Secrecy Outage Performance Analysis of Wirelessly Powered IoT System with Randomly Moving Receiving Nodes

Due to the need for the implementation of various IoT services, novel generation networks are often characterized by a constant requirement for their expansion and a rising number of nodes. The IoT network nodes are usually low power, so security becomes a challenging issue as conventional cryptographic techniques are hard to implement due to power and computational limitations. Besides, wireless power transfer is an appealing approach for powering IoT systems in scenarios where many nodes are placed in hardly accessible areas. Finally, due to a variety of applications, network nodes are often mobile. Motivated by these facts, in this paper, we investigate physical layer security in IoT systems powered by means of a power beacon, where a legitimate user or eavesdropper can be mobile. The closed-form approximate secrecy outage probability expressions are derived for the Nakagami-m fading environment and three scenarios of receiving node mobility, described by using a random waypoint model with mobility patterns in one, two or three dimensions. The accuracy of the obtained analytical expressions is corroborated by an independently developed simulation model.