  The effect of signals on stability, throughput region, and delay in a
two-user slotted ALOHA based random-access system with collisions is
considered. This work gives rise to the development of random access
G-networks, which can model virus attacks or other malfunctions and introduce
load balancing in highly interacting networks. The users are equipped with
infinite capacity buffers accepting external bursty arrivals. We consider both
negative and triggering signals. Negative signals delete a packet from a user
queue, while triggering signals cause the instantaneous transfer of packets
among user queues. We obtain the exact stability region, and show that the
stable throughput region is a subset of it. Moreover, we perform a compact
mathematical analysis to obtain exact expressions for the queueing delay by
solving a Riemann boundary value problem. A computationally efficient way to
obtain explicit bounds for the queueing delay is also presented. The
theoretical findings are numerically evaluated and insights regarding the
system performance are derived.
