Two-Stage Matching for Energy-Efficient Resource Management in D2D Cooperative Relay Communications

Device-to-device (D2D) cooperative relay can assist users with inferior channel conditions to implement multi-hop transmissions, improving network coverage and throughput. However, energy efficiency is an important issue to be optimized because of the limited battery capacity of handheld equipments. Considering a two-hop D2D relay communication scenario, this paper proposes a resource management approach that jointly optimizes relay selection, spectrum allocation, and power control, so that the total energy efficiency of D2D links is maximized while guaranteeing the quality of service (QoS) requirements of D2D and cellular links at the same time. Since the formulated joint optimization problem involves a four-dimensional matching that is NP-hard, we propose a pricing-based two-stage matching algorithm to reduce dimensionality and provide a tractable solution. In the first stage, the spectrum resources reused by relay-to-receiver links are determined by a two-dimensional matching. Then, a three- dimensional matching is conducted to match users, relays, and the spectrum resources reused by transmitter-to-relay links. The optimal transmit power is solved during the preference establishment process in the second stage. As shown in simulation results, the proposed algorithm not only performs good on energy efficiency, but also enhances the average number of served users in comparison to the case without any relay.