Joint power loading and mode selection for network-assisted device-to-device communication

In this paper, a novel algorithm is proposed for joint power loading and resource allocation in network-assisted device-to-device (D2D) underlay communications. The non-convex problem of minimizing sum transmit power of system while satisfying per user rate constraints is solved via successive convex approximation (SCA). A single cell system with a number of D2D pairs is considered, where the communication links are allocated to operate in either cellular, orthogonal or direct D2D mode depending on the system setting. The robustness of the algorithm is guaranteed by utilizing augmented Lagrangian relaxation of the rate constraints with additional quadratic penalty terms. Numerical results indicate that the proposed algorithm is efficiently allocating the optimal power and resources for the D2D pairs. Furthermore, the sum power performance is improved when comparing to the scenario where all links are allocated solely either to the D2D mode or cellular transmissions modes.