MIMO with Energy Recycling

TL;DR

This paper explores a MISO system where antennas can switch between transmitting and harvesting energy, demonstrating that energy recycling can surpass traditional capacity limits and validating this with hardware experiments.

Contribution

It introduces an energy recycling scheme for MISO systems, develops efficient algorithms, and provides experimental validation of the benefits and practical considerations.

Findings

Recycling allows exceeding classical capacity limits.

An almost linear algorithm achieves near-optimal rates.

Hardware experiments confirm minimal rate loss with proper antenna spacing.

Abstract

We consider a Multiple Input Single Output (MISO) point-to-point communication system in which the transmitter is designed such that, each antenna can transmit information or harvest energy at any given point in time. We evaluate the achievable rate by such an energy-recycling MISO system under an average transmission power constraint. Our achievable scheme carefully switches the mode of the antennas between transmission and wireless harvesting, where most of the harvesting happens from the neighboring antennas' transmissions, i.e., recycling. We show that, with recycling, it is possible to exceed the capacity of the classical non-harvesting counterpart. As the complexity of the achievable algorithm is exponential with the number of antennas, we also provide an almost linear algorithm that has a minimal degradation in achievable rate. To address the major questions on the capability of recycling and the impacts of antenna coupling, we also develop a hardware setup and experimental results for a 4-antenna transmitter, based on a uniform linear array (ULA). We demonstrate that the loss in the rate due to antenna coupling can be made negligible with sufficient antenna spacing and provide hardware measurements for the power recycled from the transmitting antennas and the power received at the target receiver, taken simultaneously. We provide refined performance measurement results, based on our actual measurements.