Cooperative Spectrum Sharing in Cognitive Radio Networks: A Game-Theoretic Approach

We consider the problem of cooperative spectrum sharing among a primary user (PU) and multiple secondary users (SUs), where the PU selects a proper set of secondary users to serve as the cooperative relays for its transmission. In return, the PU leases portion of channel access time to the selected SUs for their transmissions. The PU decides the portion of channel access time it will leave for the selected SUs (i.e., the cooperative relays), and the cooperative relays decide their respective power level used to help PU's transmission in order to achieve proportional access time to the channel. We assume that the PU and SUs are rational and selfish, i.e., they only aim at maximizing their own utility. Since an SU's utility is a function of its own transmission rate and the power cost for PU's transmission, it will choose a proper power level to meet the tradeoff between transmission rate and power cost. The PU will choose a proper portion of channel access time for the cooperative relays to attract them to employ higher power level. We formulate the problem as a noncooperative game between the PU and the SUs, and prove that the proposed game converges to a unique Stackelberg equilibrium. By employing an iterative updating algorithm, we can achieve the unique equilibrium point.