Analysis of outage probability for in-band device-to-device communications underlaying cellular network

Summary One of the key strategies for jointly increasing throughput and optimum resource allocation in 5G is device-to-device (D2D) communications, which can be obtained by minimizing the outage probability considered as an objective function of optimization problem. To minimize this objective function, we found that outage probability should be modeled by jointly considering the effect of interference, noise, and multipath phenomena. In this paper, the exact formulas for outage probability of in-band D2D communications underlying cellular network are proposed. In the proposed model, additive white Gaussian noise and Rayleigh multipath fading are considered into 2 radio resource reuse scenarios. In the first scenario, each D2D pair is allowed to reuse radio resource block of one cellular user, whereas in the second scenario, 2 resources of 2 cellular users can be reused. The proposed formulas are compared to the approximate (nonexact) ones, which models additive white Gaussian noise by a constant variance. The numerical analysis for the first and second scenarios show that the approximate formulas and respected exact ones are in accordance with simulation results in MATLAB. Moreover, based on nonorthogonal multiple access approach, 2 approximations for the nonexact and the proposed formulas are extracted, which are acceptable for multiple resource reuse scenario. As a remarkable result, simulation results show that when the distance of the D2D pair from the respected cellular user is more than 71 m (2 times greater than average distance between the D2D nodes), multiple-reuse scenarios offer higher throughput compared to 1-reuse scenario in an acceptable outage probability.