  Recently, joint wireless information and energy transfer (JWIET) methods have
been proposed to relieve the battery limitation of wireless devices. However,
the JWIET in a general K-user MIMO interference channel (IFC) has been
unexplored so far. In this paper, we investigate for the first time the JWIET
in K-user MIMO IFC, in which receivers either decode the incoming information
data (information decoding, ID) or harvest the RF energy (energy harvesting,
EH). In the K-user IFC, we consider three different scenarios according to the
receiver mode -- i) multiple EH receivers and a single ID receiver, ii)
multiple IDs and a single EH, and iii) multiple IDs and multiple EHs. For all
scenarios, we have found a common necessary condition of the optimal
transmission strategy and, accordingly, developed the transmission strategy
that satisfies the common necessary condition, in which all the transmitters
transferring energy exploit a rank-one energy beamforming. Furthermore, we have
also proposed an iterative algorithm to optimize the covariance matrices of the
transmitters that transfer information and the powers of the energy beamforming
transmitters simultaneously, and identified the corresponding achievable
rate-energy tradeoff region. Finally, we have shown that by selecting EH
receivers according to their signal-to-leakage-and-harvested energy-ratio
(SLER), we can improve the achievable rate-energy region further.
