  An underlay cognitive radio network with energy harvesting is considered
which operates in slotted fashion. The primary user (PU) transmits with a
constant power in each slot, while the secondary user (SU) either harvests
energy from primary's transmission or transmits its data. We propose an optimal
offline harvest-or-transmit strategy where in each slot, SU takes a decision
whether to harvest energy or transmit its data limiting interference at the
primary receiver. We aim to maximize the achievable rate of SU under energy
causality and interference constraints. The optimization problem is formulated
as a mixed integer non-linear program and the optimal harvest-or-transmit
policy is obtained using generalized Benders decomposition algorithm. Through
simulations, we analyze the effects of various system parameters and
interference constraint at the primary receiver on the optimal policy.
