Mobility-Aware Performance in Hybrid RF and Terahertz Wireless Networks

TL;DR

This paper develops a stochastic geometry-based framework to analyze the performance of mobile users in hybrid RF and terahertz networks, accounting for mobility, molecular noise, and coverage, providing new insights into network design.

Contribution

It introduces novel analytical expressions for handoff probability, coverage, and molecular noise impact in hybrid RF-THz networks, validated by simulations.

Findings

Increasing TBS density significantly raises handoff probability.

High molecular absorption can reduce interference and noise, benefiting coverage.

Small increases in TBS density have a larger impact on handoff than equivalent RF base station increases.

Abstract

Using tools from stochastic geometry, this paper develops a tractable framework to analyze the performance of a mobile user in a two-tier wireless network operating on sub-6GHz and terahertz (THz) transmission frequencies. Specifically, using an equivalence distance approach, we characterize the overall handoff (HO) probability in terms of the horizontal and vertical HO and mobility-aware coverage probability. In addition, we characterize novel coverage probability expressions for THz network in the presence of molecular absorption noise and highlight its significant impact on the users' performance. Specifically, we derive a novel closed-form expression for the Laplace Transform of the cumulative molecular noise and interference observed by a mobile user in a hybrid RF-THz network. Furthermore, we provide a novel approximation to derive the conditional distance distributions of a typical user in a hybrid RF-THz network. Finally, using the overall HO probability and coverage probability expressions, the mobility-aware probability of coverage has been derived in a hybrid RF-THz network. Our mathematical results validate the correctness of the derived expressions using Monte-Carlo simulations. The results offer insights into the adverse impact of users' mobility and molecular noise in THz transmissions on the probability of coverage of mobile users. Our results demonstrate that a small increase in the intensity of terahertz base-stations (TBSs) (about 5 times) can increase the HO probability much more compared to the case when the intensity of RF BSs (RBSs) is increased by 100 times. Furthermore, we note that high molecular absorption can be beneficial (in terms of minimizing interference and molecular noise) for specific deployment intensity of TBSs and the benefits can outweigh the drawbacks of signal degradation due to molecular absorption.