Advanced Coding and Signal Processing Methods for Multiuser MIMO Systems

Resumo

Wireless communication systems have experienced a non-stopping growth in the last few years and are expected to grow even more in the following years, supported in their deployment by novel coding and signal processing techniques. Multimedia and mobile data-based services are increasingly in demand for online work and socialization purposes, and novel coding and signal processing techniques are required to cope with their implementation. These techniques are expected to accomplish improvements in terms of data rates, energy efficiency, reliability, etc. The use of encoding techniques plays an essential role in the deployment of emerging wireless communications networks. Nowadays, most communication systems are designed following a digital approach and according to the separation principle. However, communication systems based on the optimization of joint source-channel coding (JSCC) still arouse the interest of researchers, especially in the case of analog signal transmission. The researchers rely on the capability of this strategy to approach theoretical limits and offer advantages over digital systems, e.g., low complexity and minimal delay. Nowadays, the application of novel signal processing techniques is essential for the implementation of emerging wireless communications networks. Specifically, in the millimeter-wave (mmWave) band—which has received high interest for the deployment of 5G and beyond—hybrid architectures have recently offered an innovative approach to increase the energy efficiency of the systems. These architectures are based on decoupling the digital precoding used in multiple-input multiple-output (MIMO) systems into a low-complexity analog part and a baseband part. Most approaches related to the source coding and the MIMO precoding are conditioned to the wireless channel, which usually remains uncontrollable. Fortunately, the paradigm of propagation environment control is being considered for emerging wireless communications networks. This paradigm had previously been used for radar and satellite applications by means of reflecting surfaces but it was not considered for mobile communications due to the inability to cope with the dynamic wireless channels because of user mobility. However, currently, the advances obtained in the study of meta-materials provide certain guarantees for reconfigurability by enabling real-time phase shifts in the intelligent reflecting surfaces (IRSs). In this thesis, we analyze and implement new coding methods for analog signals based on the JSCC optimization principle. We also analyze and implement novel signal processing techniques applied to hybrid architectures in the mmWave band. Finally, we develop signal processing techniques for better control of the propagation environment through the IRSs.