Channel Estimation and Low-complexity Beamforming Design for Passive Intelligent Surface Assisted MISO Wireless Energy Transfer

TLDR

Passive intelligent surfaces are emerging as a low‑cost, green alternative to massive antenna arrays for achieving high energy‑beamforming gains. The study proposes a novel channel‑estimation protocol for passive‑intelligent‑surface assisted energy transfer from a multi‑antenna power beacon to a single‑antenna energy‑harvesting user. All computations are performed at the power beacon, which uses the channel estimates to derive near‑optimal active and passive beamforming designs that enable efficient energy transfer over extended coherence blocks. Numerical results show that with sufficient passive elements, the proposed designs achieve the target beamforming gain while reducing the active array size at the power beacon, and provide insights into the relative importance of array sizes at the surface and beacon.

Abstract

Usage of passive intelligent surface (PIS) is emerging as a low-cost green alternative to massive antenna systems for realizing high energy beamforming (EB) gains. To maximize its realistic utility, we present a novel channel estimation (CE) protocol for PIS-assisted energy transfer (PET) from a multiantenna power beacon (PB) to a single-antenna energy harvesting (EH) user. Noting the practical limitations of PIS and EH user, all computations are carried out at PB having required active components and radio resources. Using these estimates, near-optimal analytical active and passive EB designs are respectively derived for PB and PIS, that enable efficient PET over a longer duration of coherence block. Nontrivial design insights on relative significance of array size at PIS and PB are also provided. Numerical results validating theoretical claims against the existing benchmarks demonstrate that with sufficient passive elements at PIS, we can achieve desired EB gain with reduced active array size at PB.