Relay selection and power allocation for device-to-device communication underlaying heterogeneous cellular networks

This paper addresses the problem of relay selection and power allocation in a device-to-device (D2D) communication underlaying heterogeneous cellular network. For the femto user equipments (FUEs) relay selection, two novel relay selection metrics are derived, which take both the intra-tier and cross-tier interferences into account. Based on the proposed metrics, centralized and distributed methods with low complexity are proposed. Finally, to maximize the coverage probability of macro user equip ment (MUE), the optimal power allocation in MUE's two-hop link is obtained. Simulation results show that the proposed relay selection schemes outperform traditional max-min scheme, and the performance of the optimal power scheme is verified.