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

Throughput capacity of large ad hoc networks has been shown to scale adversely with the size of network n. However the need for the nodes to find or repair routes has not been analyzed in this context. In this paper, we explicitly take route discovery into account and obtain the scaling law for the throughput capacity under general assumptions on the network environment, node behavior, and the quality of route discovery algorithms. We also discuss a number of possible scenarios and show that the need for route discovery may change the scaling for the throughput capacity dramatically.

The performance of an ad hoc network that contains many nodes within circular clusters with fixed node density is studied. These clusters lie within a finite square area, and the space between clusters is filled with nodes such that the density of nodes is much smaller than the density of nodes in the clusters. We obtain an upper bound on the throughput and investigate the achievability of the upper bound. Through these studies, the effect of clustering on throughput is uncovered. The impact of changing the finite square area, in which the system resides, called the system size, becomes evident. In particular, we show that in clustered networks, the size of the network is important, and in particular, the behavior of the network changes greatly for small and large networks

We obtain an upper bound on the throughput of an ad hoc network which contains a square-shaped cluster with n nodes acting as sources communicating with another square-shaped cluster with n destination nodes. We consider the cases where the two clusters have no overlap, partial overlap, and complete overlap. We also investigate the achievability of the upper bound in the no overlap case and show that it can be achieved up to a typically small additive term.

The delay-limited throughput of an ad hoc wireless network confined to a finite region is investigated. An approximate expression for the achievable throughput as a function of the maximum allowable delay is obtained. It is found that: 1) for moderate values of the delay d, the throughput that can be achieved by taking advantage of the motion increases as d/sup 2/3/ and 2) for a fixed value of d, the dependence of the achievable throughput on the number of nodes n is n/sup -1/3/. A transmission and relaying strategy ensuring continuous information flow is constructed. It is shown that there exists a critical value of the delay such that: 1) for values of the delay d below the critical delay, the throughput does not benefit appreciably from the motion and 2) the dependence of the critical delay on the number of nodes is a very slowly increasing function (n/sup 1/14/). Finally, asymptotic optimality of the proposed strategy in a certain class is shown.

The delay limited capacity of an ad hoc wireless network confined to a finite region is investigated. A transmission and relaying strategy making use of the nodes' motion to maximize the throughput is constructed. An approximate expression for the capacity as a function of the maximum allowable delay is obtained. It is found that there exists a critical value of the delay such that: (1) for values of the delay d below critical, the capacity does not benefit appreciably from the motion, (2) for moderate values of the delay d above critical, the capacity that can be achieved by taking advantage of the motion increases as d2/3, (3) the dependence of the critical delay on the number of nodes is a very slowly increasing function (n1/14). Finally, asymptotic optimality of the proposed strategy in a certain class is shown.

The problem of capacity of a wireless ad hoc network in the presence of a uniform end-to-end delay constraint is explored. A general model for the random motion of the nodes is used. An approximate expression for the capacity as a function of the maximum allowable delay is obtained, and the asymptotic optimality of the proposed transmission strategy in a certain class is shown.