Receiver-Aware Near-Field Wavefront Engineering for sub-Terahertz Wireless Communications

Sub-terahertz and terahertz communication systems have brought practical propagation distances into the near field, where conventional far-field beamforming faces performance degradation. Therefore, various alternative electromagnetic wavefronts have been recently studied for near-field (sub-)terahertz communication systems to enhance the link performance. However, when investigating near-field wavefronts, most works to date focus primarily on the transmitter side (what kind of wavefront or beam type can be generated) but ignore entirely or, at best, notably simplify the receiver model (how this new custom wavefront can be received in practice). To address this gap, for the first time in this work, we derive the mathematical formulation of a wavefront optimization model that leverages additional information on the receiver side. Particularly, we show that receiver capabilities, orientations, and aperture sizes provide profound insights into the choice of wavefront to transmit. We formulate a relevant RX-aware performance metric (conjugate received power) and offer a new intuition for wavefront optimization in end-to-end near-field communication systems. Based on these principles, we present novel RX-aware wavefronts, including quadri-beams that achieve on average a 4.5 dB improvement compared to conventional focused beams - currently presumed optimal for LOS near-field scenarios - across 1000 randomly simulated LOS environments, which is further validated by preliminary D-band experiments.