  We analyze the performance of coded slotted ALOHA systems for a scenario
where users have different error protection requirements and correspondingly
can be divided into user classes. The main goal is to design the system so that
the requirements for each class are satisfied. To that end, we derive
analytical error floor approximations of the packet loss rate for each class in
the finite frame length regime, as well as the density evolution in the
asymptotic case. Based on this analysis, we propose a heuristic approach for
the optimization of the degree distributions to provide the required unequal
error protection. In addition, we analyze the decoding delay for users in
different classes and show that better protected users experience a smaller
average decoding delay.
