Frame-Asynchronous Coded Slotted ALOHA with MDS Component Codes

An extension of the frame-asynchronous coded slotted ALOHA (FA-CSA) protocol for grant-free access, based on packet fragmentation and fragment erasure coding, is investigated. In the analyzed scheme, active users employ maximum distance separable erasure codes at fragment level and transmit encoded fragments on orthogonal subcarriers. Fragment decoding errors at physical layer, even in absence of collisions, are included in the analysis. Asymptotic load threshold values approaching the upper limit are obtained by density evolution over a large efficiency range. At finite frame length, FA-CSA configurations with a very good reliability versus scalability tradeoff are obtained, together with accurate error floor estimation.