- A modified version of the datagram capacity assignment of the FODA access scheme, named FODA/IBEA, is briefly presented. The main difference from the previous version (besides the fade countermeasure feature) is the possibility of the system to migrate, depending on the overall loading conditions, from a sort of fixed TDMA (called pre-assignment mode), in which each active station shares the spare capacity with all the others, to a more complex mechanism. The response of the system to a step of traffic at one of the active stations is studied, and the analytical expressions of the most significant variables are derived. The results of the analysis are first compared with the experimental ones and then used to show the sensitivity of the system's behavior with respect to some parameters. The possibility of adopting the capacity allocation algorithm in a distributed mode is also discussed. Key words: Demand assignment TDMA, Satellite access scheme, FODA/IBEA, Anisochronous traffic...