Simultaneous wireless information and power transfer with energy-preserving relaying

Conventional simultaneous wireless information and power transfer (SWIPT) schemes generally assume that only the currently harvested energy will be used for the following signal forwarding. As a result, it is impossible to amplify the signal in theory. And even unfortunately, the forwarded signal power is splitted and the forwarded signal will be subject to severe attenuation when compared to the received signal, since there will be energy loss of circuit. On the other hand, in most cases, the signal is transmitted intermittently, i.e. sometimes the relay node will be idle, during which it can still harvest energy from the radio frequency interference around. And the harvested energy can be stored for future use. In this case, we analyze the optimal power splitting ratio and the maximal system throughput in full-duplex (FD) and half-duplex (HD) modes respectively. Numerical results show that the FD relay generally outperforms the HD relay but excessive energy supply will decrease the system throughput due to the increasing self-interference. The system throughput of HD relay will remain constant after it reaches a peak. Also, the impacts of other key system parameters, such as source power and distance, on the throughput of the energy-preserving FD/HD relay systems are analyzed.