Joint Spectrum and Power Allocation for D2D Communications Underlaying Cellular Networks.

This paper addresses the joint spectrum sharing and power allocation problem for <bold>device-to-device</bold> (D2D) communications underlaying a <bold>cellular network</bold> (CN). In the context of <bold>orthogonal frequency-division multiple-access</bold> systems, with the uplink resources shared with D2D links, both centralized and decentralized methods are proposed. Assuming global <bold>channel state information</bold> (CSI), the resource allocation problem is first formulated as a nonconvex optimization problem, which is solved using convex approximation techniques. We prove that the approximation method converges to a suboptimal solution and is often very close to the global optimal solution. On the other hand, by exploiting the decentralized network structure with only local CSI at each node, the Stackelberg game model is then adopted to devise a distributed resource allocation scheme. In this game-theoretic model, the base station (BS), which is modeled as the leader, coordinates the interference from the D2D transmission to the <bold>cellular users</bold> (CUs) by pricing the interference. Subsequently, the D2D pairs, as followers, compete for the spectrum in a noncooperative fashion. Sufficient conditions for the existence of the <bold>Nash equilibrium</bold> (NE) and the uniqueness of the solution are presented, and an iterative algorithm is proposed to solve the problem. In addition, the signaling overhead is compared between the centralized and decentralized schemes. Finally, numerical results are presented to verify the proposed schemes. It is shown that the distributed scheme is effective for the resource allocation and could protect the CUs with limited signaling overhead. [ABSTRACT FROM AUTHOR]