  Simultaneous wireless information and power transfer (SWIPT) provides a
promising solution for enabling perpetual wireless networks. As energy
efficiency (EE) is an im- portant evaluation of system performance, this thesis
studies energy-efficient resource allocation algorithm designs in SWIPT
systems. We first investigate the trade-off between the EE for information
transmission, the EE for power transfer, and the total transmit power in a
basic SWIPT system with separated receivers. A multi-objective optimization
problem is formulated under the constraint of maximum transmit power. We
propose an algorithm which achieves flexible resource allocation for energy
efficiencies maxi- mization and transmit power minimization. The trade-off
region of the system design objectives is shown in simulation results. Further,
we consider secure communication in a SWIPT system with power splitting
receivers. Artificial noise is injected to the com- munication channel to
combat the eavesdropping capability of potential eavesdroppers. A
power-efficient resource allocation algorithm is developed when multiple
legitimate information receivers and multi-antenna potential eavesdroppers
co-exist in the system. Simulation results demonstrate a significant
performance gain by the proposed optimal algorithm compared to suboptimal
baseline schemes.
