Digital design and experimental validation of high-performance real-time OFDM systems

The goal of this Ph.D. dissertation is to address a number of challenges encountered in the digital baseband design of modern and future wireless communication systems. The fast and continuous evolution of wireless communications has been driven by the ambitious goal of providing ubiquitous services that could guarantee high throughput, reliability of the communication link and satisfy the increasing demand for efficient re-utilization of the heavily populated wireless spectrum. To cope with these ever-growing performance requirements, researchers around the world have introduced sophisticated broadband physical (PHY)-layer communication schemes able to accommodate higher bandwidth, which indicatively include multiple antennas at the transmitter and receiver and are capable of delivering improved spectral efficiency by applying interference management policies. The merging of Multiple Input Multiple Output (MIMO) schemes with the Orthogonal Frequency Division Multiplexing (OFDM) offers a flexible signal processing substrate to implement the PHY-layer of various modern wireless communication systems. This is mainly due to the fact that this technology combination is able to provide increased channel capacity and robustness against multipath fading channels. Additionally, Orthogonal Frequency Division Multiple Access (OFDMA) is augmenting the capacities of the MIMO-OFDMtechnology to serve various mobile subscribers at the same time. A prominent scheme proposed to capitalize the benefits of diversity is the closed-loop MIMO communications, where the receiver is providing information to the transmitter related to the current channel conditions by means of a dedicated feedback channel. In the transmitter, the Channel State Information (CSI) is exploited to adapt at run-time the transmission and, thus, take advantage of the capacities provided by MIMO-OFDM(A). The increased performance and flexible PHY-layer features of communication systems featuring MIMO-OFDM come at a cost of an increased computational load at baseband. Thus, innovating algorithmic, design and implementation solutions are required to provide the required PHY-layer schemes. Indeed, many levels of innovation are required to pass from a high-level model-based description of the system and its embedded algorithms to their digital realization. In fact, innovating digital design techniques aiming at maximizing the parallelization and resource re-utilization of the baseband Digital Signal Processing