Secrecy Capacity Analysis in D2D-Enabled Cellular Networks Under Power Control

Secrecy capacity is critical to support many security-sensitive applications in D2D-enabled cellular networks. Previous works on the study of secrecy capacity mainly consider a simple scenario with one base station (BS) and neglect the important issue of power control. To explore secrecy capacity under a general scenario with multiple BSs and power control, this paper uses stochastic geometry to develop a theoretical framework for the secrecy capacity analysis. With power control, each user equipment (UE), which has a maximum power constraint, can adjust its transmission power such that the received signal power in each BS is no less than a target threshold. To this end, we first derive the probability density function (PDF) of transmission power for each cellular UE and D2D one, and the corresponding moment of transmission power. Then, we proceed to derive the Laplace transform of the total interference at a typical BS and an eavesdropper, respectively. Based on these results, we further derive the rate of channel between a transmitting cellular UE and a BS and that between the cellular UE and a malicious eavesdropper. Finally, we obtain an expression for the expected secrecy capacity of cellular UE, which fully considers the issues of power control and interference from D2D UEs and cellular ones.