Most wireless communications systems currently operate in the far field, at transmitter-receiver
distances that are large with respect to their antenna sizes. Recently, interest has grown to
investigate wireless links in the radiative near-field, at distances smaller than or comparable to the
antenna system‘s dimensions. Such reduced distances yield stronger received signals while the
radiative near-field’s complexity offers more degrees of freedom for spatial multiplexing and 3D
focusing. In spite of the many research efforts, a systematic and synergistic approach, jointly
tackling all challenges on antenna system design, propagation channel characterization, and
analog/digital multi-antenna signal processing, is still lacking.
We first study the near-field channel characteristics for distributed antenna systems of growing
complexity and with optimized topology. Results are incorporated in our near-field channel model,
previously developed for wireless power transfer. This model serves as a foundation for novel
hybrid focusing and spatial multiplexing algorithms that increase the signal-to-noise-andinterference
ratio and the data throughput. A stochastic framework accounts for performance
degradations, due to random variations in the antenna’s positions and orientations, and imperfect
channel state information. All newly developed techniques are validated through experiments on
proof-of-principle implementations.