Polarization and index modulationsa theoretical and practical perspective

Resumo

Radiocommunication systems have evolved significantly in recent years in order to meet present and future demands. Historically, time, frequency and more recently, spatial dimensions have been used to improve capacity and robustness. Paradoxically, radiocommunications that leverage the polarization dimension have not evolved at the same pace. In particular, these communications are widely used by satellites, where several streams are multiplexed in each orthogonal polarization. Current communication trends advocate for simplifying and unifying different frameworks in order to increase flexibility and address future needs. Due to this, systems that do not require channel information are progressively gaining traction, as they help to improve the overall quality of the network instead of that of specific users only. The search for new paradigms aimed at improving the quality of wireless communications is unstoppable. In order to increase the capacity of current communications systems, new horizons and physical dimensions must be explored. This dissertation aims at challenging this perspective and promoting the use of polarization in new radiocommunication systems. Consequently, the goal of this thesis is twofold: first, we aim at increasing the current capacity of point-to-point and point-to-multipoint links. Secondly, we introduce new mechanisms to increase the robustness of communications in particularly hostile environments. In this context, this thesis advocates for the use of polarization as a dimension to be exploited in radiocommunications. In addition to the use of polarization, index modulations help increase transmission rates whilst improving robustness against errors and imperfections with a low computational complexity. Thus, the study of polarization in these systems is essential. This dissertation explores primordial aspects in this area, such as channel capacity, transmitter and receiver design and performance benchmarking with current systems. Finally, we identify and discuss various characteristic aspects of polarization. In this thesis, the reader will navigate the mathematical foundations of the proposed concepts as well as their implementation in real-life scenarios.