  In this paper, we consider an energy harvesting cognitive radio network
(EH-CRN), where a primary and a secondary user coexist in underlay mode. Both
the transmitters have energy harvesting capability and are equipped with finite
capacity battery to store the harvested energy. In addition, the secondary user
(SU) has an independent energy transfer unit such that it can transfer some
portion of it's harvested energy to the primary user (PU). We obtain an optimal
transmit power and energy transfer policy for single-slot and a suboptimal
policy for multi-slot scenario maximizing the number of bits transmitted by SU
under the primary sum-rate constraint in an offline setting. For both cases,
the effect of energy cooperation on the system performance is studied and it is
observed that energy cooperation results in higher SU throughput.
