Region-Fault Tolerant Geometric Spanners

  • Authors:
  • M. A. Abam;M. de Berg;M. Farshi;J. Gudmundsson

  • Affiliations:
  • Aarhus University, MADALGO Center, Department of Computer Science, Aarhus, Denmark;TU Eindhoven, Department of Computer Science, P.O. Box 513, 5600 MB, Eindhoven, The Netherlands;Carleton University, School of Computer Science, K1S 5B6, Ottawa, ON, Canada and Yazd University, Department of Computer Science, P.O. Box 89195-741, Yazd, Iran;NICTA, Sydney, Australia

  • Venue:
  • Discrete & Computational Geometry
  • Year:
  • 2009

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Abstract

We introduce the concept of region-fault tolerant spanners for planar point sets and prove the existence of region-fault tolerant spanners of small size. For a geometric graph $\mathcal{G}$on a point set P and a region F, we define $\mathcal{G}\ominus F$to be what remains of $\mathcal{G}$after the vertices and edges of $\mathcal{G}$intersecting F have been removed. A  $\mathcal{C}$-fault tolerant t-spanner is a geometric graph  $\mathcal{G}$on P such that for any convex region F, the graph $\mathcal{G}\ominus F$is a t-spanner for $\mathcal{G}_{c}(P)\ominus F$, where $\mathcal{G}_{c}(P)$is the complete geometric graph on P. We prove that any set P of n points admits a $\mathcal{C}$-fault tolerant (1+ε)-spanner of size $\mathcal{O}(n\log n)$for any constant ε0; if adding Steiner points is allowed, then the size of the spanner reduces to  $\mathcal{O}(n)$, and for several special cases, we show how to obtain region-fault tolerant spanners of $\mathcal{O}(n)$size without using Steiner points. We also consider fault-tolerant geodesic t -spanners: this is a variant where, for any disk D, the distance in $\mathcal{G}\ominus D$between any two points u,v∈P∖D is at most t times the geodesic distance between u and v in ℝ2∖D. We prove that for any P, we can add $\mathcal{O}(n)$Steiner points to obtain a fault-tolerant geodesic (1+ε)-spanner of size  $\mathcal{O}(n)$.