Topologies for ad-hoc networks utilizing directional antennas with restricted fields of view

Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, February 2006.Includes bibliographical references (p. 63-64).ORCLE (Optical/RF Combined Link Experiment), is an airborne network in which aircraft have multiple directional antennas that are restricted in their pointing direction. A pair of aircraft in ORCLE can be linked if they both have an antenna pointing at each other. Four topology algorithms, which coordinate the pointing of the antennas and attempt to maximize a connectedness metric, are presented and analyzed using a custom 2D simulation platform. Three of the algorithms are based on the Relative Neighbor Graph (RNG): the first constrains the RNG to requirements of the ORCLE network, the second augments the constrained RNG with edges from the Delaunay Triangulation, and the third algorithm tries to improve on the second by adding edges to reduce the diameter. The final algorithm uses a novel concept of overlapping sets of nested convex hulls to select the links of the network. All algorithms are stateless and interface with a Target Transition Layer, which gradually migrates topologies to prevent a large number of edges from being lost simultaneously. Scenes with varying node density, number of terminals per node, fields of view, and re-targeting delays are used to test the algorithms against a wide range of possible situations.by Brian C. Anderson.M.Eng

Distributed dynamic storage in wireless networks

This paper assumes a set of identical wireless hosts, each one aware of its location. The network is described by a unit distance graph whose vertices are points on the plane two of which are connected if their distance is at most one. The goal of this paper is to design local distributed solutions that require a constant number of communication rounds, independently of the network size or diameter. This is achieved through a combination of distributed computing and computational complexity tools. Starting with a unit distance graph, the paper shows: 1. How to extract a triangulated planar spanner; 2. Several algorithms are proposed to construct spanning trees of the triangulation. Also, it is described how to construct three spanning trees of the Delaunay, triangulation having pairwise empty intersection, with high probability. These algorithms are interesting in their own right, since trees are a popular structure used by many network algorithms; 3. A load balanced distributed storage strategy on top of the trees is presented, that spreads replicas of delta stored in the hosts in a way that the difference between the number of replicas stored by any two hosts is small. Each of the algorithms presented is local, and hence so is the final distributed storage solution, obtained by composing all of them. This implies that the solution adapts very quickly, in constant time, to network topology changes. We present a thorough experimental evaluation of each of the algorithms supporting our claims