Opportunistic access in slotted ALOHA adapted to decentralized CSI

We develop a model for decentralized opportunistic transmissions of a finite (n) user slotted ALOHA system that relies on decentralized channel state information (D-CSI). D-CSI refers to each user node having access only to its own uplink channel gain. Every user adapts both rate and re-transmission probability to D-CSI in every slot. Due to the variable transmission rate from slot to slot, incoming packets with fixed length are re-assembled to deliver as many bits as possible per slot. By modeling the number of bits in queues as a discrete Markov chain, we analyze the stability region and the maximum stable throughput (MST). In addition, we derive a decentralized opportunistic scheme and show that it achieves a fraction (1-1/n)^n-1 of its centralized counterpart´s throughput, where (1-1/n)^n-1 is a factor due to the inherent contention in random access.