  In this work, we consider a random access Internet of Things IoT wireless
network assisted by two aggregators collecting information from two disjoint
groups of sensors. The nodes and the aggregators are transmitting in a random
access manner under slotted time, the aggregators perform network-level
cooperation for the data collection. The aggregators are equipped with queues
to store data packets that are transmitted by the network nodes and relaying
them to the destination node. We characterize the throughput performance of the
IoT network and we obtain the stability conditions for the queues at the
aggregators. We apply the theory of boundary value problems to analyze the
delay performance. Our results show that the presence of the aggregators
provides significant gains in the IoT network performance, in addition, we
provide useful insights regarding the scalability of the IoT network.
