Capture Effects in Opportunistic Slotted ALOHA over Rayleigh Fading Channels

This paper studies the throughput, average packet delay and average power consumption for opportunistic slotted ALOHA (OS-ALOHA) in Rayleigh fading channels. The basic idea of the opportunistic transmission is to control the transmission probability of each user based on the channel quality. If the channel is good, a user transmits the packet; otherwise it holds the packet. A finite state Markov chain (FSMC) channel is modeled and the capture effect is considered in this paper. The channel fading is assumed to be correlated from slot to slot and channel state transition is incorporated into the analysis of system performance. The system performance for OS-ALOHA is investigated considering packet traffic statistics. Compared to conventional slotted ALOHA, OS-ALOHA systems show a higher throughput, smaller average delay and higher power efficiency.