Ambient IoT Connectivity Topologies: Technology Enablers, Applications, and Challenges

Sustainability and energy efficiency are anticipated to be foundational goals of sixth-generation (6G) networks, motivating the development of ultra-low-power communication solutions. The emerging concept of ambient Internet of things (A-IoT), currently under study by the third generation partnership project (3GPP), aims to enable ultra-low-power, battery-free connectivity over cellular networks to support the massive deployment of Internet of things (IoT) devices. Leveraging backscatter communication as a key enabler, A-IoT introduces a new class of devices designed to operate at ultra-low power levels, making it a promising candidate for sustainable 6G applications. In this article, we investigate the connectivity topologies of A-IoT based on backscatter communication. We analyze the enabling technologies in the context of each topology, highlighting how deployment constraints influence their design and feasibility. A comparative performance evaluation is presented, with an emphasis on the outage probability across the different topologies. Furthermore, we explore a range of applications specific to each topology and provide insights into practical challenges, alongside prospective solutions.