Wireless Powered Cooperative Communication Using Two Relays: Protocol Design and Performance Analysis

This paper develops an adaptive cooperative transmission scheme with relays harvesting wireless energy. Two relays are adopted to alternately forward source data to the destination using the two-path successive relaying (TPSR) protocol. When one relay forwards previous data along with source transmitting current data, using the power-splitting technique, the other relay will harvest energy and decode the current data from the received composite signal. If the TPSR cannot be performed due to the failure of data decoding at either relay, the decode-and-forward (DF) protocol will be performed by selecting a better relay. If one relay joins in the DF relaying, it will harvest energy and decode source data using the PS technique, while the other relay will always harvest energy from the received signal. If neither TPSR nor DF relaying can be performed, the source will transfer wireless power to both relays. The transmit powers of relays and the PS ratio are judiciously determined through analyzing the occurrence probability, average power fading, and success probability of each case. Numerical results show that our adaptive relaying scheme can achieve a much higher throughput than the single-relay DF scheme and the TPSR-only scheme.