Age of information offloading optimization in integrated satellite-terrestrial networks

The progress in wireless communications and networking technology has led to a globally connected society in which a wide range of wireless devices, effortlessly communicate with one another. The freshness of the transmitted status updates information in these systems is very crucial. Time-critical information can be characterized by using real-time status updates which are messages encapsulated in packets including their timestamp of generation. We study single-buffer single-source and single-buffer multiple-source with various queuing models of a status update system in integrated satellite-terrestrial networks (ISTN), which consists of the terrestrial network (TN) and non-terrestrial network (NTN). Therefore, LEO satellites are the preferred choice for deploying satellite IoT systems. Next, we aim to obtain the exact distributions of the average age of information (AoI) and peak AoI (PAoI) and by determining the time average of the instantaneous AoI, the average freshness of the information across time will be measured. When the measured instantaneous AoI is higher than the threshold bounded AoI, the terrestrial network will offload the data to the LEO satellite. Otherwise, the data flow will continue to transmit packets within TN. Thus, the decision-making process will be reduced to a binary selection with the implementation of this approach. This approach can be considered as a threshold-based policy in which an improved heuristic algorithm is used for network optimization. Proposed algorithm's accuracy is verified by comparing our results to simulations and existing literature in specific sub-cases.