On the maximum stable throughput problem in random networks with directional antennas

Abstract

We consider the problem of determining rates of growth for the maximum stable throughput achievable in dense wireless networks. We formulate this problem as one of finding maximum flows on random unit-disk graphs. Equipped with the max-flow/min-cut theorem as our basic analysis tool, we obtain rates of growth under three models of communication: (a) omnidirectional transmissions; (b) simple directional transmissions, in which sending nodes generate a single beam aimed at a particular receiver; and (c) directional transmissions, in which sending nodes generate multiple beams aimed at multiple receivers. Our main finding is that an increase of Θlog2n in maximum stable throughput is all that can be achieved by allowing arbitrarily complex signal processing (in the form of generation of directed beams) at the transmitters and receivers. We conclude therefore that neither directional antennas, nor the ability to communicate simultaneously with multiple nodes, can be expected in practice to effectively circumvent the constriction on capacity in dense networks that results from the geometric layout of nodes in space.