Capacity of clustered ad hoc networks: how large is "Large"?

We study the capacity of a large clustered wireless ad hoc network in which clusters of nodes are scattered in a sea of relatively low-density nodes. We fix the density of nodes and clusters and study behavior as we increase the total network area (or, equivalently, the total number of nodes), which we call the network size. The main result is that the capacity switches behavior at a critical network size, which depends on the cluster size and the density of clusters within the network. Thus, the clustering parameters of the network allow us to quantify the meaning of a "large" network, i.e., such that further size increase entails degradation of throughput capacity