  There is a growing demand for wireless services with different requirements
in a dense and heterogeneous wireless environment. Handling this complex
ecosystem is becoming a challenging issue, and wireless virtualization emerges
as an efficient solution. Although the inclusion of virtualization in wireless
networks ensures a better use of resources, current approaches adopted for
wireless virtualization can cause an underutilization of resources, since the
resource allocated to a virtual wireless network is not shared with other one.
This problem can be overcome by combining wireless virtualization with the
cognitive radio (CR) technology and dynamic access spectrum (DSA) techniques.
Thus, virtual wireless networks with different access priorities to resources
(e.g., primary and secondary) can be deployed in an overlay form and share the
same substrate wireless network, where the secondary networks use the resources
opportunistically. However, challenges emerge in this new scenario, ranging
from the mapping to the operation of these networks. This paper is the first to
propose the cognitive radio virtual network environment and to formulate the
problem of mapping the secondary virtual networks (SVNs) onto the wireless
substrate network based on CR. To this end, a multi-objective formulation is
designed. Moreover, an analysis of the metrics defined in the problem is
performed in order to give the reader useful assistance in designing schemes to
solve the problem of mapping SVNs onto substrate networks.
