Beyond 5G: THz-Based Medium Access Protocol for Mobile Heterogeneous Networks

TLDR

Small cells provide a cost‑effective way to expand coverage and boost capacity, and the ultra‑high bandwidth of millimeter‑wave and Terahertz frequencies enables short‑range links for applications such as driver‑less cars, data backhauling, and ultra‑high‑definition infotainment. The paper introduces a software‑defined networking framework that allows vehicle transceivers to dynamically switch between THz and mmWave bands. It proposes an SDN‑controlled admission policy that handoffs between mmWave and THz cells, analytically derives network capacity by accounting for channel characteristics and contact times, formulates an optimal scheduling procedure for multiple vehicles, and implements a polynomial‑time algorithm executed at the SDN controller. The authors demonstrate that the scheduling problem is NP‑hard, present a polynomial‑time algorithm that outperforms random access and approaches optimal performance, and validate its advantages in a Boston data‑center backhauling simulation.

Abstract

Small cells are a cost-effective way to reliably expand network coverage and provide significantly increased capacity for end users. The ultra-high bandwidth available at millimeter (mmWave) and Terahertz (THz) frequencies can effectively realize short-range wireless access links in small cells enabling potential uses cases such as driver-less cars, data backhauling and ultra-high-definition infotainment services. This paper describes a new software defined network (SDN) framework for vehicles equipped with transceivers capable of dynamically switching between THz and mmWave bands. We present a novel SDN controlled admission policy that preferentially handoffs between the mmWave and THz small cells, accommodates asymmetric uplink/downlink traffic, performs error recovery and handles distinct link states that arise due to motion along practical vehicular paths. We then analytically derive the resulting capacity of such a small cell network by accounting for the channel characteristics unique to both these spectrum bands, relative distance and the contact times between a given transceiver pair. We then formulate the optimal procedure for scheduling multiple vehicles at a given infrastructure tower, with regards to practical road congestion scenarios. The search for the optimal schedule is shown to be a NP-hard problem. Hence, we design a computationally-feasible polynomial-time scheduling algorithm that runs at the SDN controller and compare its performance against the optimal procedure and random access. Additionally, we present a simulation-based case study for the use case of data center backhauling in Boston city to showcase the benefits of our approach.