Exact analysis on network capacity of airborne MANETS with digital beamforming antennas

Recently, the use of digital beamforming (DBF) antennas has been drawing lots of interest in airborne platforms for resolving the network partition problem in airborne mobile ad hoc networks (MANETs). In this paper, properties of the network capacity of an airborne MANET with DBF antennas are investigated. This paper considers an ad hoc network consisting of a number of uniformly distributed airborne platforms in a bounded area. These platforms are either directly or indirectly connected with each other through DBF antennas, and form an airborne MANET. We first formulate a digital beamforming antenna system model, referred to as the omni-direction plus sector (OPS) model, and then carry out an exact analysis for the network capacity. The OPS model characterizes the radiation pattern of a DBF antenna. Under the condition that a Hamiltonian path exists in the network, an explicit expression is derived for the network capacity. We show that, for fixed values of the OPS model, the network capacity increases as the network size increases until it reaches an optimal value. If the network size continues to increase, the network capacity will decrease until it reaches zero. Explicit expressions for the optimal network size and the maximum network capacity are also obtained. Finally, numerical results are presented. It is shown that both the optimal network size and the maximum network capacity increase as the antenna beamwidth decreases. They increase slowly when the beamwidth is large, but as the antenna beam becomes narrower, they increase faster.