Symbol Synchronization Of Digital Communication Systems Using Digital Methods

This practical guide helps readers to learn how to develop and implement synchronization functions in digital communication systems.

"Timing synchronization plays an important role in recovering the original transmitted signal in telecommunication systems. In order to have a communication system that operates at the correct time and in the correct order, it is necessary to synchronize to the transmitter’s symbol timing. Synchronization can be accomplished when the receiver clock tracks the periodic timing information in a transmitted signal to reproduce the original signal. In this thesis work, we report the design, implementation and evaluation of a timing synchronization algorithm based on the technique first proposed by Gardner [1], applied to wireless communication using the Alamouti spacetime code [2] under QPSK modulation with halfsine pulses. To achieve this, a mathematical model is introduced which includes software design of communication algorithms. In this modeling, we simulate the Gardner algorithm in MATLAB. Then, five techniques are introduced to improve the performance of the loop filter in the digital receiver, and they are successfully implemented and evaluated in Matlab. These five techniques prove that there is an improvement in digital receiver performance in terms of the convergence speed and the communication system complexity. On the other hand, the optimum decoding of the Alamouti spacetime code, as initially proposed, makes the nontrivial assumption that the communication system is perfectly synchronized. Realistic wireless environments contain additive white Gaussian noise (AWGN), multipath fading, and it is not perfectly synchronized. In this thesis, the Alamouti spacetime code technique is written for QPSK modulation scheme to work in realistic environment that involves a timing synchronization technique. We compare the bit error rate (BER) of the Alamouti decoder when synchronized using the proposed algorithms with the ideal results found in the literature, and we find them to be similar, proving that the synchronization algorithm is in fact achieving optimum synchronization. This thesis presents synchronization algorithms that are necessary for a complete working wireless Alamouti technique. Also, this thesis improves the communication system performance in terms of the convergence speed with reducing the computational complexity of the communication system design."--Abstract.

Signal-space methods provide a unifying framework for modulation, detection and coding concpets. Three chapters on coding provide valuable design information for communications systems

Synchronization is a critical function in digital communications; its failures may have catastrophic effects on the transmission system performance. Furthermore, synchronization circuits comprehend such a large part of the receiver hardware that their implementation has a substantial impact on the overall costs. For these reasons design engineers are particularly concerned with the development of new and more efficient synchronization structures. Unfortunately, the advent of digital VLSI technology has radically affected modem design rules, to a point that most analog techniques employed so far have become totally obsolete. Although digital synchronization methods are well established by now in the literature, they only appear in the form of technical papers, often concentrating on specific performance or implementation issues. As a consequence they are hardly useful to give a unified view of an otherwise seemingly heterogeneous field. It is widely recognized that a fundamental understanding of digital synchronization can only be reached by providing the designer with a solid theoretical framework, or else he will not know where to adjust his methods when he attempts to apply them to new situations. The task of the present book is just to develop such a framework.

Introduction to Digital Communications explores the basic principles in the analysis and design of digital communication systems, including design objectives, constraints and trade-offs. After portraying the big picture and laying the background material, this book lucidly progresses to a comprehensive and detailed discussion of all critical elements and key functions in digital communications. The first undergraduate-level textbook exclusively on digital communications, with a complete coverage of source and channel coding, modulation, and synchronization. Discusses major aspects of communication networks and multiuser communications Provides insightful descriptions and intuitive explanations of all complex concepts Focuses on practical applications and illustrative examples. A companion Web site includes solutions to end-of-chapter problems and computer exercises, lecture slides, and figures and tables from the text

One of the first books in this area, this text focuses on important aspects of the system operation, analysis and performance evaluation of selected chaos-based digital communications systems – a hot topic in communications and signal processing.