Simplified Models in Evaluating the Performance of the Non-orthogonal Slotted Aloha Protocol

In this paper, two simplified models are proposed to evaluate both effectively and accurately the performance of the Non-Orthogonal Slotted Aloha (NOSA) protocol particularly suitable for satellite communications. As the NOSA system is constructed on the basis of the Sparse Code Multiple Access (SCMA) technique in a complete random fashion, it is found that the performance of the NOSA system depends mainly on the codebook collision conditions as well as power differences among colliding packets. In this case, a fitting function is first proposed to approximate the detection performance of the SCMA system in the physical layer, based on which a simplified physical model as well as an analytical model are proposed to evaluate the performance of the NOSA system. Numerical results show that both the models could effectively and accurately approximate the performance of the NOSA system, paving the way for the NOSA system to be quickly evaluated and deployed in the practice.