Deep Learning Methods for Nonlinearity Mitigation in Coherent Fiber-Optic Communication Links

Nowadays, the demand for telecommunication services is rapidly growing. To meet this everincreasing connectivity demand telecommunication industry needs to maintain the exponential growth of capacity supply. One of the central efforts in this initiative is directed towards coherent fiber-optic communication systems, the backbone of modern telecommunication infrastructure. Nonlinear distortions, i.e., the ones dependent on the transmitted signal, are widely considered to be one of the major limiting factors of these systems. When mitigating these distortions, we can’t rely on the pre-recorded information about channel properties, which is often missing or incorrect, and, therefore, have to resort to adaptive mitigation techniques, learning the link properties by themselves. Unfortunately, the existing practical approaches are suboptimal: they assume weak nonlinear distortion and propose its compensation via a cascade of separately trained sub-optimal algorithms. Deep learning, a subclass of machine learning very popular nowadays, proposes a way to address these problems. First, deep learning solutions can approximate well an arbitrary nonlinear function without making any prior assumptions about it. Second, deep learning solutions can effectively optimize a cluster of single-purpose algorithms, which leads them to a global performance optimum. In this thesis, two deep-learning solutions for nonlinearity mitigation in high-baudrate coherent fiber-optic communication links are proposed. The first one is the data augmentation technique for improving the training of supervised-learned algorithms for the compensation of nonlinear distortion. Data augmentation encircles a set of approaches for enhancing the size and the quality of training datasets so that they can lead us to better supervised learned models. This thesis shows that specially designed data augmentation techniques can be a very efficient tool for the development of powerful supervised-learned nonlinearity compensation algorithms. In various testcases studied both numerically and experimentally, the suggested augmentation is shown to lead to the reduction of up to 6× in the size of the dataset required to achieve the desired performance and a nearly 2× reduction in the training complexity of a nonlinearity compensation algorithm. The proposed approach is generic and can be applied to enhance a multitude of supervised-learned nonlinearity compensation techniques. The second one is the end-to-end learning procedure enabling optimization of the joint probabilistic and geometric shaping of symbol sequences. In a general end-to-end learning approach, the whole system is implemented as a single trainable NN from bits-in to bits-out. The novelty of the proposed approach is in using cost-effective channel model based on the perturbation theory and the refined symbol probabilities training procedure. The learned constellation shaping demonstrates a considerable mutual information gains in single-channel 64 GBd transmission through both single-span 170 km and multi-span 30x80 km single-mode fiber links. The suggested end-to-end learning procedure is applicable to an arbitrary coherent fiber-optic communication link

A Study of Creative Conflict Management and Christian Reconciliation With a Proposed Seminar for Seventh-day Adventist Ministers in the Caribbean and West Indies Unions

An important field of expanding interest is the management of differences in the church. Changes have taken place which challenge the very existence and fibre of organizational structure and relationship growth in the church setting. There are several reasons for the increasing need for efficiency in the field of conflict management. One basic reason is the potential for dysfunctional and functional effects that conflict can have on any congregation. Adequate conflict management can prove to be a critical skill for the healthy management of differences. Consequently, potential and practicing ministers need special and continuing training in this field. It was the intent of this present study to design seminar materials that might bring deeper awareness and sensitization to some of the various aspects of conflict management to the ministers of the Caribbean and West Indies Unions of Seventh-day Adventists. The theological, social, andragogical, and methodological approaches to the study served to undergird the development of the six-module seminar. This seminar gives ministers exposure to skills which aid interpersonal relationships: listening, assertiveness, conflict resolution, collaborative problem-solving, and skill selection. The findings of the literature suggest that the successful church administrator will also demonstrate proficiency in interpersonal relationships and creative conflict management. The position of this project is that when ministers become sensitized to the origin, process, and potential of conflicts, they can significantly influence the route that conflicts take by utilizing certain skills associated with conflict management and creative problem solving

Novel multiple antenna techniques for improved diversity in wireless communication systems

The focus of this thesis is to enhance the performance of wireless communication systems through the exploitation of multiple antennas at both the transmitter and the receiver ends of a communication link. Such a multiple-input multiple-output (MIMO) connection can theoretically provide spatially independent channels which can be exploited to provide diversity gain and thereby mitigate the problem of channel fading. To integrate such MIMO technology with emerging wireless systems such as third generation code division multiple access (CDMA) and fourth generation orthogonal division multiple access (OFDMA) based-approaches novel advanced signal processing techniques are required. The major advantages of MIMO systems, including array, diversity and multiplexing gains, are initially reviewed. Diversity gain is identified as the key property, which leverages the spatial independent channels to increase the robustness of the communication link. The family of space-time block codes is then introduced as a low computational complexity scheme to benefit from diversity gain within wireless systems. In particular, extended-orthogonal and quasi-orthogonal space-time block codes (EO-/QO-STBCs) are introduced for systems with four transmit antennas which can operate either in open or closed-loop forms. New EO-STBC and QO-STBC wideband CDMA transmission schemes are proposed which when operating in closed-loop mode, i.e. channel state information is exploited at the transmitter, is shown to attain full diversity and thereby outperform previous schemes in terms of attain able symbol error rate performance. This advantage is then utilized in MIMO-OFDM transmission schemes and similar frame error rate (FER) performance advantage is attained. Finally, to mitigate multiuser interference within the proposed MIMO-OFDM system a novel two-step combined parallel interference canceller and multiuser detection scheme is proposed. Simulation studies based upon FER confirm the efficacy of the technique

Codificación para corrección de errores con aplicación en sistemas de transmisión y almacenamiento de información

Tesis (DCI)--FCEFN-UNC, 2013Trata de una técnica de diseño de códigos de chequeo de paridad de baja densidad ( más conocidas por sigla en ingles como LDPC) y un nuevo algoritmo de post- procesamiento para la reducción del piso de erro

Blind source separation for interference cancellation in CDMA systems

Communication is the science of "reliable" transfer of information between two parties, in the sense that the information reaches the intended party with as few errors as possible. Modern wireless systems have many interfering sources that hinder reliable communication. The performance of receivers severely deteriorates in the presence of unknown or unaccounted interference. The goal of a receiver is then to combat these sources of interference in a robust manner while trying to optimize the trade-off between gain and computational complexity. Conventional methods mitigate these sources of interference by taking into account all available information and at times seeking additional information e.g., channel characteristics, direction of arrival, etc. This usually costs bandwidth. This thesis examines the issue of developing mitigating algorithms that utilize as little as possible or no prior information about the nature of the interference. These methods are either semi-blind, in the former case, or blind in the latter case. Blind source separation (BSS) involves solving a source separation problem with very little prior information. A popular framework for solving the BSS problem is independent component analysis (ICA). This thesis combines techniques of ICA with conventional signal detection to cancel out unaccounted sources of interference. Combining an ICA element to standard techniques enables a robust and computationally efficient structure. This thesis proposes switching techniques based on BSS/ICA effectively to combat interference. Additionally, a structure based on a generalized framework termed as denoising source separation (DSS) is presented. In cases where more information is known about the nature of interference, it is natural to incorporate this knowledge in the separation process, so finally this thesis looks at the issue of using some prior knowledge in these techniques. In the simple case, the advantage of using priors should at least lead to faster algorithms.reviewe

Traitement du signal pour les communications numériques au travers de canaux radio-mobiles

This manuscript of ''Habilitation à diriger les Recherches'' (Habilitation to conduct researches) gives me the opportunity to take stock of the last 14 years on my associate professor activities and on my research works in the field of signal processing for digital communications, particularly for radio-mobile communications. The purpose of this signal processing is generally to obtain a robust transmission, despite the passage of digital information through a communication channel disrupted by the mobility between the transmitter and the receiver (Doppler effect), the phenomenon of echoes (multi-path propagation), the addition of noise or interference, or by limitations in bandwidth, in transmitted power or in signal-to-noise ratio. In order to recover properly the digital information, the receiver needs in general to have an accurate knowledge of the channel state. Much of my work has focused on receiver synchronization or more generally on the dynamic estimation of the channel parameters (delays, phases, amplitudes, Doppler shifts, ...). We have developed estimators and studied their performance in asymptotic variance, and have compared them to minimum lower bound (Cramer-rao or Bayesian Cramer Rao bounds). Some other studies have focused only on the recovering of information (''detection'' or ''equalization'' task) by the receiver after channel estimation, or proposed and analyzed emission / reception schemes, reliable for certain scenarios (transmit diversity scheme for flat fading channel, scheme with high energy efficiency, ...).Ce mémoire de HDR est l'occasion de dresser un bilan des 14 dernières années concernant mes activités d'enseignant-chercheur et mes travaux de recherche dans le domaine du traitement du signal pour les communications numériques, et plus particulièrement les communications radio-mobiles. L'objet de ce traitement du signal est globalement l'obtention d'une transmission robuste, malgré le passage de l'information numérique au travers d'un canal de communication perturbé par la mobilité entre l'émetteur et le récepteur (effet Doppler), le phénomène d'échos, l'addition de bruit ou d'interférence, ou encore par des limitations en bande-passante, en puissance transmise ou en rapport-signal à bruit. Afin de restituer au mieux l'information numérique, le récepteur a en général besoin de disposer d'une connaissance précise du canal. Une grande partie de mes travaux s'est intéressé à l'estimation dynamique des paramètres de ce canal (retards, phases, amplitudes, décalages Doppler, ...), et en particulier à la synchronisation du récepteur. Quelques autres travaux se sont intéressés seulement à la restitution de l'information (tâches de ''détection'' ou d' ''égalisation'') par le récepteur une fois le canal estimé, ou à des schémas d'émission / réception spécifiques. La synthèse des travaux commence par une introduction générale décrivant les ''canaux de communications'' et leurs problèmes potentiels, et positionne chacun de mes travaux en ces termes. Une première partie s'intéresse aux techniques de réception pour les signaux à spectre étalé des systèmes d'accès multiple à répartition par codes (CDMA). Ces systèmes large-bande offrent un fort pouvoir de résolution temporelle et des degrés de liberté, que nous avons exploités pour étudier l'égalisation et la synchronisation (de retard et de phase) en présence de trajets multiples et d'utilisateurs multiples. La première partie regroupe aussi d'autres schémas d'émission/réception, proposés pour leur robustesse dans différents scénarios (schéma à diversité pour canaux à évanouissement plats, schéma à forte efficacité énergétique, ...). La seconde partie est consacrée à l'estimation dynamique Bayésienne des paramètres du canal. On suppose ici qu'une partie des paramètres à estimer exhibe des variations temporelles aléatoires selon une certaine loi à priori. Nous proposons d'abord des estimateurs et des bornes minimales d'estimation pour des modèles de transmission relativement complexes, en raison de la distorsion temporelle due à la forte mobilité en modulation multi-porteuse (OFDM), ou de la présence de plusieurs paramètres à estimer conjointement, ou encore de non linéarités dans les modèles. Nous nous focalisons ensuite sur le problème d'estimation des amplitudes complexes des trajets d'un canal à évolution lente (à 1 ou plusieurs bonds). Nous proposons des estimateurs récursifs (dénommés CATL, pour ''Complex Amplitude Tracking Loop'') à structure imposée inspirée par les boucles à verrouillage de phase numériques, de performance asymptotiques proches des bornes minimales. Les formules analytiques approchées de performances asymptotiques et de réglages de ces estimateurs sont établies sous forme de simples fonctions des paramètres physiques (spectre Doppler, retards, niveau de bruit). Puis étant donné les liens établis entre ces estimateurs CATL et certains filtres de Kalman (construits pour des modèles d'état de type marche aléatoire intégrée), les formules approchées de performances asymptotiques et de réglage de ces filtres de Kalman sont aussi dérivées

The Whitworthian 1983-1984

The Whitworthian student newspaper, September 1983-May 1984.https://digitalcommons.whitworth.edu/whitworthian/1067/thumbnail.jp

Risk and expression: Physical and material risk states in computational music practices

This research investigates qualities of physical and material risk within musical performance practices and the value that such properties may hold for less physical engagements afforded by computational instruments. The two studies designed for this research draw upon the experiences of practitioners directly, allowing them to speak about their creative processes, values, and priorities, and how risk and expressivity might factor into their practice. Through comparative studies, artifact design, in-depth discussions, and the application of Thematic Analysis I am able to share the perceptions and experiences of practitioners as they themselves describe. By identifying the value that physical and material risk, uncertainty, and the potential for failure play in the creative process we can potentially provide a compelling argument for the importance of such qualities in practices which do not naturally engage with them. Designing for risk and assessing the experiences of practitioners within the field of experimental media performance will contribute to a better understanding of the value of physical and corporeal materials within digital practices and present potential guidelines for the creation and use of new instruments for creative musical expression.Ph.D