Radio Graceful Labelling of Graphs

Radio labelling problem of graphs have their roots in communication problem known as \emph{Channel Assignment Problem}. For a simple connected graph $G=(V(G), E(G))$, a radio labeling is a mapping $f \colon V(G)\rightarrow \{0,1,2,\ldots\}$ such that $|f(u)-f(v)|\geq {\rm diam}(G)+1-d(u,v)$ for each pair of distinct vertices $u,v\in V(G)$, where $\rm{diam}(G)$ is the diameter of $G$ and $d(u,v)$ is the distance between $u$ and $v$. A radio labeling $f$ of a graph $G$ is a \emph{radio graceful labeling} of $G$ if $f(V(G)) = \{0,1,\ldots, |V(G)|-1\}$. A graph for which a radio graceful labeling exists is called \emph{radio graceful}. In this article, we study radio graceful labeling for general graphs in terms of some new parameters

Radio Number of Hamming Graphs of Diameter 3

For $G$ a simple, connected graph, a vertex labeling $f:V(G)\to \Z_+$ is called a \emph{radio labeling of $G$} if it satisfies |f(u)-f(v)|\geq\diam(G)+1-d(u,v) for all distinct vertices $u,v\in V(G)$. The \emph{radio number of $G$} is the minimal span over all radio labelings of $G$. If a bijective radio labeling onto $\{1,2,\dots,|V(G)|\}$ exists, $G$ is called a \emph{radio graceful} graph. We determine the radio number of all diameter 3 Hamming graphs and show that an infinite subset of them is radio graceful

Radio Graceful Hamming Graphs

For $k \in \mathbb{Z}_+$ and $G$ a simple, connected graph, a $k$-radio labeling $f : V (G) \rightarrow \mathbb{Z}_+$ of $G$ requires all pairs of distinct vertices $u$ and $v$ to satisfy $|f(u) − f(v)| \ge k + 1 − d(u, v)$. We consider $k$-radio labelings of $G$ when $k = \text{diam} (G)$. In this setting, $f$ is injective; if $f$ is also surjective onto ${1, 2, . . ., |V (G)|}$, then $f$ is a consecutive radio labeling. Graphs that can be labeled with such a labeling are called radio graceful. In this paper, we give two results on the existence of radio graceful Hamming graphs. The main result shows that the Cartesian product of $t$ copies of a complete graph is radio graceful for certain $t$. Graphs of this form provide infinitely many examples of radio graceful graphs of arbitrary diameter. We also show that these graphs are not radio graceful for large $t$

Radio Graceful Hamming Graphs

For k ∈ ℤ+ and G a simple, connected graph, a k-radio labeling f : V (G) → ℤ+ of G requires all pairs of distinct vertices u and v to satisfy |f(u) − f(v)| ≥ k + 1 − d(u, v). We consider k-radio labelings of G when k = diam(G). In this setting, f is injective; if f is also surjective onto {1, 2, . . . , |V (G)|}, then f is a consecutive radio labeling. Graphs that can be labeled with such a labeling are called radio graceful. In this paper, we give two results on the existence of radio graceful Hamming graphs. The main result shows that the Cartesian product of t copies of a complete graph is radio graceful for certain t. Graphs of this form provide infinitely many examples of radio graceful graphs of arbitrary diameter. We also show that these graphs are not radio graceful for large t