Laboratory Evaluation of a Channel-Sensitive Slotted Aloha Access Algorithm for Landmobile Satellite Communications.

Abstract

Land mobile satellite communication is handicapped by fading and shadowing effects in zones with low elevation angles. Slotted Aloha is a relatively simple and attractive random access scheme for such applications since its performance does not degrade as fast as that of other schemes. A Slotted Aloha-based modified channel access strategy for highly unreliable channels is presented, which requires all mobile stations in a network to estimate the link quality before starting their transmissions. This improved Slotted Aloha with channel sensing, requiring little more complexity, is analysed in its dynamics under channel influence with the help of a hybrid evaluation tool. The simulation concept combines software routines and hardware communication devices and includes measured channel data. Our results show the improvement of the suggested scheme in comparison to the conventional Slotted Aloha.