  We investigate the spectrum sharing problem of a radio frequency (RF)-powered
cognitive radio network, where a multi-antenna secondary user (SU) harvests
energy from RF signals radiated by a primary user (PU) to boost its available
energy before information transmission. In this paper, we consider that both
the PU and SU are rational and self-interested. Based on whether the SU helps
forward the PU's information, we develop two different operation modes for the
considered network, termed as non-cooperative and cooperative modes. In the
non-cooperative mode, the SU harvests energy from the PU and then use its
available energy to transmit its own information without generating any
interference to the primary link. In the cooperative mode, the PU employs the
SU to relay its information by providing monetary incentives and the SU splits
its energy for forwarding the PU's information as well as transmitting its own
information. Optimization problems are respectively formulated for both
operation modes, which constitute a Stackelberg game with the PU as a leader
and the SU as a follower. We analyze the Stackelberg game by deriving solutions
to the optimization problems and the Stackelberg Equilibrium (SE) is
subsequently obtained. Simulation results show that the performance of the
Stackelberg game can approach that of the centralized optimization scheme when
the distance between the SU and its receiver is large enough.
