Two-level game for relay-based throughput enhancement via D2D communications in LTE networks

In this paper, we facilitate device-to-device (D2D) communications to provide relay assistance to cell-edge user equipments (UEs) with the objective of improving system throughput. We first formulate a joint problem of relay node selection which helps cell-edge UEs find the proper relay nodes, as well as spectrum allocation for D2D links to maximize the system throughput with interference constraints to both D2D and traditional cellular UEs. Furthermore, we propose a distributed algorithm adopting a two-level game model which consists of inner and outer levels to solve the formulated problem. In the inner level, we use the Stackelberg game to select relay nodes for cell-edge UEs, where the relay nodes act as the leaders and the cell-edge UEs act as the followers. In the outer level, the coalition formation game is used to allocate proper spectrum for the D2D links between cell-edge UEs and their relay nodes. The games do not proceed separately, but are dependent on each other, which improves the efficiency of the proposed game model. Simulation results demonstrate that the proposed algorithm outperforms the benchmarks in terms of system throughput.