On the Physical Layer Security Analysis of Hybrid Millimeter Wave Networks

TLDR

Millimeter‑wave bands are being adopted for 5G to meet rising data demands, yet their high propagation loss and blockage sensitivity require advanced techniques such as optimal precoding, spatial reuse, and hybrid mmWave‑overlaid microwave deployments. This study evaluates the security performance of hybrid mmWave‑overlaid microwave cellular networks. We formulate a mathematical framework that derives connection outage, secrecy outage, and average secrecy rate expressions—including fading and blockage effects—and propose a received‑signal‑strength based association scheme between mmWave and microwave tiers, with exact secrecy rate obtained via moment‑generating and Laplace transforms. The derived formulas are corroborated by simulations, demonstrating how antenna gain, eavesdropper density, base‑station density, and blockage density influence secrecy performance.

Abstract

To cope up with the explosive growth of mobile data demand, the fifth-generation mobile network intents to exploit the available spectrum in millimeter-wave (mmWave) band to boost the communication capacity. However, for a potential mmWave communication to happen, challenges, as propagation losses and blockages, have to be dealt with. Abundant literature illustrating techniques to circumvent these challenges and increase the cellular capacity can be found. Among the approaches used to overcome the challenges in mmWave networks, optimal transmit precoding design, spatial reuse of mmWave base stations (BSs), and mmWave-overlaid microwave (μWave) cellular networks are employed. This paper focuses on the performance analysis of mmWave-overlaid microwave cellular networks, from security perspective. We particularly developed a mathematical framework to analyze the connection outage probability, the secrecy outage probability, and the achievable average secrecy rate of the hybrid mmWave network, while taking fading and the impact of blockages into consideration. Moreover, based on the received signal strength, we formulated a scheme for a generic mobile user to be associated with either the mmWave or μWave network. The exact average secrecy rate of mmWave networks is also formulated using moment generating and Laplace functions as a tool. The derived analytic expressions are validated via simulation results; for different antenna gain, eavesdropper density, BS, and blockage density.