  This study investigates wireless information and energy transfer for dual-hop
amplify-and-forward full-duplex relaying systems. By forming energy efficiency
(EE) maximization problem into a concave fractional program of transmission
power, three relay control schemes are separately designed to enable energy
harvesting and full-duplex information relaying. With Rician fading modeled
residual self-interference channel, analytical expressions of outage
probability and ergodic capacity are presented for the maximum relay,
signal-to-interference-plus-noise-ratio (SINR) relay, and target relay. It has
shown that EE maximization problem of the maximum relay is concave for time
switching factor, so that bisection method has been applied to obtain the
optimized value. By incorporating instantaneous channel information, the SINR
relay with collateral time switching factor achieves an improved EE over the
maximum relay in delay-limited and delay-tolerant transmissions. Without
requiring channel information for the second-hop, the target relay ensures a
competitive performance for outage probability, ergodic capacity, and EE.
Comparing to the direct source-destination transmission, numerical results show
that the proposed relaying scheme is beneficial in achieving a comparable EE
for low-rate delay-limited transmission.
