FREQUENCY RECOVERY AND RECEIVER DESIGN ISSUES IN FBMC WIRELESS SYSTEMS

This Ph.D. dissertation deals with one of the most prominent example of MC modulation, Filter Bank MultiCarrier (FBMC) modulation, and aims at reporting the main results of our research activity carried out over the last three years in the field of FBMC wireless systems. The first chapter introduces the basic concepts of wireless communication channels and multicarrier modulation. In the first part, FBMC modulation is presented. We provide a detailed description of the modulator and demodulator architecture which are based on digital signal processing techniques. The last section is devoted to an overview of the main physical aspects of the recent TEDS ETSI standard for PMR/PAMR communications, which relies on the FBMC technique. The core topic of the second chapter is carrier frequency offset recovery (CFO) for FBMC transmission over time-frequency selective fading channels. After a brief statement of the problem, we analyse three different frequency estimation algorithms that arise from the maximum likelihood principle. Specifically the schemes exhibit an open-loop structure, intended for burst transmissions, and are all based on the use of known pilot symbols scattered across the transmitted burst. Performance analysis quantifies the accuracy of the proposed algorithms in typical mobile wireless scenarios, showing they outperform conventional NDA frequency recovery even combined with a lower computational complexity. The third chapter deals with receiver design issues for FBMC burst transmission over doubly selective fading channels with emphasis on synchronization and channel estimation aspects. Specifically, a ML-derived symbol timing recovery algorithm is proposed that relies on the transmission of a short known preamble. The carrier synchronization task is implicitly carried out by a properly modified Bayesian channel estimation algorithm that exploits pilot symbols uniformly spaced throughout the subcarriers. The proposed receiver architecture is thoroughly discussed and the schemes are assessed, evaluating their impact on the receiver performance in terms of FER in typical mobile wireless channel conditions.