Simultaneous wireless information and power transfer in relay interference channels

Abstract

In this chapter, we extend our previous works [24, 25] to a more general scenario of relay interference channels with energy harvesting relays equipped with multiple antennas. It is worth pointing out that implementing multiple antennas at the relays is particularly appealing in practice since it can not only boost the amount of harvesting energy at the relay in the first hop but also enhance the strength of the received signal at the destination by exploiting the transmit diversity technique in the second hop. The power splitting technique is assumed to implement at relays. Specifically, each relay node splits the signal received from all sources into two parts according to a power splitting ratio: one part is sent to the information processing unit, and the rest is used to harvest energy for forwarding the received information in the second time slot. We consider that each link's performance is characterized by its achievable rate and thus regard the sum-rate of all links as a network-wide performance metric. However, the network-wide sum-rate maximization problem of the considered system is shown to be analytically non-tractable due to its complexity and non-convexity. Motivated by this, we propose a heuristic two-stage network optimization approach. Specifically, considering the energy harvesting feature of the relays, we first figure out that the maximum ratio combining/maximal ratio transmission (MRC/MRT) scheme would be a particularly appropriate signal processing technique for the relays in practice owing to its low complexity and light requirement of channel state information (CSI). In the second stage, we optimize the power splitting ratios of the relays with the selected MRC/MRT technique.