An adaptive MAC layer protocol for ATM-based LEO satellite networks

German Aerospace Center (DLR), Fraunhofer FOKUS.cats, and Tesat-Spacecom have designed a future multimedia ATM-based LEO satellite network. Part of the development was an adaptive MAC and FEC scheme which is presented in this paper. The FEC implementation switches on the fly during a connection between several FEC and modulation modes to guarantee a maximum ATM cell error rate of 10 -6. In order to prevent influences of the changing FEC scheme on the user-level data rate, the MAC dynamically changes its packet lengths. Additionally, to minimize contention on the up-link, the MAC structures its TDMA frame into a fixed assigned part and a contention specific part. The boarder in between the two is dynamically altered according to the current link utilization.