Fairness-Oriented Link Scheduling for a D2D-enabled LTE-U/Wi-Fi Coexistence Network

To avoid spectrum crunch and improve spectrum efficiency, the use of unlicensed spectra and the introduction of D2D communication will be areas of focus in communication development. However, in the existing unlicensed spectrum coexistence mechanism, different ways of communication are seen as hindering each other. In this paper, we deliberate the coexistence of a D2D-enabled LTE network with Wi-Fi under an unlicensed band. Unlike previous coexistence mechanisms, we allow co-channel transmission, and our goal is to make full use of the advantages of D2D proximity communication and achieve fairness in co-channel transmission. First, we modeled the coexistence network and derived the expressions coverage probability of all types of receivers. Based on the analytical model and simulation results, we prove that D2D communication can be exploited to achieve fairness requirements in co-channel transmission over the unlicensed band. We rephrase the fairness schedule problem as a mixed-integer nonlinear optimization problem for D2D density and transmit power, and we use an Ortho-MADS algorithm to solve it. The simulation results show that the proposed scheme can use D2D communication to improve the fairness of the system