Ergodic capacity in D2D underlay networks with varying user distribution

This paper provides a tractable framework to understand the performance of Device-to-device (D2D) underlay cellular networks. D2D communication can improve range, data rates and energy efficiency of cellular networks. However, analyzing performance of D2D techniques is non-trivial. In this paper, ergodic capacity of D2D underlay cellular networks is investigated using Poisson point process (PPP) models. Line-of-sight (LoS) components in D2D direct links are characterized via a Rician fading model. In addition, locations of D2D receiving users (DRUs) are assumed to be random with varying distribution. Specifically, we investigate two different cases of DRUs: (1) distance between a D2D user (DU) pair follows a uniform distribution and (2) a DRU is distributed uniformly in the circular area around its serving D2D transmit user (DTU). We derive, for the first time, closed-form results for ergodic capacity of D2D communications for a practical case with path loss exponent of 4. We demonstrate that our new analytical results better approximate the actual capacity relative to prior approaches.