  In a multiple access channel, autonomous stations are able to transmit and
listen to a shared device. A fundamental problem, called \textit{contention
resolution}, is to allow any station to successfully deliver its message by
resolving the conflicts that arise when several stations transmit
simultaneously. Despite a long history on such a problem, most of the results
deal with the static setting when all stations start simultaneously, while many
fundamental questions remain open in the realistic scenario when stations can
join the channel at arbitrary times.
  In this paper, we explore the impact that three major channel features
(asynchrony among stations, knowledge of the number of contenders and
possibility of switching off stations after a successful transmission) can have
on the time complexity of non-adaptive deterministic algorithms. We establish
upper and lower bounds allowing to understand which parameters permit
time-efficient contention resolution and which do not.
