In this chapter, we first review the state-of-the-art schemes for nonorthogonal multiple access where multiple users share the satellite channel radio resources. Among different grant-based and grant-free access schemes, we focus on nonslotted techniques, we study some decoding strategies to improve the performance of asynchronous contention resolution diversity ALOHA. Our preliminary results show that the performance of the decoder can be improved significantly if the information on overlapping bursts' powers and the exact differential delay among the incoming bursts are known at the receiver. We present the simulation results for a simple model and discuss the possible generalizations to a more realistic system scenario. Finally, we shortly discuss the efficiency of the physical layer abstraction methods under our model assumptions.
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