A User Association and Energy Efficiency Analysis of D2D Communication under HetNets

Device-to-Device (D2D) communication bypassing the use of cell towers has been proposed in Long Term Evolution-Advanced (LTE-A) for supporting Proximity Services. This technology could provide improvements in both energy efficiency (EE) and spectrum efficiency (SE). In this paper, we investigate the D2D communication under heterogeneous cellular network (i.e., HetNets) and analyze system EE. First, user association of HetNets-supported D2D communication is formulated based on maximizing received power to associate users with macro cell, small cell, or D2D communication. Second, we applied a resource allocation algorithm, namely Sequential Max Search (SMS), for users communicating via D2D link. SMS algorithm minimizes interference from D2D users to cellular users and maximizes overall network throughput. Finally, we evaluate overall EE of the proposed system. Numerical evaluation of the proposed model shows improvement in terms of overall throughput and EE. Achieved EE of the system was approximately 85% for the upper bound using brute force.