Near-far effect on slotted ALOHA channels with shadowing and capture

Signal statistics are modelled in an environment of shadowing and ground wave path loss. This propagation model is used to investigate the channel performance of a slotted ALOHA network. The results are presented as receiver capture probability vs. packet propagation distance, with the log-normal variance and the offered traffic as parameters. Log-normal spatial distributions and uniform distributions of users over the coverage area are compared. The former facilitate the analysis of mobile packet-radio channels with near-far effect and shadowing and can often approximate the latter type of distribution. It is shown that stability and throughput cannot be realistically studied by (quasi-) uniform distributions. The log-normal subscriber density with a spatial spread of 8.68 dB gives a viable alternative to the study of the heavily loaded collision-type multiple-access channel