Investigation of slotted ALOHA under Nakagami fading with synchronized and asynchronous cochannel cells

The throughput performance of slotted ALOHA (S-ALOHA) in a cellular system and Nakagami fading environment is studied. Based on the signal capture model, the effects of the multiple access interference (MAI) from in-cell users and the cochannel interference (CCI) from cochannel cells are quantified analytically. Especially considered are the cases when asynchronism of cochannel cells is present, for which an approximation of the interference distribution is successfully applied to get a highly precise expression of the system throughput. Our study shows that though the MAI level and capture effect determine the basic behavior of the S-ALOHA, CCI significantly reduces the throughput of S-ALOHA and asynchronous CCI introduces an especially severe impairment. Our analytical framework is also able to incorporate additional channel conditions and system parameters like lognormal shadowing and the cellular cluster size.