  This letter analyzes the performance of simultaneous wireless
information-and-power transfer (SWIPT) in an overlay cognitive radio network
(CRN) under Nakagami-$m$ fading. A pair of secondary users (SUs) is considered
in which one SU facilitates relay cooperation for communications between two
primary users (PUs). In return, SUs make use of primary users' signals for
energy harvesting (EH) and realize their own communications. In such a network,
end-to-end bidirectional communications between the two PUs and unidirectional
information exchange between the SUs can be performed in three phases. A power
splitting (PS) based approach is adopted for enabling SWIPT. The relaying SU
applies an amplify-and-forward (AF) protocol to broadcast primary and secondary
signals, whereas the PUs perform selection combining to access the active
direct link. Accurate expressions of the outage probability (OP) and throughput
are derived for the primary system by considering a nonlinear energy harvester
at the relaying SU under Nakagami-m fading
