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With increasing demand on wireless internet and personal multimedia, the data rate of wireless communications is expected to increase dramatically. Future wireless networks face challenges of supporting data rates higher than one gigabits per second. Among various technologies, multi-antennas, also known as multiple-input multiple-output (MIMO), are undoubtedly the most promising to enable higher data rates. By employing the extra degrees of freedom in the spatial domain, multi-antenna techniques enhance the wireless communication systems through array gain, spatial diversity, and spatial multiplexing. Although multi-antenna systems have been utilized for more than ten years, a thorough analysis of various aspects of multi-antenna systems and the potential applications of MIMO technology need to be explored.
In this dissertation, we explore some new features of multi-antenna systems. After introducing the fundamentals of radio propagations, we first study long-range channel prediction and the I/Q imbalance compensation in MIMO-OFDM systems. A novel multi-block linear channel predictor is proposed for limited feedback precoded spatial multiplexing MIMO-OFDM systems, and a new virtual channel method is proposed to analyze the I/Q imbalances in a MIMO-OFDM wireless communication system over multipath fading channels. We then provide a detailed study of recent advances in distributed MIMO technologies in cooperative wireless networks. We also utilize the MIMO technique to enhance the self-encoded spread spectrum (SESS) systems, resulting in a robust MIMO-SESS system. Finally, we present a novel physical-layer technique to secure wireless communications by transmitting artificially generated jamming noise signals that can deteriorate the signal quality at the eavesdroppers.
Advisor: Yaoqing (Lamar) Yang