Performance Analysis of Cooperative-Aerial-IRS-Assisted Heterogeneous Networks

Unmanned-aerial-vehicle (UAV) communications assisted by aerial intelligent reflecting surfaces (A-IRSs) have emerged as a highly regarded technology aiming to increase the communication capacity of cellular networks and improve user communication quality. However, the performance of combining UAV-carried A-IRSs with heterogeneous cellular networks (HetNets) has not been fully investigated. In this article, we develop a novel framework to analyze the downlink (DL) performance of an UAV-carried cooperative A-IRSs-enhanced HetNet. First, we model the cascaded fading of the A-IRS-assisted communication channel as a mixture of gamma variables and approximate its distribution function by using the moment matching method. Next, we obtain the exact closed-form expressions of the user-association probability and the probability density function (PDF) of the distance between any user and its serving BS. Then, we derive the Laplace transform of the received signal and the interference power of all types of users for our proposed A-IRS deployment strategy. Finally, we derive analytic expressions of the DL coverage probability and the energy efficiency of UAV networks, which are validated by the simulation results. The results demonstrate that our proposed theoretical framework significantly enhances the precision of analysis, and aligns closely with real-world scenarios. We also show the performance enhancement brought by cooperative A-IRSs, the advantages of our proposed A-IRS deployment strategy within HetNet, as well as the impact of the interference introduced by A-IRSs on direct transmissions.