MIMO Broadcasting for Simultaneous Wireless Information and Power Transfer

TLDR

Wireless power transfer offers a convenient, perpetual energy source for wireless networks and can be implemented via inductive coupling, magnetic resonance, or electromagnetic radiation for short‑ to long‑range applications. This study focuses on electromagnetic (radio‑signal) enabled wireless power transfer. The authors analyze a MIMO broadcast system with a common transmitter, an energy‑harvesting receiver, and an information‑decoding receiver, examining both separated and co‑located receiver configurations with multiple antennas. They derive the optimal transmission strategy and rate‑energy region for separated receivers, establish an outer bound for co‑located receivers, and evaluate time‑switching and power‑splitting designs against this bound.

Abstract

Wireless power transfer (WPT) is a promising new solution to provide convenient and perpetual energy supplies to wireless networks. In practice, WPT is implementable by various technologies such as inductive coupling, magnetic resonate coupling, and electromagnetic (EM) radiation, for short-/mid-/long-range applications, respectively. In this paper, we consider the EM or radio signal enabled WPT in particular. Since radio signals can carry energy as well as information at the same time, a unified study on simultaneous wireless information and power transfer (SWIPT) is pursued. Specifically, this paper studies a multiple-input multiple-output (MIMO) wireless broadcast system consisting of three nodes, where one receiver harvests energy and another receiver decodes information separately from the signals sent by a common transmitter, and all the transmitter and receivers may be equipped with multiple antennas. Two scenarios are examined, in which the information receiver and energy receiver are separated and see different MIMO channels from the transmitter, or co-located and see the identical MIMO channel from the transmitter. For the case of separated receivers, we derive the optimal transmission strategy to achieve different tradeoffs for maximal information rate versus energy transfer, which are characterized by the boundary of a so-called rate-energy (R-E) region. For the case of co-located receivers, we show an outer bound for the achievable R-E region due to the potential limitation that practical energy harvesting receivers are not yet able to decode information directly. Under this constraint, we investigate two practical designs for the co-located receiver case, namely time switching and power splitting, and characterize their achievable R-E regions in comparison to the outer bound.