Throughput of Wireless-Powered Relaying Systems With Buffer-Aided Hybrid Relay

In this paper, we study a wireless powered co-operative communication system, which consists of a hybrid relay node ( RN), a source node ( SN), and a destination node ( DN). It is assumed that the hybrid RN has a constant power supply while the SN has no embedded power supply. Thus, the SN needs to first harvest energy from the radio frequency ( RF) signal broadcasted by the hybrid RN before transmitting information to the hybrid RN. By assuming that the RN has an information buffer and can temporarily store the information it received, we investigate the long-term throughput of two different blockwise cooperative protocols, namely the block-wise harvest-and-transmit ( BW-HaT) protocol and the block-wise mode adaptation ( BW-MA) protocol. For the BW-HaT protocol, the throughput expression is obtained in closed form. For the BW-MA protocol, the optimal mode adaptation method that maximizes the throughput of the system is presented and the maximum throughput is given for different system setups. It is shown that through simultaneously transmitting information and energy to the DN and SN, respectively, the proposed transmission schemes can significantly increase the system throughput.