Age of Information Optimization for Multi-Hop VLC/RF IoT Sensor Networks

This paper presents an analysis of the Age of Information (AoI) in a wireless sensor network consisting of multiple IoT sensors. This network consists of three nodes: a wireless power source (WPS), sensors, and an access point (AP). We exploit hybrid visible light communication/radio frequency (VLC/RF) for the sensors with the orthogonal frequency bands. Power domain non-orthogonal multiple access (PD-NOMA) and successive interference cancellation (SIC) are also adopted for the sensors and the AP. Finally, we present two main optimization problems for average AoI with the sensor's transmit power constraint. We analyze the average AoI in a hybrid VLC/RF network, and we obtain the global optimum value for the average AoI of each sensor by considering the probability of sensors being charged, the probability of choosing the links, calculating the probability of successful decoding. According to the optimization results based on the Particle Swarm Optimization (PSO) method, the average AoI for each sensor and the total average AoI in the proposed system are reduced by 10% and 15%, respectively.