  This paper investigates the simultaneous wireless information and power
transfer (SWIPT) precoding scheme for K-user multiple-input-multiple-output
(MIMO) interference channels (IC). In IC, interference alignment (IA) schemes
provide optimal precoders to achieve full degrees-of-freedom (DoF) gain. To
study a trade-off between harvested energy and sum rate, the transceiver design
problem is suboptimally formulated in literature via convex relaxations, which
is still computationally intensive, especially for battery limited nodes
running on harvested energy. In this paper, we propose a systematic method
using chordal distance (CD) decomposition to obtain the balanced precoding,
which achieves the improved trade-off. Analysis shows that given the
nonnegative value of CD, the achieved harvested energy for the proposed
precoder is higher than that for perfect IA precoder. Moreover, energy
constraints can be achieved, while maintaining a constant rate loss without
losing DoFs via tuning the CD value and splitting factor. Simulation results
verify the analysis and add that the IA schemes based on max-SINR or
mean-squared error are better suited for SWIPT maximization than subspace or
leakage minimization methods.
