  Virtualization is a topic of great interest in the area of mobile and
wireless communication systems. However the term virtualization is used in an
inexact manner which makes it difficult to compare and contrast work that has
been carried out to date. The purpose of this paper is twofold. In the first
place, the paper develops a formal theory for defining virtualization. In the
second instance, this theory is used as a way of surveying a body of work in
the field of wireless link virtualization, a subspace of wireless network
virtualization. The formal theory provides a means for distinguishing work that
should be classed as resource allocation as distinct from virtualization. It
also facilitates a further classification of the representation level at which
the virtualization occurs, which makes comparison of work more meaningful. The
paper provides a comprehensive survey and highlights gaps in the research that
make for fruitful future work.
