Artificial Spatial Bandwidth

Bandwidth is an indispensable resource for wireless communication, positioning, and sensing, critically determining how fast a signal can vary in time. With congestion in the established radio bands and difficulties to tame new spectrum, space has gradually become the complementary realm on which to seek “bandwidth”. That space-domain counterpart to the bandwidth is the spatial bandwidth, which dictates how fast a signal can vary over space. And, just like the reciprocal of the bandwidth specifies how finely data symbols can be slotted in time, the reciprocal of the spatial bandwidth dictates how tightly antennas can be packed that spatially multiplex data, and how sharply positions can be resolved.

Determined by the richness of directions on which energy flows from transmitter to receiver, the spatial bandwidth has hitherto been governed by the propagation environment, to which systems can only adapt. The performance is therefore at the mercy of the ambient scattering. Moreover, the propagation thins out and becomes increasingly volatile as we push up in frequency seeking more bandwidth for the time domain. Thus, in the realm where the most bandwidth can be afforded, the spatial bandwidth is scant and erratic.

Now, with the emergence of reconfigurable intelligent surfaces, an active manipulation of the environment’s electromagnetic behavior is about to be feasible. While research has thus far focused on their role in enhancing the received power and sidestepping blockages, the true potential of these surfaces might lie elsewhere: they could serve as artificial scatterers, programmable and on-demand. Fending off the propagation thinning and ensuring tailored conditions, intelligent surfaces could deliver spatial bandwidths that are orders of magnitude superior and far more dependable. ARTBAND targets foundational work on how, to what extent, and at what expense, the inherent spatial bandwidth of natural settings can indeed be augmented.