Optimal Irregular Repetition Slotted ALOHA Under Total Transmit Power Constraint in IoT-Oriented Satellite Networks

Abstract

In this article, we propose an optimal irregular repetition slotted ALOHA (IRSA) under total transmit power constraint for random access (RA) in the Internet-of-Things (IoT)-oriented satellite networks, which is named as an optimal power-limited IRSA (PL-IRSA). In this proposal, the total transmit power for each satellite machine-type device (SMD) within a frame is considered to be the same and equally allocated into its multiple packet replicas. Due to a variant number of packet replicas, the transmit power of each packet replica for different SMDs may be different. The difference of transmit powers of packet replicas and path loss enhance the received power diversity, which is able to improve the throughput by using the capture effect. At the receiver side, we introduce a semi-analytical (SEA) model to approximate the physical-layer decoding and derive an asymptotic packet loss rate (PLR) based on this SEA model. From the derived results, an optimization problem is formulated and solved to find out the optimal degree distributions for different total transmit powers and code rates, which maximize the normalized system throughput. The simulation results demonstrate that the proposed optimal PL-IRSA can lead to significant performance improvement with respect to conventional ones.