Resource allocation and power control for underlay device-to-device communication in fractional frequency reuse cellular networks

The current state of device-to-device (D2D) communication in the presence of cellular network addresses two major challenges of interference as well as throughput inadequacy. Specifically, a D2D communication underlaying fractional frequency reuse (FFR) cellular network exhibits rather high interferences due to higher occurrence of band crossing within a shared spectrum. However, due to the considerable impact of D2D communications on spectral efficiency and system capacity, the remedy for those issues may include efficient techniques of interference mitigation and average spectral efficiency maximization. In this paper, we propose a resource block (RB) allocation scheme to reduce the co-channel interference by providing and maintaining adequate distance between D2D user equipment (DUE) and cellular user equipment (CUE), and between the macrocell base station and DUEs that are using the same RB. In the proposed scheme, we initially introduce a plan with one omnidirectional and three directional antennas be used to serve the CUE in the inner and outer regions of the FFR cell, respectively. In addition, DUE in each region uses the RBs that are orthogonal to those used by CUE. It is shown that by using two different ranges for inner region of cellular and D2D communication, the overall performance is improved. Furthermore, we formulate an optimization problem for maximizing average spectral efficiency while guaranteeing CUE signal-to-interference-plus-noise-ratio and achieve efficient solutions to the different average spectral efficiency maximization problems. The results demonstrate the efficiency of the proposed scheme. In addition, it is shown that significant improvement in system spectral efficiency is obtained through the optimization of DUE power. That is, the achieved throughput is much higher than that of the random resource allocation and 1.5–2 times of the previous works.