Transmission capacity of device-to-device communication under heterogeneous networks with cellular users assisted

This paper analyzes the transmission capacity of D2D (Device-to-Device) network in cellular and D2D heterogeneous networks(HetNets) with cellular users (CeUEs) assisted. The D2D network capacity can be enhanced by allocating a part of CeUE transmission power to assist D2D communication. By utilizing stochastic geometry, we first model the HetNets by homogeneous Poisson point process (HPPP). Secondly, we get the existence probability and the link distance expectation of the assisted CeUE. Thirdly, we analyze the scenario that the CeUE assists D2D communication and then obtain the successful transmission probabilities of the system. So we get the D2D network capacity and the system constraints. With the help of convex optimization, we deduce the optimal D2D density and the maximum D2D network capacity when the assisted CeUE power allocation coefficient is fixed. Then we proposed an algorithm to search the optimal D2D network capacity. At last, the simulation results demonstrate the optimal D2D network capacity and the optimal D2D density are impacted by the other system parameters as well as the interference of the HetNets.