Millimeter wave (mmWave) communications have garnered considerable attention in recent years due to their potential to deliver extremely high data rates by leveraging the large available bandwidth at high frequencies. However, the directional nature of mmWave propagation, along with its sensitivity to blockage and mobility, imposes strict requirements on how devices align and maintain their beams. Fully digital transceivers, while offering great flexibility, are impractical at these frequencies due to cost, size and power consumption. As a result, there is a growing interest in more hardware efficient analog and hybrid digital-analog (HDA) architectures, which call for novel signal processing strategies to manage beams effectively under resource constraints. This thesis focuses on beam management, encompassing the problems of alignment, refinement, and tracking. Beam alignment (BA) refers to the task of discovering viable directions for transmission and reception, based on predefined beamforming codebooks. Refinement aims to improve upon this initial choice, moving from a coarse grid of directions to a more accurate, unconstrained solution. Tracking is the process of maintaining alignment over time as users move. Throughout the thesis, we explore how tools and concepts from integrated sensing and communication (ISAC) can support beam management by enabling the extraction of spatial and temporal information without dedicated signaling. BA is studied in two representative scenarios: outdoor cellular networks and indoor device-to-device (D2D) networks. These environments present fundamentally different channel characteristics and system constraints. Outdoor cellular systems face long ranges, low pre-beamforming signal to noise ratios (SNRs), and centralized coordination, while indoor D2D networks operate over shorter distances, often with better SNR but stricter constraints on energy and hardware. The thesis proposes tailored methods for each of these cases, taking into account their unique challenges and exploiting their respective advantages. Beam tracking (BT) is investigated primarily in outdoor mobile scenarios, where mobility is higher and maintaining alignment over time becomes expensive in terms of overhead. The choice of beamforming architecture among fully analog, HDA or digital has a strong impact on the feasibility and accuracy of tracking strategies. We show that different classes of architectures require distinct algorithmic approaches, and we explore the trade-offs between implementation complexity, energy efficiency, and tracking precision. In summary, the thesis presents a set of scalable, hardware friendly solutions for beam management in mmWave networks, with particular emphasis on leveraging sensing capabilities and adapting to the practical limitations of constrained transceiver designs. The results demonstrate that efficient and reliable mmWave communication is achievable, even in the presence of hardware limitations, paving the way for the integration of such systems into future wireless standards.
Fernando Pedraza Nieto (Thu,) studied this question.