Performance evaluation of channel-sensitive, stabilized multiple access schemes for land-mobile satellite services using a hybrid simulation tool

A hybrid simulation tool for real-time performance measurements of complete networks is presented. The simulation tool combines the advantages of software and hardware modules. Recorded channel data are included. They allow the reproduction of realistic situations in the laboratory. Synchronization problems and noise are considered. As an example, stabilized slotted ALOHA access protocols were implemented and investigated in land-mobile satellite environments. A slotted ALOHA-based modified channel access strategy for highly unreliable channels is proposed requiring all mobile stations to estimate the link quality before starting a transmission. The different strategies are analyzed by simulation as well as the analytical methods. Transmission parameters are determined and optimized using a combination of analysis and simulation. The results show the power of the simulation tool and the better performance of stabilized slotted ALOHA with link-quality estimation in city channels