Ultra-Massive MIMO Communications in the Millimeter Wave and Terahertz Bands for Terrestrial and Space Wireless Systems
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Wireless communication systems have experienced substantial progress over the past few years. In parallel to the massive growth in the total number of wirelessly connected devices, there has been an increasing demand for higher speed wireless communication. Following this trend, wireless multi-hundred gigabit-per-second (Gbps) and terabit-per-second (Tbps) links are expected to become a reality in the next several years. In this context, millimeter wave (mmWave, 30–300 GHz) and terahertz (THz)-band (300 GHz–10 THz) communications are envisioned as key wireless technologies in the fifth generation (5G) and beyond eras. The very large available bandwidth at mmWave (with up to 10 GHz of consecutive bandwidth) and THz-band (with several hundreds of GHz) frequencies will alleviate the spectrum scarcity problem and capacity limitations in current wireless networks. Nevertheless, a major challenge at these frequencies is the limited communication distance, which results from the very high channel path loss and the limited transmission power of mmWave and THz transceivers. The objective of this thesis is to address the important problem inherent in these frequency bands for their applications in both terrestrial and space wireless systems. First, for the terrestrial wireless system, especially in the indoor communication scenario, a theoretical design of the Intelligent Communication Environments based on the ultra-massive multiple-input multiple-output (UM MIMO) platform is proposed. The aims of this design are to increase the communication distance and to extend coverage for users not directly visible to access points at mmWave and THz-band frequencies. The UM MIMO system, which is enabled by a type of two-dimensional artificial material of metasurfaces in mmWave or plasmonic antenna arrays at THz band, allows precise control and engineering of electromagnetic waves with sub-wavelength resolution. Second, with the utilization of large antenna arrays as reconfigurable reflectarrays in the Intelligent Communication Environments, in order to provide received signal strength improvement at end users, beamforming solutions for metasurface-based reflectarray are proposed. Dynamic radiation pattern design based on phase-gradient metasurfaces is presented. A further extension on polarization diversity is analyzed with a dual-polarization channel enabled by metasurfaces' polarization-tuning functionality. Third, an extended Kalman filtering approach is proposed and analyzed for the dominant path tracking at THz band, which provides an effective path-tracking solution in a non-stationary channel in a typical indoor office environment. Fourth, for future inter-satellite communications, the channel peculiarities in both the Earth's upper atmosphere and deep space on inter-satellite links (ISLs) operated in the mmWave and THz bands are characterized. In particular, effects of the charged particles on channel impairments and their impact on beam angle misalignment are analyzed. Last but not the least, owing to the benefit of the abundant spectrum resources at mmWave and THz bands, a multi-band communication for small satellites to meet the throughput requirements for inter-satellite data-intensive applications is proposed. This architecture can significantly leverage the capabilities of current small satellite networks, and will pave the way for the development of future satellite networks in the 6G and beyond era.