Novel Design of Two-Tier Slotted-ALOHA OWC/RF IoT Networks with Adaptive Control

In this work, we present a novel design of a two-tier slotted-ALOHA system for massive Internet of Things (IoT) systems. Indoor IoT devices access the network via optical wireless communication (OWC), and relay data via a back-haul radio frequency low-power wide-area network (LPWAN). The main motivation of system under consideration is to reduce the connection density of LPWANs by offloading indoor devices to the OWC-based IoT. The first OWC tier employs slotted-ALOHA random access protocol with multi-packet reception and capture effect in the presence of interfering users, while the second LPWAN is based on slotted-ALOHA with different slot rates compared to the OWC tier. The aim of the presented analysis is to offer design insights for the two-tier OWC/RF system, while focusing on the adaptive selection of the data rates of OWC and LPWAN networks.