  For a positive integer $n$, let $\mZ$ be the set of all non-negative integers
modulo $n$ and $\sP(\mZ)$ be its power set. A modular sumset valuation or a
modular sumset labeling of a given graph $G$ is an injective function $f:V(G)
\to \sP(\mZ)$ such that the induced function $f^+:E(G) \to \sP(\mZ)$ defined by
$f^+ (uv) = f(u)+ f(v)$. A sumset indexer of a graph $G$ is an injective sumset
valued function $f:V(G) \to \sP(\mZ)$ such that the induced function $f^+:E(G)
\to \sP(\mZ)$ is also injective. In this paper, some properties and
characteristics of this type of modular sumset labeling of graphs are being
studied.
