THz Network Placement and Mobility-Aware Resource Allocation for Indoor Hybrid THz/VLC Wireless Networks

This paper focuses on the energy and spectral efficient design of an indoor communication system that leverages terahertz (THz) and visible light communication (VLC). We first optimize THz access points (APs) deployment in an indoor environment equipped with VLC APs such that uniform data rate can be guaranteed for all arbitrarily located users in the room. We discretize the placement problem and then apply fractional programming techniques and a Majorization-Minimization (MM) approach to solve it. Then, we develop a novel mobility-aware resource allocation framework to optimize user-AP assignment, subchannel allocation (SA), and power allocation (PA) to maximize the handoff (HO)-aware sum rate and energy efficiency (EE) of hybrid THz/VLC networks. The HO-aware sum rate and EE adapts according to the HOs experienced by users. The proposed framework constrains users’ quality-of-service demands, transmit power budgets, molecular absorption loss thresholds, illumination requirements, and minimum electromagnetic field exposure. This joint problem is a mixed integer nonlinear programming problem which is generally intractable and mostly solved by decomposing into multiple sub-problems via alternating optimization. Different from the traditional approach, we cast this problem as a multi-objective optimization problem and obtain a solution that jointly optimizes all variables using quadratic optimization and MM approach. Computational complexity analysis is presented for both solutions. The proposed placement solution is much faster than the optimal solution. Moreover, the time complexity does not increase with augmenting the number of THz APs. Also, the proposed mobility-aware joint resource allocation solution significantly outperforms the existing benchmarks.