  Scavenging energy from ambient radio signals, namely wireless energy
harvesting (WEH), has recently drawn significant attention. In this paper, we
consider a point-to-point wireless link over the flat-fading channel, where the
receiver replenishes energy via WEH from the signals sent by the transmitter.
We consider a SISO (single-input single-output) system where the single-antenna
receiver cannot decode information and harvest energy independently from the
same signal received. Under this practical constraint, we propose a dynamic
power splitting (DPS) scheme, where the received signal is split into two
streams with adjustable power levels for information decoding and energy
harvesting separately based on the instantaneous channel condition that is
assumed to be known at the receiver. We derive the optimal power splitting rule
at the receiver to achieve various trade-offs between the maximum ergodic
capacity for information transfer and the maximum average harvested energy for
power transfer. Moreover, for the case when the channel state information is
also known at the transmitter, we investigate the joint optimization of
transmitter power control and receiver power splitting. Finally, we extend the
result for DPS to the SIMO (single-input multiple-output) system and
investigate a low-complexity power splitting scheme termed antenna switching.
