Power control for device-to-device communications as an underlay to cellular system

In this work, we consider Quality of Service (QoS) guarantee for Device to Device (D2D) users co-existing with a cellular system where the D2D communication links are sharing radio spectrum resources with macrocell users in the downlink. Despite the lofty advantages associated with D2D communications, one major concern is the resulting interference from the D2D users, which should not infringe on the service quality requirements of the User Equipments (UEs). In this work, we investigate the scenario in which D2D communications operates simultaneously with downlink transmissions from the Evolved Node B (eNB). Power control problem for the D2D users is formulated in order to optimize the energy efficiency of the eNB users as well as to ensure that QoS of D2D devices and UEs does not fall below the acceptable target. The feasible conditions of the power control problem are derived and then the centralized and the distributed solutions are obtained. We further suggest jointly designed dynamic power control and channel re-allocation algorithm that will guarantee the priority of the UEs. Effectiveness of the proposed scheme is demonstrated through extensive simulations.