Power control for underlay in-band spectrum sharing in device-to-device communications

In this work, we consider a cellular cell with D2D links being activated. Besides, the transmission scheme is assumed to be OFDM. With the underlay in-band spectrum sharing scheme, the D2D links can access the spectrum occupied by the cellular links. Hence, the D2D links may interfere with the existing cellular links. Moreover, since the D2D links´ channels could overlap, the D2D links are modeled as parallel Gaussian interference channels. Our objective is to design a power control algorithm to maintain the existing cellular links´ performance and to maximize each D2D links´ transmission rate. The existing cellular links´ performance is measured by the outage probability of each subchannel. We formulate a generalized Nash game which is analyzed with the variational inequality theory. The players of the game is the D2D links and the coupled constraints of the players are the outage probability constraints of the cellular links. However, the problem is a non-convex one. By observing the problem structure, we are able to propose an efficient heuristic algorithm which can be implemented distributively. In the end, the performance of the algorithm is demonstrated with simulation results.