Link Budget Analysis for Backscatter-Based Passive IoT

Massive connectivity of billions of communicating devices for fifth-generation (5G) and beyond networks requires the deployment of self-sustaining, maintenance-free, and low-cost communication paradigms. Could passive Internet of Things (IoT) solve these challenges? Passive IoT can be realized with the backscatter communication (BackCom) paradigm, which uses ultra-low power, inexpensive passive tags to support massive connectivity. However, a comprehensive link budget analysis for BackCom networks has not yet been available. It is something that is necessary for practitioners and researchers to evaluate the potential of BackCom. This survey is organized as follows. First, we describe the BackCom configurations, passive IoT design targets, backscatter channel statistics, and the different components and operations of the backscatter tag. Second, we develop the forward link budget and the overall link budget. All the relevant parameters are described in detail. Third, we give numerical and simulation results to get insights on the achievable performance of BackCom networks. Since additive path losses and excess fading can limit the performance of BackCom networks, we examine potential solutions to overcome the resulting limitations, enabling massive IoT networks. We also discuss integrating BackCom with existing wireless technologies. We further highlight some applications and address open issues, challenges, and future research directions.