New bounds for the L(h, k) number of regular grids

  • Authors:
  • Tiziana Calamoneri;Saverio Caminiti;Guillaume Fertin

  • Affiliations:
  • Dipartimento di Informatica, Universita degli Studi di Roma;La Sapienza;, Via Salaria 113, Roma 00198, Italy.

  • Venue:
  • International Journal of Mobile Network Design and Innovation
  • Year:
  • 2006

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Abstract

For any non-negative real values h and k, an L(h, k)-labellingof a graph G = (V,E) is a function L : V → R such that |L(u)− L(v)| ≥ h if (u, v) ∈ E and |L(u) − L(v)|≥ k if there exists w ∈ V such that (u,w) ∈ E and (w,v) ∈ E. The span of an L(h, k)-labelling is the differencebetween the largest and the smallest value of L. We denote byλh,k(G) the smallest real λ such that graph G has anL(h, k)-labelling of span λ. The aim of the L(h,k)-labelling problem is to satisfy the distance constraints usingthe minimum span. In this paper, we study the L (h, k)-labellingproblem on regular grids of degree 3, 4 and 6 for those values of hand k whose λh,k is either not known or not tight. We alsoinitiate the study of the problem for grids of degree 8. For allconsidered grids, in some cases we provide exact results, while inthe other ones we give very close upper and lower bounds.