  We consider wireless communication networks where network users are subject
to critical events such as emergencies and crises. If a critical event occurs
to a user, the user needs to send critical traffic as early as possible.
However, most existing medium access control (MAC) protocols are not adequate
to meet the urgent need for data transmission by users with critical traffic.
In this paper, we devise a class of distributed MAC protocols that achieve
coordination using the finite-length memory of users containing their own
observations and traffic types. We formulate a protocol design problem and find
optimal protocols that solve the problem. We show that the proposed protocols
enable a user with critical traffic to transmit its critical traffic without
interruption from other users after a short delay while allowing users to share
the channel efficiently when there is no critical traffic. Moreover, the
proposed protocols require short memory and can be implemented without explicit
message passing.
