Complete Targets Coverage in Energy Harvesting Internet of Things With Ambient Backscatter

This article considers deriving set covers or the set of active nodes that are responsible for monitoring all targets in an Internet of Things (IoT) network. A key distinction to prior works is that this article considers sensor nodes aided by backscatter communications, which allow them to communicate with negligible energy cost using ambient radio frequency (RF) signals. The article contains three main novelties. First, it presents a mixed integer linear program (MILP) that can be used to compute the global optimal solution. Second, it also outlines a centralized greedy scheduling (CGS) algorithm that selects nodes based on their energy and the number of covered targets. Third, it presents a distributed greedy scheduling (DGS) algorithm that selects nodes according to their energy level. The simulation results show that equipping nodes with ambient backscattering capability increases the ratio of complete targets coverage by more than 100% as compared to existing techniques.

I. Introduction

Sensor nodes operating in Internet of Things (IoT) networks are widely used to monitor one or more static targets, where a target can be a vehicle, the exit/entrance of a building or an asset [1]. Of interest in this article is complete targets coverage [1], where each target is monitored by at least one sensor node at all times. Referring to Fig. 1, we see sensor nodes that are placed strategically to monitor targets. An example of complete targets coverage is to activate sensor nodes , , , and to watch targets; these nodes form a so called set cover. Another example set cover consists of nodes , , , and .