Local Routing in Graphs Embedded on Surfaces of Arbitrary Genus

TL;DR

This paper introduces a local routing algorithm, GFR, for connected graphs on surfaces of arbitrary genus, guaranteeing delivery with bounded memory and time, generalizing Face Routing to higher-genus surfaces.

Contribution

The paper presents GFR, a novel local routing algorithm for graphs embedded on surfaces of any genus, extending Face Routing to non-planar surfaces using homology basis techniques.

Findings

GFR guarantees delivery in graphs on surfaces of any genus.

GFR uses O(g log n) memory and runs in O(g^2 n^2) time.

The algorithm is applicable to sensor networks on complex surfaces.

Abstract

We present a local routing algorithm which guarantees delivery in all connected graphs embedded on a known surface of genus $g$. The algorithm transports $O(g\log n)$ memory and finishes in time $O(g^2n^2)$, where $n$ is the size of the graph. It requires access to a homology basis for the surface. This algorithm, GFR, may be viewed as a suitable generalization of Face Routing (FR), the well-known algorithm for plane graphs, which we previously showed does {\it not} guarantee delivery in graphs embedded on positive genus surfaces. The problem for such surfaces is the potential presence of homologically non-trivial closed walks which may be traversed by the right-hand rule. We use an interesting mathematical property of homology bases (proven in Lemma \ref{lem:connectFaceBdr}) to show that such walks will not impede GFR. FR is at the base of most routing algorithms used in modern (2D) ad hoc networks: these algorithms all involve additional local techniques to deal with edge-crossings so FR may be applied. GFR should be viewed in the same light, as a base algorithm which could for example be tailored to sensor networks on surfaces in 3D. Currently there are no known efficient local, logarithmic memory algorithms for 3D ad hoc networks. From a theoretical point of view our work suggests that the efficiency advantages from which FR benefits are related to the codimension one nature of an embedded graph in a surface rather than the flatness of that surface (planarity).