Signal Acquisition and Tracking for Fixed Wireless Access Multiple Input Multiple Output Orthogonal Frequency Division Multiplexing

To, My father, Narendra and my mother, Jyotsna for their patience and support for all these years. iii PREFACE This thesis is an attempt to provide a holistic solution to the receiver implementation for the broadband fixed wireless access (BFWA) multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) systems. OFDM has been adopted into several wire-line and wireless standards for telecommunications. This is due to its ease in implementation and its robustness to the multi-path wireless channels. In addition, OFDM allows adaptive bit loading which can utilize the channel in an efficient manner. OFDM and MIMO form a strong companionship and complement each other in their capabilities. MIMO systems are slowly obtaining a wider acceptability because of the increasing capabilities of the digital signal processing (DSP) chips, application specific integrated circuits (ASICs) and field programmable gate array(FPGA)s, rendering the implementation of advanced signal processing algorithms no longer a difficult task. In addition, a strong demand for high-speed wireless applications has breathed a new life into research in these areas. In spite of all its advantages, such systems suffer from implementation and complexity issues which must be addressed before their successful deployment. MIMO systems require sophisticated algorithms and accurate system modeling for an efficient implementation. The implementation algorithms must focus on signal acquisition and tracking problems. Signal acquisition consists of time and radio frequency (RF) oscillator synchronization, sampling frequency (SF) offset estimation and correction, phase noise estimation and correction and finally channel estimation. Signal tracking consists of tracking all these parameters. In addition, a bench mark is needed to test the performance of these algorithms and this is can be obtained by deriving the Cramér-Rao bounds for such systems. So far, most authors have focussed on these issues individually and for single-input single-output (SISO) OFDM systems. Most of these problems are interconnected and need iv joint estimation for an efficient system implementation. Hence in this thesis we first try and understand this problem by developing a comprehensive system model for a MIMO-OFDM system under all these impairments [66], and later attempt to provide a solution to estimate the various parameters. We believe that this is just a starting point for this research and it will serve as a beginning for many more contributions in the future. v ACKNOWLEDGEMENTS First and foremost, I wish to express my deepest sense of gratitude to my advisor, Dr. Gordon L. Stüber, for being my mentor …