6. Power Control in D2D Underlay Distributed Antenna Systems

A new scenario is considered that device-to-device (D2D) communication users underlay the spectrum resource of cellular user in distributed antenna systems (DAS) is discussed in this paper. We mainly focus on how to improve spectral efficiency (SE) and energy efficiency (EE) of the system. Under the maximum transmit power constraint per antenna unit, we propose two resource allocation algorithms to solve the optimal problems of maximum SE and EE. The first problem can be transformed into a difference of convex (DC) structure problem by function recombination, then the concave-convex procedure (CCCP) algorithm and the interior point method which are adopted to get the optimal solutions for the maximum SE. Subsequently, by using the Dinkelbach algorithm based on the parameter method, a power allocation algorithm for energy efficiency is developed to solve the maximum EE optimization problem. The optimal solutions are also obtained by the CCCP algorithm and the interior point method. Simulation results show that compared to co-located antenna systems (CAS) with D2D users, the SE and EE performances of the proposed system have a significant improvement.