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Channel Estimation Overhead Reduction For Downlink Fdd Massive Mimo Systems, Abderrahmane Mayouche
Channel Estimation Overhead Reduction For Downlink Fdd Massive Mimo Systems, Abderrahmane Mayouche
Graduate Theses and Dissertations
Massive multiple-input multiple-output (MIMO) is the concept of deploying a very large number of antennas at the base stations (BS) of cellular networks. Frequency-division duplexing (FDD) massive MIMO systems in the downlink (DL) suffer significantly from the channel estimation overhead. In this thesis, we propose a minimum mean square error (MMSE)-based channel estimation framework that exploits the spatial correlation between the antennas at the BS to reduce the latter overhead. We investigate how the number of antennas at the BS affects the channel estimation error through analytical and asymptotic analysis. In addition, we derive a lower bound on the spectral …
High Step-Up/Down Transformerless Multilevel Converter For Renewable Energy Applications, Haider Ghazi Mhiesan
High Step-Up/Down Transformerless Multilevel Converter For Renewable Energy Applications, Haider Ghazi Mhiesan
Graduate Theses and Dissertations
This thesis focuses on a high step-up/down transformerless dc-dc modular multilevel converter (MMC) that would be applicable to dc power systems. The design achieves high voltage ratios for interfacing renewable energy sources such as photovoltaic and line interactive Uninterruptible Power System (UPS) systems. The circuit topology provides for high step-up/down dc-dc conversion ratios using an MMC approach operating in resonant mode in order to improve overall efficiency. This topology operates to step-up the input voltage with 1:10 or larger conversion ratio. As a bidirectional converter, it also provides step-down capability at the same voltage ratio (10:1 or greater). The MMC …