IEEE Signal Processing Society

As wireless technology begins to utilize physically larger arrays and/or higher frequencies, the transmitter and receiver will reside in each other’s radiative near field. This fact gives rise to unusual propagation phenomena, such as spherical wavefronts and beam focusing, creating the impression that new spatial dimensions—called degrees of freedom (DOF)—can be exploited in the near field.

Multichannel signal processing technologies are moving toward the deployment of small and densely packed sensors yielding extremely large aperture arrays (ELAAs) in order to provide higher angular resolution and beamforming gain. In particular, technologies are moving beyond the fifth-generation (5G) networks, wherein the adoption of ELAAs or surfaces and the exploitation of higher-frequency bands, e.g., terahertz