Simultaneous Wireless Information and Power Transfer with Finite-Alphabet Inputs

Simultaneous wireless information and power transfer (SWIPT) is a promising solution to carry energy as well as information at the same time for wireless networks. In this paper, we consider a precoding matrix design for multiple-input multiple-output (MIMO) SWIPT systems with finite-alphabet inputs. The problem can be formulated as maximizing the mutual information given the energy level and the power constraint for achieving a so-called rate-energy region. The formulated problem is non-concave, which can be reduced to a convex power allocation problem by the proposed gradient-descend design of the precoding matrix. Several rate-energy regions can be achieved by trading off between the information rate and the harvested energy with different schemes. Simulation results indicate that the proposed scheme with finite-alphabet inputs provides significant performance gain over existing schemes with Gaussian inputs.