New bounds for the L(h, k) number of regular grids Online publication date: Tue, 05-Sep-2006
by Tiziana Calamoneri, Saverio Caminiti, Guillaume Fertin
International Journal of Mobile Network Design and Innovation (IJMNDI), Vol. 1, No. 2, 2006
Abstract: For any non-negative real values h and k, an L(h, k)-labelling of 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 difference between the largest and the
smallest value of L. We denote by λh,k(G) the smallest real λ such that graph G
has an L(h, k)-labelling of span λ. The aim of the L(h, k)-labelling problem is to
satisfy the distance constraints using the minimum span. In this paper, we study
the L (h, k)-labelling problem on regular grids of degree 3, 4 and 6 for those values of h
and k whose λh,k is either not known or not tight. We also initiate the study of the
problem for grids of degree 8. For all considered grids, in some cases we provide exact results,
while in the other ones we give very close upper and lower bounds.
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