renewed attention in the wake of the need for increasing spectral efficiency in wireless and optical fibre communication. FTN surrenders the concept of transmitting orthogonal signal elements for the benefit of tighter packing of data into time-frequency resources and thus higher data rates in the same Fourier bandwidth. In this presentation, we will revisit the underlying principles of FTN, including the associated achievable rates, and we will elaborate on its pros and cons for modern communication systems. We will illustrate its use in the domains of wireless and optical fibre communication and present selected numerical results to highlight its potential as an resource efficient signaling scheme

Multidimensional Index Modulation for 5G and Beyond Wireless Networks

This study examines the flexible utilization of existing IM techniques in a comprehensive manner to satisfy the challenging and diverse requirements of 5G and beyond services. After spatial modulation (SM), which transmits information bits through antenna indices, application of IM to orthogonal frequency division multiplexing (OFDM) subcarriers has opened the door for the extension of IM into different dimensions, such as radio frequency (RF) mirrors, time slots, codes, and dispersion matrices. Recent studies have introduced the concept of multidimensional IM by various combinations of one-dimensional IM techniques to provide higher spectral efficiency (SE) and better bit error rate (BER) performance at the expense of higher transmitter (Tx) and receiver (Rx) complexity. Despite the ongoing research on the design of new IM techniques and their implementation challenges, proper use of the available IM techniques to address different requirements of 5G and beyond networks is an open research area in the literature. For this reason, we first provide the dimensional-based categorization of available IM domains and review the existing IM types regarding this categorization. Then, we develop a framework that investigates the efficient utilization of these techniques and establishes a link between the IM schemes and 5G services, namely enhanced mobile broadband (eMBB), massive machine-type communications (mMTC), and ultra-reliable low-latency communication (URLLC). Additionally, this work defines key performance indicators (KPIs) to quantify the advantages and disadvantages of IM techniques in time, frequency, space, and code dimensions. Finally, future recommendations are given regarding the design of flexible IM-based communication systems for 5G and beyond wireless networks.Comment: This work has been submitted to Proceedings of the IEEE for possible publicatio

Achievable information rates estimates in optically amplified transmission systems using nonlinearity compensation and probabilistic shaping

Achievable information rates (AIRs) of wideband optical communication systems using a ∼40  nm (∼5  THz)∼40  nm (∼5  THz) erbium-doped fiber amplifier and ∼100  nm (∼12.5  THz)∼100  nm (∼12.5  THz) distributed Raman amplification are estimated based on a first-order perturbation analysis. The AIRs of each individual channel have been evaluated for DP-64QAM, DP-256QAM, and DP-1024QAM modulation formats. The impact of full-field nonlinear compensation (FF-NLC) and probabilistically shaped constellations using a Maxwell–Boltzmann distribution were studied and compared to electronic dispersion compensation. It has been found that a probabilistically shaped DP-1024QAM constellation, combined with FF-NLC, yields achievable information rates of ∼75  Tbit/s∼75  Tbit/s for the EDFA scheme and ∼223  Tbit/s∼223  Tbit/s for the Raman amplification scheme over a 2000 km standard single-mode fiber transmission

Enabling Technology in Optical Fiber Communications: From Device, System to Networking

This book explores the enabling technology in optical fiber communications. It focuses on the state-of-the-art advances from fundamental theories, devices, and subsystems to networking applications as well as future perspectives of optical fiber communications. The topics cover include integrated photonics, fiber optics, fiber and free-space optical communications, and optical networking

Doctor of Philosophy

dissertationThis dissertation deals with blind modulation identification of quadrature amplitude modulations (QAM) and phase-shift keying (PSK) signals in dual-polarized channels in digital communication systems. The problems addressed in this dissertation are as follows: First, blind modulation identification of QAM and PSK signals in single noisy channels and multipath channels are explored. Second, methods for blind separation of two information streams in a dual-polarized channel and identification of the modulation types of the two information streams are developed. A likelihood-based blind modulation identification for QAM and PSK signals in a single channel with additive white Gaussian noise (AWGN) is developed first. This algorithm selects the modulation type that maximizes a log-likelihood function based on the known probability distribution associated with the phase or amplitude of the received signals for the candidate modulation types. The approach of this paper does not need prior knowledge of carrier frequency or baud rate. Comparisons of theory and simulation demonstrate good agreement in the probability of successful modulation identification under different signal-to-noise ratios (SNRs). Simulation results show that for the signals in AWGN channels containing 10000 symbols and 20 samples per symbol, the system can identify BPSK, QPSK, 8PSK and QAMs of order 16, 32, 64, 128 and 256 with better than 99% accuracy at 4 dB SNR. Under the same condition, the simulation results indicate the two competing methods available in the literature can only reach at most 85% accuracy even at 20 dB SNR for all the modulation types. The simulation results also suggest that when the symbol length decreases, the system needs higher SNRs in order to get accurate identification results. Simulations using different noisy environments indicate that the algorithm is robust to variations of noise environments from the models assumed for derivation of the algorithm. In addition, the combination of a constant modulus amplitude (CMA) equalizer and the likelihood-based modulation identification algorithm is able to identify the QAM signals in multipath channels in a wide range of SNRs. When compared with the results for the signals in AWGN channels, the combination of the CMA equalizer and the likelihood-based modulation identification algorithm needs higher SNRs and longer signal lengths in order to obtain accurate identification results. The second contribution of this dissertation is a new method for blindly identifying PSK and QAM signals in dual-polarized channels. The system combines a likelihood-based adaptive blind source separation (BSS) method and the likelihood-based blind modulation identification method. The BSS algorithm is based on the likelihood functions of the amplitude of the transmitted signals. This system tracks the time-varying polarization coefficients and recovers the input signals to the two channels. The simulation results presented in this paper demonstrate that the likelihood-based adaptive BSS method is able to recover the source signals of different modulation types for a wide range of input SNRs. Comparisons with a natural gradient-based BSS algorithm indicate that the likelihood-based method results in smaller symbol error rates. When a modulation identification algorithm is applied to the separated signals, the overall system is able to identify different PSK and QAM signals with high accuracy at sufficiently high SNRs. For example, with 20,000 symbols, the system identified BPSK and 16-QAM signals with better than 99% accuracy when the input SNR was 8dB and the polarization coefficients rotated with a rate of 1.3 ms. Higher SNRs are needed to obtain similar levels of accuracy when the polarization changes faster or when the number of input symbols is shorter. When compared with the identification results for signals in AWGN channels, the system needs higher SNRs and longer signal length to obtain accurate results for signals in dual-polarized channels

Cost-Effective Spectrally-Efficient Optical Transceiver Architectures for Metropolitan and Regional Links

The work presented herein explores cost-effective optical transceiver architectures for access, metropolitan and regional links. The primary requirement in such links is cost-effectiveness and secondly, spectral efficiency. The bandwidth/data demand is driven by data-intensive Internet applications, such as cloud-based services and video-on-demand, and is rapidly increasing in access and metro links. Therefore, cost-effective optical transceiver architectures offering high information spectral densities (ISDs > 1(b/s)/Hz) need to be implemented over metropolitan distances. Then, a key question for each link length and application is whether coherent- or direct (non-coherent) detection technology offers the best cost and performance trade-off. The performance and complexity limits of both technologies have been studied. Single polarization direct detection transceivers have been reviewed, focusing on their achievable ISDs and reach. It is concluded that subcarrier modulation (SCM) technique combined with single sideband (SSB) and high-order quadrature amplitude modulation (QAM) signaling, enabled by digital signal processing (DSP) based optical transceivers, must be implemented in order to exceed an ISD of 1 (b/s)/Hz in direct-detection links. The complexity can be shifted from the optical to the electrical domain using such transceivers, and hence, the cost can be minimized. In this regard, a detailed performance comparison of two spectrally-efficient direct detection SCM techniques, namely Nyquist-SCM and OFDM, is presented by means of simulations. It is found out that Nyquist-SCM format offers the transmission distances more than double that of OFDM due to its higher resilience to signal-signal beating interference. Following this, dispersion-precompensated SSB 4- and 16-QAM Nyquist-SCM signal formats were experimentally demonstrated using in-phase and quadrature (IQ)-modulators at net optical ISDs of 1.2 and 2 (b/s)/Hz over 800 km and 323 km of standard single-mode fibre (SSMF), respectively. These demonstrations represent record net optical ISDs over such distances among the reported single polarization wavelength division multiplexed (WDM) systems. Furthermore, since the cost-effectiveness is crucial, the optical complexity of Nyquist-SCM transmitters can be significantly reduced by using low-cost modulators and high-linewidth lasers. A comprehensive theoretical study on SSB signal generation using IQ- and dual-drive Mach-Zehnder modulators (DD-MZMs) was carried out to assess their performance for WDM direct detection links. This was followed by an experimental demonstration of WDM transmission over 242 km of SSMF with a net optical ISD of 1.5 (b/s)/Hz, the highest achieved ISD using a DD-MZM-based transmitter. Following the assessment of direct detection technology using various transmitter designs, cost-effective simplified coherent receiver architectures for access and metro networks have been investigated. The optical complexity of the conventional (polarization- and phase-diverse) coherent receiver is significantly simplified, i.e., consisting of a single 3 dB coupler and balanced photodetector, utilizing heterodyne reception and Alamouti polarization-time block coding. Although the achievable net optical ISD is halved compared to a conventional coherent receiver due to Alamouti coding, its receiver sensitivity provides significant gain over a direct detection receiver at M-ary QAM formats where M ≥16