  In this paper, we investigate joint antenna selection and spatial switching
(SS) for quality-of-service (QoS)-constrained energy efficiency (EE)
optimization in a multiple-input multiple-output (MIMO) simultaneous wireless
information and power transfer (SWIPT) system. A practical linear power model
taking into account the entire transmit-receive chain is accordingly utilized.
The corresponding fractional-combinatorial and non-convex EE problem, involving
joint optimization of eigen-channel assignment, power allocation, and active
receive antenna set selection, subject to satisfying minimum sum-rate and power
transfer constraints, is extremely difficult to solve directly. In order to
tackle this, we separate the eigen-channel assignment and power allocation
procedure with the antenna selection functionality. In particular, we first
tackle the EE maximization problem under fixed receive antenna set using
Dinkelbach-based convex programming, iterative joint eigen-channel assignment
and power allocation, and low-complexity multi-objective optimization
(MOO)-based approach. On the other hand, the number of active receive antennas
induces a trade-off in the achievable sum-rate and power transfer versus the
transmit-independent power consumption. We provide a fundamental study of the
achievable EE with antenna selection and accordingly develop dynamic optimal
exhaustive search and Frobenius-norm-based schemes. Simulation results confirm
the theoretical findings and demonstrate that the proposed resource allocation
algorithms can efficiently approach the optimal EE.
