Habilitation Theses:

S. Schwarz:
"Mobile Wireless Communications for a Society in Motion";
TU Wien/ETIT, 2019.

English abstract:
This habilitation thesis is based on a collection of journal articles and conference publications dealing with single- and multi-point transmission optimization and analysis of mobile wireless communications, with main focus on time-variant scenarios. The motivating communication scenario underlying this thesis is determined by tomorrow´s Society in Motion, in which large numbers of mobile users (humans and autonomous machines) with varying quality of service requirements (throughput, latency, reliability) will simultaneously
demand high performance dependable wireless connectivity. Satisfying such requirements poses significant challenges on mobile wireless communications, in particular when users are moving with relatively high velocity through the network coverage area. In this thesis, I
present my research within four closely connected research fields addressing these challenges to enable efficient and dependable wireless communications for the Society in Motion: Link and System Level Modeling and Simulation: Link and system level simulations
build the basis for accurate and realistic performance investigation of mobile communication systems. They are indispensable for rapid prototyping of novel signal processing methods and enable benchmarking against state-of-the-art standardized approaches. I present our
link and system level simulation methodologies and abstraction techniques, which provide the means to analyze the transceiver designs developed in this thesis within realistic environments, in order to gauge their practical value. Acquisition of Channel State Information at the Transmitter: Channel state information at the transmitter (CSIT) builds the fundamental basis for advanced multi-antenna and multipoint transceiver optimization. However, acquiring accurate CSIT with acceptable overhead is challenging, especially in high mobility scenarios and frequency division duplex (FDD) systems. I provide a general classification scheme of CSIT acquisition methods and present
my contributions within the field of so-called limited feedback techniques. Specifically, I discuss my implicit and explicit channel state information (CSI) feedback algorithms, which exploit the algebraic topological structure imposed by specific classes of transmission schemes, as well as, the characteristics of the wireless propagation environment to achieve an efficient CSI quantization.
Multi-User Resource Allocation and Robust Transmission Optimization: Having CSIT available allows to optimize the multi-user resource allocation and the multi-antenna transmit processing to achieve satisfactory, efficient and reliable transmissions. However, CSIT
imperfections due to estimation and quantization errors, as well as, channel aging, fundamentally impair the achievable performance. I provide a discussion on theoretical performance limitations imposed by imperfect CSIT concerning the outage probability and the achievable
degrees of freedom of the wireless transmissions. I moreover present my transceiver designs that account for CSIT imperfections to enhance the robustness and resilience of the communication system, in order to provide efficient and dependable wireless connectivity even with imperfect CSIT. Coordinated Transmission and Interference Management: Spatial densification of wireless networks is the major approach to sustain the ever-increasing capacity demands of mobile networks. However, increasing mutual interference amongst transmission points restricts the achievable spectral efficiency and impairs the reliability of the wireless connectivity. These interference limitations can be mitigated through multi-point coordination and joint transmission. I provide an overview of multi-point interference management techniques for unicast and multicast transmissions. I discuss the importance of multicast transmissions for cellular-assisted vehicular communications, which is one of the central use-cases underlying the Society in Motion. I furthermore present my multi-point coordination techniques for the multi-antenna multicast interference channel, which support weighted sum-rate maximization through distributed transmission optimization. The scientific results discussed within this thesis support reliable and efficient multiantenna and multi-point wireless communications, while providing robustness with respect to CSI imperfections, thus building a corner stone for mobile communication systems that are capable of supporting the requirements imposed by the envisioned Society in Motion.

Electronic version of the publication:

Created from the Publication Database of the Vienna University of Technology.