Comments on a widely used capture model for slotted ALOHA

Previously (see ibid., vol.41, no.9, p.1364, 1993), the capture phenomenon in nonbit-synchronous mobile packet radio networks for binary phase shift keying (BPSK) and differential phase shift keying (DPSK) modulation was investigated. Most of the analysis is correct. Unfortunately, the mathematical expressions for state transition probabilities, adopted from previous work, have errors. Over a decade, these mathematical formulas have been used repeatedly to analyze various capture models with a finite number of users in the traditional slotted ALOHA system. In this note, we present a corrected version of the state transition probabilities.