TY  - THES
T1  - Synchronization Algorithms for OFDM Systems (IEEE802.11a, DVB-T) : Analysis, Simulation, Optimization and Implementation Aspects
A1  - El Hajjar,Charbel
Y1  - 2008/05/06
N2  - Orthogonal Frequency Division Multiplexing (OFDM) or Multi-carrier Modulation (MCM) is a digital modulation technique that supports high-rate data with sufficient robustness to radio channel impairments (especially multi-path propagation). Due to that, it is emerging as the modulation technique used for the new generation of wireless communication systems (IEEE802.11a and DVB-T). However, one of the arguments against OFDM is that it is highly sensitive to synchronization errors. This raises up the need for optimum synchronization algorithms for OFDM applications such as IEEE802.11a and DVB-T. In this thesis several synchronization algorithms are presented. We focus on the implementation aspects of synchronization algorithms and propose optimizations which lead to well performing and robust fixed point implementations. In addition, complexity and cost needed for such a project are analyzed leading to a model for classifying different algorithms depending on cost, time-to-market, and performance. Chapter 1 is a short introduction. The use of OFDM in high data-rate communication systems is presented. In addition, the necessity of synchronization in OFDM systems opens way for the research done in the following chapters. Chapter 2 is a general overview of OFDM systems. It deals with the basics of the OFDM technique in addition to the IEEE802.11a Wireless Local Area Network (WLAN) standard and the DVB-T standard which are explained briefly. Two important synchronization problems are presented: Timing and frequency errors and their consequences. Chapter 3 gives an overview on synchronization principles of IEEE802.11a and DVB-T which will be used later in Chapter 4 and 5. The above chapters give the needed background for the research done in this thesis. In addition, the following chapters deal with the newly performed results for the two OFDM applications: IEEE802.11a and DVB-T, which include algorithmic and implementational optimizations. In chapter 4, IEEE802.11a synchronization is treated in details. This includes a fixed point implementation of an IEEE802.11a in SystemC. In addition, possible algorithmic optimizations aiming at decreasing the complexity of an IEEE802.11a synchronizer and maintaining a very well performance are presented. In chapter 5 a similar treatment for the DVB-T system is presented. A fixed point implementation is studied, as well as algorithmic optimizations for increasing the performance and robustness of the DVB-T synchronizer with the lowest cost are discussed. Cost analysis methods are presented in chapter 6. Effort and manpower for the studied algorithms are estimated. The new optimization ideas presented in the previous chapters are used to develop a new model for choosing the optimal synchronization algorithm depending on the cost, time-to-market, and performance desired. The thesis concludes in chapter 7 which is a general overview summary of the work, opening new issues for further continuing research.
KW  - OFDM
KW  - DVB-T
KW  - Maximum-Likelihood-Schätzung
CY  - Erlangen
PB  - Universitätsbibliothek der Universität Erlangen-Nürnberg
SN  - 978-3-8167-7590-4
AD  - Universitätsstraße. 4, 91054 Erlangen
L2  - http://www.opus.ub.uni-erlangen.de/opus/volltexte/2008/912
ER  -