  Physical layer security is known as a promising paradigm to ensure security
for the beyond 5G (B5G) networks in the presence of eavesdroppers. In this
paper, we elaborate on a tractable analysis framework to evaluate the
reliability and security of wireless-powered decode-and-forward (DF)
multi-relay networks. The nonlinear energy harvesters, in-phase and
quadrature-phase imbalance (IQI) and channel estimation errors (CEEs) are taken
into account in the considered system. To further improve the secure
performance, two relay selection strategies are presented: 1) suboptimal relay
selection (SRS); 2) optimal relay selection (ORS). Specifically, exact
analytical expressions for the outage probability (OP) and the intercept
probability (IP) are derived in closed-form. For the IP, we consider that the
eavesdropper can wiretap the signal from the source or the relay. In order to
obtain more useful insights, we carry out the asymptotic analysis and diversity
orders for the OP in the high signal-to-noise ratio (SNR) regime under
non-ideal and ideal conditions. Numerical results show that: 1) Although the
mismatches of amplitude/phase of transmitter (TX)/receiver (RX) limit the OP
performance, it can enhance IP performance; 2) Large number of relays yields
better OP performance; 3) There are error floors for the OP because of the
CEEs; 4) There is a trade-off for the OP and IO to obtain the balance between
reliability and security.
