Date Added: Jun 2011
Cognitive Radio Networks (CRNs) are being studied intensively. The major motivation for this is the heavily underutilized frequency spectrum. CRN has the capability to utilize the unutilized frequency spectrum. Routing in CRN is a challenging task due the diversity in the available channels and data rates. In this paper, the authors present a survey of the state-of-the-art routing techniques in CRNs. They first outline the design challenges for routing protocols in CRNs followed by a comprehensive survey of different routing techniques. Furthermore, they classified these routing protocols into spectrum aware-based, multipath-based, local coordination-based, reactive source-based and tree-based routing techniques depending on the protocol operation.