What happens with a proportional fair cellular scheduling when D2D communications underlay a cellular network?

Device-to-Device (D2D) communications are seen as promising technology for future wireless systems. However, while underlying cellular networks they can negatively affect the performance of cellular communications when intra-cell spectrum sharing is enabled. The impact of D2D communications is not only seen on the cellular throughput, but also on the decision-making of the cellular scheduling policy. In this paper, we provide an impact assessment of D2D communications on the performance of Proportional Fair (PF) scheduling for a Long Term Evolution (LTE) multi-cell scenario through system-level simulations. Results show that due to excessive interference generated by D2D communications and depending on the accuracy of the link quality measure used to estimate the instantaneous data rate, a PF cellular scheduling policy may get stuck in an infinite loop and continuously selects the same User Equipments (UEs), which reduces the cellular throughput, or even approaches the performance of a Maximum Rate (MR)-based policy, thus affecting service coverage and fairness.