Departament de Tecnologies de la Informació i les Comunicacionshttp://hdl.handle.net/10230/59222024-03-19T13:38:21Z2024-03-19T13:38:21ZLine-of-sight MIMO via intelligent reflecting surfaceLozano Solsona, Angelhttp://hdl.handle.net/10230/594902024-03-19T07:39:51Z2023-01-01T00:00:00ZLine-of-sight MIMO via intelligent reflecting surface
Lozano Solsona, Angel
2023-01-01T00:00:00ZPrecoding and reception for ULA-based wide-aperture MIMOMojahedian, Mohammad M.Lozano Solsona, Angelhttp://hdl.handle.net/10230/594892024-03-19T13:36:32Z2023-01-01T00:00:00ZPrecoding and reception for ULA-based wide-aperture MIMO
Mojahedian, Mohammad M.; Lozano Solsona, Angel
An approach is presented to compute the capacity-achieving precoder and receiver for wide-aperture MIMO with uniform linear arrays in O(N2min) operations as opposed to the O(N2minNmax) required by the singular-value decomposition of the channel matrix; Nmin and Nmax are the smallest and largest of the numbers of transmit and receive antennas. This hefty reduction in complexity comes at no cost in performance provided a parabolic wavefront model applies over the arrays, which is the case if the array apertures are not overly large relative to the range. Then, as the number of antennas grows larger, the proposed approach evolves into DFT-based precoders and receivers that are even more easily computable.
2023-01-01T00:00:00ZParabolic wavefront model for line-of-sight MIMO channelsDo, HeedongLee, NamyoonLozano Solsona, Angelhttp://hdl.handle.net/10230/594882024-03-19T13:30:59Z2023-01-01T00:00:00ZParabolic wavefront model for line-of-sight MIMO channels
Do, Heedong; Lee, Namyoon; Lozano Solsona, Angel
Motivated by the widespread adoption of the parabolic wavefront model for line-of-sight (LOS) multiple-input multiple-output (MIMO) communication, this paper presents a comprehensive analysis of this model’s validity and simple conditions that ensure its applicability. Then, with the model’s scope clearly delineated, the paper expounds a number of properties of the channel that results from applying it. Connections are drawn among these properties under the umbrella of a Fourier interpretation, and their significance to LOS MIMO communication is substantiated.
2023-01-01T00:00:00ZNeural geometrodynamics, complexity, and plasticity: a psychedelics perspectiveRuffini, GiulioLopez-Sola, EdmundoVohryzek, JakubSanchez Todo, Roserhttp://hdl.handle.net/10230/594742024-03-19T10:19:17Z2024-01-01T00:00:00ZNeural geometrodynamics, complexity, and plasticity: a psychedelics perspective
Ruffini, Giulio; Lopez-Sola, Edmundo; Vohryzek, Jakub; Sanchez Todo, Roser
We explore the intersection of neural dynamics and the effects of psychedelics in light of distinct timescales in a framework integrating concepts from dynamics, complexity, and plasticity. We call this framework neural geometrodynamics for its parallels with general relativity’s description of the interplay of spacetime and matter. The geometry of trajectories within the dynamical landscape of “fast time” dynamics are shaped by the structure of a differential equation and its connectivity parameters, which themselves evolve over “slow time” driven by state-dependent and state-independent plasticity mechanisms. Finally, the adjustment of plasticity processes (metaplasticity) takes place in an “ultraslow” time scale. Psychedelics flatten the neural landscape, leading to heightened entropy and complexity of neural dynamics, as observed in neuroimaging and modeling studies linking increases in complexity with a disruption of functional integration. We highlight the relationship between criticality, the complexity of fast neural dynamics, and synaptic plasticity. Pathological, rigid, or “canalized” neural dynamics result in an ultrastable confined repertoire, allowing slower plastic changes to consolidate them further. However, under the influence of psychedelics, the destabilizing emergence of complex dynamics leads to a more fluid and adaptable neural state in a process that is amplified by the plasticity-enhancing effects of psychedelics. This shift manifests as an acute systemic increase of disorder and a possibly longer-lasting increase in complexity affecting both short-term dynamics and long-term plastic processes. Our framework offers a holistic perspective on the acute effects of these substances and their potential long-term impacts on neural structure and function.
2024-01-01T00:00:00Z