Secrecy-Rate Analysis in Multitier Heterogeneous Networks Under Generalized Fading Model

In this paper, the secrecy-rate characteristics of multitier downlink heterogeneous networks under generalized fading model is investigated for two types of base-station (BS)-user(s) association scenarios. Each tier within the network has a single multiantenna BS that intends to serve multiple single-antenna mobile users. These users are assumed to be distributed according to homogeneous Poisson point process (PPP) with particular density parameter. Single-antenna eavesdroppers which intend to wiretap the communication between the chosen BS and intended mobile user are also assumed to coexist within the network distributed as PPP with different intensity parameter. We have adopted the maximum received path gain, rather than distance, as a metric to describe the association scenario between a BS and typical user. Therefore, a typical user associates itself with: 1) a BS that provides the user with the maximum path gain or 2) any potential BS that provides the kth maximum path gain to the user. Using stochastic geometry as a tool, the received path gain distributions and the achievable average secrecy rate expressions from the perspective of association with the “best” and the kth best BS are analyzed analytically. Tractable numerical and simulation results are presented under various assumptions of fading scenario, path loss exponent, eavesdropper density, and antenna figures to support the lemmas and propositions stated within this paper.