  In this paper, we consider a two-hop amplify-and-forward (AF) relaying
system, where the relay node is energy-constrained and harvests energy from the
source node. In the literature, there are three main energy-harvesting (EH)
protocols, namely, time-switching relaying (TSR), power-splitting (PS) relaying
(PSR) and ideal relaying receiver (IRR). Unlike the existing studies, in this
paper, we consider $\alpha$-$\mu$ fading channels. In this respect, we derive
accurate unified analytical expressions for the ergodic capacity for the
aforementioned protocols over independent but not identically distributed
(i.n.i.d) $\alpha$-$\mu$ fading channels. Three special cases of the
$\alpha$-$\mu$ model, namely, Rayleigh, Nakagami-mandWeibull fading channels
were investigated. Our analysis is verified through numerical and simulation
results. It is shown that finding the optimal value of the PS factor for the
PSR protocol and the EH time fraction for the TSR protocol is a crucial step in
achieving the best network performance.
